FACIES RELATIONSHIPS IN A PATCH REEF OF THE UPPER MURAL LIMESTONE IN SOUTHEASTERN ARIZONA. G retch en Hoffman Roybal

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1 FACIES RELATIONSHIPS IN A PATCH REEF OF THE UPPER MURAL LIMESTONE IN SOUTHEASTERN ARIZONA by G retch en Hoffman Roybal A T hesis Subm itted to th e F a c u lty of th e DEPARTMENT OF GEOSCIENCES In P a r t i a l F u lf illm e n t of th e R equirem ents For th e D egree of MASTER OF SCIENCE In th e G raduate C ollege THE UNIVERSITY OF ARIZONA

2 STATEMENT BY AUTHOR T h is t h e s i s h as b een su b m itted in p a r t i a l f u l f i l l m e n t o f r e q u irem en ts fo r an advanced d e g r e e a t The U n iv e r s it y o f A rizo n a and i s d e p o s ite d in th e U n iv e r s it y L ib ra ry to be made a v a i l a b l e to b o rrow ers under r u l e s o f th e L ib r a r y. B r ie f q u o t a t io n s from t h i s t h e s i s a r e a llo w a b le w ith o u t s p e c i a l p e r m is s io n, p r o v id e d th a t a c c u r a te acknow ledgm ent o f s o u r c e i s made. R e q u e sts f o r p e r m is s io n f o r ex ten d ed q u o ta tio n from or r e p r o d u c tio n of t h i s m a n u sc r ip t in w h ole or in p a r t may be g r a n te d by th e head o f th e m ajor d ep artm en t or th e Dean o f th e G rad u ate C o lle g e when in h i s ju d g ment th e p rop osed u s e o f th e m a t e r ia l i s in th e i n t e r e s t s o f s c h o la r s h ip. In a l l o th e r i n s t a n c e s, h ow ever, p e r m is s io n m ust be o b ta in e d from th e a u th o r. SIGNED: APPROVAL BY THESIS DIRECTOR T h is t h e s i s has been approved on th e d a t e shown b elo w : V ^ 1/9 79 K. W. FLESSA <7 D ate A s s i s t a n t P r o fe s s o r o f G e o s c ie n c e s

3 ACKNOWLEDGMENTS I am d eep ly in d ebted to Dr. K arl F le s s a, d ir e c to r of t h i s r e se a rc h, f o r h is a s s is ta n c e and c o n s tr u c tiv e c r itic is m. I am a ls o g r a te f u l to R obert W. S c o tt, of Amoco P ro d u ctio n, T u lsa, Oklahoma, fo r h elp in id e n tif y in g th e fauna and sh a rin g h is knowledge o f th e a re a w ith me. S p e c ial th an k s to Bob W arzeski of SUNY Binghamton fo r su p p ly in g me w ith s e v e ra l re fe re n c e s and sh a rin g tim e in th e f i e l d. Both D r. R ichard W ilson and Dr. Joseph F. S c h re ib e r, J r. were in s tru m e n ta l in h e lp in g me to com plete t h i s re s e a rc h p r o je c t, and t h e i r h elp i s g r e a tly a p p re c ia te d. Support fo r t h i s re s e a rc h came from a G raduate C o lleg e R esearch G rant and a f in a n c ia l award th ro u g h th e D epartm ent o f G eosciences from th e B ert S. B u tle r award fund. Both of th e se g ra n ts helped to d e fra y th e expense of doing t h i s p r o je c t. A s p e c ia l thanks to my f i e l d a s s i s t a n t and companion, Tony R oybal, f o r h is h e lp, p a tie n c e, and encouragem ent th ro u g h o u t t h i s p r o j e c t. F in a lly, a n o te o f thanks to Dr. Richard P e te rso n and D r.. R ichard Burroughs f o r t h e i r encouragem ent and fo r in tro d u c in g me to geology. iii

