Stratigraphy And Petrology Of The Quiburis ... Near Mammoth, Pinal County, Arizona B Y

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STRATIGRAPHY AND PETROLOGY OF THE QUIBURIS FORMATION NEAR MAMMOTH, PINAL COUNTY, ARIZONA by Thom as W a lter Ladd A T h e s is Su bm itted to th e F a c u lty o f th e DEPARTMENT OF GEOSCIENCES In P artial F u lfillm en t o f th e R equirem ents For the D eg ree o f MASTER OF SCIENCE In th e G raduate C o lle g e THE UNIVERSITY OF ARIZONA 19 7 5 STATEMENT BY AUTHOR This th e sis has been submitted in partial fulfillm ent of re­ quirements for an advanced degree at The U niversity of Arizona and is deposited in the U niversity Library to be made available to borrowers under rules of the Library. Brief quotations from this th e sis are allow able without sp ecia l perm ission, provided that accurate acknowledgment of source is m ade. Requests for perm ission for extended quotation from or reproduction of this manuscript in whole or in part may be granted by the head of the major department or the Dean of the Graduate C ollege when in his judg­ ment the proposed use of the material is in the interests of scholar­ ship. In all other in s ta n c e s , how ever, perm ission must be obtained from the author. SIGNED: / 6 / APPROVAL BY THESIS DIRECTOR This th e sis has been approved on the date shown below: fOSEPH F . SCHREIBER , Professor of G eo scien ces Date * ^ ACKNOWLEDGMENTS A ck n ow led gm en t is due my t h e s i s d ir e c to r , D r . J o sep h F . S c h r e ib e r, Jr. I am g r a te fu l to him for th e a d v ic e , c r it ic is m , s u g g e s ­ t i o n s , g u id a n c e , and h is m any id e a s during th is s tu d y . I w is h to thank m em bers o f my graduate c o m m itte e , D r s . Richard F . W ils o n and D ietm ar S ch u m a ch er, for th e ir rea d in g o f th e m an u scrip t and h e lp fu l s u g g e s t i o n s . I thank D r . M ic h a e l J . D rake o f th e Lunar and P la n eta ry Labora­ tory for a llo w in g me r e s e a r c h tim e on th e s c a n n in g e le c tr o n m ic r o sc o p e quantom eter under th e in stru m en t d ir e c tio n o f M r. Thom as T e s k a . T his t h e s i s w a s m ade p o s s ib le b y a r e s e a r c h grant from my w i f e , D ia n n e . M any th an k s g o to her for th e en co u ra g em en t and hard w ork during my graduate s t u d ie s . iii TABLE OF CONTENTS Page LIST OF ILLUSTRATIONS........................................... vi ABSTRACT . . ............................................................ ix IN T R O D U C T IO N ............................................................................................................... t o CO t o S ta tem en t o f th e Problem P u r p o se .................................. L o c a t i o n ............................... P rev io u s S t u d i e s .............. 1 REGIONAL SE T T IN G ........................................................................................................ 7 P h y s io g r a p h y ............................................................................. G e o lo g y . . .................................................................................................... 7 7 STRATIGRAPHIC NOM ENCLATURE.......................................................................... 10 METHOD OF ST U D Y ........................................................................................................ 11 F ie ld S t u d y ............................................................................................................... L aboratory S t u d y ..................................................................................................... S iz e A n a l y s i s .................................................................................................. P etrographic S t u d i e s ................................................................................. X -ray A n a l y s i s .............................................................................................. S can n in g E lectron M i c r o s c o p e ............................................................. 11 11 11 12 12 12 QUIBURIS FORM ATION.................................................................................................. 13 G r a v e l ......................................................................................................................... D istr ib u tio n and T h i c k n e s s ................................................................... T e x t u r e ............................................................................................................... Sedim en tary S t r u c t u r e s ............................................................................. C o m p o s itio n ..................................................................................................... S a n d ................................................................................................................................ D istr ib u tio n and T h i c k n e s s ................................................................... T e x t u r e ............................................................................................................... S ed im en tary S t r u c t u r e s ............................................................................. C o m p o s itio n ..................................................................................................... S i l t ................................................................................................................................ D istr ib u tio n and T h i c k n e s s ................................................................... T e x t u r e ............................................................................................................... S ed im en tary S t r u c t u r e s ............................................................................. C o m p o s itio n ..................................................................................................... 13 13 22 24 24 24 24 26 27 28 29 29 31 31 32 iv / V TABLE OF CONTENTS— C on tin u ed Page H e a v y M i n e r a l s ..................................................................................................... L im e s t o n e ................................................................................................................... V o lc a n ic S e d i m e n t s ............................................................................................... D i a t o m i t e ................................................................................................................... S ilty O p a l- C r is t o b a lit e ........................................................................................ F ie ld C h a r a c t e r is t ic s ................................................................................. X -ray A n a l y s i s ..................................................... P etrograp h ic A n a ly s is ................................................................................. S ca n n in g E lectro n M ic r o sc o p e A n a l y s i s ......................................... O rigin and D i a g e n e s i s .............................................................................. 34 37 39 41 43 43 46 51 54 54 ENVIRONMENT OF D E P O S IT IO N .............................................................................. 62 SU M M A R Y ..................................................... 67 APPENDIX A: DESCRIPTION OF MEASURED S E C T IO N S ............................... 69 APPENDIX B: STATISTICAL MEASURES OF CLASTIC SEDIMENTS, QUIBURIS FO RM A TIO N .................................................................... 95 REFERENCES 99 LIST OF ILLUSTRATIONS Figure Page 1. In d ex map sh o w in g lo c a tio n o f stu d y a r e a ......................................... 3 2. In d ex map sh o w in g lo c a tio n o f m easu red str a tig r a p h ic s e c t i o n s ........................................................................................................ 4 3. G e o lo g ic map o f stu d y a r e a ....................................................................... 9 4. T extu ral c la s s if i c a t i o n for Q u ib u ris Form ation s e d im e n ts c o n ta in in g g r a v e l ............................................................. 14 H isto g ra m s sh o w in g p e r c e n ta g e o f sed im e n t in s e le c t e d sa n d s a m p l e s .......................................................................... 15 H istogram sh o w in g v a r ia tio n o f so rtin g v a lu e s for sa n d s a m p l e s ............................................................................................... 16 7. P lot o f m ean s i z e v e r s u s so rtin g v a lu e s for sa n d sa m p le s 17 8. T extu ral c la s s if i c a t i o n for Q uiburis Form ation s e d im e n ts la c k in g g r a v e l .........................................'......................... 18 H isto g ra m s sh o w in g p e r c e n ta g e o f se d im e n t in s e le c t e d s i l t s a m p le s .............................................................................. 19 H istogram sh o w in g v a r ia tio n o f so rtin g v a lu e s for s i l t s a m p le s .................................................................................................. 20 11. P lot o f m ean s iz e v e r s u s so rtin g v a lu e s for s i l t s a m p le s . . . 21 12. M ea su red str a tig r a p h ic s e c t io n s o f th e Q uiburis Form ation n ear M am m oth, A r izo n a ........................... ... 5. 6. 9. 10. . . in p o c k e t 13. V iew o f m easu red str a tig r a p h ic s e c t io n C C - 6 ............................... 23 14. C h a n n e l-s c o u r c o n ta c t and e r o s io n a l u n c o n fo r m ity ..................... 25 15. In terb ed d in g o f d ia to m ite and s i l t .......................................................... 30 16. L am inated b ed d in g o f d ia to m ite and s i l t ............................................ 30 17. C r o s s - s t r a t if ic a t io n in s i l t u n i t ............................................................. 33 vi vii LIST OF ILLUSTRATIONS--C on tin u ed F igure 18. P age Cut hand sp e c im e n o f p i s o l i t i c and e lo n g a te (mat) a lg a l sa n d y l i m e s t o n e ........................................ 38 19. Photom icrograph o f a lg a l p i s o l i t e s ....................... 38 20. S o ft sed im e n t d eform ation sh ow n b y irregular bottom c o n ta c t o f v o lc a n ic a s h b e d ................................................................ 40 21. S can n in g e le c tr o n m icrograph o f d e v itr ify in g a s h shard 42 22. S ca n n in g e le c tr o n m icrograph o f diatom h a s h ........................ 23. O p a l-c r is to b a lite b e n ch o f m easu red str a tig r a p h ic s e c t io n C C - 2 .............................................................................................. 24. . . . . 44 44 V iew lo o k in g north in to m easu red str a tig r a p h ic s e c t io n C C - 2 .................................................................................... 45 25. U n d u latory su r fa c e o f s i l t y o p a l- c r is t o b a l it e ........................ 45 26. Cut hand s p e c im e n o f t y p ic a l b ed d ed s ilt y o p a lc r is to b a lite , sh o w in g la m in a tio n s and b la c k c a r b o n a c e o u s l a y e r s .............................................................................. 47 X -ray d iffractogram s o f Q uiburis d ia to m ite and s i l t y o p a l - c r i s t o b a l i t e .......................................................................... 49 X -ra y d iffractogram s o f Q uiburis s ilt y o p a lc r is to b a lite .................................................................................................. 50 27. 28. 29. Photom icrograph o f v ery s ilt y o p a l - c r i s t o b a l i t e ................. 30. Photom icrograph o f g a stro p o d in s ilt y o p a l- c r is t o b a lit e . . . . 52 31. Photom icrograph o f u n id e n tifie d m ic r o fo s s il in s ilt y o p a l- c r is t o b a l it e ........................................................................................ 53 32. Photom icrograph o f co llo fo rm c r is to b a lite lin in g c a v ity . . . . 53 33. S ca n n in g e le c tr o n m icrograp hs o f c r is to b a lite m icro s p h e r u le s lin in g c a v i t i e s .......................................................... 55 S ca n n in g e le c tr o n m icrograph o f c r is to b a lite m ic r o s p h e r u le s ........................................................................................... 56 34. 35. C ut hand sp e c im e n o f o p a l- c r is t o b a lit e n o d u l e ................. 52 60 viii LIST OF ILLUSTRATIONS— C ontinued Figure 36. P age C o n c e p tu a l v ie w o f th e San Pedro V a lle y near M am m oth, A rizo n a , during d e p o s itio n o f th e Q u ib u ris F o r m a t io n ................................................................................. 63 ABSTRACT The m id dle P lio c e n e Q uiburis Form ation in th e San Pedro V a lle y a p p roxim ately 10 m ile s (16 km) s o u th e a s t o f M am m oth, A rizona c o n s i s t s p r in c ip a lly o f sa n d y s i l t . In a d d itio n , minor am ounts o f v o lc a n ic a s h , b e n t o n ite , lim e s t o n e , d ia to m ite , and s ilt y s ilic e o u s ro ck s o ccu r b e ­ tw e e n th e dom inant s i l t y u n it s . T h e se fin er g ra in ed d e p o s it s grade ra p id ly from th e c e n te r o f th e v a lle y in to c o a r se r s a n d s and g r a v e ls t o ­ ward th e b a s in m argin . S ed im en tary data in d ic a te th at th e San Pedro V a lle y w a s a flu v io la c u s tr in e b a s in during th e d e p o s itio n o f th e Q uiburis F orm ation . The G aliuro M ountain m a ss to th e e a s t w a s th e primary so u rce o f c l a s t i c d e b r is . R e su lts o f X -r a y d iffr a c tio n , p e tr o g r a p h ic , and sc a n n in g e l e c ­ tron m ic r o s c o p ic s tu d ie s g iv e p o s itiv e e v id e n c e th a t th e s ilt y s ilic e o u s r o c k s are co m p o se d o f s i l t - s i z e c l a s t i c g ra in s in an o p a l- c r is t o b a lit e m a tr ix . E v id e n c e s u g g e s t s th a t th e s i l t y o p a l- c r is t o b a lit e s w ere in it ia lly d e p o s ite d a s a s i l i c a g e l co n te m p o ra n eo u sly w ith th e Q uiburis F orm ation. ix INTRODUCTION The O uiburis Form ation w a s fir s t nam ed by H ein d l (1963) for th e v a lle y - w id e sed im en ta ry r o ck s o f m id dle P lio c e n e a g e d e p o s ite d in th e c lo s e d b a s in now o c c u p ie d b y th e San Pedro R iv er. H ein d l (1 9 6 3 , p . E 21-E 22) did not g iv e a ty p e s e c t io n " . . . b e c a u s e rapid v e r t ic a l and . la te r a l c h a n g e s p r e clu d e an y s in g le area o f e x p o su r e b e in g c o n s id e r e d a s t y p ic a l." M ore r e c e n t s tu d ie s o f th e C e n o z o ic g e o lo g y o f th e lo w er San Pedro V a lle y h a v e y e t to p r o p o se a ty p e s e c t io n for th e Q u iburis Form ation or d e s c r ib e it s lith o lo g y in an y d e t a il . The Q u ib u ris Form ation is g e n e r a lly d e s c r ib e d a s c o n s is t in g o f v ery fin e gra in ed e l a s t i c s , b ed d ed t u f f s , v o lc a n ic a s h - f a l l d e p o s it s , d ia to m a c e o u s b e d s , lim e s t o n e s , and g r ee n ch erty b e d s in th e la k e b e d s e c t i o n s . T h e se fin er gra in ed d e p o s it s grade outw ard r a p id ly in to c o a r s e sa n d s and sa n d y g r a v e l s . S ta tem en t o f th e Problem P a st s tu d ie s o f th e C e n o z o ic g e o lo g y o f s o u th e a s te r n A rizona h a v e b e e n la r g e ly in th e d is c ip lin e s o f g e o c h r o n o lo g y and g e o h y d r o lo g y . The S a ffo rd -S a n Sim on V a lle y , T u c so n B a s in , northern Sulphur S p rin gs V a lle y , and San Pedro V a lle y h a v e b e e n th e c h ie f a r ea s o f in t e r e s t , w ith r e s e a r c h in h y d r o lo g y , s e d im e n ta tio n , str a tig r a p h y , g e n e r a l lit h o lo g y , p a le o n t o lo g y , and r e la te d f i e l d s . T h e se in itia l s tu d ie s h a v e b e e n s o m e ­ w h at broad c o v e r a g e s b e c a u s e o f th e s iz e o f th e g e o g r a p h ic a r e a s . A more d e ta ile d str a tig r a p h ic and p e tr o lo g ic stu d y i s n e e d e d to further th e u n d ersta n d in g o f th e C e n o z o ic b a s in g e o lo g y o f s o u th e a s te r n A rizo n a . 1 2 P urpose The p u rp ose o f th e current stu d y is to p r e se n t a d e ta ile d s tr a ti­ grap h ic and p e tr o lo g ic p ictu re o f the e x p o s e d portion o f th e Q uiburis Form ation near M am m oth, P in al C o u n ty , A rizona (f ig . 1 ). T his area h a s b e e n c h o s e n b e c a u s e o f go o d e x p o s u r e s , th e v a r ia b ility o f th e lit h o lo ­ g i e s , a c c e s s i b i l i t y o f th e a r e a , and th e proxim ity to a p o te n tia l e c o n o m ic d ia to m ite d e p o s it . The p r in c ip a l g o a ls o f th is stu d y w ere to determ in e (1) th e nature o f th e lit h o f a c ie s w ith in th e la k e b e d s e c t io n p rop er, (2) th e lit h o f a c ie s r e la tio n s h ip b e tw e e n th e la k e b e d s e c t io n and th e a llu v ia l g r a v e l d e p o s it s , and (3) th e o r ig in and d ia g e n e s is o f th e "chert b ed s" crop p in g out w ith in th e la k e b e d s e c t i o n . L o ca tio n The p ortion o f th e Q uiburis Form ation s tu d ie d in th is report is abou t 35 m ile s (56 km) n o r th e a st o f T u c so n , A rizona and abou t 10 m ile s (16 km) s o u th -s o u th e a s t o f th e tow n o f M am m oth, A rizona (f ig . 1 ). The area c o m p r is e s about 3 sq u are m ile s (4 .8 km2) in th e v ic in it y o f R hodes Ranch Road and W h itlo c k W a s h . The in term ed ia te w a sh h a s b e e n g e n ­ e r a lly nam ed C am el C anyon W a s h . The en tire area l i e s w ith in P in a l C oun ty in s e c s . 2 0 , 2 1 , 2 8 , and 2 9 , T . 9 S . , R. 18 E . , P e p p er sa u c e W ash and C lark Ranch q u a d ra n g les (f ig . 