4 TABLE OF CONTENTS Page LIST OF ILLUSTRATIONS... ABSTRACT... v v i i 1. INTRODUCTION... 1 P rev io u s Work... Method of Study... S tra tig ra p h y and G eologic S e ttin g D e p o sitio n a l H isto ry.... vo Ln to to 2. FACIES DESCRIPTION D ebris F a c ie s C oral F a c i e s M icro so le n a -s tr o m a to lite F a c ie s R u d ist F a c ie s T r a n s itio n a l A reas R id in g 's (1977) C la s s if ic a tio n of Reef F a c ies D en sity and D iv e rs ity C lu ste r A n aly sis ENVIRONMENTAL INTERPRETATION Fore Reef Reef F r o n t Reef C r e s t Reef F l a t Back R e e f COMPARISON TO CONTEMPORANEOUS REEFS IN TEXAS CONCLUSIONS APPENDIX A: QUADRAT D A T A APPENDIX B: PEEL NEGATIVES ' REFERENCES CITED iv

5 LIST OF ILLUSTRATIONS F ig u re Page 1. Index Map o f Study A r e a P hotograph of Study A r e a Topographic Map of Study A r e a S tr a tig r a p h ic Column, B isbee Group, Mule M ountains P aleo g eo g rap h ic Maps of S o u th east A rizona (Hayes, 1970a) Rock C la s s if ic a tio n C hart (Embry and Klovan, 1971) F a c ies Map of Study A r e a C oral F a c i e s R e c r y s ta lliz a tio n o f C o r a l s Growth Form of M icrosolena in th e M icro so lenas tr o m a to lite F acies Sketch o f M icro so le n a -s tr o m a to lite A sso c ia tio n Sketch of M icro so len a-s tr o m a to lite Growth Forms F in e Mud in R u d ist M antle C a v i t y P a l l i a l C anal F i l l i n g in a C ap rin id P e ta lo d o n tia S u b facies C ap rin id S u b facies T r a n s itio n a l A r e a D ebris F a c i e s R id in g 's Three-com ponent Diagram F a c ies P lo tte d on R id in g 's Three-com ponent Diagram C lu ste r A n aly sis D e n d ro g ra m v

6 vi LIST OF ILLUSTRATIONS C ontinued F ig u re Page 22. Summary of F a c ies C h a r a c te r is tic s D e p o sitio n s! Model of R e e f... 47

7 ABSTRACT P atch r e e f s w ith in th e M ural Lim estone (B isbee Group, C retaceo u s, s o u th e a s t A rizona) a r e dom inated by s c le r a c tin ia n c o r a ls, a lg a l stro m a t o l i t e s, and r u d i s t b iv a lv e s. Reef developm ent o ccu rred d u rin g th e m aximum tra n s g re s s io n in to th e Chihuahua Trough, a n o rth w est e x te n sio n of th e Tethyan seaway. One p a tc h r e e f (270 x 120 m) was stu d ie d in d e t a i l. S p ecies abundance and grow th form w ere e stim ate d in each of 57 q u a d ra ts of 1 m^ along 10 tr a n s e c ts. F a c ie s developm ent i s c o n tro lle d by wave energy. The c r e s c e n t shaped f r o n t i s dom inated by b ran ch in g and m assive c o r a ls. The c r e s t i s a b u ild -u p of lam in ar M icro so len a (c o ra l) along w ith a lg a l s tr o m a to lite s. R u d ists dom inate th e back r e e f. The P e ta lo d o n tia f a c ie s i s c lo s e s t to th e r e e f c r e s t and c o n s is ts of th ic k e ts of th e g re g a rio u s, th ic k -w a lle d P e ta lo d o n tia and a few c o r a ls. The c a p rin id f a c ie s i s f a r t h e s t from th e r e e f c r e s t and c o n ta in s c o r a ls and m olluscan d e b ris w ith s c a tte r e d cap - r i n i d s. A "h alo " d e b ris f a c ie s o f m olluscan fragm ents su rro u n d s th e r e e f. A lthough th e M ural r e e f s a r e roughly c o r r e la tiv e w ith th e E arly A lbian r u d i s t r e e f s of th e Lower Glen Rose of Texas, im p o rtan t e c o lo g ic a l d if f e r e n c e s a r e a p p a re n t. R u d ists a r e m ajor r e e f - b u ild e r s in th e Glen Rose, n o t c o r a ls, su g g e stin g more norm al s a l i n i t i e s f o r th e M ural r e e f s. vii