2 ). P r e v io u s S tu d ie s P rev io u s g e o lo g ic s tu d ie s o f th e San Pedro V a lle y h a v e b e e n p r in c ip a lly g e n e r a l g e o lo g y , p a le o n t o lo g y , and g ro u n d -w a ter in v e s t ig a ­ t i o n s . The f ir s t s tu d ie s o f th e San Pedro V a lle y near M ammoth w ere c o n ­ cern ed w ith th e d ia to m ite d e p o s i t s . B lake (1 9 0 2 , 1903) d is c u s s e d th e "^WINKELMAN M AM M OTH O RACLE S A N 0' MANUEL PINAL C O. PIMA CO. R E D IN G T O N O ' GRAHAM CO COCHISE CO ,ARI Z. TUCSON 1 inch p 1 0 miles F igure 1 . In d ex map sh o w in g lo c a tio n o f stu d y area R. 18 E. 5 ; ^ M e a s u r e d S tra tig ra p h ic Section Figure 2. $ Q u a rry 4 0 - f t contour in te r v a l Index map showing location of measured stratigraphic sectio n s 1 m ile 5 p h y s io c h e m ic a l p ro p e r tie s o f th e d ia to m ite and th eir p o s s ib le la c u str in e or m arine o rig in and c o n c lu d e d th a t m ost o f the d ia to m s w ere o f fr e s h ­ w a ter o r ig in . The e r o s io n a l s u r fa c e s o f th e San Pedro V a lle y w ere d is c u s s e d b y Bryan (1 9 2 6 ), w ho referred to s e d im e n ts a s "G ila C o n g lo m e r a te ." The stru ctu ral r e la tio n s h ip o f th e G aliu ro M ou n tain s and th e a d ja c e n t b a s in w a s d is c u s s e d b y D a v is and Brooks (1 9 3 0 ). M ore r e c e n t p h y sio g r a p h ic s tu d ie s o f th e San Pedro V a lle y in c lu d e Tuan (1 9 5 9 , 1962) and M elto n ( I 9 6 0 , 1 9 6 5 ). H e in d l (1 9 5 4 , 1 9 5 8 , 1 9 6 2 , 1963) w a s th e fir s t to q u e s tio n th e u s e o f th e term "G ila C on glom erate" for th e b a s i n - f i l l d e p o s its in s o u th ­ e a s te r n A r iz o n a . H e in d l (1963) p ro p o sed th a t G ila C on glom erate be r a is e d to group s ta tu s in th e M ammoth area to in c lu d e th e San M a n u e l, Q u ib u r is, and S a c a to n F o r m a tio n s. K rieger, C o r n w a ll, and Banks (1974) dropped th e term "G ila Group" and ab an d on ed th e u s e o f th e S a c a to n Form ation in th e R ay-S an M an u el a rea in favor o f P le is t o c e n e and H o lo ­ cen e g r a v e ls . S e v e r a l grad u ate s tu d e n ts from The U n iv e r s ity o f A rizona h a v e c o n d u cted g e o lo g ic s tu d ie s c o n c er n in g th e San Pedro V a lle y . A genbroad (1967) s tu d ie d th e C e n o z o ic stra tig ra p h y and p a le o h y d r o lo g y o f th e R ed in g to n -S a n M an u el a r e a . The area o f my stu d y i s w ith in th e a rea in v e s tig a te d b y A gen b road . G ray (1965) and Sm ith (1968) s tu d ie d th e C e n o z o ic stra tig ra p h y o f a r e a s to th e so u th o f my stu d y a r e a . M ajor p a le o n t o lo g ic a l s tu d ie s w ere fir s t c o n d u c te d b y G id le y (1 9 2 2 , 1 9 2 6 ). G a zin (1942) stu d ie d th e la te C e n o z o ic v e r te b r a te s near B e n so n . L ance (1 9 6 0 , 1963) rep orted f o s s i l l o c a l i t i e s to th e so u th o f 6 o f th is p r e se n t stu d y area . The m ost r e c e n t v erteb ra te p a le o n to lo g ic a l stu d y w a s by J a co b s (1 9 7 3 ), w ho d e s c r ib e d th e sm a ll mammal fau na o f th e Q u ib u r is. G rou n d -w ater in v e s t ig a t io n s o f th e lo w er San Pedro V a lle y h a v e b e e n c o n d u cted by H ein d l (1952) and P age (1 9 6 3 ). M ontgom ery (1963) stu d ie d th e g e o lo g y and ground w a ter o f th e Tres A lam os r e g io n . G e o c h e m istr y and a g e d a tin g o f v o lc a n ic a s h b e d s o f th e Q u i­ bu ris Form ation w ere don e b y Scarborough (1 9 7 5 ). M any o f S ca rb o ro u g h 's sa m p le lo c a tio n s are w ith in th e p r e se n t stu d y a rea and are num bered for c r o s s r e fe r e n c e in A p p en d ix A . REGIONAL SETTING A b r ie f d is c u s s io n o f th e p h y sio g r a p h y and g e o lo g y o f th e lo w er San Pedro V a lle y and a d jo in in g r e g io n s f o l l o w s . T his d is c u s s io n sh o u ld a c q u a in t th e read er w ith th e m ajor landform s and th e ir g e o lo g ic m a k e-u p s o th a t th e rea d er can b e tte r e v a lu a te th e c o n c lu s io n s regard in g d e p o s itio n a l en v iro n m en ts and so u r c e a r ea s o f th e Q u ib u ris F orm ation . The fo llo w in g d is c u s s io n is p rim arily ta k e n from C r e a s e y (1 9 6 5 , 1 9 6 7 ), H e in d l (1 9 6 3 ), and K rieger (1 9 6 8 a , 1 9 6 8 b , 1 9 6 8 c , 1 9 6 8 d ). P h y sio g ra p h y The San Pedro V a lle y i s a n o r th w e s t-tr e n d in g , interm on tane stru ctu ra l b a s in ly in g w ith in th e B a sin and Range p r o v in c e . The lo w er San Pedro V a lle y is bounded on th e e a s t b y the G aliu ro M ou n tain s and on th e w e s t b y th e S an ta C a ta lin a M ou n tain s and th e B lack H i l l s , w ith about a 2 0 -m ile (32 km) d is ta n c e b e tw e e n th e tw o b o u n d a r ie s. The b a s in h a s b e e n f ille d b y s e d im e n ts s o th a t th e fla n k s are g e n tly s lo p in g tow ard th e San Pedro R iver. Tributary w a s h e s in c is e d by r e c e n t e r o s io n m ay e x te n d s e v e r a l m ile s up th e f la n k s . The San Pedro R iver e x te n d s from northern M e x ic o for more th an 130 m ile s (208 km) to th e c o n flu e n c e o f th e San Pedro and G ila R iv e r s . G e o lo g y The lo w er San Pedro V a lle y i s a stru ctu ra l b a s in w h ic h is a lm o st e n tir e ly c o v e r e d by p o s t-C r e ta c e o u s (?) te r r e str ia l s e d im e n ts . Pre -L a te C r e ta c e o u s r o c k s crop ou t w ith in both th e Santa C a ta lin a M o u n ta in s and 7 8 th e B lack H ills on th e w e ste r n v a lle y boundary and w ith in the G aliuro M ou n tain s on th e e a s te r n v a lle y b o u n d a ry . Precam brian ro ck s in c lu d e th e P in al S c h is t , quartz m o n z o n ite , d ia b a s e , and th e sed im en ta ry A pache G roup. P a le o z o ic and M e s o z o ic r o ck s are a ls o e x p o s e d a lo n g th e fla n k s o f th e v a lle y b o u n d a r ie s. T h e se r o ck s are prim arily lim e s to n e , d o lo m ite , s i l t s t o n e , s h a le , s a n d s t o n e , and q u a r tz ite . U p p e r -C r e ta c e o u s (? )-T ertia ry r o ck s in c lu d e the te r r e str ia l s e d i ­ m ents f illin g th e San Pedro V a lle y and th e G aliuro M ountain m a s s , th e e a s te r n boundary o f th e v a l l e y . The form ation s m aking up the te r r e str ia l s e d im e n ts in th e Mammoth area in c lu d e th e C lo u d b u r st, San M a n u e l, and Q uiburis F o r m a tio n s. T h e se form ation s are ca p p ed b y .P le is t o c e n e and H o lo c e n e a llu v ia l and p ed im en t g r a v e ls (Krieger and o t h e r s , 1 9 7 4 ). The G aliuro M ountain m a ss i s co m p o se d prim arily o f a v o lc a n ic rock s e q u e n c e o f f lo w s , a g g lo m e r a te s , t u f f s , and w e ld e d t u f f s . The c o m p o sitio n o f th e v o lc a n ic r o ck s v a r ie s from b a s a lt to r h y o lite . P o st-Q u ib u r is d eform ation h a s r e s u lte d in m inor fo ld in g and fa u ltin g o f th e fo rm a tio n . A m o n o clin a l fold tren d in g n o r th -n o r th w e st i s in th e c e n te r o f s e c t io n 29 in th e stu d y area and d is p la c e s b e d s a p p ro x i­ m a tely 100 f e e t (30 m ). Figure 3 is a g e n e r a liz e d g e o lo g ic map o f th e stu d y a r e a . Figure 3 . G eologic map of study area— M odified from Agenbroad (1967) STRATIGRAPHIC NOMENCLATURE The in a d e q u a c ie s o f u s in g th e G ila C on glom erate a s a fo rm a tio n a l u n it to d e s c r ib e th e C e n o z o ic b a s i n - f i l l d e p o s its w a s fir s t s u g g e s te d by H ein d l (1 9 5 4 , 1 9 5 8 , 1 9 6 2 , 1 9 6 3 ). H ein d l (1 9 5 8 , 1963) p ro p o sed th at th e G ila C on glom erate be r a is e d to group s ta tu s and in c lu d e th o s e d e ­ p o s it s la id dow n during th e con tem p o ra n eo u s d e v e lo p m e n t o f th e s tr u c ­ tural b a s in in w h ic h th e y w ere d e p o s it e d . In th e M ammoth a r e a , th e G ila Group w o u ld in c lu d e a ll d e p o s it s you n ger th an th e m iddle (?) T ertiary v o lc a n ic r o ck s and o ld e r th an th e upper Q uaternary d e p o s i t s . The fo r­ m a tio n s r e p r e se n te d in th e G ila Group w ou ld b e , in a s c e n d in g o rd er, th e San M a n u e l, Q u ib u r is, and S a c a to n Form ations a s p ro p o sed by H ein d l (1 9 6 3 ). Krieger and o th ers (1 9 7 4 ), h o w e v e r , do not r e c o g n iz e th e G ila Group and th e S a c a to n Form ation in th e Mammoth a r e a . The San M anuel and Q uiburis F orm ations are c o n s id e r e d to h ave b e e n d e p o s ite d in b a s in s th a t d e v e lo p e d at d iffe r e n t t i m e s . The S a c a to n Form ation o f H ein d l (1963) is c o n s id e r e d b y Krieger and o th er s (1974) to be P le is t o c e n e and H o lo ­ c e n e a llu v ia l and p ed im en t g r a v e ls d e p o s ite d a fter in c e p tio n o f p r e se n t through d ra in a g e o f th e San Pedro R iv er. The r e la tio n s h ip o f th e Q u ib u ris Form ation to o th er C e n o z o ic form ation s is com m on ly u n c le a r . In th e stu d y area o n ly th e Q uiburis Form ation is to be stu d ie d ; th e r e fo r e , th e Q uiburis w ill be c o n s id e r e d a s a s in g le form ation ca p p ed by unnam ed P le is t o c e n e and H o lo c e n e a l ­ lu v ia l and p ed im en t g r a v e ls . 10 METHOD OF STUDY F ie ld Study A r e c o n n a is s a n c e su r v e y o f the Mammoth d ia to m ite d e p o s it w a s c o n d u c te d o v e r a p eriod o f s e v e r a l d a y s . The v ic in it y o f R hodes Ranch Road and W h itlo c k W a sh w a s f in a lly c h o s e n for th is stu d y b e c a u s e o f good e x p o s u r e s , th e v a r ia b ility o f th e li t h o l o g i e s , and e a s y a c c e s s o f th e a r e a . The sed im en ta ry u n its w ere m easu red at s e le c t e d l o c a lit ie s w ith th e u s e o f a Jacob s t a f f and c a rp en te r's s c a l e . Each u n it w a s d e ­ sc r ib e d in th e fie ld and sa m p le s c o lle c t e d for further lab oratory a n a l y s i s . L aboratory Study S iz e A n a ly s is The stand ard proced ure for g r a in - s iz e a n a ly s is b y s ie v e and p ip e tte m eth od s w a s fo llo w e d (F o lk , 1 9 6 8 ). The g r a in - s iz e c l a s s i f i c a ­ tio n and s t a t is t ic a l p aram eters o f F olk (1968) for c l a s t i c se d im e n ts w ere u s e d a s w e l l . C u m u lative c u r v e s w ere p lo tte d on a rith m etic p r o b a b ility s c a le p a p e r , and ph i W) p e r c e n t ile s w ere th en read d ir e c tly from th e graph to c a lc u la te th e fo llo w in g s t a t is t ic a l p aram eters: 1. G raphic m ean (Mz ) . 2. I n c lu s iv e grap h ic stand ard d e v ia tio n (d"i). 3. I n c lu s iv e g ra p h ic s k e w n e s s (S k j). 4. G raphic k u r to sis (Kq ) . 11 12 P etrograp h ic S tu d ie s Thin s e c t io n s w ere c u t o f " cherts" and lim e s to n e u n its for rou tin e p etro g ra p h ic s t u d i e s . S lid e s o f h e a v y m ineral a s s e m b la g e s w ere m ade o f s e le c t e d se d im e n t u n it s . T otal c o m p o sitio n o f s e le c t e d s p e c i ­ m ens w a s a ls o s tu d ie d u s in g p etro g ra p h ic and b in o cu la r m ic r o sc o p ic t e c h n iq u e s . X -ra y A n a ly s is The " c h e r t s ," d ia t o m ite , a s h e s , and c la y s w ere e x a m in ed by X -ra y d iffr a c tio n t e c h n iq u e s . A N o r e lc o X -ray d iffra cto m eter u n it u s in g N i- f ilt e r e d co p p er K -alp h a ra d ia tio n w a s e m p lo y e d . S ca n n in g E lectron M ic r o s c o p e The U n iv e r s ity o f A rizo n a 's ARL s c a n n in g e le c tr o n m icroprobe q u antom eter (SEMQ) w a s u s e d for d e ta ile d o b se r v a tio n o f th e " c h e r ts." S p e c im e n s w ere prepared in th e stand ard m anner for SEM r e s e a r c h . QUIBURIS FORMATION The m iddle P lio c e n e Q uiburis Form ation w a s fir s t nam ed b y H ein d l (1 9 6 3 ). The form ation is g e n e r a lly d e s c r ib e d a s c o n s is t in g o f v ery fin e g ra in ed c l a s t i c s e d im e n ts , b ed d ed t u f f s , v o lc a n ic a s h - f a l l d e p o s i t s , d ia to m ite , lim e s t o n e s , and g r ee n ch erty b e d s in th e la k e b e d s e c t i o n s . T h e se fin er g ra in ed d e p o s it s grade r a p id ly in to c o a r s e sa n d s and g r a v e ls a lo n g th e v a lle y m argin . The d e p o s itio n a l en viron m en t is in terp reted to be flu v io la c u s t r in e . A d e ta ile d d is c u s s io n o f th e Q u iburis Form ation in th e v ic in it y o f R hodes Ranch Road and W h itlo c k W a sh is p r e se n te d b e lo w . The area i s a p p ro x im a tely 10 m ile s (16 km) s o u th s o u th e a s t o f th e tow n o f M am m oth, A rizo n a . F ig u res 4 through 11 are g ra p h ic r e p r e s e n ta tio n s o f th e s t a t i s t i c a l data c o m p iled from a n a ly s e s o f Q uiburis s e d im e n t s . G ra v el The grave 1 b e d s crop ping out w ith in th e Q uiburis Form ation are o f tw o ty p e s : (1) th e a llu v ia l s e d im e n ts e x p o s e d a lo n g th e m argin o f th e b a s in ( f i g . 3) and (2) c h a n n e l d e p o s it s in terb ed d ed w ith in th e fin er grain ed c l a s t i c s e q u e n c e s . T h e se tw o ty p e s are s u f f ic ie n t ly d iffe r e n t to be r e p r e se n te d in th e str a tig r a p h ic s e c t io n s (f ig . 1 2 , in p o ck et) by d is t in c t s y m b o ls . D istr ib u tio n and T h ic k n e s s The a llu v ia l g r a v e l crop s ou t a t tw o lo c a l i t i e s a lo n g the e a s te r n v a lle y m argin o f th e stu d y a r e a , s e p a r a te d by a fin er g ra in ed sed im e n t 13 14 GRAVEL 9:1 SAND EXPLANATION G~ Gravel g-Gravelly S-Sand s-Sandy M-Mud m-Muddy •-sam ple (g)-Slightly gravelly Figure 4 . T extural c l a s s if i c a t i o n for Q u ib u ris Form ation s e d l - " m ents c o n ta in in g g r a v e l C la s s if ic a t io n is th at o f F olk (1 9 6 8 ). 15 • /• CC- 4-1 2 20- g r a v e lly san d CC-1-67 san d C C-2-22 s ilt y san d GRAVEL Figure 5 . sa n d sa m p le s SAND CLAY H istogram s sh o w in g p e r ce n ta g e o f sed im e n t in s e le c t e d P oorly F igure 6 . Sorted- 2.5 3 .0 V e r y P o o r l y Sor ted H istogram sh o w in g v a r ia tio n o f so rtin g v a lu e s for sa n d sa m p le s CD SORTING VALUES(cr) F igure 7 . IN PHI UNITS P lot o f m ean s i z e v e r s u s so rtin g v a lu e s for sand s a m p le s N um ber d e n o te s str a tig r a p h ic s e c tio n ; c d e n o te s c h a n n el d e p o s it . x3 18 SAND CLAY EXPLANATION c S - C l a y e y sa n d m S - M u d d y sand s C - Sandy clay zS - Silty sand s M - S a n d y mud sZ - Sandy silt S - Sand C-Clay Z - Silt M'Mud - sample F igure 8 . T extural c la s s if i c a t i o n for Q uiburis Form ation s e d i ­ m en ts la c k in g g r a v e l C la s s if ic a t io n i s th a t o f Folk (1 9 6 8 ). 19 CC-5-11 s lig h t ly g r a v e lly , sa n d y s i l t 40-i CC- 1-1 sa n d y s i l t C C -2-33 GRAVEL SAND CLAY Figure 9 . H istogram s sh o w in g p e r ce n ta g e o f sed im e n t in s e le c t e d s i l t sa m p le s V) 1 o 3.5 orin 0 Poorly S o r t e d F igure 1 0 . Very Poorly S o r t e d H istogram s h o w in g v a r ia tio n o f so rtin g v a lu e s for s i l t s a m p le s O 7 0.5 1.0 1.5 2.0 SORTING VALUES(c^) Figure 1 1 . 2.5 IN PHI UNITS Plot o f m ean s i z e v e r s u s so r tin g v a lu e s for s i l t s a m p le s C om p iled from s tr a tig r a p h ic s e c t io n s C C - 1 , C C - 2 , C C - 3 , C C - 4 , C C - 5 . 3.0 3.5 22 s e q u e n c e (f ig . 3 ). S tratigrap h ic s e c t io n C C -6 ( f ig s . 5 , 1 2 , 13) sh o w s an in c o m p le te e x p o s e d s e c t io n o f a llu v ia l g r a v e l abou t 55 fe e t (17 m) t h ic k . S ed im en ts grade la te r a lly from true a llu v ia l g r a v e ls to in te r b ed d ed sa n d y g r a v e ls and s lig h t ly g r a v e lly s i l t y sa n d s and sa n d y s i l t s w ith in a d is ta n c e o f 300 f e e t (90 m) to th e w e s t . C h a n n el g r a v e ls are r e la t iv e ly fe w . T hey are m ost com m on near th e e a s te r n m argin o f th e stu d y area and in th e top p o rtio n s o f th e form a­ t io n . The u n its vary from th in l e n s e s 1 to 3 in c h e s ( 2 . 5 to 7 . 6 cm) th ic k and 1 to 10 fe e t ( 0 . 3 to 3 m) lo n g to e x te n s iv e b ed s 5 to 20 in c h e s (13 to 51 cm) th ic k th a t c a n b e tr a c ed for s e v e r a l hundred f e e t . T exture The s i z e d istr ib u tio n o f th e a llu v ia l c o n g lo m e r a te s v a r ie s from s m a ll b o u ld e r - s iz e c l a s t s to m ud. P e b b le - s iz e c l a s t s are the m ost abun­ d a n t. The a n g u la rity and s p h e r ic ity o f th e c la s t s d ep en d on th e grain s iz e and c o m p o s itio n . Larger g ra in s are t y p ic a lly more rounded th an sm a lle r g r a in s . P e b b le s co m p o se d o f s c h is t are rounded and e lo n g a t e . Other p e b b le rock ty p e s are a n g u la r. W eath erin g d e c o m p o sitio n o f the c l a s t s is com m on . The se d im e n t i s e n tir e ly u n c o n s o lid a te d . In c o n tr a s t to th e a llu v ia l g r a v e ls , th e c h a n n el g r a v e ls are s ilt y - s a n d y g r a v e ls (fig . 4) w ith th e p e b b le s no larger than on e in c h ( 2 . 5 cm) in d ia m e te r . The g r a in s are v ery an gu lar to su b an gu lar and at p la c e s w e ll indurated w ith c a lc a r e o u s c e m e n t. By the nature o f th eir c l a s s i f i c a t i o n , both g r a v e ls are v e r y p o o rly s o r te d . 23 Figure 13. View of measured stratigraphic section CC-6 The h ill in background is a volcan ic block outlier. 24 S edim en tary Stru ctu res S e v e r a l d ia g n o s t ic sed im en ta ry fe a tu r e s o f th e g r a v e ls are r e c o g n iz e d th a t illu s tr a te th eir mode o f tra n sp o rt. T h e se fe a tu r e s are: 1. Crude s tr a tific a tio n . The a llu v ia l g r a v e ls se e m to be c ru d ely h o r iz o n ta lly s tr a tifie d . 2. G raded b e d d in g . A p r o g r e s s iv e d e c r e a s e in grain s i z e from the bottom to th e top o f th e b ed is com m only p r e se n t in both th e „ c h a n n e l and a llu v ia l g r a v e ls . 3. Scour. Sharp un d u latory b a s a l c o n ta c ts are ty p ic a l in the c h a n ­ n e l g r a v e ls (f ig . 1 4 ). C o m p o sitio n The c o m p o sitio n o f th e tw o g r a v e ls s e e m s to d iffe r o n ly in th e ra tio o f major lit h o lo g ic ty p e s p r e s e n t . A d a r k -g r a y , fin e -g r a in e d a n ­ d e s it e w ith p h e n o c r y s ts o f p la g io c la s e is th e m o st abundant v o lc a n ic c l a s t in th e a llu v ia l g r a v e ls , w h ile f e l s i t e and r h y o lite fragm en ts are m o st com m on in th e c h a n n e l g r a v e ls . O ther lit h o lo g ie s p r e s e n t , found g e n e r a lly in a c c e s s o r y a m o u n ts, in c lu d e , in d e c r e a s in g order o f ab u n ­ d a n c e , q u a r tz ite , s c h i s t , a g g lo m e r a te , and c h a lc e d o n ic quartz g r a in s . Sand D istr ib u tio n and T h ic k n e s s Sand b e d s , lik e c h a n n e l g r a v e ls , are fe w in number but o c cu r a t m o st str a tig r a p h ic lo c a t i o n s . The d istr ib u tio n p attern o f th e sa n d b e d s s h o w s an in c r e a s e in ab u n d an ce tow ard th e v a lle y m argin and a g e n e r a l th in n in g o f th e b e d s tow ard th e b a s in c e n te r . The sa n d b e d s are to o 25 Figure 14. C hannel-scour contact and erosion al unconformity Channel scour indicated by dashed line; solid line drawn at unconformity between P leistocen e and H olocene gravels and Quiburis Formation. Located in N E1/4SE1/4N E1/4 s e c . 21, T. 9 S . , R. 18 E. Note s c a le , 5-foot (1.5 m) Jacob sta ff. 26 fe w in number to r e c o g n iz e a trend in th e ir v e r tic a l d istr ib u tio n and se e m erra tic in th eir o c c u r r e n c e . Som e o f th e sa n d u n its are o b v io u s c h a n n el l e n s e s , w h ile m o st b e d s h a v e m o d era tely e x t e n s iv e la te r a l d im e n sio n s and range from 2 to 30 in c h e s (5 to 76 cm) in t h i c k n e s s . Texture T ex tu ra lly c l a s s i f i e d , th e sa n d s range from g r a v e lly sa n d to s i l t y san d ( f ig s . 4 and 8 ) . The m ean o f th e g ra p h ic m ean (Mz ) is 2 . 9 7 ' r f , w ith a stand ard d e v ia tio n o f 0 .9 3 for th e 16 sa n d sa m p le s a n a ly z e d . The sa n d s th at are g r a v e lly or s lig h t ly g r a v e lly g e n e r a lly o c cu r near th e v a lle y m argin. A h isto g ra m sh o w in g th e v a r ia tio n o f so rtin g v a lu e s is p r e se n te d in figu re 6 . A ccordin g to the v e rb a l c l a s s if i c a t i o n o f Folk (1 9 6 8 ), th e s a n d s range from m o d era tely so rted to v ery p o o rly s o r te d . Figure 6 sh o w s th e d is tr ib u tio n is su c h th a t o v e r 90 p e r ce n t o f th e sa m p le s h a v e a s o r t­ in g v a lu e g r ea ter th an 1 . 0 0 (p oorly s o r t e d ) . F igure 7 is a p lo t o f g ra p h ic m ean (Mz ) v e r s u s so rtin g v a lu e s (C j). A trend is o b s e r v a b le w ith o n ly th e fe w sa m p le s a n a ly z e d (and p r e s e n t ) . S an d s w ith a fin e r gra in ed m ean s iz e h a v e a lo w er so rtin g v a lu e and are found in th e b a s in c e n te r a r e a . The c o a r se r g ra in ed s a n d s h a v e a h ig h er so rtin g v a lu e and are found n ea rer th e v a lle y m argin . Figure 7 a ls o s h o w s a fe w s a m p le s th at are lo c a te d in th e b a s in c e n te r area and h a v e a c o a r s e r gra in ed m ean s i z e and a h ig h er so rtin g v a lu e . T h e se a n om alou s s a m p le s com e from o b v io u s c h a n n e l d e p o s it s , w h ile th e oth er s a m p le s are m o d era tely e x t e n s iv e in th e ir la te r a l d im e n s io n s . The r e s u lt s may h a v e c h a n g e d w ith more d a ta . 