8 CHAPTER 1 INTRODUCTION R eefs a r e o rg a n ic b u ild -u p s t h a t d is p la y ev id en ce of a wave r e s is ta n c e o r grow th in tu rb u le n t w ater (H eckel, 1974). C o rals a r e commonly m ajor r e e f - b u ild e r s along w ith a lg a e, b u t a t a few sta g e s in g e o lo g ic tim e o th e r groups have been th e dom inant r e e f - b u ild e r s. In th e l a t e J u r a s s ic, a m assive s h e lle d g re g a rio u s b iv a lv e, th e r u d i s t, became an im p o rta n t component of r e e f s. By C retaceous tim e th e r u d i s t s had r e p laced herm atypic c o r a ls a s th e dom inant r e e f - b u ild in g organism. In th e C retaceous, r u d i s t r e e f s flo u r is h e d th ro u g h o u t th e Tethyan sea (Gordon, 1973; C o ates, 1973). These g re g a rio u s b iv a lv e s formed c lu s t e r s and c re a te d frameworks on sh allo w c a rb o n a te p la tfo rm s of th e w estern and e a s te r n hem ispheres. In N orth America r u d i s t r e e f s a r e reco g n ized b o th on th e s u rfa c e and in th e s u b su rfa c e in c e n tr a l and w est Texas, e a s te rn M exico, and th e C aribbean (T ucker, 1962; H endrick s, 1967; Kauffman and S ohl, 1974). The Texas r e e f s a re r e p r e s e n ta tiv e of th e ru d ist-d o m in a te d fram eworks observed th ro u g h o u t th e Tethyan re g io n. H erm atypic c o r a ls a r e a s s o c ia te d w ith th e r u d i s t r e e f s in many a re a s of Texas. The c o ra ls a r e o f secondary im portance in th e r e e f s in Texas, b u t a re dom inant in r e e f s of th e Lower C retaceo u s in s o u th e a s te rn A rizona. The predom inance of c o r a ls and a s s o c ia te d s tr o m a to lite s i s an u n u su al and u n iq u e s itu a t i o n in th e E a rly C retaceous. T his stu d y d e s c rib e s th e b io f a c ie s and a s s o c ia te lith o lo g y o f a sm all p a tc h r e e f in s o u th e a s t A rizona. The f a c ie s p a tte r n s form a b a s is 1

9 2 fo r a d e ta ile d p aleo en v iro n m en tal re c o n s tr u c tio n of th e r e e f. T his w ell-exposed r e e f se rv e s as a model and a s a b a s is fo r com parison to th e more p redom in an tly r u d i s t assem blages of e q u iv a le n t age in Texas. P rev io u s Work The p a tc h r e e f s of s o u th e a s t A rizona occur in th e upper member o f th e M ural Lim estone of th e B isbee Group. The B isbee Group was named by Ransome in The M ural Lim estone was a ls o named by Ransome, fo r 650 f t of lim e sto n es and c a lc a re o u s s i l t y san d sto n es in th e Mule Mount a in s, n e a r B isb ee, A rizona. Ransome su b d iv id ed th e M ural in to upper and low er members. A re c o n n a issa n c e g e o lo g ic map of th e a re a by Cooper (1959) used th e s tr a tig r a p h ic d iv is io n s of Ransome. The f i r s t p a le o n to lo g ic a l work in th e a re a was done by Stoyanow (1949). On th e b a s is of th e am m onites, D o u v ille ic e r a s (?) m uralense and Im m unitoceras immunitum, Stoyanow a ssig n e d an E arly A lbian age to th e Upper M ural L im estone. He a ls o recognized th e r u d i s t bioherm s p re s e n t in th e M ural and su g g ested a sh allo w -m arin e environm ent of d e p o s itio n f o r th e u n it. Cooper (1955) c o lle c te d brach io p o d s s o u th e a s t of B isbee in what he assumed to be p a r t of th e Upper M ural Lim estone. The b ra c h i opods were a s s o c ia te d w ith sm all o y s te rs and r u d i s t s and a few p o o rly p reserv ed e c h in o id s. Cooper i d e n tif ie d n in e sp e c ie s of b rach io p o d ; s ix of th e se w ere new s p e c ie s. Hayes (1970a), in a p aleo g eo g rap h ic s tu d y, noted th a t th e M ural r e e f s developed d u rin g th e L ate A ptian to E a rly A lbian maximum tra n s g r e s s io n of th e Lower C retaceous Tethyan seaway in to so u th e a s te rn A rizo n a.

10 3 R ecent work on th e s tr a tig r a p h y of th e Upper M ural was done by Grocock (1975). In th is work, th e c arb o n ate f a c ie s w ere c l a s s i f i e d by lith o lo g y and fauna. From th e lith o lo g y and fa u n a, th e enviro n m en tal s ig n ific a n c e was d eterm in ed. A stu d y by S c o tt and B renckle (1977) desc rib e d th e g e n e ra l b i o t i c su ccessio n w ith in th e r u d i s t p a tc h r e e f s of th e Upper M ural. S c o tt and B renckle concluded th a t c o r a ls and stro m a to l i t e s a ls o played an im p o rtan t r o le in th e developm ent o f p a tc h r e e f s in s o u th e a s t A rizona. R. W arzeski (in p r e p.) Is w orking on th e sedim entology and p e tro lo g y o f th e M ural Lim estone in n o rth e rn Mexico (Ph.D. d i s s e r t a tio n, S ta te U n iv e rs ity of New York a t Bingham ton). S c o tt (in p re s s ) has a more e x te n s iv e paper on th e d e p o s itio h a l model of th e r e e f s in A rizona based on h is p re v io u s work. S c o tt concludes th e r e a r e two geome t r i e s w ith in th e M ural r e e f s ; mounds dom inated by r u d i s t s, and p a tc h r e e f s of c o r a ls, a lg a l s tr o m a to lite s, and r u d is ts. Method o f Study The a re a stu d ie d i s in C ochise County, s o u th e a s te rn A rizona, 24.2 km s o u th e a s t of B isbee on U.S. Highway 80 (15* B isbee q u a d ra n g le, SE^fi, NEi$, Sec. 36, T. 23 S., R. 25 E.) (F ig u re 1 ). The M ural Lim estone cro p s o u t in s e v e ra l k n o lls on th e e a s te rn s id e of th e Mule M ountains. Many of th e se k n o lls a re w ith in easy a c c e ss from th e road in c lu d in g th o se n o rth and so u th o f Highway 80, 8 km n o rth of P au l Spur. The stu d y a re a i s on th e n o rth s id e of U.S. 80 and i s betw een two sm a lle r k n o lls. F a u ltin g ap p ears to be p re s e n t betw een th e k n o lls w ith th e m id d le k n o ll being th e u p th r u s t b lo c k on b o th s id e s. The good exposure of th e many

11 MULE MTS Bisbee Lowell PERILLA MTS Douglas MEXICO V / A Lower Cretaceous Outcrops ARIZONA NEW MEXICO, i KILOMETERS MILES 0 5 AREA OF MAP F ig u r e 1. Index Map of Study A rea.