27 The sand g r a in s sh o w v e r y lit t le r o u n d n e ss and are b e s t d e ­ sc r ib e d a s v ery angu lar to su b a n g u la r , a cco rd in g to P o w er's (1953) c l a s s i f i c a t i o n . The d e g r ee o f a n g u la rity is c o n s is t e n t throughout the stu d y area and for e a c h s i z e fr a c tio n w ith in a p a rticu la r sa n d s a m p le . A lthough fe w in num ber, rounded to w e ll-r o u n d e d z ir c o n g ra in s are p r e s ­ e n t . T h e se rounded g r a in s are probab ly d eriv ed from a rew orked s e d i ­ m entary s o u r c e . The a p p lic a tio n o f s k e w n e s s and k u r to sis m e a su r es to s e d im e n ­ ta tio n s tu d ie s i s n o t a s w e ll u n d ersto o d a s th o s e o f s iz e and s o r tin g . In th e in te r e s t o f co n trib u tin g data on s k e w n e s s and k u rto sis v a lu e s for c o n tin e n ta l s e d im e n ts for future s t u d ie s . A ppendix B h a s b e e n p r e p a r ed . The d ata in d ic a te th a t th e sa n d s are g e n e r a lly fin e s k e w e d and h a v e a le p to k u r tic fr e q u e n c y c u r v e . S ed im en tary S tru ctu res S e v e r a l d ia g n o s t ic sed im e n ta r y fe a tu r e s o f th e sa n d s are r e c ­ o g n iz e d th at illu s tr a te th eir m ode o f transport and d e p o s itio n a l e n v ir o n ­ m en t. T h e se str u c tu r es are d e s c r ib e d a s fo llo w s : 1. Graded b e d d in g . A p r o g r e s s iv e d e c r e a s e in th e s i z e o f th e c l a s t s from th e bottom to th e top o f th e san d bed is com m only p r e se n t in th e th ic k e r u n i t s . 2. Sharp c o n t a c t . Top and b a s a l c o n ta c ts appear sharp in many o f th e s a n d s . 3. L a m in a tio n s . san d b e d s . H e a v y m in eral la m in a tio n s are common in th e 28 4. C r o s s - s t r a t if ic a t io n . The o ccu rren ce o f c r o s s - s t r a t if ic a t io n is lim ite d . A fe w e x a m p le s are o b se r v e d in th e v ic in it y o f s e c tio n C C -5 . C o m p o sitio n The 4 £ and 5 & s i z e fr a c tio n s o f s e le c t e d s p e c im e n s w ere m ounted on s l i d e s . The c o a r se r g ra in ed fr a c tio n s (= 4 jzO w ere e x a m in ed w ith a b in o cu la r m ic r o s c o p e . The r e s u ltin g data d em on strated th at th e c o a r se r san d and g r a n u le s in th e sa n d b e d s c o n s is t p r in c ip a lly o f rock fragm en ts sim ila r to th o s e o f th e c o n g lo m e r a te s d is c u s s e d e a r lie r . The fragm en ts are p rim arily f e l s i t e , r h y o lit e , and minor q u a r tz ite . In th e 4 and 5 & s i z e f r a c t io n s , quartz g r a in s are th e m o st ab u n d an t. In g e n e r a l th ere s e e m s to be lit t le v a r ia tio n o f c o m p o sitio n b e tw e e n sa m p le s w ith in th e area s tu d ie d . Other abundant g ra in s in clu d e f e ld s p a r s , h e a v y m in­ e r a ls , and v o lc a n ic a s h s h a r d s . M in e r a lo g ic a lly ,. th e sa n d s w ould be c l a s s i f i e d a s s u b a r k o s e , a c co r d in g to F olk (1 9 6 8 ). P la g io c la s e fe ld s p a r s are more abundant than p o ta sh f e ld s p a r s . There are m any turbid g r a in s in th e se d im e n ts th at are in terp reted to be fe ld s p a r s a lte r in g to c l a y . In th in s e c t io n , t h e s e g ra in s are n ea rly op aq u e w ith o n ly p in p o in t b ir e fr in g e n c e . A pplying r e fle c te d lig h t to th e s u r f a c e s , th e turbid g r a in s are a n on tran sp aren t w h itis h c o lo r . Som e o f th e l e s s a lte r e d g r a in s sh o w tw in n in g ty p ic a l o f p la g io c la s e f e ld s p a r s . H ea v y m in era ls and v o lc a n ic a s h shards are o ften im portant c l a s t i c fr a c tio n s in many o f th e s a n d s . The p e r c e n ta g e o f e a c h c o n s t it u ­ en t may be a s h ig h a s 5 p e r c e n t w ith in a s in g le s a m p le . Both h e a v y m in er a ls and v o lc a n ic a sh are d is c u s s e d under sep a ra te h e a d in g s . 29 S ilt The s i l t b e d s rank fir s t in ab u n d an ce r e la tiv e to oth er s e d im e n ts . As a g r o u p , th e y c o n s is t e s s e n t i a l l y o f g r a y ish orange pin k (r e d d is h ), p oorly c o n s o lid a te d s e d im e n t. Y e llo w is h -g r a y (g reen ish ) s i l t b e d s are com m on in str a tig r a p h ic s e c t io n s G C - 1 , C C - 2 , C C - 3 , and C C -5 (s e e A ppendix A ). The r ed d ish and g r e e n is h se d im e n ts s e e m to h a v e lit t le d iffe r e n c e s b e s id e s c o lo r . The g r e e n is h c o lo r , " . . . r e p r e s e n ta tiv e o f a r ed u cin g en v iro n m en t, r e s u lt s from th e p r e se n c e o f m in era ls w ith a h igh ferric iron c o n te n t . . . , th u s i s in d ic a tiv e o f 'd eep ' w a ter c o n d i­ tio n s" (R e e v e s , 1 9 6 8 , p . 7 8 ). "D eep" r efer s to w a ter d e p th s g rea ter than a fe w in c h e s . The r ed d ish c o lo r is ty p ic a lly iron o x id e and co m ­ m only o c c u r s in o x id iz in g e n v ir o n m e n ts. The s ig n ific a n c e o f c o lo r is d is c u s s e d further under en viron m en t o f d e p o s itio n . D istr ib u tio n and T h ic k n e s s In th e area s tu d ie d , th e Q uiburis Form ation c o n s is t s prim arily o f m any in d iv id u a l s i l t b e d s . The t h ic k n e s s o f the b e d s i s v ery seld o m o v er 10 fe e t (3 m) and more com m on ly is b e tw e e n 1 and 7 fe e t (0 .3 and 2 m) in th ic k n e s s before v e r t ic a lly interrupted b y an oth er sed im e n t t y p e . The t h ic k e s t a c cu m u la tio n o f s i l t s in terb ed d ed w ith s a n d s o c c u r s in s e c t io n C C -4 and th e top portion o f s e c t io n C C -3 (f ig . 1 2 ). The th in ­ n e s t b e d s are found in th e form o f b e d s and la m in a tio n s a lte r n a tin g w ith la y e r s o f d ia to m ite ( f i g s . 15 and 1 6 ). The d istr ib u tio n o f th e s i l t s is not c o n fin e d to any o n e a r e a . T hey o ccu r from th e v a lle y b a s in to th e e a ste r n m argin o f th e a rea stu d ie d w here th e s i l t i s in ju x ta p o s itio n w ith a T ertiary v o lc a n ic b lo c k 30 Figure 15. Interbedding of diatomite and silt V olcanic-ash seam (dark gray) is 4 .3 feet (1.3 m) up from bot­ tom. Located in SE1/4N W 1/4SW 1/ 4 se c . 29, T. 9 S . , R. 18 E. Note s c a le , 5-foot (1.5 m) Jacob sta ff. Figure 16. Laminated bedding of diatomite and silt Note plant stem s (a) and burrows (b). Located in SE1/4SE1/4 NW 1/4 s e c . 29, T. 29 S . , R. 18 E. Note 6-inch (15 cm) s c a le . 31 ( f i g . 3 ). The a llu v ia l g r a v e l a ls o crop s out a lo n g th e v a lle y margin; h o w e v e r , it i s sep a r a te d by th e s i l t y s e q u e n c e th a t e x te n d s to th e e d g e o f th e v o lc a n ic o u t lie r . T exture T ex tu ra lly c l a s s i f i e d , th e s i l t s range from s lig h t ly g r a v e lly s i l t to s i l t ( f i g s . 4 and 8 ). The g ra p h ic m ean (Mz ) is 5 .3 9 ^ w ith a stand ard d e v ia tio n o f 0 .6 7 for th e 60 sa m p le s a n a ly z e d . Like th e s a n d s , th e s i l t s nearer th e m argin o f th e b a s in are found to c o n ta in the g r a n u le - s iz e g r a in s . The so rtin g v a lu e s range from m o d era tely so rted to v ery p o o rly s o r te d , a s sh ow n in fig u re 1 0 . The d istr ib u tio n o f so rtin g v a lu e s i s su c h th at o v e r 96 p e r ce n t o f th e sa m p le s are g r ea ter than 1 .0 ^ (poorly s o r te d ). A p lo t o f g ra p h ic m ean (Mz ) v e r s u s so rtin g v a lu e s (d"%) ( f ig . 11) s h o w s a pattern o f in c r e a s in g ly poorer so rted s i l t s tow ard th e v a lle y m argin . A trend in m ean s i z e , h o w e v e r , is not w e ll d e fin e d . The c l a s t i c g r a in s in th e s i l t se d im e n ts sh o w a h ig h d e g r ee o f a n g u la r ity . A fe w rounded z ir c o n g ra in s are found in th e h e a v y m in eral s u i t e s , in d ic a tin g rew orkin g from on e or more sed im en ta ry s o u r c e s . S k e w n e s s and k u r to sis d a ta are lis t e d in A ppendix B . The s i l t s ca n be g e n e r a lly c l a s s i f i e d a s str o n g ly fin e sk e w e d and h a v e a le p to k u r t ic fr e q u e n c y c u r v e . S ed im en tary S tru ctu res The fo llo w in g d ia g n o s t ic sed im en ta ry fe a tu r e s o f th e s i l t s w ere r e c o g n iz e d th a t illu s tr a te th eir mode o f transport and d e p o s itio n a l e n ­ viron m en t . 32 1. L a m in a tio n s. Thin la y e r s o f s i l t com m only o c c u r in th e d ia t o - m ite b e d s , a s w e ll a s h e a v y m ineral la m in a tio n s in th e s i l t u n its p rop er. 2. Sharp c o n t a c t s . Top and b a s a l c o n ta c ts are o fte n s h a r p . 3. C r o s s - s t r a t if ic a t io n . The o c cu rr e n c e o f c r o s s - s t r a t if ic a t io n is lim ite d . O nly on e w e ll- d e f in e d ex a m p le (f ig . 17) w a s found n ea r s e c t io n C C - 3 . O ther e x a m p le s are v e ry o b s c u r e . C o m p o sitio n The c o m p o s itio n o f th e s i l t s is sim ila r to th at o f th e s a n d s . F e l s i t e , r h y o lit e , and q u a rtzite fragm en ts dom inate th e c l a s t s in th e c o a r s e - s a n d fr a c tio n o f th e s i l t , w h ile q u a r tz , turbid f e ld s p a r s , f e ld ­ sp a rs , h e a v y m in e r a ls , and v o lc a n ic a s h sh a rd s make up th e fin e r c o n ­ s titu e n ts . D ia to m s are a ls o com m on ly found in th e s i l t u n its and b eco m e more abundant w h en th e s i l t is in c l o s e proxim ity to a d ia to m ite b e d . The to ta l carb on ate c o n te n t o f a fe w s i l t sa m p le s w a s d e te r ­ m ined in th e lab oratory b y th e w e ig h t lo s s through th e h y d ro ch lo ric a c id iz a tio n m eth o d . The p e r c e n ta g e o f carb on ate ranged b e tw e e n 1 to 1 .5 p e r c e n t, p rob ab ly in th e form o f m ic r itic p a r t ic le s . The ca rb o n a te c o n te n t i s c o n s id e r e d m inor and d id not in flu e n c e th e s iz e a n a ly s is o f th e s i l t s . It i s in te r e stin g to n o te th e p a u c ity o f c la y both a s a c la y fr a c ­ tio n in th e s i l t s and a s sed im en ta ry u n it s . The p e r c e n ta g e o f c la y in th e s i l t s r a n g e s from 3 .3 6 to 3 0 .2 7 p e r ce n t w ith a m ean o f 1 3 .2 6 p e r ce n t and a standard d e v ia tio n o f 7 .1 1 p e r c e n t. The X -ra y d iffr a c tio n a n a ly s is o f c la y from s i l t sa m p le s C C - 1 - 5 9 and C C -1 -4 6 sh o w s th e m on tm orillon ite 33 Figure 17. C ross-stratification in silt unit Located in NE1/4NW 1/4NE1/4 s e c . 29 , T . 9 S . # R. 18 E . Note 6-inch (15 cm) sca le in shadow. 34 c la y group p r e se n t a s a broad p e a k . Q u a r tz , c a l c i t e , and h a lite are a ls o p r e s e n t. C la y b e d s are not p r e se n t in th e a rea s tu d ie d . The c l o s e s t s e d im e n ts to a c la y tex tu re are a fe w mud b e d s found in s e c t io n C C - 2 . The a b s e n c e o f c la y se d im e n t and it s s ig n ific a n c e are d is c u s s e d further under en viron m en t o f d e p o s it io n . H ea v y M in era ls The h e a v y m in era ls in th e Q uiburis s e d im e n ts are r e la t iv e ly a b u n d a n t. The 4 and 5 s i z e fr a c tio n s o f s e le c t e d sa m p le s w ere a n a ly z e d . The r e s u lt s are ta b u la te d in ta b le 1 . The d ata sh o w lit t le v a r ia tio n o f th e h e a v y m in eral c o n te n t e x c e p t for a fe w b io t itic s a m p le s and a v o lc a n ic a s h , sa m p le C C - 1 - 1 2 , w h ic h i s d om in ated by b a s a lt ic h o r n b le n d e . The fo llo w in g paragraphs are a d is c u s s io n o f th o s e m iner­ a ls id e n t if ie d . The op aq u e m in er a ls c o n s is t p r in c ip a lly o f m a g n etite and i l m enite u n d iffe r e n tia te d . Both fractured and eu h ed ra l g ra in s are p r e s e n t . A lteration to h e m a tite and le u c o x e n e is com m on, but m ost g r a in s sh o w a good b la c k is h m e t a llic lu s t e r . The m in eral e p id o te is m ost a b u n d a n t. The g ra in s w ere id e n ­ tif ie d by th e ir lig h t-g r e e n to c le a r c o lo r , s lig h t p le o c h r o is m , and by th eir b r illia n t g r e e n purple red rin g ed in ter fe r en ce c o l o r s . G rains ty p ic a l ly h a v e c o n c h o id a l s u r fa c e s and are v ery tran sp aren t w ith a v itr e o u s lu s t e r . The am p h ib ole m in er a ls are u s u a lly d a r k -g re e n or d a rk -b ro w n , e lo n g a te g r a in s w ith stron g p le o c h r o is m . S a w -to o th e d e d g e s are common in d ic a tin g som e d is s o lu t io n o f th e m in er a l. The brow n v a r ie t y , b a s a lt ic T ab le 1 . R e su lts o f h e a v y m in era l grain c o u n ts from s e le c t e d s a m p le s , Q u ib u ris Form ation (Op— o p a q u e s; E pi— e p id o te ; Amp— a m p h ib o le s; B io — b io tite ; A pat— a p a tite ; Z irc— zirc o n ; Rut— r u tile ; Garn— g a r n e t s .) Sam ple N o . Op Epi Amp Bio Apat Zirc Rut Garn 4 0 1 1 1 0 2 0 0 0 0 0 0 1 4 4 2 5 3 3 300 300 300 300 300 1 4 2 ’ 0 0 0 1 1 0 0 3 2 0 1 1 4 1 1 1 1 300 300 300 300 300 U nknow n T otal C O -1 -1 C C -1 -1 0 C C -1 - 1 2 C G -l-1 5 C C -1 -2 2 4 4 4 4 4 55 62 17 14 55 95 116 10 27 129 25 34 164 24 73 94 56 101 224 20 C C -1 -2 6 C C -l-4 6 C C -1 -5 9 C C -1 -6 9 C C -1 -7 2 4 4 4 4 4 72 89 8 10 62 118 117 72 87 155 64 58 35 47 54 29 11 178 149 17 23 26 2 6 15 0 17 3 5 9 C C -1 -7 3 C C -1 -8 0 C C -2 -1 8 C C —3 —16 C C -4 -1 4 4 4 4 4 4 25 31 76 75 76 165 182 139 161 147 89 58 63 30 53 7 20 6 6 ' 6 11 3 12 17 8 1 1 2 1 4 0 0 0 2 0 0 2 0 6 4 3 3 2 2 2 300 300 300 3 00 300 C C -5 -7 C C -1 -1 0 C C -1 -1 5 C C -1 -2 2 C C -1 -5 9 4 5 5 5 5 127 86 29 48 12 145 125 153 133 152 8 55 70 83 81 1 7 39 15 34 7 20 1 14 14 7 5 2 2 3 1 1 1 1 2 2 1 1 2 1 2 0 4 2 1 3 00 300 300 300 300 C C -1 -6 9 C C -1 -7 2 C C -1 -7 3 5 5 5 13 32 37 144 146 155 97 65 67 28 26 12 9 17 20 2 2 1 0 2 3 4 4 3 3 6 3 300 300 300 . CO on 36 h o r n b le n d e , is com m on in m ost s a m p le s . In th e v o lc a n ic a s h , sam p le C C - 1 - 1 2 , th e b a s a lt ic h ornb len de m ak es up more th an 50 p e r ce n t o f th e h e a v y m in erals p r e s e n t , in d ic a tin g an e o lia n tran sp ort a lo n g w ith th e v o lc a n ic a sh s h a r d s . B io tite i s found a s a n o th er major c o n s titu e n t in th e h e a v y m in­ e r a l s u i t e . Its id e n t ific a tio n i s r e la t iv e ly e a s y b e c a u s e o f it s p la ty h a b it, brown p le o c h r o ic c o lo r , and g ood in te r fe r e n c e fig u r e . A p a tite , z ir c o n , r u t ile , and g a rn et are l e s s com m on a c c e s s o r y m in e r a ls . A p atite o c cu rs a s p r ism a tic g r a in s w ith rounded c o r n e r s . T hey t y p ic a lly h a v e in c lu s io n s p a r a lle l to th e lon g a x i s . In terferen ce c o lo r s are fir s t-o r d e r gra y to w h ite and a p s e u d o - b ia x ia l figu re is com m on . Z ircon is p r e se n t m o s tly a s d o u b ly term in ated eu h ed ra l g r a in s . A fe w w e ll-r o u n d e d g ra in s o c cu r and p rob ab ly in d ic a te a so u r ce from o n e or more rew ork ed sed im e n ta r y r o c k s . The c o lo r le s s h ig h r e li e f i s in d ic a tiv e o f th e m in er a l. R utile i s a v e r y d e e p red to a lm o st o p a q u e . G arnet i s is o tr o p ic and is found a s e u h ed ra l and c o n c h o id a lly fractured g r a in s . The h e a v y m in era ls illu s tr a te th e te x tu ra l im m aturity o f the s e d im e n ts and th erefo re a nearby s o u r c e . The v a r ie ty o f ro ck ty p e s su r­ rounding th e low er San Pedro V a lle y w ere b r ie fly d is c u s s e d under r e g io n ­ a l s e t t in g . N o g e n e r a l c o n c lu s io n o f o n e rock ty p e so u r ce is in d ic a te d ; h o w e v e r , th e h e a v y m in eral d ata at le a s t s u g g e s t a m ajor v o lc a n ic rock s o u r c e . The so u r c e is no doubt a co m b in a tio n o f th e ro ck ty p e s w here th e G aliuro M ou n tain m a s s i s th e major co n trib u to r. 37 L im esto n e L im eston e b e d s are fe w in number and crop o u t at str a tig r a p h ic s e c t io n s C C -2 and G C - 5 . The th ic k n e s s o f th e b e d s are g e n e r a lly l e s s th an 12 in c h e s (0 .3 1 m ). The lim e s to n e is o f primary o r ig in rather th an a c o n c e n tr a tio n o f in o rg a n ic c a lc i t e from p r e e x is tin g s e d im e n ts . T h is c o n c lu s io n is b a s e d on th e o r g a n ic str u c tu r es w ith in th e lim e s to n e s a m p le s . The tw o lim e s to n e b e d s o f s e c t io n C C -5 are v e ry f in e ly c r y s t a l­ l i n e , lig h t-g r a y c a l c i t e . Sm all e tc h e d g a str o p o d s (5 mm) are found s p o r a d ic a lly d istr ib u te d on th e w e a th e re d su r fa c e o f th e o u tc r o p . In th in s e c t io n , s i l t - s i z e quartz g r a in s o ccu r in s c a tte r e d am ou nts and sm a ll v u g s are com m only f ille d w ith c h a lc e d o n y . The lim e s to n e s h a v e n e a r ly a pure c o m p o s itio n o f m icrite and m ic r o s p a r ite . T h e se p a rticu la r b e d s are near th e b a s in m argin and w ere probab ly p r e c ip ita te d in a sm a ll pond se p a r a te d from th e m ain b o d y o f w a ter in th e b a s in c e n te r b y sw am p and g r a s s y a r e a s . The lim e s to n e bed o f stra tig ra p h ic s e c t io n C C -2 is e n tir e ly d iffe re n t th an th o s e o f s e c t io n C C - 5 . T his g r a y -g r e e n b ed h a s a un iqu e c o m p o sitio n o f a lg a l p i s o l i t e s and e lo n g a te (m atlike) s tr u c tu r e s , a s w e ll a s abundant sa n d g r a in s . The p i s o l i t e s a v e ra g e 3 mm in d ia m eter and surround rock fragm en ts and m in eral g r a in s . The m atty str u c tu r es are 1 to 2 mm th ic k and range in le n g th from 3 to 25 mm (f ig . 1 8 ). The m ats h a v e a preferred h o r iz o n ta l a lig n m en t and g iv e the ap p ea ra n ce o f b e in g in t r a c la s t ic . P artial r e p la c e m e n t o f c a lc it e by m ic r o c r y s ta llin e quartz is o b v io u s on th e w e a th e re d su r fa c e and in th in s e c t io n (f ig . 1 9 ). A sim ila r Q uiburis lim e s to n e w a s rep orted by Sm ith (1968) near R ed in g to n , A rizo n a . J Figure 18. Cut hand specim en of p iso litic and elongate (mat) algal sandy lim estone Sample C C -2 -2 0 . Scale in centim eters. Figure 19. Photomicrograph of algal p is o lite s C rystalline quartz (light areas) is replacing ca lcite (darker ringed a r e a s). Sample C C -2 -2 0 , cross n ic o ls , 50 X. Bar is 200 39 P is o lit e s w o u ld g e n e r a lly in d ic a te a pond en v iro n m en t. The c o a r s e san d and th e in t r a c la s t ic ap p ea ra n ce o f the e lo n g a te stru ctu res h o w ev er s u g g e s t a c h a n n e l-ty p e en v iro n m en t. The Q uiburis a lg a l lim e ­ sto n e p rob ab ly form ed in slo w -m o v in g w a ter th at had p e r io d s o f q u ie s ­ c e n c e a llo w in g a lg a l g r o w th . The u n it g ra d es upward in to a lim y sa n d s to n e th a t e x h ib its la m in a tio n s and c o n v o lu te d b e d d in g . V o lc a n ic S ed im en ts Thin b e d s o f v o lc a n ic a s h and rare b e n to n ite are abundant throughout th e b a s in c e n te r . Their th ic k n e s s r a n g e s from 0 . 2 5 in ch (6 mm) to 18 in c h e s (46 cm) and p r o v e s to be in v a lu a b le for th e p u rp o se o f c o r r e la tio n . M o st o f th e v o lc a n ic s e d im e n ts are c o m p o se d o f u n u s u a lly fr e s h , v e ry lig h t g r a y , s i l t - s i z e p u m ic eo u s s h a r d s . B a s a ltic h ornb len de and b io t it e , p o s s ib ly o f prim ary o r ig in and b lo w n in w ith th e s h a r d s , and d e tr ita l quartz are s c a tte r e d w ith in th e a s h . Both top and bottom c o n ­ t a c t s are u s u a lly s h a r p . The bottom su r fa c e at p la c e s is co n to rted (fig . 