12 5 f a c ie s of th e r e e f and i t s la r g e a re a (3.2 x 10^ m^) fo r sam pling p u r poses were reaso n s f o r choosing t h i s p a r tic u la r stu d y a re a (F ig u re 2 ). A conto u r map was p repared (p lan e ta b le m ethod) u sin g 10 f t conto u r i n t e r v a l s. Ten tr a n s e c ts p e rp e n d ic u la r to th e le n g th of th e long a x is of th e o u tcro p and p a r a l l e l to d ip slo p e were spaced 30 m (100 f t ) o r 15 m (50 f t ) a p a r t, depending on th e com plexity o f th e f a c ie s. A O 1 m q u a d ra t was p la c e d a t 15 m in te r v a ls along each tr a n s e c t. At each of th e 57 q u a d ra ts f o s s i l s w ere te n ta tiv e l y id e n t i f i e d or d e sc rib e d, t h e i r abundance and o r ie n ta tio n were n o te d, and g e n e ra l o b s e rv a tio n s of lith o lo g y w ere made (F ig u re 3 ). Samples w ere taken a t each q u a d ra t and w ere c u t f o r p o lish e d s la b s and p e e ls. The p e e ls and s la b s were used f o r f u r th e r fa u n a l id e n t i f i c a t i o n and f o r d e ta ile d stu d y of th e lith o lo g y. F a c ie s w ere d e fin e d by b o th f i e l d and la b o ra to ry c r i t e r i a ; namely, r e l a t i v e abundance of s p e c ie s, d iv e r s ity of th e.f a u n a, grow th morphology o f th e c o r a ls, m a trix, and p e r s i s t e n t c o -o c cu rren c e s o f ta x a. The geo g rap h ic d i s t r i b u t i o n of th e f a c ie s led to th e developm ent of a model of th e d e p o s itio n a l environm ents in which th e d i f f e r e n t b io f a c ie s o ccu rred. S tra tig ra p h y and G eologic S e ttin g The M ural Lim estone i s exposed in fla n k s of n o rth - tre n d in g mounta in s, such as th e Mule and P e r i l l a M ountains. These m ountains a r e re p r e s e n ta tiv e o f b a s in and ran g e topography p re v a le n t in s o u th e a s t A rizona. F a u ltin g i s common th ro u g h o u t th e exposures o f th e M ural causin g d i s co n tin u o u s o u tc ro p s. The semi a r id d e s e r t environm ent w eath ers th e

13 F ig u r e 2. P hotograph o f Study A rea.

14 7 J u F ig u re 3. T opographic Map o f Study A rea.

15 th ic k lim e sto n e s in a way th a t em phasizes th e s k e l e t a l components of th e 8 ro c k. V e g e ta tio n and s o i l developm ent a re s p a rse on M ural o u tc ro p s and only become dom inant in b a s in s t h a t a r e f i l l e d by re c e n t allu v iu m. The B isbee Group in th e Mule M ountains re p re s e n ts 1700 m (5666 f t ) of sed im en tary ro ck. The G lance C onglom erate, th e lo w est fo rm atio n in th e group, o v e r lie s an ir r e g u la r e ro s io n a l s u rfa c e on ro cks ran g in g from Precam brian to J u r a s s ic in age. The b a s a l conglom erate in th e Mule M ountains i s made up o f p o o rly s o r te d, subrounded co b b les and pebb le s in red-brow n to s i l t y to sandy m udstone (Hayes, 1970b). The G lance C onglom erate g rades upward in to th e san d sto n es and s i l t s t o n e s of th e M o rita Form ation. The G lance has few exposures in th e Mule M ountains and g e n e r a lly i s th in n e r (18 m) th e r e th a n to th e w est where i t re ach es th ic k n e s s e s of m ( f t ) in th e Huachuca M ountains (H ayes, 1970b). The M o rita Form ation i s 900 m (3000 f t ) th ic k and has e x te n s iv e o u tcro p s in th e Mule M ountains. The M o rita c o n s is ts o f in te rb e d d e d s h a le s and lim e sto n e s. A g e n e ra l f in in g upward sequence i s e v id e n t in t h i s fo rm atio n (Hayes, 1970b). The u p per c o n ta c t of th e M o rita w ith th e o v e rly in g M ural i s d e fin e d as th e to p o f th e upperm ost san d sto n e bed in th e M o rita, in d ic a tin g a change from a c l a s t i c to a c arb o n ate sequence (Hayes, 1970b). The M ural Lim estone i s d iv id e d in to two members. The low er memb e r i s 130 m th ic k and i s a sequence of c a lc a re o u s m udstones, s i l t s t o n e s, and san d sto n es in te rb e d d ed w ith f o s s i l i f e r o u s lim e s to n e s. member i s 95 m o f th ic k ly bedded f o s s i l i f e r o u s lim e sto n e s. The upper In th e