2 0 ), p rob ab ly from th e su d d en a ccu m u la tio n o f th e a s h - f a l l c a u s in g s o ft se d im e n t d e fo r m a tio n . P o ta ssiu m -a rg o n d a tin g (Scarborough, 1975) g iv e s an a g e o f 5 .6 to 5 .8 m . y . for th e a s h . The b e n to n ite o c c u r s a s a w h ite c la y w ith a g r e a s y lu s te r and f e e l . It t y p ic a lly s w e l l s w h en im m ersed in w a te r . X -ra y d iffr a ctio n a n a ly s is sh o w s th e b e n to n ite to be co m p o se d a lm o st e n tir e ly o f m o n tm o r illo n ite . N o z e o li t e m in er a ls are p r e s e n t . D e v itr ifie d a s h sh a rd s are com m on in th e l e s s b e n to n itic u n i t s . T h e se u n its are d is tin g u is h e d from fr e sh a sh and w e ll- d e v e lo p e d 40 Figure 20. Soft sediment deformation shown by irregular bottom contact of volcan ic ash b ed . Sample C C -1 -2 5 . Scale is 6 inches (15 cm). 41 b e n to n ite by th e ir p in k is h -g r a y b e n to n itic tex tu re and r e s id u a l a s h . In th in s e c t io n , in c ip ie n t d e v itr ific a tio n is r ep r e se n te d b y w hat ap p ears to b e sm a ll fra ctu res running through the sh a r d . A c lo s e r v ie w w ith th e SEM sh o w s th e in it ia l d e v itr ify in g s ta g e ta k e s p la c e on th e su r fa c e o f th e a s h shard (fig . 2 1 ). F resh a s h , on th e c o n tra ry , is c r y s ta l c le a r . I n c lu s io n s in th e form o f bu bble tr a in s are com m on, and h e a v y m in era ls surrounded b y g l a s s are o c c a s io n a lly fo u n d . D ia to m ite D ia to m ite , in terb ed d ed w ith s i l t , ranks s e c o n d in abu ndan ce o n ly to th e s i l t b e d s . T h ese fin e -g r a in e d d e p o s its o f d ia to m ite r e s e m b le c h a lk in a p p e a r a n c e . In pure s a m p le s , th e y are w h it e , firm , v ery lig h t in w e ig h t, and form v e r t ic a l c lif f s in narrow c a n y o n s . In th e m easu red s e c t i o n s , a bed is g e n e r a lly no th ic k e r than 2 f e e t ( 0 .6 m) b efo re v e r ­ t ic a lly interrupted by s i l t u n i t s . The d ia to m ite b e d s do th ic k e n to th e north o f th e stu d y area to more th an 100 f e e t (30 m) th ic k (Long and O ls o n , 1 9 5 7 ). A lthough th e e x p o s u r e s to th e north w ere not p e r s o n a lly f ie ld c h e c k e d , it sh o u ld be m en tio n ed th a t low er c lif f e x p o s u r e s are draped by a v ery th in v e n e e r o f s i l t - and c l a y - s i z e se d im e n t w a sh e d dow n from th e upper u n i t s . At a c a s u a l g l a n c e , th e lo w er p ortion o f a c lif f may th erefore app ear to be th e sam e c o m p o sitio n a s th e upper por­ t io n , w h ile , in f a c t , m ay a c tu a lly be a ltern a tin g b e d s . The d ia to m s p r e s e n t are m o stly c a n o e -s h a p e d N a y ic u la s . S p e c im e n s o f Synedra make up th e rem ainin g 20 to 30 p e r ce n t a lo n g w ith s c a tte r e d sp o n g e s p ic u le s (Long and O ls o n , 1 9 5 7 ). V o lc a n ic a sh sh ard s and s i l t - s i z e c l a s t i c g r a in s are a ls o p r e se n t in minor a m o u n ts. The 42 Figure 21. Scanning electron micrograph of devitrifying ash shard Alteration product (light rough material) is on the surface and interior as shown in the x -se c tio n of the broken shard. Volcanic g la ss is the darker sm ooth-surfaced a r e a s. Mounds may represent bubbles. Sample C C -3-5; 5 , 000X. Bar is 2 p. I 43 u n its are com m on ly c o m p o se d o f f o s s i l h a sh (f ig . 22); h o w e v e r , b e d s c o n ta in in g g o o d d iatom s p e c im e n s are p r e s e n t. S ilty Q p a l-C r is to b a lite B lake (1903) fir s t a n a ly z e d th e s ilic e o u s la y e r s o f th e Q uiburis Form ation and c o n c lu d e d th em to b e o f " o p a lin e s ilic a " c o m p o s itio n . Other s tu d ie s (T risch k a , 1929; A g en b ro a d , 1967; S m ith , 1968) h a v e g e n e r a liz e d and d e s c r ib e d th e s ilic e o u s la y e r s a s c h e r t, p ro b a b ly b e - ' c a u s e ch ert w a s a c o n v e n ie n t f ie ld term . In th e s tr ic t p e tr o lo g ic m ea n ­ in g , ch ert is a sed im en ta ry ro ck co m p o se d o f m ic r o c r y s ta llin e quartz and c h a lc e d o n y . As a r e s u lt o f th e p r e se n t d e ta ile d stu d y o f t h e s e s i l i ­ c e o u s l a y e r s , it turns ou t th a t B lake w a s v e r y .c lo s e to th e tru th , w h ile th e term "chert" o b s c u r e s im portant d ata regard in g c o m p o sitio n and d ia ­ g e n e s is . A stu d y o f th e Q uiburis " cherts" by X -ra y d iffra cto m eter t e c h ­ n iq u e s h a s sh o w n them to b e s i l t y o p a l- c r is t o b a l it e . For c o n v e n ie n c e , s ilt y p o r c e la n ite is u s e d in A pp en dix A and figu re 12 a s a fie ld term . F o r c e la n ite is a d a p ted from B ram lette (1 9 4 6 ), Ernst and C a lv ert (1 9 6 9 ), and C a lv ert (1 9 7 4 ). F ie ld C h a r a c te r is tic s The lig h t o liv e g r ee n s i l t y o p a l- c r is t o b a lit e s are p r e v a le n t b en ch -fo rm in g b e d s w ith in th e b a s in c e n te r ( f ig s . 23 and 2 4 ). Two b e d s a ls o crop out n ear th e b a s in m argin and ca n be tr a c ed e a s t from m ea ­ su red str a tig r a p h ic s e c t io n C G -5 to th e near c o n ta c t o f th e T ertiary v o l­ c a n ic b lo c k o u t lie r . O ther sm a ll o u tcr o p s c a n b e found a lo n g W h itlo c k W ash in th e c e n te r o f s e c . 2 1 , T . 9 S . , R. 18 E . The top su r fa c e o f th e s ilt y o p a l c r is t o b a lit e s com m on ly is un dulatory (fig . 2 5 ). C olor and 44 Figure 22. Scanning electron micrograph of diatom hash Sample C C -1 -3 2 , 5,000X . Bar is 2 p . View is looking ea st with Galiuro Mountains in background. 45 Figure 24. View looking north into measured stratigraphic s e c ­ tion CC-2 Note dipping beds of monoclinal fold e a st of section C C -2 . Figure 25. Undulatory surface of silty op al-cristob alite Bed is found in measured stratigraphic section C C -1 . Scale is 5 feet (1.5 m ). 46 lu s te r v a r ie s w ith th e d e g r ee o f d e tr ita l m a teria l p r e s e n t . F ew er c l a s t i c g ra in s g e n e r a lly g iv e a darker c o lo r and a more v itr e o u s lu s t e r . T his ch a n g e m ay o c cu r from bed to b ed or e v e n w ith in a p a rticu la r s a m p le . A b ed form s a d e fin ite stra tu m ; h o w e v e r , n o n co n tig u o u s n o d u le s are com m on. The th ic k n e s s v a r ie s from 1 in c h (3 cm) to a s th ic k a s a 4 fo o t (1 .2 m) s e q u e n c e . The ro ck i s h a rd , d e n s e , and b r ittle and g e n ­ e r a lly fra ctu res c o n c h o id a lly . W here c l a s t i c s i l t g r a in s are a dom inant c o n s titu e n t, fla g g y s p littin g p r e v a ils . F igure 26 sh o w s th e ty p ic a l h o r iz o n ta l la m in a tio n s and c a r ­ b o n a c e o u s la y e r s found in m o st b e d s . C a rb o n a ceo u s p la n t d e b r is is lo c a lly en c o u n ter e d on h o r iz o n ta lly broken s u r f a c e s . At o n e s ilt y o p a lc r is to b a lite outcrop in m easu red str a tig r a p h ic s e c t io n C G -2 , bon e frag­ m ents are a b u n d a n t. In th e sam e b e d , a sm a ll p o c k e t o f v itr e o u s s i l t y o p a l- c r is t o b a lit e c o n ta in s s c a tte r e d g a stro p o d s h e l l s . X -rav A n a ly s is The Q uiburis Form ation " cherts" and r e la te d s e d im e n ts w ere stu d ie d b y X -ra y d iffr a c tio n t e c h n iq u e s . A N o r e lc o X -ra y d iffra cto m eter u n it u s in g N i- f ilt e r e d cop p er K -alp h a r a d ia tio n at 40 kV and 20 mA w a s e m p lo y e d . For e a c h d iffr a cto m eter run o f the " c h e r ts ," a p attern id e n ­ t if ie d a s th at o f o p a l- c r is t o b a lit e w a s o b ta in e d . Further stu d y o f the d iffractogram s sh o w ed them to be v ery sim ila r to th o s e o b ta in e d from c r is t o b a lit e - r ic h T ertiary d e e p - s e a s e d im e n ts (R ex, 1 9 6 9 , 1970; W is e and K e lts , 1972; W is e , B u ie , and W e a v e r , 1972; v o n Rad and R o sc h , 1 9 7 2 ). O p a l- c r is t o b a lit e , lo w - c r is t o b a lit e , and a lp h a - c r is t o b a lit e are com m only u s e d term s to d e s c r ib e th e X -ra y d iffr a c tio n p a ttern s p rod u ced Figure 26. Cut hand specim en of typical bedded silty op alcristo b a lite , showing laminations and black carbonaceous layers . Sample C C -1 -3 1 . Scale is in centim eters. 48 b y su ch s ilic e o u s r o c k s . The term " s ilty o p a l- c r is t o b a l it e " i s th e p re­ ferred ter m in o lo g y to d e p ic t th e s i l i c e o u s r o c k s o f th e Q uiburis Forma­ t io n . O pal and s i l t are u s e d b e c a u s e o f the t y p ic a l is o tr o p ic nature o f th e m atrix surrounding th e abundant s i l t - s i z e c l a s t i c g r a in s . Figure 27 com p ares a s i l t y o p a l- c r is t o b a lit e X -ray d iffr a ctio n pattern w ith on e r e s u ltin g from a d ia to m ite s a m p le . The d ia to m ite p a t­ tern (f ig . 27a) s h o w s a v ery b ro a d , lo w - in t e n s it y r e fle c tio n from about o o o 3 .5 6 A to 4 .9 3 A and c e n te r e d a t a p p ro x im a tely 4 .0 9 A . T his subd ued r e fle c tio n s u g g e s t s som e c r y s ta llo g r a p h ic order in th e "amorphous" s ilic e o u s r e m a in s . Q uartz is a ls o p r e se n t a s c l a s t i c g r a in s . The o p a lc r is to b a lite p attern (f ig . 27b) d is p la y s a sim ila r b r o a d -b a se d r e fle c tio n ; o h o w e v e r , in a d d itio n , it e x h ib its a strong p ea k at 4 .1 3 A and a w e a k r e fle c tio n at 2 .5 A . Two extrem e d iffractogram s p r e se n t in figu re 28 sh o w th e v a r ia b ility o f th e Q u ib u ris o p a l- c r is t o b a l it e . Figure 28a i l l u s ­ tr a te s a v ery p o o rly ordered structure a s w e ll a s th e abu ndan ce o f d e tr ita l m a te r ia l. Figure 2 8 b , on th e oth er h a n d , r e s u lte d from a s p e c im e n h a v in g r e la t iv e ly w e ll d e v e lo p e d c r y s t a l s . The prom inent r e f le c tio n s on th e righ t fla n k o f the c r is to b a lite p e a k ( f ig s . 27b and 28b) are a ttrib u ta b le to trid ym ite s i l i c a la y e r s in te r str a tifie d w ith c r is to b a lite s i l i c a la y e r s (E ite l, 1957; H eron , 1969; C a l­ v e r t , 1971; Jon es and S e g n it, 1 9 7 1 ). Jon es and S e g n it s u g g e s te d th a t th is s ta c k in g d iso r d e r a ls o c a u s e s a ch a n g e in th e o o a lp h a -c r is to b a lite from 4 .0 4 A to 4 .1 1 A. 101 lin e s p a c in g o f 49 C Figure 2 7 . o p a l- c r is t o b a lit e X -ra y d iffra cto g ra m s o f Q u ib u ris d ia to m ite and s i l t y A . Q uiburis d ia t o m ite , sa m p le C C - 1 - 3 2 . B. Q uiburis s ilt y o p a l- c r is t o b a l it e , sa m p le C C - 1 - 7 7 . C = c r is to b a lite ; Q = d e tr ita l q u a r tz . 50 C D egrees 29 Figure 2 8 . c r is to b a lite X -ra y d iffra cto g ra m s o f Q uiburis s ilt y o p a l- A . Q uiburis s i l t y o p a l- c r is t o b a lit e sh o w in g p o o rly ordered structure and abundant d e tr ita l m a te r ia l, sa m p le C C - 3 - 9 . B . X -ra y d iffractogram o f Q u ib u ris s i l t y o p a l- c r is t o b a lit e h a v in g w e ll- d e v e lo p e d c r y s t a ls , sam p le C C - 5 - 1 9 . C = c r is to b a lite ; Q = d e tr ita l q u a r tz . 51 P etrographic A n a ly s is P etrograp h ic a n a ly s is e lu c id a t e s th e impure nature o f th e Q u ibu ris o p a l - c r i s t o b a l i t e s . F igure 29 illu s t r a t e s th e a b u n d a n ce o f s i l t s iz e d e tr ita l g r a in s in an app arent is o tr o p ic c e m e n t. L e s s d e n s e , f lo a t ­ in g c l a s t i c g ra in s are a ls o com m on ly found surrounded b y a n e a r ly is o tr o p ic m a trix . The c o m p o sitio n o f th e c l a s t i c g ra in s c o n ta in e d in th e s ilt y o p a l- c r is t o b a lit e s is sim ila r to the g ra in s m aking up th e s i l t u n its d is c u s s e d e a r lie r and w ill not be m en tion ed h e r e . F o s s il d eb ris m en tion ed under fie ld c h a r a c t e r is tic s are a ls o v is ib le in th in s e c t io n . T hey in c lu d e bone fr a g m e n ts , g a str o p o d s (fig . 30) and c e llu la r p la n t s tr u c tu r e s . E x p lic it e v id e n c e o f s il i c e o u s m icro ­ f o s s i l s h a s not b e e n o b s e r v e d in th e o p a l- c r is t o b a l it e s . It is s a fe to a ssu m e th a t d ia to m s w ere d e p o s ite d w ith in th e o r ig in a l m a teria l b e c a u s e o f th e p roxim ity o f d ia to m ite to the s i l i c e o u s r o c k s . P r e se r v a tio n o f th e o p a lin e d iatom t e s t s th erefo re s e e m s v e ry u n lik e ly . D ia g e n e s is h a s prob­ a b ly d e s tr o y e d a n y d ia to m s th a t w o u ld h a v e b e e n p r e s e n t . The o n ly oth er trace m ic r o fo s s il th a t o c c u r s c o n s is t e n t ly in the o p a l- c r is t o b a lit e s ilt s t o n e s is illu s tr a te d in figu re 3 1 . The u n id e n tifie d rem ain s ap p ear to b e o r g a n ic c e l l s tr u c tu r e s , p o s s ib ly a lg a e . T hey are d is tin g u is h e d from p la n t d e b r is b y th eir c h a in lik e , irreg u la rly form ed c e llu la r fram ew ork. P lant m ateria l i s r e c o g n iz e d by w e ll- d e f in e d ro w s o f r e g u la r ly sh a p e d c e lls . C olloform c r is t o b a lit e , lin in g c a v it ie s w ith in f ille d s e c o n d a r y c h a lc e d o n y , is com m on ly o b s e r v e d in th in s e c t io n (f ig . 3 2 ). The r a d ia t­ in g c r is to b a lite lin in g i s brown com pared to th e c le a r c h a lc e d o n y . B e­ tw e e n c r o s s e d n i c o l s , th e m in eral sh o w s v e ry w e a k b ir e fr in g e n c e w ith 52 Figure 29. Photomicrograph of very silty op al-cristob alite C la stic grains are primarily quartz in an isotropic matrix. Sample C C -2 -1 9 . Cross n ic o ls , 125X. Bar is 100 p . Figure 30. cristobalite Photomicrograph of gastropod in silty op al- Sample C C -2 -4 9 . Cross n ic o ls , SOX. Bar is 200 p . 53 Figure 31. op al-cristob alite Photomicrograph of unidentified m icrofossil in silty Structure may be of algal origin. Sample C C -1 -3 6 , plane lig h t, 125X. Bar is 100 p . cavity Figure 32. Photomicrograph of colloform cristobalite lining Sample C C -1 -3 1 , plane lig h t, 286X. Bar is 25 p . 54 e x tin c tio n p a r a lle lin g th e fib er le n g th . C r isto b a lite i s further d iffe r e n ti­ a te d from c h a lc e d o n ic in f illin g by it s lo w er in d e x o f r e fr a c tio n and h igh r e li e f . S can n in g E lectron M ic r o sc o p e A n a ly s is SEM o b s e r v a tio n s proved to be e x tr em e ly u s e f u l in th e id e n t i­ fic a tio n o f c r is to b a lite and to further c o rr e la te s im ila r itie s b e tw e e n th e Q uiburis o p a l- c r is t o b a lit e and d e e p - s e a c r is t o b a lit e . F ig u res 33 and 34 are SEM m icrograp hs o f Q u ib u ris c r is t o b a lit e . Fractured s u r fa c e s are u n u s u a lly sm o o th . C r is to b a lite is o b se r v e d o n ly a s c a v ity lin in g w here free c r y s ta l grow th h a s d e v e lo p e d . The c r y s ta ls form m ic r o sp h e r u lit e s o f r e la t iv e ly uniform s i z e , a v e ra g in g 10 m icrons in d ia m e te r . W e ll-fo r m e d b la d e s ra d ia te from th e c en te r in w hat appear to be random o r ie n t a t io n s . There is a str ik in g r e se m b la n c e b e tw e e n d e e p - s e a c r i s t o b a lit e s and th o s e found in th e Q u ib u ris F orm ation. The m orp h ologic s im ila r itie s s u g g e s t th at c r is to b a lite s p h e r u le s form in a w id e range o f g e o lo g ic e n v ir o n m e n ts . D iatom rem a in s w ere not found in th e s ilt y o p a l- c r is t o b a lit e sa m p le s v ie w e d . H o w e v er , w ith more SEM v ie w in g and c a r e fu l s e a r c h ­ in g , tr a c e s o f s i l i c e o u s o r g a n ism s m ay be fo u n d . O rigin and D ia g e n e s is C r is to b a lite h a s b e e n g e n e r a lly c o n s id e r e d a h ig h -tem p era tu re polym orph o f quartz w ith a s t a b ilit y range b e tw e e n 1 ,4 7 0 ° and 1 ,7 2 8 ° C . The d is c o v e r y o f d e e p - s e a s e d im e n ts rich in c r is to b a lite b ea rs e v id e n c e th a t it i s r e la t iv e ly s ta b le at lo w er te m p e r a tu r e s . H eath and M oberly (1971) e s tim a te th at th e in - s it u tem perature at w h ich th e ra tio o f 55 Figure 33. Scanning electron micrographs of cristob alite microspherules lining d avities A. Sample C C -1 -7 7 , 200X. Bar is 50 p . 1 , 600X. Bar is 5 ju. B. Sample C C -1 -7 7 , 56 Figure 3 4 . S can n in g e le c tr o n m icrograph o f c r is to b a lite m icro­ sp h e r u le s M icr o sp h e r u le s are co m p o sed o f sm a ll b la d e -s h a p e d r a d ia tin g c r y s t a ls . C h a lc e d o n y is p a r tia lly c o v erin g m ic r o s p h e r u le s . Sam ple C C 1 - 1 7 7 , 5 , 000X . Bar i s 2 p . 57 c r is to b a lite to quartz is a maximum in th e d e e p - s e a s ilic e o u s ro ck s a n a ly z e d is 1 5 ° C . The a g e and therm al h isto r y se e m im portant in flu ­ e n c e s on c r is to b a lite m in era lo g y and are a ls o d is c u s s e d by H eath and M o b e r ly . R esea rch is proving th a t th ere is a ls o a w id e sp r e a d o ccu rr e n c e o f low -tem p era tu re c r is to b a lite in g e o lo g ic a lly youn g "cherts" (H eron, R o b in so n , and J o h n so n , 1965; H ero n , 1969; W is e and W e a v e r , 1973; B ram lette, 1946; Ernst and C a lv e r t, 1 9 6 9 ). A P lio c e n e te r r e str ia l o c c u r ­ ren ce o f lo w -tem p era tu re c r is to b a lite w a s found in th e O g a lla la Forma­ tio n (Sw ineford and F r a n k s, 1 9 5 9 ). The Q uiburis Form ation is both g e o lo g ic a lly youn g and o f lo w -tem p era tu re o r ig in . H em p h illia n v e r te ­ brate f o s s i l s and K-Ar d a te s o f a s h e s c o n ta in e d in th e Q uiburis in d ic a te a m iddle P lio c e n e a g e (J a c o b s , 1973; S carb orou gh , 1 9 7 5 ). The s e d im e n ts w ere p rob ab ly n ev er d e e p ly buried; h e n c e , th e am b ien t tem perature a t an y tim e may not h a v e e x c e e d e d 1 0 0 ° C . An o rig in for o p a l- c r is t o b a lit e " cherts" h a s b e e n p r o p o se d b y s e v e r a l in v e s t ig a t o r s . Three b a s ic h y p o th e s e s e x i s t . F ir s t, th e m ost w id e ly a c c e p te d th eo ry for th e d e e p - s e a c r is to b a lite i s th e r e a c tio n : b io g e n o u s o p a l -» c r is to b a lite -» q u a r tz -r ic h ch ert (Ernst and C a lv e r t, 1969; R ex, 1969; H eath and M o b e rly , 1 9 7 1 ). S e c o n d , R ieck and S t e v e ls (1951) and Gruner (1940) report a c h e m ic a lly p r e c ip ita te d o rig in o f s e d i ­ m entary c r is to b a lite a s a com m on product o f d e v itr ifie d v o lc a n ic a sh and b e n to n ite . F in a lly , c r is t o b a lit ic o p a l p r e c ip ita tin g from s ilic a - s a t u r a t e d w ater h a s b e e n o b s e r v e d in th e S team b oat S p rin gs therm al area (W h ite, T hom p son , and S a n d b erg , 1 9 6 4 ). It is e v id e n t th at lo w -tem p era tu re c r is to b a lite may form in a v a r ie ty o f e n v ir o n m e n ts . T his c o m p lic a te s a n y p ro p o sed o rig in for th e 58 Q uiburis s ilic e o u s r o c k s . D ia to m ite , v o lc a n ic s e d im e n ts , and s i l i c i c T ertiary v o lc a n ic flo w s w ere a ll p r e se n t a s p o te n tia l s i l i c a s o u r c e s . The origin through th e a lte r a tio n o f v o lc a n ic a s h , h o w e v e r , is ruled o u t. The u n u su a l fr e s h n e s s o f m o st a s h b e d s and th e a b s e n c e o f z e o l i t e s is th e b a s is for d is c o u n tin g an im m ed iate s i l i c a so u rce from th e s e d e p o s it s . N o n e t h e le s s , th e u ltim a te so u r ce o f s i l i c a from v o lc a n ic eru p tio n s sh o u ld not be n e g le c t e d . Warm sp r in g s may h a v e flo w e d ou t o f th e G aliuro M ountain v o lc a n ic m a ss during P lio c e n e tim e . T h e se w a te rs c o u ld h a v e b e e n sa tu ra ted w ith S iO g . The s ilic a - r ic h in flo w and th e v o lc a n ic eru p tion w ere p rob ab ly en ou gh to sa tu r a te th e C u ib u ris flu v io la c u s tr in e s y s t e m . Q u ib u ris w a te rs m ust h a v e b een w e ll su p p lie d w ith s i l i c a to h a v e had th e flo u r ish o f diatom grow th now r e p r e se n te d a s m a s s iv e b e d s . The d e e p - s e a th eory o f d is s o lv in g d ia to m ite and r e p r e c ip ita tin g it in pore s p a c e a s o p a l- c r is t o b a lit e w ith in the bed is not r e a lly c o n s id e r e d . The r e a s o n s are th r e e fo ld . F ir s t, th ere i s no apparent lo s s o f bed t h ic k n e s s w here th e s i l t y o p a l- c r is t o b a lit e s are found in th e d ia to m ite . S e c o n d ly , s ilt y o p a l- c r is t o b a lit e s are a ls o in terb ed d ed w ith s ilt u n it s . But th e s e in terb ed d ed u n its are s t i l l in c lo s e p ro x im ity to d ia to m ite in the b a s in c e n te r . F in a lly , s i l t y o p a l- c r is t o b a lit e s su r p r isin g ly crop out near th e b a s in m argin w here th ere i s no o b v io u s r e la tio n s h ip to th e d ia to m ite . It can n ot be s ta te d u n e q u iv o c a lly w hat typ e o f Q uiburis s e d im e n ts h a s b e e n erod ed a w ay in th e m arginal area; but a llu v ia l g r a v e l is probab ly a s a fe r a ssu m p tio n than d ia to m ite and fin e -g r a in e d la k e d e p o s it s . F ie ld and lab oratory e v id e n c e in d ic a te s th at th e s ilt y o p a lc r is to b a lite m ay h a v e b e e n in it ia lly d e p o s ite d a s a s i l i c a g e l 59 con tem p oran eou s w ith th e Q u ib u ris Form ation. V o lc a n ic eru p tio n s and tr ib u ta r ies from the G aliu ro M ountain m a ss p rob ab ly su p p lie d more th an enough s i l i c a for fa v o ra b le diatom g ro w th . The w a te rs b ecam e su p e r ­ sa tu ra ted w ith r e s p e c t to S i 0 2 , e ith e r b y c o n tin u a l r ep len ish m e n t or e v a p o r a tiv e c o n c e n tr a tio n during dryer p arts o f th e s e a s o n . U nder o p I timum c o n d it io n s , c o llo id a l s i l i c a p r e c ip ita te s a s flo c c u le n t m a s s e s in g e l form (K rauskopf, 1956; W h ite , B rannock, and M u rata, 1 9 5 6 ). T his r e a c tio n is h ere p ro p o sed a s th e m ech a n ism for th e in it ia l s ta g e o f th e Q uiburis o p a l- c r is t o b a l it e . C o n ta ct w ith th e o p a lin e diatom t e s t no doubt w a s a fa v o ra b le n u c le a tin g a g e n t. F ie ld and lab oratory e v id e n c e s u g g e s tin g th at th e o p a lc r is to b a lite w a s in it ia lly d e p o s ite d a s a s i l i c a g e l in c lu d e th e f o llo w ­ ing: 1. U n d u latory s u r f a c e s . The c h a r a c te r is tic u n d u latory te x tu re on th e top c o n ta c t g iv e s an a p p ea ra n ce o f a o n e -tim e g e l c o n s i s ­ te n c y . 2. S ilic if ie d c o n t a c t s . C o n ta c ts b e tw e e n s i l t u n its and th en o p a l­ in e ro ck s are com m on ly s i l i c i f i e d and in d ic a te co n tin u e d d e p o ­ s itio n o v er th e s i l i c a g e l and a s lig h t sin k in g o f th e s i l t s in to th e g e l . 3. F lo a tin g g r a in s . In th in s e c t io n , c l a s t i c g ra in s com m only are e n tir e ly surrounded b y an is o tr o p ic m a trix . It sh o u ld be m en tio n ed th a t on e c o n tra d icto ry o p a lin e ro ck n od u le ap p ears to be o f a s e c o n d a r y pore f illin g o r ig in . The ro ck i s found a p p ro x im a tely 200 f e e t (60 m) to th e e a s t o f str a tig r a p h ic s e c t io n C C -2 in C am el C a n ­ y o n W a s h . I llu s tr a te d in figu re 3 5 , th is a n o m a lo u s sa m p le c o n ta in s 60 i Figure 35. Cut hand specim en of op al-cristob alite nodule Specimen contains laterally continuous laminations (a) and m asses of pure op al-cristob alite (b). Scale in centim eters. 61 lam in ated stru ctu res th at are la te r a lly co n tin u o u s into the surrounding s e d im e n t. A ls o , c o m p le te ly d iffe re n t from a n y oth er sp e c im e n is th e p r e s e n c e o f a pure tr a n slu c e n t and g l a s s y , dark o liv e g r ee n m a teria l in m a s s e s a s large a s 6 mm a c r o s s . X -ray d iffr a ctio n a n a ly s is con firm s an o p a l- c r is t o b a lit e c o m p o s itio n . C o a rse sa n d and gran u le c l a s t i c g ra in s are a ls o found in s i l t y p o r c e la n ite sa m p le C C - 2 - 4 9 . An e x p la n a tio n for th is an om alou s sa m p le is th a t th e se d im e n ts b e lo w th e g e l w ere v ery porous and p e r m e a b le . The g e l may h ave sim p ly p erm eated the c o a r se r d e p o s it and f ille d in th e pore s p a c e . The e v id e n c e in d ic a tin g an o r ig in a l s i l i c a g e l is s t i l l q u e s tio n ­ a b le ; th e r e fo r e , a p r e c is e o rig in o f th e Q uiburis o p a l- c r is t o b a lit e ca n n o t be s a t is f a c t o r ily e s t a b lis h e d . A fter o n ce a ssu m in g s i l i c a d e p o s itio n and c r is to b a lite c r y s t a lliz a t io n , a d ia g e n e tic in v e r sio n to ch ert can be im ­ a g in e d . Ernst and C a lv e rt (1969) s u g g e s te d th e M on terey o p a lc r is to b a lite i s an in term ed ia te p h ra se in th e d ia g e n e tic m o d ific a tio n to c h e r t. The a b s e n c e o f c r is to b a lite in p r e -C e n o z o ic c h e rts su p p orts th is argum ent. At on e d e e p - s e a d r illin g s i t e . H eath and M oberly (1971) r e ­ ported th e m in era lo g y o f s i l i c a a d ja ce n t to an in tr u siv e b a s a lt i s com ­ p o s e d e n tir e ly o f q u a r tz . Time and therm al e n e rg y s o u r c e s are ap p a ren tly tw o im portant req u irem en ts in th e d ia g e n e s is o f lo w -tem p era tu re c r is t o ­ b a lite to q u a rtz. G iv en tim e or p erh ap s a h e a t s o u r c e , it s e e m s th at Q u ib u ris o p a l- c r is t o b a lit e w o u ld p o s s ib ly in vert to quartz (c h e r t). Such a p r o p o sa l is o p en to r e s e a r c h and p o s s ib ly c o u ld be s o lv e d through th e stu d y o f s e q u e n tia lly a g e d " cherts" found w ith in so u th w e ste rn U n ited S ta te s C e n o z o ic b a s i n - f i l l s e d im e n ts . ENVIRONMENT OF DEPOSITION The d e p o s itio n a l environ m en t o f th e Q uiburis Form ation s e d i­ m ents in th e v ic in it y o f M am m oth, A r izo n a , i s in terp reted to be f lu v io la c u s t r in e . C riteria for it s r e c o g n itio n are b a s e d on g e n e r a l str a tig r a p h ic r e la t io n s , s i z e a n a l y s e s , sed im en ta ry s tr u c tu r e s , and p a le o n to lo g y . Figure 36 illu s t r a t e s th e h y p o th e tic a l d e p o s itio n a l en v iro n m en t. M elto n (1965) s u g g e s te d th at through d rain age o f th e a n c e s tr a l San Pedro R iver w a s b lo c k e d b y v o lc a n is m and u p lift in the P h o en ix a r e a . This a ffe c te d th e d rain age o v er a large part o f so u th e a s te r n A rizo n a . In a d d itio n to M e lto n 's th e o r y , a more lo c a l c a u s e m ay h a v e b e e n a llu v ia l fan d am m in g. The Big Dom e Form ation is a llu v ia l (Krieger and o t h e r s , 1974) and crop s ou t s lig h t ly north o f th e Q uiburis F orm ation. The r e la ­ tio n s h ip b e tw e e n t h e s e tw o form ation s is n ot c e r ta in . It s e e m s h ig h ly p o s s ib le th a t th e Big Dom e Form ation may h a v e had lo c a l in flu e n c e by dam ming or at le a s t s lo w in g th e through d rain age and p erh ap s in itia tin g th e d e p o s itio n o f th e Q u ib u r is. By w hat e v e r m e a n s , w e ll-in te g r a te d d rain age w a s r e p la c e d by l a k e s , sm a ll s tr e a m s , and g r a s s y s w a m p s. F resh w a ter d ia to m s (B la k e, 1903) are p o s it iv e e v id e n c e for a la k e en v ir o n m e n t. The r e la tiv e th ic k n e s s o f th e d ia to m ite com m only in terb ed d ed w ith g r e e n is h s i l t s i s som e in d ic a tio n o f sta n d in g d e e p w a te r . R e e v e s (1968) s u g g e s t e d g r e e n la c u str in e se d im e n t is e v id e n c e o f w a ter depth e x c e e d in g a fe w in c h e s and red c o lo r s are t y p ic a l o f o x id iz in g e n ­ viron m en ts . The o c c u r r e n c e o f both red and g r ee n s i l t s in th e Q uiburis 62 G A L I U R 0 0 u N T A I N S -1. i grav Vvsand P R E - Q U IB U R IS Figure 36. Conceptual view of the San Pedro Valley near Mammoth, Arizona, during d ep osition of the Quiburis Formation "Slow" arrow in d ica tes drainage from south to north. CT> W 64 d e m o n str a te s th e p e r io d ic c h a n g e s from an o x id iz in g to a red u cin g e n ­ vironm ent . At m any l o c a l i t i e s , p la n t-s te m ty p e str u c tu r es are abundant in th e s i l t u n i t s . T hey are g e n e r a lly sm a lle r than 6 mm in d ia m eter and 1 to 2 in c h e s (3 to 5 cm) in le n g th . T hey are found in a v e r tic a l p o s it io n . T heir p r e s e n c e im p lie s o p en g r a s s la n d or sw am py g r a s s a r ea s surround­ in g th e w a te r b o d ie s . The la k e and g r a s s la n d c o n c e p t is a ls o su p p orted by fa u n a l e v id e n c e (J a c o b s , 1 9 7 3 ). In a d d itio n , san d and g r a v e l l e n s e s com m only crop out w ith in th e b a s in c e n te r . T hey probab ly r ep r e se n t s m a ll d ra in a g e c h a n n e ls com in g from the h ig h er e le v a t e d b a s in margin and c h a n n e lw a y in te r c o n n e c tin g larger b o d ie s o f w a te r . The p a u c ity o f c la y s e d im e n ts w ith in th e Q uiburis Form ation s tu d ie d o ffe r s an in te r e s tin g p ro b lem . Two r e a s o n s m ay a c c o u n t for th e ir a b s e n c e . F ir s t, c l a y - s i z e m a teria l may sim p ly n ot h a v e b e e n a v a ila b le . S e c o n d ly , the e n e rg y in v o lv e d in transport m ay h a v e b e e n to o g r ea t to a llo w for c la y d e p o s it io n . The o c cu rr e n c e o f d ia to m ite s e e m s to be at it s so u th ern e x trem ity ; h e n c e n e a r -la k e shore en viron m en t and h ig h er e n e rg y is a p o s s i b i l i t y . S iz e a n a ly s is o f Q uiburis s e d im e n ts to th e north o f th e stu d y area m ay prove to sh o w an in c r e a s e d c la y c o n te n t. The u n a v a ila b ility o f c la y and a s lig h tly in c r e a s e d e n e rg y le v e l are p rob ab ly both in v o lv e d in th e s c a r c ity o f c la y s e d im e n t s . The Q u ib u ris Form ation i s about 1 ,7 0 0 f e e t (530 m) in to t a l th ic k n e s s and form s a s h a llo w s y n c lin e w ith th e a x is ro u g h ly p a r a lle l to but s lig h t ly e a s t o f th e p r e s e n t San Pedro R iver (H e in d l, 1 9 6 3 ). The d ip s o f th e b e d s at th e b a s in m argin range from 3 to 5 d e g r e e s and strik e e a s t e r ly . A lthough th e m arginal u n its are h ig h er in e le v a t io n th an th e 65 b a s in c e n te r d e p o s i t s , th e s lig h t dip o f 3 to 5 d e g r e e s ca n e a s i l y dem on­ stra te tim e str a tig r a p h ic c o n tin u ity b e tw e e n th e e x p o s e d a llu v ia l and la k e b e d s e d im e n t s . The b e n to n ite bed o f str a tig r a p h ic s e c t io n C G -7 is p rob ab ly c o r r e la tiv e to on e o f th e v o lc a n ic sed im en ta ry u n its crop ping ou t in str a tig r a p h ic s e c t io n G C - 4 . C ertain c o n c lu s io n s for th e p h y s ic o c h e m ic a l c h a ra cter o f th e lak e w a te r s ca n be in ferred from th e d ia to m ite o c c u r r e n c e . A su p p ly o f s i l i c a h a s a lr e a d y b e e n m en tio n ed a s a fa v o ra b le c o n d itio n for diatom gro w th . C onger (1942) c la im e d lo w tem perature i s a ls o an im portant f a c ­ tor c o n tr o llin g th e ir e x i s t e n c e . C o o l w ater in h ib its b a c te r ia l a c tiv ity and u ltim a te ly r e d u c e s a c id it y . The w a ter w a s prob ab ly ca lm and d e v o id o f su r fa c e d is tu r b a n c e s , w h ic h w o u ld h a v e r e s tr ic te d th e lif e o f f r e e flo a tin g d ia to m s b y m eans o f f lo c c u la t io n . A nd erson (1962) s u g g e s t e d th e clim a te o f the S o u th w e st c h a n g ed from su b tr o p ic a l to c o o le r tem p era tu res during m id dle T ertiary tim e . In m iddle M io c e n e , th e so u th ern end o f th e Sierra N e v a d a b eg a n r isin g and c a u s e d a rain sh a d o w to th e e a s t . By m iddle P lio c e n e , th e c o o lin g trend co n tin u e d and th e S o u th w e st had ta k e n on an arid ch a r a cter sim ila r to th at w h ic h e x i s t s to d a y . The Q u ib u ris Form ation a p p ea rs to h a v e b e e n d e p o s ite d in a r e l­ a t iv e ly la r g e , s lo w -m o v in g , interm ontane d ra in a g e s y s t e m . Long p e r io d s o f q u ie s c e n c e and a b s e n c e o f muddy w a ter p r e v a ile d . The d epth o f th e w a ter is q u e s tio n a b le ; h o w e v e r , it m ust h a v e b e e n a s d e e p a s th e th ic k ­ e s t v o lc a n ic a s h - f a l l d e p o s it . O pen g r a s s la n d s or g r a s s y sw am p s su r­ rounded th e b o d ie s o f w a te r . The u p lifte d v o lc a n ic m a ss to th e e a s t w a s th e prim ary so u r ce o f c l a s t i c d e b r is . A llu v ia l fa n s com m only r ea c h e d th e e d g e o f th e flu v io la c u s tr in e s y s te m o r, a s in th e c a s e o f th e stu d y a r e a , w ere p a r tia lly dam med by v o lc a n ic b lo c k o u t lie r s . The c lim a te w a s p rob ab ly c o o le r and s lig h t ly more humid than the c lim a te th at e x i s t s to d a y . SUMMARY The m iddle P lio c e n e Q uiburis Form ation is in terp reted to be d e p o s ite d in a flu v io la c u s tr in e en v iro n m en t. Long p e r io d s o f q u ie s c e n c e and a b s e n c e o f muddy w a ter p r e v a ile d . S ed im en ts c o n s is t prim arily o f sa n d y s i l t s w ith minor am ounts o f lim e s t o n e , v o lc a n ic s e d im e n t s , d ia to m ite , and s i l t y o p a l- c r is t o b a lit e u n its in the b a s in c e n te r . T h ese fin er grain ed s e d im e n ts grade ra p id ly from th e c en te r o f th e v a lle y into c o a r s e r sa n d s and g r a v e ls tow ard th e b a s in m argin . The g r a v e ls are allu v iu m d e r iv ed from th e d eg ra d a tio n o f th e u p lifte d G aliuro M ountain v o lc a n ic m a ss w h ic h li e s th ree m ile s to th e e a s t . The sa n d y s i l t s are th e m o st abundant o f th e Q uiburis Form ation s e d im e n ts . T hey c o n s i s t o f p o o r ly so rted q u a rtz , fe ld s p a r , and h e a v y m in eral g r a in s in th e fin er s iz e f r a c t io n s . V o lc a n ic rock fragm en ts made up th e c o a r se r c o n s t it u e n t s . G r a n u le -s iz e c l a s t i c g r a in s are more co m ­ mon nearer th e b a s in m a rg in . Two lim e s to n e v a r ie t ie s are p r e se n t in th e Q uiburis and are: 1. An a lm o st pure m icrite h a v in g o n ly minor quartz g r a in s and g a stro p o d s h e l l s . 2. A sa n d y a lg a l lim e s to n e c o n s is t in g o f a lg a l p i s o l i t e s and m atty str u c tu r es a lo n g w ith sa n d g r a in s .' V o lc a n ic s e d im e n ts are com m only in terb ed d ed in both s i l t and d ia to m ite . T hey range from v e r y fr e sh a s h - f a l l to a c o m p le te ly a lte r ed a sh (b e n to n ite ). P o ta ssiu m -a r g o n d a te a n a ly s is g iv e s a l e s s than 6 .0 67 68 m .y . a g e for th e fr e sh a s h (Scarborough, 1 9 7 5 ). Z e o lite m in era ls w ere not e n c o u n tered in any v o lc a n ic sed im e n t a n a ly z e d . D ia to m ite b e d s are th e s e c o n d m o st abundant u n its in th e stu d y a r e a . The b e d s in c r e a s e in t h ic k n e s s to th e north and appear to be at th e ir so u th ern m o st e x trem ity in th e stu d y a r e a . B ed s are co m p o sed m o s t­ ly o f diatom h a s h com m on ly w ith c l a s t i c d e b r is . The b ed d ed s ilt y s il i c e o u s ro ck s proved to be an in te r e stin g o c c u r r e n c e . X -ray a n a ly s is sh o w s th e s ilic e o u s r o ck s to b e c o m p o se d o f o p a l- c r is t o b a l it e . The Q uiburis s i l t y o p a l- c r is t o b a lit e s h a v e m any o f th e s im ila r itie s e x h ib ite d by th e c r is t o b a lit e - r ic h d e e p - s e a s e d im e n t s . Q uiburis w a te rs are in terp reted to h a v e b e e n sa tu ra ted w ith r e s p e c t to s i l i c a . The d iatom s w ere u n a b le to u s e up th e s i l i c a during s e a s o n s o f su p e r sa tu ra tio n c a u s e d b y e v a p o r a tiv e c o n c e n tr a tio n , and s i l i c a p r e c ip i­ ta tio n in th e form o f a g e l r e s u lt e d . The a b s e n c e o f c r is to b a lite in p r e C e n o z o ic c h e r ts s u g g e s t s th at lo w -tem p era tu re c r is to b a lite is an in term ed ia te d ia g e n e tic p h a se o f c h e r t. M ore stu d y i s n e c e s s a r y to u n d erstan d fu lly th e o c cu rr e n c e and s ig n ific a n c e o f o p a l- c r is t o b a lit e in th e Q u ib u ris Form ation and it s r e la tio n s h ip to oth er te r r e str ia l d e p o s it s . APPENDIX A DESCRIPTION OF MEASURED SECTIONS The c o lo r d e s ig n a tio n s in the fo llo w in g d e s c r ip tio n s are th o s e o f th e R o ck -C o lo r Chart (R ock -C olor Chart C o m m itte e , 1 9 4 8 ). 69 70 Stratigraphic Section CC-1 L ocated in N W 1 /2 N E 1 /4 S W 1 /4 s e c . 2 9 , T . 9 S . , R. 18 E , P ep p ers a u c e W ash q u a d r a n g le , a lo n g a m o d era tely s te e p ridge in bad land top ograp hy in C am el C anyon W ash; e x p o s u r e s are g ood ; b a s e o f s e c t io n is lo c a te d under p o w e r -lin e c a b le th at e x te n d s o v er C am el C anyon W ash; b e d s d ip 0 ° to 5 ° N .; b a s e e le v a t io n is a p p ro x im a tely 2 ,6 2 0 fe e t (812 m ). U n it N o. D e s c r ip tio n T h ic k n e ss in m eter Ft E rosion s u r fa c e . P le is t o c e n e and H o lo c e n e : 59 A llu v ia l and p ed im en t g r a v e ls 3 0 0 .9 2 3 3 .9 9 P o r c e la n ite , s i l t y , lig h t o liv e brown (5Y 5 /6 ); ' w e a th e rin g to c o a r s e sand s iz e p a r tic le s and crum bly c la y ; b a s e s h a r p ........................ 4 .10 S ilt , s a n d y , g r a y is h - y e llo w (5Y 8 /4 ) to y e llo w is h - g r a y (5Y 7 /2 ) ; c o a r s e s i l t , v e ry fin e s a n d , minor c l a y , som e d ia ­ to m ite la m in a tio n s; l o o s e , m oderate s lo p e , s lig h t ly la m in a te d , b a s e sharp . . 4 .10 E rosion s u r f a c e . P lio c e n e : Q uiburis Form ation (in co m p le te ): 58 57 56 55 54 53 D ia to m ite , im p u re, w h ite (N 9); prim arily d ia to m s w ith c l a s t i c im p u rities; l o o s e , m oderate s lo p e , w e a th e rin g crum bly; top u n co n fo r m a b le , b a s e s h a r p ..................... D ia to m ite , im p u re, w h ite (N 9) to y e llo w is h gray (5Y 7 /2 ) ; prim arily d ia to m s w ith sa n d y s i l t im p u r itie s; g ood e x p o s u r e , firm , m oderate s lo p e , lam in ated ; b a s e s h a r p .......................................................................... 2 4 .7 1 S a n d , s i l t y , y e llo w is h - g r a y (5Y 7 /2 ) ; v ery fin e s a n d , c o a r s e s ilt ; l o o s e , s lo p e , s lig h t ly lam in a ted ; b a s e sharp; sa m p le C C - 1 - 8 0 .................................................................... 1 0 .3 1 Diatomite, impure; similar to unit 55 . . . . 1 0 .61 71 U n it N o. 52 51 50 D e s c r ip tio n T h ic k n e ss in m eter Ft P o r c e la n ite , s i l t y , g r a y ish y e llo w g reen (5GY 7 /2 ) on w e a th e re d s u r f a c e , g r e e n is h - g r a y (5GY 6 /1 ) on fresh su r fa c e; v itr e o u s lu s te r com m on; s i l t g r a in s in o p a l i n e - s i l i c a m a trix , c o n c h o id a l fr a c tu r e , v ery h ard , b r ittle; forms b e n c h , w e a th e r s b lo c k y , preferred h o r iz o n ta l a lig n m en t o f g r a in s , c o n ta c ts sharp but u n dulatory t e x tu r e , d e fin ite h o rizo n but not c o n tig u ­ o u s , t h ic k n e s s v a r ia b le , bottom portion h a s o r a n g ish iron o x id e r in g le t s t a i n s , h o r iz o n ta lly a lig n e d b la c k c a rb o n a c e o u s p la n t d e b r is com m on; b a s e s h a r p .............. 5 S a n d , s i l t y , g r a y ish orange pink (SYR 7 /2 ) ; v e ry fin e sa n d and c o a r s e s ilt; n o n c o n ­ tig u o u s u n its b e tw e e n tw o s i l t y p o r c e l­ a n ite s ; l o o s e , sp o r a d ic grow th o f c a lc it e c r y s ta ls up to 1 in . (3 cm) lo n g . 1 .0 3 0 .1 3 P o r c e la n ite , s ilty ; s im ila r to u n it 52; b a s e sharp; sa m p le C C - 1 - 7 7 .................................. 1 2 .3 6 D ia t o m it e - s ilt s e q u e n c e , w h ite (N 9) to y e llo w is h - g r a y (5Y 8 /1 ) ; d ia to m s , c o a r s e s ilt ; firm , c l i f f , th in a lte r n a tin g b e d s o f d ia to m ite and s i l t , rhythm ic; b a s e s h a r p ............................................ .................... 1 6 .4 6 S ilt , s a n d y , y e llo w is h - g r a y (5Y 7 /2 ) to m oderate y e llo w (5Y 9 /6 ) ; c o a r s e s i l t , v ery fin e s a n d , minor c la y ; lo o s e ; iron o x id e r in g le t s ta in s common; b a s e sharp .......................................................................... 2 .0 5 47 P o r c e la n ite , s ilty ; sim ila r to u n it 5 2 .............. 4 .1 0 48 S i l t , v e ry s a n d y , y e llo w is h - g r a y (5Y 7 /2 ) ; v ery fin e s a n d , c o a r s e s i l t , minor c la y ; lo o s e ; b a s e sharp; sa m p le C C -1 -7 3 . . . 4 .4 1 4 .4 1 49 48 45 S i l t , v ery p a le g r a y ish orange (10YR 7 /2 ) ; s i l t , c l a y , minor s a n d , s lig h t ly c a l ­ c a r e o u s; lo o s e ; b a s e sharp; sa m p le C C - 1 - 7 2 .................................................................... 1 1 72 Unit No. 44 43 42 41 40 Description Thickness in meter Ft D ia to m ite , p u r e , w h ite (N 9); g ood e x p o s u r e , firm , b e n c h , c l i f f , no apparent b ed d in g; b a s e s h a r p ................................................................ .61 S i l t , v ery s a n d y , y e llo w is h - g r a y (5Y 7 /2 ) ; c o a r s e s i l t , v ery fin e s a n d , minor c la y , v e ry s lig h t ly c a lc a r e o u s ; l o o s e , v e ry th in b e d d in g , a p p a ren tly due to s lig h t c o lo r v a r ia tio n ; b a s e sharp; sa m p le C C - 1 - 6 9 .................................................................... .10 Sandy s ilt-d ia to m ite s e q u e n c e , y e l l o w i s h gray (5Y 7 /2 ) to w h ite (N 9); c o a r s e s i l t , v ery fin e s a n d , c la y ; firm , v ery th in a lte r n a tin g b e d s o f d ia to m ite and s i l t , rhythm ic; b a s e sharp; sam p le C C - 1 - 6 8 . .3 1 S a n d , v e ry p a le g r a y ish orange (10YR 7 /2 ) ; fin e to v ery fin e s a n d , q u a rtz , and h e a v y m in eral g r a in s; m o d era tely so rted ; lo o s e ; sharp b a s e ; sa m p le C C -1 -6 7 . . . .0 8 San dy s ilt - d ia t o m it e s e q u e n c e , sim ila r to u n it 4 2 ....................................................................... .1 3 39 S a n d , s im ila r to u n it 4 1 ......................................... 38 S i l t , s a n d y , g r a y ish orange pink (SYR 7 / 2 ) , grad in g in to y e llo w is h - g r a y (5Y 7 /2 ) ; c o a r s e s i l t , v ery fin e s a n d , c la y , s lig h t ­ ly c a lc a r e o u s ; l o o s e , v e ry th in b ed d in g s lig h t ly apparent; b a s e sh a rp . . ................. 2 .0 5 10 .2 5 37 D ia t o m it e - s ilt s e q u e n c e , sim ila r to u n it 49 1 6 .4 6 36 S il t , s a n d y , g r a y ish orange pink (SYR 7 / 2 ) , grading in to y e llo w is h - g r a y (5Y 8 /1 ) ; c o a r s e s i l t , v e ry fin e s a n d , c la y , m od­ e r a te ly c a lc a r e o u s , m a fic m ineral g r a in s abundant; firm , c l i f f , v ery th in b ed d in g due to grain s iz e c h a n g e s and s lig h t c o lo r v a r ia tio n ; iron o x id e r in g le t s ta in s at top; b a s e sharp; sa m p le C C -1 -6 2 . . . 3 6 1 .0 7 D ia t o m it e - s ilt s e q u e n c e , sim ila r to u n it 49; sam p le C C - 1 - 5 9 ................................................... 5 11 1 .8 0 35 73 Unit No. 34 33 32 31 30 29 28 27 Description S i l t , s a n d y , g r a y ish orange pink (SYR 7 /2 ) ; c o a r s e s i l t , v e ry fin e s a n d , minor c l a y , m a fic m in eral g ra in s a b u n d a n t, m o d era te­ ly c a lc a r e o u s ; firm to l o o s e , s te e p s lo p e ; v e r y th in b ed d in g due to ban din g o f m a fic m in eral g r a in s and sa n d y la y e r s ; b a s e s h a r p .......................................................................... Ft 1 Thickness in meter 7 .4 8 A sh , v o lc a n ic , v e ry lig h t gray (N 8); c o a r s e s i l t , fr e sh u n a ltered p u m iceo u s v o lc a n ic g l a s s s h a r d s , w e ll so rted ; lo o s e ; b a s e sharp but i r r e g u l a r ................. S i l t , s a n d y , sim ila r to u n it 34; sa m p le C C -1 -5 5 .................................................................... .5 7 0 .0 1 2 .1 4 S ilt s t o n e , c a lc a r e o u s , g r a y ish orange pin k (SYR 7 /2 ) to w h ite (N 9); c o a r s e s i l t , v e ry fin e s a n d , c a lc a r e o u s cem en t; hard to fr ia b le , form s b en ch ; s lig h t b ed d in g to v e ry th in b e d d in g , s p lit s fla g g y a t top; b a s e s h a r p ................................................... 4 .1 0 D ia to m ite , s i l t y , y e llo w is h - g r a y (5Y 8 /1 ) ; d ia to m s , s i l t , s lig h t ly c a lc a r e o u s ; firm , no apparent b ed d in g ; b a s e g r a d a tio n a l . 6 .1 5 6 2 .2 9 1 .0 3 7 4 .7 5 S i l t , s a n d y , sim ila r to u n it 34; sa m p le C C -1 -5 1 .................................................................... 7 S a n d s to n e , c a lc a r e o u s b io t it ic , v e r y lig h t gray (N 8) to lig h t-g r a y (N 7); v ery fin e to fin e s a n d , m o s tly quartz w ith abundant fr e sh b i o t i t e , c a lc a r e o u s cem en t; form s s lig h t b e n c h , hard to fr ia b le , t h ic k n e s s v a r ie s from 0 . 5 to 3 in c h e s ( 1 .5 cm to 8 cm); b a s e s h a r p ................................................ S i l t , s a n d y , sim ila r to u n it 34; s a m p le s C C - 1 - 4 9 and C C - 1 - 4 6 ...................................... 15 74 Unit No. 26 25 24 23 22 21 Description S ilt-d ia to m ite s e q u e n c e , y e llo w is h -g r a y (5Y 8 /1 ) to g r a y ish orange pink (SYR 7 /2 ) to w h ite (N 9); s i l t , d ia to m s , s lig h t ly c a lc a r e o u s ; firm , v e ry th in to th in a lte r ­ n a tin g b e d s o f d ia to m ite , y e llo w is h - g r a y s i l t and g r a y ish oran ge p in k s i l t , rhyth­ m ic , y e llo w is h - g r a y s i l t may h a v e iron o x id e r in g le ts ; abundant g a s tr o p o d s , 4 in c h e s (10 cm) up from bottom c o n ta c t; b a s e s h a r p .................................................. ... 4 5 1 .3 5 P o r c e la n ite , s i l t y , s im ila r to u n it 52; y e llo w is h - g r a y (5Y 7 /2 ) w e a th e r e d , p a le - o l iv e (10Y 6 /2 ) fr e sh (co lo r and l u s ­ te r vary w ith th e d e g r ee o f c l a s t i c grain c o n te n t , the l e s s c l a s t i c s e d im e n ts g e n ­ e r a lly g iv e s a darker c o lo r and more v itr e o u s lu s te r and v ic e v e r s a , o th e r w is e th e s i l t y p o r c e la n ite u n its are a ll s im i­ lar); sa m p le C G - 1 - 3 6 ..................................... 1 0 .3 1 4 0 1 .2 2 D ia t o m it e - s ilt s e q u e n c e , sim ila r to u n it 4 9 , w h ite (N 9) to p a le g r e e n is h y e llo w (10Y 8 /2 ) to y e llo w is h - g r a y (5Y 7 /2 ) ; d ia ­ to m , s i l t , s lig h t ly c a lc a r e o u s to n o n c a lc a r e o u s ; firm , c l i f f , th in a lte r n a tin g b e d s o f d ia to m ite and s i l t , m a in ly d ia ­ to m ite; b a s e s h a r p ............................................ S ilt to s ilt y p o r c e la n it e , y e llo w is h - g r a y (5Y 7 /2 ) to lig h t o liv e brown (5Y 5 /6 ) ; s ilt ; s i l t irreg u la rly s i l i c i f i e d , nodular; firm to hard; b a s e s h a r p ................. ................ D ia t o m it e - s ilt s e q u e n c e , sim ila r to u n it 24; f o s s i l to o th e n a m e l found in d ia to m ite ; sa m p le C C - 1 - 3 2 ................................................... 6 2 D ia t o m it e - s ilt s e q u e n c e , sim ila r to u n it 24 19 P o r c e la n ite , s i l t y , sim ila r to u n it 5 2 , sa m p le C C - 1 - 3 1 ................................................... Diatom ite-silt sequence, similar to unit 24 .1 5 6 A sh , v o lc a n ic , s im ila r to u n it 33 (sam p le 6 / a , S carb orou g h , 1 9 7 5 ) .................................. 20 18 Thickness in meter Ft .7 9 .2 5 .0 1 5 .1 3 1 0 .3 1 1 4 .41 75 U n it N o. 17 D e s c r ip tio n T h ic k n e ss in m eter Ft S il t , s a n d y , g r a y ish -o r a n g e (10YR 7 /4 ) ; c o a r s e s i l t , v e r y fin e s a n d , c l a y , s lig h t ly c a lc a r e o u s ; firm c liff; b a s e s h a r p .......................................................................... 1 0 16 D ia t o m it e - s ilt s e q u e n c e , sim ila r to u n it 24 1 11 15 S i l t , s a n d y , g r a y ish orange pink (SYR 7 /2 ) ; c o a r s e s i l t , v e ry fin e s a n d , minor c la y , a sh shard g r a in s , v ery s lig h t ly c a lc a r e ­ o u s; l o o s e , v ery th in b ed d in g a p p aren t, sed im en ta ry grad in g o f a s h sh ard s; b a s e sharp; sa m p le C C - 1 - 2 6 .................................. 5 0 1 .5 3 A sh , v o lc a n ic , s im ila r to u n it 33; sa m p le C C - 1 - 2 5 (sam p le 6 1 , S carb orou gh , 1 9 7 5 ) .......................................................................... 1 0 .3 1 13 S i l t , s a n d y , s im ila r to u n it 3 4 ........................... 1 0 .3 1 12 D ia t o m it e - s ilt s e q u e n c e , sim ila r to u n it 2 4 , s i l t c o lo r s vary from y e llo w is h gray (5Y 8 /1 ) to g r a y ish orange pink (5YR 7 /2 ) to p a le y e llo w is h brown (10YR 6 /2 ); s a m p le s C C -1 -2 1 and C C - 1 - 2 2 ................. 1 14 11 10 9 S il t , s a n d y , y e llo w is h - g r a y (5Y 7 /2 ) ; c o a r s e s i l t , v ery fin e s a n d , minor c la y , s lig h t ly c a lc a r e o u s ; firm; b a s e sharp; sa m p le C C - 1 - 1 9 ................................................... S il t , s a n d y , p a le y e llo w is h brown (10YR 6 /2 ) to v e ry p a le orange (10YR 8 /2 ) ; c o a r s e s i l t , v e ry fin e s a n d , minor c la y , m a fic m ineral g r a in s , s lig h t ly c a lc a r e o u s ; firm , s lo p e , la m in a ted to v e ry th in b ed d in g ; b a s e sharp; sa m p le C C - 1 - 1 8 ........................ S i l t , y e llo w is h - g r a y (5Y 7 /2 ) ; s i l t , minor sa n d and c l a y , s lig h t ly c a lc a r e o u s ; firm , s lig h t ly la m in a ted ; b a s e sharp; sam p le C O - 1 - 1 5 ................................................................... 8 D ia t o m it e - s ilt s e q u e n c e , sim ila r to u n it 49 7 Silt, sandy, similar to unit 3 4 ....................... 2 0 .3 1 .5 8 4 .4 1 2 .0 5 1 .6 4 7 .1 8 3 3.5 .0 8 .09 76 U n it N o. 6 5 4 3 2 1 Ft D e s c r ip tio n A sh , v o lc a n ic , sim ila r to u n it 33; bottom c o n ta c t h ig h ly irregular; s o ft sed im e n t d eform ation ; sa m p le C G - 1 - 1 2 ..................... S i l t , s a n d y , sim ila r to u n it 34; c a lc a r e o u s sa n d s to n e l e n s e s p r e se n t; sam p le C C - 1 - 1 0 .................................................................... 8 A sh , v o lc a n ic , sim ila r to u n it 6; sa m p le C O -1 -1 9 (s a m p le 6 1 k , S ca rb o ro u g h , in p r e p .) ............................................ .............................. 11 S il t s t o n e , s a n d y , g r a y ish orange pink (SYR 7 /2 ) ; s i l t , v ery fin e s a n d , s ilic e o u s c e m e n t, s lig h t ly c a lc a r e o u s ; form s b en ch , h ard , b reak s b lo c k y , s lig h t la m in a tio n due to m a fic m in eral g r a in s; b a s e s h a r p . in a d d itio n 5 in c h e s cm) lo n g , and C C - 1 - 2 B a se c o v e r e d b y w a s h . T otal th ic k n e s s o f s e c t io n 3 .5 0 .0 9 0 2 .4 4 1 .5 S il t , s a n d y , sim ila r to u n it 34; c a lic h e n o d u le s in upper 6 f e e t ( 1 .8 m ), c a lc a r e ­ o u s s a n d sto n e l e n s e s 1 to 2 in c h e s (3 to 5 cm) th ic k and maximum o f 10 in c h e s (30 cm lo n g , w e ll c em en ted ; s a m p le s C C - 1 - 4 and C C - 1 - 7 ......................................... S i l t , s a n d y , sim ila r to u n it 34; h a s l e n s e s o f g r a v e lly s a n d , (13'cm ) th ic k , 18 in c h e s (54 c a lc a r e o u s ; sa m p le s C G -1 -1 T h ic k n e ss in m eter 4 .0 4 5 3 .4 8 8 .20 9 1 .4 5 3 3 7 .2 9 ____ 122 77 S tra tig ra p h ic S e c tio n C C -2 L o ca ted in S E 1 /2 S E 1 /4 N W 1 /4 s e c . 2 9 , T . 9 S . , R. 18 E . , P ep p ers a u c e W ash and C lark Ranch q u a d r a n g le s , a lo n g a g e n tly slo p in g rid g e in b ad lan d top ograp h y in C am el C anyon W ash 300 fe e t (90 m) e a s t o f d ia to m ite quarry; e x p o su r e are good ; b ed s dip 0 ° to 1 0 ° , strik e N . 6 5 ° W .; e le v a t io n at b a s e is a p p ro x im a tely 2 ,6 8 0 fe e t (831 m ). U n it N o. D e s c r ip tio n T h ic k n e ss in m eter Ft E ro sio n s u r f a c e . P le is t o c e n e and H o lo c e n e ; 70 A llu v ia l and p ed im en t g r a v e l s ........................... 10 0 3 .0 5 3 0 .9 2 1 .0 3 8 .5 3 .0 8 1 3 .3 3 E rosion s u r fa c e . P lio c e n e : Q u ib u ris Form ation (in co m p le te ): 69 68 D ia t o m it e - s ilt s e q u e n c e , w h ite (N 9) to y e llo w is h - g r a y (5Y 9 /2 ) ; d ia t o m s , s ilt ; good e x p o s u r e , firm , c l i f f , m ain ly th in d ia to m ite b e d s a lte r n a tin g w ith v e r y th in s i l t b e d s; s i l t h a s w h ite s ilic e o u s p la n t ste m s in v e r t ic a l p o s it io n , fe w mm in d i­ a m e te r, ra d ia tin g structure in c r o s s s e c ­ tio n ; top un con form ab le; b a s e sharp . . . F o r c e la n ite , s i l t y , lig h t o liv e gray (5Y 5 /2 ) to lig h t o liv e brow n (5Y 5 /6 ) ; s i l t , o p a l i n e - s i l i c a m atrix; d e fin ite h o rizo n but n ot c o n tig u o u s , th ic k n e s s v a r ia b le , nodular; b a s e s h a r p ............................................ 67 D ia t o m it e - s ilt s e q u e n c e , sim ila r to u n it 69 66 A sh , v o lc a n ic , v e ry lig h t gray (N 8); c o a r s e s i l t , fr e sh u n a lte re d p u m iceo u s v o lc a n ic g l a s s s h a r d s , w e ll so rted ; lo o s e ; b a s e sharp (sam p le 6 1 i, S ca rb o ro u g h , in p r e p .) ........................................................................... 65 D ia t o m it e - s ilt s e q u e n c e , sim ila r to u n it 69 1 11 78 U n it N o. 64 63 62 61 60 D e s c r ip tio n T h ic k n e ss in m eter Ft S i l t , s a n d y , y e llo w is h - g r a y (5Y 7 /2 ) ; c o a r s e s i l t , v e r y fin e s a n d , c la y ; firm , c l i f f , s lig h t ly la m in a ted ; b a s e gra d a ­ tio n a l; sa m p le C C - 2 - 5 7 .................................. 3 0 .0 8 S i l t , s a n d y , p a le g r a y ish orange (10YR 7 /2 ) ; c o a r s e s i l t , v e r y fin e s a n d , c la y , s lig h t ly c a lc a r e o u s ; lo o s e to firm , c l i f f , s lig h t ly lam in a ted ; b a s e sharp; sa m p le C C —1 - 5 4 ...................................................... 9 .2 3 A sh , v o lc a n ic , s im ila r to u n it 66; (sam ple 6 1 h , S carb orou g h , in p r e p . ) ........................ 5 .1 3 S i l t , s a n d y , sim ila r to u n it 64; in a d d itio n , s e c o n d a r y gyp su m n o d u le s are com m on . 10. .2 5 S il t , s a n d y , p a le g r a y ish orange (10YR 7 /2 ) ; c o a r s e s i l t , v e r y fin e s a n d s , c l a y , s lig h t ly c a lc a r e o u s ; g o o d e x p o s u r e , lo o s e to firm , h a s th in la m in a tio n s o f d ia to m ite , w h ite s il i c e o u s p la n t ste m s in grow th p o s itio n ; b a s e g r a d a tio n a l............................... 4 2 1 .2 7 59 S i l t , s a n d y , sim ila r to u n it 6 4 ........................... 1 0 .3 1 58 A sh , v o lc a n ic , sim ila r to u n it 66 (sa m p le 6 1 f, S carb orou g h , 1 9 7 5 ) .................................. 2 .0 5 2 1 .8 8 57 S an d y s ilt - d ia t o m it e s e q u e n c e , y e l l o w i s h gray (5Y 7 /2 ) to w h ite (N 9); c o a r s e , s i l t , v e ry fin e s a n d , c la y , d ia to m s , m o d era tely c a lc a r e o u s , lo o s e to firm , c l i f f , th in ly b e d d e d , s ilt y p o r c e la n ite ty p e o f h o r iz o n 3 fe e t (0 .9 m) up from b a s e ; w h ite s il i c e o u s p la n t ste m s co m ­ m on , som e bon e fragm en ts; b a s e sharp . 6 56 S i l t , s a n d y , sim ila r to u n it 6 3 ........................... 9 .2 3 55 A sh , v o lc a n ic , s im ila r to u n it 66 (sam p le 6 1 c , S ca rb o ro u g h , 1 9 7 5 ).................................. 2 .0 5 0 .3 1 54 S il t , s a n d y , sim ila r to u n it 6 3 ........................... 1 79 Unit No. 53 Description Thickness in meter Ft S i l t , d ia t o m it ic , y e llo w is h - g r a y (5Y 8 /1 ) ; s i l t grading in to purer d ia to m ite , c a l ­ c a r e o u s ; l o o s e , s lig h t ly lam in ated ; b a s e s h a r p ................................................................ 2 0 .0 5 52 S il t , s a n d y , sim ila r to u n it 63 1 4 .4 1 51 S i l t , d ia t o m itic , sim ila r to u n it 53 2 3 .6 9 50 P o r c e la n ite , s i l t y , g r a y ish y e llo w g reen (5GY 7 /2 ) on w e a th e r s u r fa c e , g r e e n is h gray (5GY 6 /1 ) on fr e sh s u r f a c e , v itr e o u s lu s te r com m on; s i l t g ra in s in o p a lin e s i l i c a m atrix, c o n c h o id a l fr a c tu r e , v e r y h ard , b r ittle ; form s b e n c h , w e a th e rs b lo c k y , preferred h o r iz o n ta l a lig n m en t o f g r a in s , c o n ta c ts sharp but u a d u la to r y , a d e fin ite h o r iz o n but th ic k n e s s v a r ia b le to d is c o n tin u o u s ; b la c k c a r b o n a c e o u s p la n t d e b r is com m on; b a s e s h a r p ........................... 1 2 .3 6 S il t , sa n d y to s i l t y sa n d y , y e llo w is h - g r a y (5Y 7 /2 ) ; c o a r s e s i l t , v ery fin e s a n d , s il i c e o u s c em en t at top; h igh s lo p e , lo o s e to s i l i c i f i e d at to p , v e ry th in b e d ­ d in g a p p a r e n t, fla g g y s p littin g a t top ; b a s e g r a d a t io n a l................................................... 3 0 .9 2 49 48 46 S a n d , g r a v e lly s i l t y , y e llo w is h - g r a y (5Y 7 /2 ) ; s a n d , c o a r s e s i l t , sm a ll p e b b le s , minor c la y ; c o a r s e g r a in s m a in ly f e l s i t e rock fr a g m e n ts , a n g u la r, p o o rly s o r te d , m o d era tely c a lc a r e o u s ; o b v io u s c h a n n e l d e p o s it , g r a d e s la te r a lly to sa n d y s ilt ; firm to l o o s e , h igh s lo p e ; bone fra g ­ m en ts com m on; b a s e sharp; sa m p le C C - 2 - 5 0 .................................................................... P o r c e la n ite , s i l t y p e b b ly , y e llo w is h - g r a y (5Y 7 /2 ) to p a le - o l iv e (10Y 6 /2 ) ; bottom 4 in c h e s (10 cm) t y p ic a l s ilt y p o r c e la n ite , sim ila r to u n it 50 but su d d en ly g r a d e s to p e b b ly c o n g lo m e r a te in o p a l i n e - s i l i c a m a trix , ro ck and bone fragm ents a b u n d a n t, b o n e s c a lc a r e o u s ; le n s y in a p p e a r a n c e , on e s m a ll p o c k e t w ith abundant g a s t r o p o d s , p la n t s te m s in v e r tic a l p o s itio n a ls o p r e s ­ en t; form s b e n c h , h a rd , w e a th e rs b lo c k y . 2 6 .7 6 80 D e s c r ip tio n d e fin ite h o rizo n but not c o n tig u o u s , v a r ia b le th ic k n e s s ; b a s e sharp; sa m p le C C -2 -4 9 .................................................................... Thickness in meter Ft 1 6 0 .4 6 45 S i l t , s a n d y , sim ila r to u n it 6 4 ............... 4 .1 0 44 P o r c e la n ite , s i l t y , sim ila r to u n it 5 0 .. 5 .1 3 43 S i l t , s a n d y , sim ila r to u n it 63; in a d d itio n , sa n d y s i l t w e d g e s in to d ia to m ite to th e n o r t h .............................................................. 9 .2 3 S i l t , s a n d y , sim ila r to u n it 64; sa m p le C G 2 - 4 3 .............................................................................. 5 42 41 S a n d , s i l t y , v ery p a le orange (10YR 8 /2 ) ; v ery fin e s a n d , c o a r s e s i l t , minor c la y , m o d era tely s o r te d , s lig h t ly c a lc a r e o u s ; lo o s e ; b a s e sharp; sa m p le G C -2 -4 2 . . . 40 P o r c e la n ite , s i l t y , sim ila r to u n it 5 0 .. 9 39 S i l t , s a n d y , sim ila r to u n it 62; sa m p le C C - 2 - 4 0 .................................................................... 2 38 P o r c e la n ite , s i l t y , sim ila r to u n it 5 0 . 5 37 M ud, p a le y e llo w is h brown (10YR 6 /2 ) ; s i l t , c la y , minor san d ; lo o s e ; b a s e sharp . . . 36 S ilty p o r c e la n ite s e q u e n c e , g r e e n is h -g r a y (5GY 6 /1 0 ) to lig h t o liv e gray (5Y 5 / 2 ) , w h ite (N 9); t y p ic a l o p a lin e s i l t s t o n e , sim ila r to u n it 5 0 , in terb ed d ed w ith w h ite s i l i c e o u s la y e r s ; w h ite la y e r s m o d era tely h ard , form s b en ch ; b a s e s h a r p .......................................................................... 35 S a n d , s i l t y , sim ila r to u n it 4 1 ........................... 34 S ilty p o r c e la n ite s e q u e n c e , sim ila r to u n it 3 6 ................................................................................. 33 32 1 3 M ud, s im ila r to u n it 36; in a d d itio n , bottom c o n ta c t s i l i c i f i e d ..................................... ... Porcelanite, silty , similar to unit 50........... 1 4 1 .6 3 3 .0 8 .2 3 6 .7 6 .1 3 5 .1 3 10 .5 6 7 .1 8 10 1 .1 7 7 .1 8 0 .31 81 Unit No. 31 30 29 28 Description Thickness in meter Ft S i l t , s a n d y , y e llo w is h - g r a y (5Y 7 /2 ) ; c o a r s e s i l t , v e r y fin e s a n d , minor c la y ; go o d e x p o s u r e , l o o s e , c l i f f , s lig h t a p ­ p ea r a n c e o f c r o s s -b e d d in g but o b sc u r ed by w a sp bore h o le s ; b a s e s h a r p ................. 1 10 S il t , p a le g r a y ish orange (10YR 7 /2 ) ; s i l t , c l a y , minor sand; firm , d o m in a te d , b a s e sharp; sa m p le C C - 2 - 3 4 .................................. 1 7 M u d , y e llo w is h - g r a y (5Y 7 /2 ) ; s i l t and c la y w ith minor sand; 1 -in c h (3 cm) s ilt y p o r c e la n ite la y e r in mud u n it; lo o s e e x c e p t for o p a lin e la y e r; b a s e sharp; sa m p le 0 0 - 2 - 3 2 .................................................................... S a n d , s i l t y , y e llo w is h - g r a y (5Y 7 /2 ) ; v ery fin e s a n d , c o a r s e s i l t , minor c l a y , m o d era tely c a lc a r e o u s ; g o o d e x p o s u r e , firm to l o o s e , very th in b ed d in g a p p a ren t, le n s y w ith s lig h t ly c o a r se r grain ed s a n d , fe w bone fragm en ts; b a s e sharp; sam p le O C -2 -3 0 ................. . ........................... ................ 2 0 .5 6 .4 8 6 .1 5 0 .6 1 10 .2 5 27 P o r c e la n ite , s i l t y , sim ila r to u n it 6 0 .............. 26 S a n d , s i l t y , sim ila r to u n it 2 8 ............................ 25 P o r c e la n ite , s i l t y , sim ila r to u n it 5 0 ............... 24 S i l t , s a n d y , sim ila r to u n it 64; sa m p le C C 2 - 2 8 .............................................................................. 1 8 .5 1 P o r c e la n ite , s i l t y , sim ila r to u n it 50; in a d ­ d it io n , p la n t ste m s com m on, s p lit s f la g ­ g y at t o p ................................................................... 1 0 .3 1 23 1 0 .3 1 3 .0 8 22 S il t , s a n d y , sim ila r to u n it 64 ............................ 3 0 .9 2 21 S ilty p o r c e la n ite s e q u e n c e , sim ila r to u n it 3 6 ....................................................................... 1 2 .3 6 M ud, y e llo w is h - g r a y (5Y 7 /2 ) ; s i l t , c l a y , minor s a n d , s lig h t ly c a lc a r e o u s ; l o o s e , s lo p e ; sa m p le C O -1 - 2 6 . . . . ..................... 5 .1 3 Silt, sandy, similar to unit 6 4 ......................... 7 .18 20 19 82 U n it N o. 18 D e s c r ip tio n Thickness in meter Ft S il t s t o n e , s a n d y , y e llo w is h - g r a y (5Y 7 /2 ) ; v e ry fin e s a n d , s i l t , s ilic e o u s c e m e n t, s lig h t ly c a lc a r e o u s ; g o o d e x p o s u r e , hard, form s b en ch ; v ery th in b ed d in g ap parent; b a s e s h a r p ............................................ 8 0 .0 5 17 P o r c e la n ite , s ilt y ; sim ila r to u n it 5 0 .............. 8 .2 0 16 S ilt s t o n e , sa n d y ; sim ila r to u n it 1 8 .............. 4 .1 0 15 S a n d , s ilt y ; sim ila r to u n it 28; Sam ple C C -2 -2 2 . ................................................................ 1 10 .5 6 S a n d s to n e , c a lc a r e o u s , y e llo w is h - g r a y (5Y 7 /2 ) ; fin e s a n d , s i l t , fin e c r y s t a l­ lin e c a lc a r e o u s cem en t; f r ia b le , form s b e n c h , v ery th in b ed d in g o b v io u s on w e a th e re d su r fa c e ; b a s e g r a d a tio n a l . . . 1 6 .4 6 10 .2 5 14 13 12 L im e sto n e , s a n d y , a lg a l, g r a y is h - y e llo w (5Y 8 /4 ) on w e a th e re d su r fa c e to d u s k y y e llo w (5Y 6 /4 ) on fr e sh su r fa c e ; fin e c r y s ta llin e lim e s t o n e , c o a r s e san d g r a in s a b u n d a n t, s i l i c e o u s r e p la c e m e n t o b v io u s on w e a th e re d su r fa c e ; g o o d e x p o s u r e , h ard , form s b en ch ; a lg a e h a s p is o l i t i c and v e ry th in in d iv id u a l m atty stru ctu res w ith maximum le n g th 1 .5 in c h ie s (4 c m ), m ats h o r iz o n ta lly a lig n ed ; b a s e sharp; sa m p le C C - 2 - 2 0 ................................................... P o r c e la n ite , s ilt y ; sim ila r to u n it 50; in a d d itio n , s p lit s f la g g y , m ica fla k e s abundant on b ed d in g p la n e s ; sam p le C C - 2 - 1 9 .................................................................... 1 0 .3 1 S il t , v ery san d y; sim ila r to u n it 63; sa m p le C C - 2 - 1 8 .................................................................... 2 0 .6 1 10 D ia t o m it e - s ilt s e q u e n c e ; sim ila r to u n it 69 1 1 .3 3 9 P o r c e la n ite , s ilt y ; s im ila r to u n it 5 0 .............. 9 .2 3 8 D ia t o m it e - s ilt s e q u e n c e ; sim ila r to u n it 67; sam p le C C - 2 - 1 6 ................................................... 2 6 .7 6 S i l t , san d y; sim ila r to u n it 63; in a d d itio n . p la n t ste m s are p r e se n t; sam p le C C -2 -1 4 2 1 .6 4 11 7 83 U n it N o. D e s c r ip tio n 6 A sh , v o lc a n ic ; sim ila r to u n it 6 6 ........................ 2 0 .0 5 5 S i l t , s a n d y , p a le g r a y ish orange (10YR 7 /4 ) ; c o a r s e s i l t , v ery fin e s a n d , c la y , c a l ­ c a r e o u s , upper 2 fe e t (0 .6 m) c a lic h if ie d ; l o o s e , s lo p e , la m in a ted b ed d in g; w h ite s il i c e o u s p lan t ste m s abundant; b a s e g r a d a tio n a l; sam p le C C - 2 - 1 1 ........................4 0 1 .2 2 0 .3 1 S i l t , sa n d y ; sim ila r to u n it 63; s a m p le s C C - 2 - 5 and C C - 2 - 4 ............................................ 13 5 4 .0 9 S a n d s to n e , c a lc a r e o u s b io t it ic , v e r y lig h t gray (N 8) to lig h t-g r a y (N 7); v ery fin e to fin e s a n d , g r a in s m o stly quartz w ith abundant u n a lte re d b io t it ic f l a k e s , c a l ­ c a r e o u s cem en t; forms s lig h t b e n c h , hard to fr ia b le , th ic k n e s s v a r ie s ; b a s e sharp . 1 4 3 2 Ft M ud, y e llo w is h - g r a y (5Y 7 /2 ) ; s i l t , c l a y , minor s a n d , s lig h t ly c a lc a r e o u s , h a s ir­ regu lar w h ite s p o ts (plant s te m s? ); l o o s e , s lo p e , th in la m in a tio n s; b a s e s h a r p .............................................................................. 1 S il t , sa n d y ; sim ila r to u n it 63; sa m p le C C - 2 - 1 .......................................................................... 9 T h ic k n e s s in m eter CO o 1 " 11 3 .0 2 8 4 0 .7 7 B a se c o v e r e d b y w a s h . T otal th ic k n e s s o f s e c t io n 133 84 S tratig ra p h ic S e c tio n C C -3 L ocated in N W 1 /4 N E 1 /4 N W 1 /4 s e c . 2 9 , T . 9 S . , R. 18 E . , Clark Ranch q u a d r a n g le , a lo n g a m o d era tely s lo p in g c l i f f about 500 fe e t (155 m) e a s t o f a d ia to m ite quarry; b e d s n ea rly h o r iz o n ta l; e x p o su re are good; b a s e e le v a t io n a p p ro x im a tely 2 ,8 5 0 f e e t (884 m ). U n it N o. • D e s c r ip tio n T h ic k n e ss Ft in m eter E rosion s u r f a c e . P le is t o c e n e and H o lo c e n e : 39 A llu v ia l and p ed im en t g r a v e l s ...............................^ 20 . 0 .,6 .1 0 ' *. ’> E rosion s u r f a c e . P lio c e n e : Q uiburis Form ation (in co m p le te ): 38 37 36 35 34 S i l t , s a n d y , lig h t-b r o w n (SYR 6 /4 ) to g r a y ish orange pink (SYR 7 /2 ) ; c o a r s e s i l t , v ery fin e s a n d , c l a y , m o d era tely c a lc a r e o u s ; l o o s e , s lig h t ly la m in a ted sa n d y le n s y la y e r s com m on; h ig h s lo p e ; top u n co n fo rm a b le , b a s e s h a r p ...................................................... 1 S a n d s to n e , s i l t y , g r a y ish orange pink (SYR 7 /2 ) ; v e r y fin e s a n d , c o a r s e s i l t , minor c la y , c a lc a r e o u s cem en t; fr ia b le; b a s e sharp; sam p le C C - 3 - 2 1 ..................................... 0 .3 1 3 .0 8 S il t , sa n d y ; sim ila r to u n it 38; sa m p le C C - 3 - 2 0 .......................................................................... 2 0 .6 1 A sh , v o lc a n ic , v ery lig h t gray (N 8); c o a r s e s i l t , fr e sh u n a lte re d p u m iceo u s v o lc a n ic g l a s s s h a r d s , w e ll- s o r t e d ; lo o s e ; b a s e sharp; (sam ple 61m , Scarb orou gh , in p r e p . ) .............................................................................. 1 5 .4 3 9 .2 3 S il t , sa n d y ; sim ila r to u n it 38; sa m p le C C -3 -1 8 85 U n it N o. 33 D e s c r ip tio n T h ic k n e ss in m eter Ft S a n d , s lig h t ly g r a v e lly s i l t y , p a le g r a y ish orange (10YR 7 /4 ) ; s a n d , s i l t , minor c la y , g r a n u le s com m on, g ra in s m ain ly q u a rtz, v o lc a n ic rock fr a g m e n ts , a n g u la r, m oder­ a t e ly c a lc a r e o u s ; l o o s e , very th in b e d ­ d in g; b a s e g r a d a tio n a l; sa m p le C C -3 -1 7 . 1 0 .3 1 32 S i l t , sa n d y ; sim ila r to u n it 3 8 ............................... 1 0 .3 6 31 S a n d , s ilt y ; sim ila r to u n it 33; sa m p le C C - 3 - 1 6 .......................... 2 0 .6 1 15 0 4 .5 8 30 S i l t , s lig h t ly g r a v e lly , g r a y ish orange pink (SYR 7 /2 ) ; c o a r s e s i l t , c l a y , minor s a n d , g r a n u le s com m on , m o d era tely c a lc a r e o u s , g r a in s m a in ly q u a r tz , v o lc a n ic rock fra g ­ m e n ts, a n g u la r, p o o rly s o r te d , l o o s e , h igh s l o p e , v ery th in b ed d in g; b a s e sharp; sa m p le C C - 3 - 1 5 ..................................... 29 A sh , v o lc a n ic ; sim ila r to u n it 3 5 ........................ 4 .1 0 28 S i l t , sa n d y ; sim ila r to u n it 38 ............................... 6 6 1 .9 8 27 A s h , v o lc a n ic ; sim ila r to u n it 35; (sam p le 61r, S carb orou gh , in p r e p .) .............................. 5 0 1 .5 3 A sh , d e v itr ifie d v o lc a n ic , p in k -g r a y (SYR 8 /1 ) ; a lte r in g p u m ic eo u s v o lc a n ic g l a s s s h a r d s , b e n to n itic ; lo o s e to firm; b a s e s h a r p .............................................................................. 5 .1 3 24 S i l t , san d y; sim ila r to u n it 3 8 ............................... 6 .1 5 23 G r a v e l, c a lc a r e o u s, s a n d y , p a le g r a y ish orange (10YR 7 .2 ) ; s a n d , g r a n u le s , g ra in s m a in ly q u a r tz , v o lc a n ic rock fr a g m e n ts , a n g u la r , p o o rly s o r te d , c a lc a r e o u s cem en t; hard to fr ia b le; b a s e s h a r p ............................... 6 .1 5 0 3 .0 5 9 .2 3 26 22 S il t , sa n d y ; sim ila r to u n it 38 ............................... 21 A sh , v o lc a n ic ; sim ila r to u n it 3 5 ........................ 20 S il t , sa n d y ; sim ila r to u n it 38; lo w er 15 f e e t (3 m) o f s e c t io n c o v er e d ; sa m p le C C -3 -1 2 31 0 9 .4 6 S il t , sa n d y ; sim ila r to u n it 38; sa m p le C C - 3 - 1 1 ....................................................................... 6 0 1 .8 3 19 10 86 Unit N o. Description 18 A sh , v o lc a n ic ; sim ila r to u n it 3 5 ........................ 17 S il t , sa n d y ; sim ila r to u n it 38; in a d d itio n , h a s c a lic h if ie d n o d u le s; sharp b a s e . . . . 16 15 14 S i l t , sa n d y ; sim ila r to u n it 38; at b a s e g ra v ­ e l l y s i l t y san d le n s e ; b a s e sharp; s a m p le s C C - 3 - 1 0 and C C - 3 - 1 0 a ..................................... 2 10 .8 6 0 .6 1 2 .0 5 3 .3 8 5 .1 3 5 2 .5 7 D ia to m ite , p u r e , w h ite (N 9); d ia to m s; g o o d e x p o s u r e , firm , m a s s iv e ; b a s e sharp . . . 11 P o r c e la n ite , s i l t y , d u s k y -y e llo w (5Y 6 /4 ) to lig h t o liv e gra y (5Y 6 /1 ) ; s i l t in o p a lin e s i l i c a m atrix, c o n c h o id a l fr a c tu r e , v e ry h ard , b r ittle ; irregular t h ic k n e s s , d e fin ite h o rizo n but not c o n t ig u o u s , preferred hor­ iz o n ta l a lig n m en t o f g r a in , th in se a m s to irregular 2 - f o o t (0 .6 1 m) th ic k b lo c k s , c h a lc e d o n ic tu b u le s in b lo c k s ; b a s e sharp; sam p le C C - 3 - 9 ......................................... 6 1 .2 2 .9 2 D ia to m ite , p u re; sim ila r to u n it 1 4 ..................... 7 0 0 12 8 4 .0 1 3 A sh , v o lc a n ic ; sim ila r to u n it 3 5 ........................ 9 .5 D ia to m ite , im p u re, w h ite (N 9); m a in ly d ia ­ to m s , som e s i l t , grading to pure d ia to m ite at top; good e x p o s u r e , firm; b a s e g rad a­ tio n a l .............................................................................. 13 10 Thickness in meter Ft D ia t o m it e - s ilt s e q u e n c e ; w h ite (N 9) to g r a y ­ is h oran ge p in k (SYR 7 /2 ) ; d ia to m s , c o a r s e s ilt ; go o d e x p o s u r e , firm , c l i f f , v ery th in to th in a lte r n a tin g b e d s o f d ia to m ite and s i l t , rhythm ic; b a s e g r a d a t io n a l..................... 2 1 8 A sh , v o lc a n ic ; s im ila r to u n it 35; sa m p le C C - 3 - 6 .......................................................................... S i l t , sa n d y ; sim ila r to u n it 38; sa m p le C C -3 -3 . ............................................................. 6 6 A sh , d e v itr ifie d , v o lc a n ic ; sim ila r to u n it 25; sa m p le C C - 3 - 5 .......................................................... Silt, sandy; similar to unit 3 8 .......................... 3 2 1 5 .1 5 1 .9 1 .0 5 .43 87 U n it N o. 5 D e sc r ip tio n Ft T h ic k n e ss m eter in S i l t , s a n d y , y e llo w is h - g r a y (5Y 7 /2 ) ; c o a r s e s i l t , v e r y fin e s a n d , c la y , v e r y s lig h t ly c a lc a r e o u s ; g ood e x p o s u r e , firm; b a s e sharp; sam p le C G - 3 - 4 .............. 8 0 .2 0 4 S i l t , sa n d y ; sim ila r to u n it 3 8 ........................... . 7 .1 5 3 S il t , sa n d y ; sim ila r to u n it 5 .................................. 3 .0 8 2 S i l t , sa n d y ; sim ila r to u n it 38; in a d d itio n , 1 fo o t (0 .3 1 m) c a lic h if ie d la y e r a t top ; b a s e s h a r p ................................................................... 4 2.85 1 S a n d , s lig h t ly g r a v e lly , s ilt y ; sim ila r to u n it 33; b a s e at bottom o f w a sh ; sa m p le C C - 3 - 1 ....................................................................... 9 10 .2 5 B ase c o v e r e d b y w a s h . T otal th ic k n e s s o f s e c t io n 148 2 45.19 88 S tratig ra p h ic S e c tio n C C -4 L o ca ted in N E 1 /4 N E 1 /4 N E 1 /4 s e c . 29 and N W 1 /4 N W 1 /4 N W 1 /4 s e c . 2 8 , T . 9 S . , R. 18 E . , C lark Ranch q u a d r a n g le , a lo n g a m o d era tely s te e p rid ge; e x p o s u r e s are g oo d ; top o f m easu red s e c t io n is ap p ro x im a tely 100 f e e t (30 m) s o u th -s o u th e a s t o f s e c t io n corner o f s e c s . 2 0 , 2 1 , 2 8 , and 29; e le v a t io n a t b a s e is a p p ro x im a tely 2 ,7 9 0 fe e t (875 m ). U n it N o. D e s c r ip tio n T h ic k n e ss in m eter Ft E rosion s u r f a c e . P le is t o c e n e and H o lo c e n e ; 15 A llu v ia l and p ed im en t g r a v e l s .............................. 29 0 8 .8 5 S a n d , g r a v e lly , s ilt y to s lig h t ly g r a v e lly , sa n d y s i l t s e q u e n c e , v ery p a le orange (10YR 8 /2 ) to g r a y ish -o r a n g e (10YR 7 /4 ) ; c o a r s e s i l t , s a n d , minor c la y , g ra n u les com m on, g r a in s m a in ly q u a rtz, v o lc a n ic rock fr a g m e n ts, a n g u la r, poor s o r tin g , s lig h t ly c a lc a r e o u s ; l o o s e , h ig h s lo p e , th in b e d d in g , g r a v e lly le n s e s com m on, c a lic h e la y e r s com m on; b a s e sharp; sa m p le s C C - 4 - 1 2 , C C - 4 - 1 4 , C C -4 -1 8 . . 103 6 3 1 .5 7 A sh , v o lc a n ic , v e ry lig h t gray (N 8); c o a r s e s i l t , fr e sh u n a lte re d p u m iceo u s v o lc a n ic g l a s s s h a r d s , w e ll- s o r t e d ; lo o s e ; b a s e s h a r p .............................................................................. 2 .0 5 4 2 .5 4 E rosion s u r f a c e . P lio c e n e : Q u ib u ris Form ation (in co m p le te ): 14 13 12 S il t , s lig h t ly g r a v e ll y , sa n d y ; sim ila r to u n it 14; in a d d itio n , w h ite s ilic e o u s p la n t ste m s v e ry com m on; b a s e s h a r p .................... 11 A sh , v o lc a n ic ; s im ila r to u n it 1 3 ................. 10 S il t , s a n d y , p a le g r a y ish orange (10YR 7 /2 ) ; c o a r s e s i l t , v e ry fin e s a n d , c la y ; lo o s e ; abundant w h ite s ilic e o u s p la n t ste m s in v e r t ic a l p o s itio n ; b a s e sharp; sa m p le C C —4 —8 a ....................................................................... 8 7 1 0 .1 8 .3 1 89 U n it N o. 9 8 D e s c r ip tio n S i l t , s lig h t ly g r a v e lly , sa n d y ; sim ila r to u n it 14 .......................................................................... 5 4 3 2 1 3 A sh , v o lc a n ic ; s im ila r to u n it 1 3 ........................ S i l t , s lig h t ly g r a v e lly , sa n d y ; sim ila r to u n it 14; sa m p le C C - 4 - 8 ..................................... 6 Thickness in meter Ft 2 A s h , d e v it r if ie d ,v o lc a n ic , w h ite (N 9); a lte r ­ in g p u m ic eo u s v o lc a n ic g l a s s s h a r d s , b e n ­ to n itic ; firm; b a s e s h a r p ..................................... 2 0 .9 7 2 .0 5 8 .8 1 6 .1 5 37 8 1 1 .4 9 5 0 1 .5 3 S i l t , s a n d y , g r a y ish oran ge pink (SYR 7 /2 ) ; c o a r s e s i l t , v ery fin e s a n d , c l a y , m oder­ a t e ly c a lc a r e o u s ; firm , c l i f f , c h a n n e l le n s e s 1 to 3 in c h e s (3 to 8 cm) th ic k and 1 to 10 fe e t (0 .3 to 3 m) long are abundant, le n s e s are w e a k to s tr o n g , c a lc a r e o u s ly c e m e n te d , a n gu la r v o lc a n ic p e b b le s , c a l i ­ c h e la y e r s com m on; b a s e sharp; s a m p le s C C - 4 - 5 and C C - 4 - 6 ............................................ 24 0 7 .3 2 S i l t , s a n d y , g r a y ish orange pink (SYR 7 /2 ) to v ery p a le orange (10YR 8 /2 ) ; c o a r s e s i l t , v e ry fin e s a n d , c l a y , s lig h t ly c a l ­ c a r e o u s ; firm , v ery th in to la m in a ted b e d ­ d in g , s p lit s fla g g y in p la c e s ; g r e e n is h y e llo w p la n t str u c tu r es com m on; b a s e sharp; sa m p le C C - 4 - 3 ......................................... 7 0 B e n to n ite , p in k -g r a y (SYR 8 /1 ) ; c l a y , s o a p y te x tu re ; b la c k s p e c k s common; g o o d e x ­ p o s u r e , firm; b a s e at bottom o f w a s h . . . . 1 0 S i l t , s lig h t ly g r a v e lly , sa n d y to s lig h t ly g r a v e lly , s ilt y sa n d s e q u e n c e ; sim ila r to u n it 14 but no g r a v e lly le n s e s ; sa m p le C C - 4 - 9 .......................................................................... C a lic h e p a le o s o l, v e ry p a le orange (10YR 8 /2 ) ; c a lic h if ie d sa n d y s i l t layer; g o o d e x p o s u r e , h ard , form s b en ch ; b a s e irregu ­ l a r ..................................................................................... 2 .1 4 .3 1 B a se c o v e r e d b y w a s h . T o ta l th ic k n e s s o f s e c t io n 224 1 6 8 .3 5 90 S tra tig ra p h ic S e c tio n C C -5 L ocated in S W 1 /4 S E 1 /4 N E 1 /4 s e c . 2 1 , T . 9 S . , R. 18 E . , C lark Ranch q u a d r a n g le , a lo n g a s te e p s lo p e d ca n y o n w a ll in W h itlo c k W ash a p p ro x im a tely 1 ,2 0 0 f e e t (366 m) s o u th e a s t o f B .M . 3209; e x p o s u r e s are good ; b e d s dip 3 ° to 7 ° S W .; e le v a t io n at b a s e is a p p ro x im a tely 3 ,1 2 0 f e e t (967 m ). U n it N o. D e s c r ip tio n T h ic k n e s s Ft in m eter E rosion s u r f a c e . P le is t o c e n e and H o lo c e n e ; 15 A llu v ia l and p ed im en t g r a v e l s ............................... 45 0 1 3 .7 3 E rosion s u r f a c e . P lio c e n e : Q u ib u ris Form ation (in co m p le te ): 14 13 12 S il t , s lig h t ly g r a v e lly , s a n d y , p a le g r e e n is h y e llo w (10Y 8 /2 ) ; c o a r s e s i l t , s a n d , c l a y , g r a n u le s , g ra in s m a in ly q u a r tz , h e a v y m in era ls com m on, p e b b ly v o lc a n ic rock fragm ents com m on; a n g u la r, poor s o r tin g , s lig h t ly c a lc a r e o u s ; l o o s e , s lo p e , v e ry th in b ed d in g apparent; top u n co n fo r m a b le , b a s e s h a r p ................................................................ P r o c e la n ite , s i l t y , y e llo w is h - g r a y (5Y 8 /1 ) on w e a th e re d s u r f a c e , lig h t o liv e gray (5Y 5 /2 ) on fr e sh s u r fa c e , v itr e o u s lu s te r com m on; s ilt g r a in s in o p a lin e s i l i c a m atrix, c o n c h o id a l fr a c tu r e , v e ry h ard, b r ittle ; good e x p o s u r e , form s b e n c h , w e a th e r s b lo c k y , preferred h o r iz o n ta l a lig n m e n t o f g r a in s , c o n ta c ts sharp but are u n d u a lto r y , d e fin ite h o rizo n but not c o n tig u o u s , v a r ia b le t h ic k n e s s ; b a s e sharp; sa m p le C C - 5 - 1 9 ..................................... L im e sto n e , y e llo w is h - g r a y (5Y 8 /1 ) ; v ery fin e c r y s ta llin e lim e s to n e ; hard to f r ia b le , no b ed d in g p r e s e n t , th ic k n e s s v a r ie s ; fe w g a str o p o d s 5 mm lon g; b a s e s h a r p .............. 2 8 .8 1 10 .2 5 6 .1 5 91 Unit No. 11 Description S i l t , s lig h t ly g r a v e lly , sa n d y ; sim ila r to u n it 15; g r a d e s in to g r a v e lly sa n d c h a n ­ n e l to th e north; b a s e s h a r p ............................... Thickness in meter Ft 1 6 0 .4 6 10 P o r c e la n ite , s ilty ; sim ila r to u n it 1 4 .................. 2 .0 5 9 L im esto n e; sim ila r to u n it 1 2 ................................... 3 .0 8 8 S il t , s lig h t ly g r a v e lly , sa n d y ; sim ila r to u n it 15; bon e fragm en ts a t upper c o n ta c t; b a s e sharp; sa m p le C C - 5 - 1 4 ........................... 3 S i l t , s lig h t ly g r a v e lly , sa n d y to s lig h t ly g r a v e lly , s i l t y sa n d s e q u e n c e , p a le g ra y ­ is h orange (10YR 7 /2 ) to y e llo w is h - g r a y (SYR 7 /2 ) ; c o a r s e s i l t , s a n d , c l a y , g r a n u le s com m on to ab u n d a n t, g r a in s m ain ly q u a rtz, h e a v y m in era ls com m on, v o lc a n ic rock fr a g m e n ts , a n g u la r , poor s o r tin g , c a lic h if ie d la y e r s com m on; lo o s e to firm , h ig h s lo p e , d is t in c t th in b ed d in g a lte r n a tin g b e tw e e n g r a y ish orange and y e llo w is h - g r a y , so m e g r a v e l­ ly sa n d b e d s or le n s e s ; b a s e g ra d a tio n a l; sa m p le s C C —5 —7 , GC—5—7 , G C —5 —9 , C C - 5 - 1 0 , C C - 5 - 1 1 , and C C - 5 - 1 3 .............. 51 0 1 5 .5 6 G r a v e l, s a n d y , p a le g r a y ish orange (10YR 7 /2 ) ; s a n d , g r a n u le s , sm a ll p e b b le s , minor s i l t and c l a y , g r a in s m ain ly quartz and v o lc a n ic ro ck fr a g m e n ts , a n g u la r, p o o rly sorted ; g o o d e x p o s u r e , firm; b a s e sharp; sa m p le C C - 5 - 5 ......................................... 1 1 .3 3 11 .8 9 7 .1 8 1 1.25 8 .20 7 6 5 4 3 2 S i l t , s lig h t ly g r a v e lly , sa n d y to s lig h t ly g r a v e lly , s ilt y san d ; sim ila r to u n it 7 . . . 7 2 S ilt , y e llo w is h - g r a y (5Y 7 /2 ) ; c o a r s e s i l t , c l a y , minor san d ; g o o d e x p o s u r e , firm . lam in ated ; b a s e g r a d a tio n a l............................... S ilt , s lig h t ly g r a v e lly , sa n d y to s lig h t ly g r a v e lly , s ilt y san d ; sim ila r to u n it 7; sa m p le C C —5 —3 .......................................................... Silt; similar to unit 4; sample CC-5-2 . . . . 4 1 .0 9 92 Unit No. 1 Description Ft S a n d , g r a v e lly ; sim ila r to u n it 7; b a s e at bottom o f w a s h ......................................................... Thickness in meter 10 0.25 8 35.28 B a se c o v e r e d by w a s h . T otal th ic k n e s s o f s e c t io n 115 93 S tra tig ra p h ic S e c tio n C C -6 L o ca ted in S W 1 /4 N E 1 /4 N E 1 /4 s e c . 2 1 , T. 9 S . , R. 18 E . , C lark Ranch q u a d r a n g le , a lo n g a c lif f e d w a ll in W h itlo c k W ash a p p ro x im a tely 1 , 3 0 0 fe e t (397 m) e a s t - n o r t h e a s t o f B . M . 3 2 0 9 ; g e n e r a l dip o f b e d s i s a fe w d e g r e e s w e stw a r d ; e le v a t io n at b a s e is a p p ro x im a tely 3 , 1 6 0 f e e t (980 m ). U n it N o. D e s c r ip tio n Ft T h ic k n e s s in m eter E ro sion s u r f a c e . P le is t o c e n e and H o lo c e n e : 2 A llu v ia l and p ed im en t g r a v e l s , approxim ate t h i c k n e s s .................................................................... 5 0 1.53 _0 16.78 0 18.30 E ro sion s u r fa c e . P lio c e n e : Q u ib u ris Form ation (in co m p le te ): 1 G r a v e l, lig h t-b r o w n (SYR 6 /4 ) ; p e b b le s , c o b b le s , s m a ll b o u ld e rs com m on in mud m a trix , g r a in s m a in ly dark c o lo r e d , f in e ­ g ra in ed a n d e s ite w ith p la g io c la s e p h e n o c r y s t s , oth er com m on grain ty p e s are r h y o lit e , a g g lo m e r a te , c h a lc e d o n ic q u a rtz, and s c h i s t , angu lar to s u b ­ rounded w ith s c h is t g r a in s com m on ly ro u n d ed , p o o rly so rted ; l o o s e , c l i f f , preferred h o r iz o n ta lly a lig n e d g r a in s , so m ew h a t graded; g r a v e l g r a d e s la te r a lly r a p id ly 300 f e e t (92 m) dow n th e w a sh in ­ to a lte r n a tin g th in b e d s o f s lig h t ly g r a v e lly s i l t y s a n d , sa n d y s i l t s , and sa n d y g r a v e ls , sco u r and grading p r e se n t; top u n co n fo rm a b le , b a s e d c o v e r e d by w a sh ; th ic k n e s s 55. a p p r o x im a te ................................................................ T otal th ic k n e s s o f s e c t io n 60 94 Stratigraphic Section CC-7 L o ca ted in N E 1 /4 S E 1 /4 S W 1 /4 s e c . 2 1 , T. 9 S . , R. 18 E . , C lark Ranch q u a d r a n g le , a lo n g a s t e e p ly s lo p e d w a ll in W h itlo c k W a sh a p ­ p ro x im a tely 3 , 0 0 0 f e e t (920 m) so u th o f B . M . 3 2 0 9 ; a s lig h t w e stw a r d dip o f b e d s ; e le v a t io n at b a s e is a p p ro x im a tely 3 , 0 4 0 f e e t (942 m ). U n it N o. D e s c r ip tio n T h ic k n e ss in m eter Ft E rosion s u r fa c e . P le is t o c e n e and H o lo c e n e : 4 A llu v ia l and p ed im en t g r a v e l s ............................... 10 0 3.05 E rosion s u r f a c e . P lio c e n e : Q u ib u ris Form ation (in co m p le te ): 3 2 1 S i l t , s lig h t ly g r a v e lly , sa n d y to g r a v e lly sa n d s e q u e n c e , g r a y ish orange p in k (SYR 7 /2 ) ; c o a r s e s i l t , s a n d , c la y , g r a n u le s com m on to a b u n d a n t, g r a in s m a in ly q u a rtz , h e a v y m in erals com m on , v o lc a n ic rock fr a g m e n ts , a n g u la r, poor s o r tin g , c a lic h if ie d la y e r s com m on; lo o s e to firm , h igh s l o p e , th in b e d d in g , g r a v e lly le n s e s com m on; top u n con form ab le, b a s e s h a r p ............................ 68 B e n to n ite , w h ite (N 9); c l a y , s o a p y tex tu re; b la c k s p e c k s com m on; firm; b a s e sharp . . 1 S i l t , s lig h t ly g r a v e lly , sa n d y ; s im ila r to u n it 3; b a s e c o v e r e d b y w a s h ........................ T o ta l th ic k n e s s o f s e c t io n 80 0 20.73 2 .3 6 10 .2 5 0 24.40 APPENDIX B STATISTICAL MEASURES OF CLASTIC SEDIMENTS, QUIBURIS FORMATION 95 96 Sam ple N o . G ravel C C -4 -6 C C -5 -5 Sand S ilt Mz <71 Ski kg 0.45 -0.45 2.93 2.01 -0.09 0.16 0.85 0.89 CC-I-2 C C -1 -6 7 C C —1 -8 0 C G -2 -2 2 C G -2 -3 0 1.34 2.74 3.57 3.81 3.97 2.31 0.81 1.27 1.18 1.44 0.22 0.14 0.21 -0.08 0.22 0.74 1.20 1.36 1.66 1.50 C C -2 -4 2 C C -2 -5 1 C C -3 -1 C C -3 -1 0 a C C -3 -1 6 2.98 2.49 3.72 2.24 3.49 1.44 3.06 2.19 3.00 1.59 0.51 -0.14 0.48 0.12 0.64 2.84 1.36 1.72 0.90 2.56 C C -3 -1 7 C C -3 -2 1 C C -4 -9 C C -4 -1 2 C C -5 -1 0 2.98 3.56 4.42 1.39 3.06 1.23 1.87 2.36 2.07 3.65 0.33 0.48 0.44 -0.16 0.07 1.29 1.93 1.86 0.87 1.15 C G —5 -1 3 1.67 2.90 0.36 0.88 C C —1 -1 C C —1—4 C C -1 -7 C C -1 -9 GG™1 - 1 0 5.28 5.13 6.09 5.55 5.01 1.94 1.66 1.98 1.43 1.46 0.43 0.30 0.29 0.18 0.71 1.29 1.36 1.08 1.04 1.58 C C -1 -1 2 C C -1 -1 5 C C -1 -1 8 C C —1 -1 9 C C -1 -2 1 5.50 5.15 4.73 4.72 5.18 1.43 1.25 1.04 0.94 1.58 0.11 0.53 0.33 0.25 0.46 1.15 1.66 1.76 1.64 1.48 C C -1 -2 2 C C -1 -2 5 C C -1 -2 6 C C -1 -4 6 C C -1 -4 9 6.03 5.32 4.85 5.35 5.39 2.06 1.40 1.47 1.81 1.64 0.35 0.09 0.32 0.44 0.43 0.92 0.90 1.49 1.57 1.45 C G -1 -5 1 C C -1 -5 5 C C -1 -5 9 C C -1 -6 2 C C —1—68 5.30 4.81 6.14 5.59 6.08 1.69 1.21 1.93 1.97 2.68 0.41 0.24 0.37 0.34 0.33 1.39 1.58 1.06 1.30 0.90 97 Mz °"I Ski C C -1 -6 8 C C -1 -6 9 C C -1 -7 2 C C -1 -7 3 C G -2 -1 6.08 4.46 6.33 4.13 5.01 2.68 1.43 2.15 1.37 1.51 0.33 -0.02 0.33 0.27 0.36 0.90 1.73 0.93 1.82 1.66 G C -2 - 4 G C -2 - 5 C C -2 -1 1 C C -2 -1 4 C C -2 -1 6 4.81 5.36 5.64 4.93 5.88 1.39 1.69 1.92 1.61 1.95 0.18 0.39 0.31 0.26 0.53 1.74 1.47 1.40 1.64 1.26 C C -2 -1 8 C C -2 -2 8 C C -2 -3 3 C C -2 -3 4 C C -2 -4 0 4.08 5.01 6.81 4.52 5.10 1.60 1.76 2.07 1.62 2.85 0.13 0.42 0.41 0.29 0.35 1.31 1.55 0.89 2.26 1.16 C C -2 -4 3 C C -2 -5 0 C C -2 -5 4 C C -2 -5 7 C G -3 -3 6.33 4.67 5.71 4.10 6.40 2.78 2.13 2.27 1.78 2.35 0.44 0.22 0.56 0.40 0.46 0.85 1.34 1.09 1.79 0.96 G C -3 -4 C C -3 -6 C C -3 -1 0 C C -3 -1 1 G G -3 -1 2 6.19 5.22 5.13 5.31 6.18 2.34 0.84 1.99 1.92 2.43 0.60 0.22 0.29 0.69 0.55 1.30 1.30 1.45 1.47 0.93 C C -3 -1 5 C C -3 -1 8 C C -3 -2 0 C C -4 -3 C C -4 -5 6.41 4.74 5.97 5.00 5.87 2.13 1.71 2.87 2.32 2.34 0.57 0.45 0.58 0.50 0.56 1.09 2.68 0.96 2.01 1.23 G C -4 -8 G C -4 - 8 a C C -4 -1 4 C C -4 -1 8 C C -5 -2 5.90 5.41 4.07 4.64 6.41 2.50 2.06 2.15 2.21 2.35 0.51 0.51 0.09 0.41 0.53 1.11 2.03 1.37 1.81 1.13 C C -5 -3 C C -5 -6 C C -5 -7 C C -5 -9 C G -5 -1 1 6.04 4.34 6.48 6.46 4.91 2.58 3.25 3.00 3.01 2.38 0.45 0.14 0.37 0.42 0.30 1.19 1.17 1.00 0.77 2.06 Sam ple N o . S ilt kg 98 Sam ple N o . Mz Skj kg S ilt C C -5 -1 4 5.38 2.24 9.55 1.59 Mud C C -2 -2 6 C C -2 -3 2 7.56 7.55 2.32 2.05 0.08 0.44 0.77 0.77 REFERENCES A genbroad, Larry D . , 1 9 6 7 , C e n o z o ic stra tig ra p h y and p a le o -h y d r o lo g y o f th e R ed in g to n -S a n M anuel a r e a , San Pedro V a lle y , A rizona: u n p u b lish e d P h . D . d is s e r t a t io n . U n iv e r s ity o f A rizo n a , 119 p . A n d erso n , Roger Y . , 1 9 6 2 , C e n o z o ic c lim a te in th e S o u th w e st: A rizona G e o l. S o c ie t y D i g e s t , v . 5 , p . 2 5 - 3 4 . B la k e , W illia m P . , 1 9 0 2 , Lake Q u ib u r is, an a n c ie n t P lio c e n e la k e in A rizona: U n iv e r s ity o f A rizona M o n th ly , v . 4 , n o . 4 , p . 1 0 7 108. __________ 1 9 0 3 , D ia to m -e a r th in A rizona: Am. I n s t . M ining E ng. T r a n s ., v . 33, p. 38-45. B ra m lette, M . 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A m erica B u l l . , v . 65, p . 1262. __________ 1 9 5 8 , C e n o z o ic a llu v ia l d e p o s its o f th e upper G ila R iv er, N e w M e x ic o and A rizona: u n p u b lish e d P h . D . t h e s i s . U n iv e r s ity o f A rizo n a , 249 p . __________ 1 9 6 2 , "Should th e term 'G ila C o n g lo m era te' be aban doned?" : A rizona G e o l. S o c . D ig e s t , v . 5 , p . 7 3 - 8 8 . __________ 1 9 6 3 , C e n o z o ic g e o lo g y in th e M ammoth a r e a , P in a l C o u n ty , A rizona: U . S . G e o l. Survey B u ll. 1 1 4 1 - E , 40 p . 101 H eron , S . D u n ca n , J r . , 1 9 6 9 , M in era lo g y o f th e B lack M ingo m udrocks: C o lu m b ia , South C a ro lin a S ta te D ev elo p m e n t B oard, D iv is io n o f G e o lo g y , G e o lo g ic N o t e s , v . 8, p . 2 7 - 4 1 . H eron , S . D u n ca n , J r . , R o b in so n , G ilb ert C . , and J o h n so n , Henry S . , J r . , 1 9 6 5 , C la y and o p a l-b e a r in g c la y s t o n e s o f th e South C aro­ lin a c o a s t a l p la in : C o lu m b ia , South C arolin a S ta te D ev elo p m en t Board, D iv is io n o f G e o lo g y , B u ll. 3 1 , 64 p . J a c o b s , L ou is L. I ll, 1 9 7 3 , Sm all mammals o f the C uib uris F orm ation, so u th e a s te r n A rizona: u n p u b lish e d M . S . t h e s i s . U n iv e r s ity o f A rizo n a , 77 p . J o n e s , J. B . , and S e g n it, E . R . , 1 9 7 1 , The nature o f o p a l. I . N om en ­ c la tu re and c o n s titu e n t p h a s e s : G e o l . S o c . A u stra lia J . , v . 1 8 , p. 57-68. K rauskopf, Konrad B . , 1 9 5 6 , D is s o lu t io n and p r e c ip ita tio n o f s i l i c a at lo w tem p eratu res: G e o c h im . e t C o sm o ch im . A c ta , v . 1 0 , p . 1-26. K rieger, M edora H . , 1 9 6 8 a , G e o lo g ic map o f th e Brandenburg M ountain q u a d r a n g le , P in al C o u n ty , A rizona: U . S . G e o l. Survey G e o l. Q u ad . Map G Q -6 6 8 . __________ 1 9 6 8 b , G e o lo g ic map o f th e H o ly Joe P eak q u a d ra n g le, P in a l C o u n ty , A rizona: U . S . G e o l. Survey G e o l. Q u a d . Map G Q 669. __________ 1 9 6 8 c , G e o lo g ic map o f th e Lookout M ountain q u a d ra n g le, P in al C o u n ty , A rizona: U . S . G e o l. Survey G e o l . Q u ad . Map GQ-670. __________ 1 9 6 8 d , G e o lo g ic map o f th e S a d d le M ountain q u a d ra n g le, P in al C o u n ty , A rizona: U . S . G e o l . Survey G e o l. Q u ad . Map G Q -6 7 1 . K rieger, M edora H . , C o r n w a ll, H enry R . , and B a n k s, Norman G . , 1 9 7 4 , Big D om e Form ation and r e v is e d T ertiary stra tig ra p h y in th e R aySan M anuel a r e a , A rizo n a , in C h a n g es in stra tig ra p h ic nom en­ cla tu re b y th e U . S . G e o lo g ic a l S u rvey 1 9 7 2 , G . V. C oh ee and W . B . W righ t, e d s . : U . S . G e o l. S u rvey B u ll. 1394A, p . A 5 4 A64. L a n c e , John F . , 1 9 6 0 , S tra tig ra p h ic and stru ctu ra l p o s itio n o f C e n o z o ic f o s s i l lo c a lit ie s in A rizona: A rizona G e o l. S o c . D ig e s t , v . 3 , p. 155-159. __________ 1 9 6 3 , P a le o n to lo g y , in G en eral p r o g r ess report for 1 9 6 2 -1 9 6 3 : G eo ch ro n o lo g y L a b o r a to r ie s, U n iv e r sity o f A rizo n a , p . 1 6 - 2 0 . L on g, John T . , J r . , and O ls o n , G eorge G . , [ l9 5 7 ] , D ia to m a c e o u s earth in A r izo n a , a fie ld and laboratory report: P h o e n ix , A rizona D e ­ v e lo p m e n t B oard, 28 p . 102 M e lto n , Mark A . , 1 9 6 0 , O rigin o f the d rain age o f so u th e a ste r n A rizona: A rizona G e o l. S o c . D ig e s t , v . 3 , p . 1 1 3 - 1 2 2 . __________ 1 9 6 5 , The g eom orp h ic and p a le o c lim a tic s ig n ific a n c e o f a llu ­ v ia l d e p o s it s in so u th ern A rizona: Jour. G e o lo g y , v . 7 3 , p . 1-38. M on tgom ery, Errol L . , 1 9 6 3 , The g e o lo g y and ground w a ter in v e s t ig a ­ tio n o f th e Tres A lam os Dam s it e area o f th e San Pedro R iver, C o c h is e C o u n ty , A rizona: u n p u b lish e d M . S . t h e s i s . U n iv e r s ity o f A r iz o n a , 69 p . P a g e , Harry G . , 1 9 6 3 , W ater reg im en o f th e inner v a lle y o f th e San Pedro River near M am m oth, A rizona: U . S . G e o l. Su rvey W a ter-S u p p ly Paper 1 6 6 9 -1 , 22 p . P o w e r s, M . C . , 1 9 5 3 , A n e w ro u n d n e ss s c a le for sed im en ta ry p a r tic le s : Jour. S e d . P e tr o lo g y , v . 2 3 , p . 1 1 7 - 1 1 9 . R e e v e s , C . C . , 1 9 6 8 , D e v e lo p m e n ts in s e d im e n to lo g y . 11 . In trod u ction to p a le o lim n o lo g y : A m sterdam , E ls e v ie r P u b lish in g C o . , 228 p . R ex , R . W . , 1 9 6 9 , X -ray m in era lo g y s t u d ie s . Leg 1 , D e ep S ea D r illin g P r o je c t, in I n itia l rep orts o f th e D e e p S ea D r illin g P r o je c t, M . E w in g , e d . : W a sh in g to n , U . S . G overnm ent Printing O ff ic e , v . 1, p . 354-367. __________ 1 9 7 0 , X -ray m in era lo g y s t u d ie s . Leg 2 , D e ep S ea D r illin g Pro­ j e c t , in I n itia l rep orts o f th e D e e p S ea D r illin g P r o je c t, M . N . A . P e te r s o n , e d . : W a sh in g to n , U . S . G overnm ent Printing O f f ic e , v . 2 , p . 3 2 9 - 3 4 6 . R ie c k , G . D . , and S t e v e l s , M . J . , 1 9 5 1 , The in flu e n c e o f som e m etal io n s on th e d e v itr ific a tio n o f g la s s : S o c . G la s s T e c h n o lo g is ts J o u r ., v . 3 5 , p . 2 8 4 - 2 8 8 . 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W is e , Sherw ood W . , J r . , and W e a v e r , Fred M . , 1 9 7 3 , O rigin o f c r is t o b a lit e - r ic h T ertiary s e d im e n ts in th e A tla n tic and G ulf c o a s t a l p la in : G u lf C o a s t A s s . G e o l. S o c . T r a n s ., v . 2 3 , p . 3 0 5 —3 2 3 . V v. 31. 0 6 1 6%pO \ tvt o — < t f t f > u uJ 2900 1 Sa X K A r-w. . . . j i" #*a (900) ■2 9 5 0 ' * i V 4*/ -vE, X“a.x XXX NOTE CHANGE OF ELEVATION :.****. 2900 CC - 2 _ A * * ' » y r 2800 o (850) T - T - Ir r '" =J— t~».**••*-,» O — : = w u##, K ^ o i.c ' ".A $fiU 2850 ... rrt A —" 2850’ 869.4) 275 0 CC-1 U .T T |{ (METERS) LI. IN F E E T — ELEVATION . . / . ^ t — 'E'-V-'-L '1 =a6m s V .:*. ------------- a “. T . 2800 W .. r • ik; -*/ h- ' f—. •T-. • 5ro~s*6 TT^ T --£L rr' ■4 — - r~»"1 . " 2790' ^ -r*-:.- — • 2700 * *r AA . *4. ‘AA. . 4A *A H »• — ■"* * ---- - Ken. — » LTi — (850) (851.0) F I G U R E 12 6ri 1 :■—w WA . 4 . 4WA MEASURED STRATIGRAPHIC SECTIONS OF THE QUIBURIS FORMATION NEAR MAMMOTH. 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