16 9 Mule M ountains th e M ural F orm ation i s 225 m (750 f t ) th ic k. P atch r e e f s as th ic k a s 18 m (60 f t ) occu r in th e low er h a lf of th e Upper M ural. The m assiv e lim e sto n e beds a r e conform ably o v e rla in by s h a le s, muds to n e s, and san d sto n e s of th e C in tu ra F orm ation. The C in tu ra, th e upperm ost fo rm atio n o f th e B isbee Group, i s 575 m (1920 f t ) th ic k in th e Mule M ountains. The fo rm atio n i s composed o f p in k -g re y san d sto n es t h a t g rad e in to s i l t s t o n e s and m udstones. I t i s exposed on th e e a s t fla n k o f th e Mules (Hayes, 1970a). The C in tu ra i s l i t h o l o g i c a l l y v e ry s im ila r to th e M o rita. The upper c o n ta c t of th e C in tu ra i s n o t exposed in th e Mule M ountains. The age of th e B isbee Group i s Neocomian to M iddle A lb ian (H ayes, 1970a). The age d e te rm in a tio n of th e B isbee Group was o r ig i n a lly based on ammonites c o lle c te d by Stoyanow (1949). Based on Stoyanow*s i n t e r p r e ta tio n o f index zones w ith th e ammonite su c c e ssio n in s o u th e a s te rn A rizona, th e M orita r e p r e s e n ts Neocomian to Lower A p tian, and th e A p tian -A lb ian boundary i s in th e upper tw o -th ird s o f th e Lower M ural (e q u iv a le n t to p a r t of Stoyanow*s Low ell F o rm atio n ). Stoyanow a ls o r e p o rte d O rb ito lin a texan a from th e top of th e Upper M ural. Coogan (1977) c o n sid e rs th e ran g e of O rb ito lin a texana zone as Upper A ptian to low er M iddle A lb ian. Stoyanow (1949) co n sid ered th e o v e rly in g C in tu ra to be M iddle A lbian on th e b a s is of am m onites. Thus, th e p a tc h r e e f s of th e Upper M ural a re m ost l i k e l y to be l a t e E arly A lbian in age (F ig u re 4 ). D e p o sitio n a l H isto ry In H ayes' (1970a) p a leo g eographic stu d y o f th e s o u th e a s t c o rn e r of A rizona, he o u tlin e d th e d e p o s itio n a l h is to r y o f th e a re a d u rin g th e

17 F ig u re 4. S tr a tig r a p h ic Column, B isbee Group, Mule M ountains. Glance Conglomerate Lower LOWER Member K) m CRETACEOUS 3 CD DJO D Upper D Member 2 m to H O Z m BISBEE GROUP H O <1 m cn m o CD H r4 O

18 11 E arly C re taceous. The fo llo w in g p aragrap h s summarize H ayes' id e a s on th e developm ent of th e a re a from Neocomian through A lb ian tim e and th e d e p o s itio n o f what i s now c a lle d th e B isbee Group. The G lance C onglom erate was d e p o site d d u rin g a tim e when an upland a re a to th e n o rth was shedding c o arse sedim ents in to th e s o u th e a s t c o rn er o f A rizona. By E a rly A p tian th e f i n e r g ra in e d sedim ents o f th e M orita w ere being d e p o site d in to a slow ly su b sid in g p la in as th e sea advanced from th e Chihuahua tro u g h to th e so u th in to A rizona (F ig u re 5 ). The supply of c l a s t i c m a te r ia l from th e n o rth w est co n tin u ed as th e sea advanced. The p re sen c e o f c l a s t i c m a te r ia l and a m arg in al c a r b o n ate environm ent c re a te d th e Lower M ural sequence o f in te rb e d d ed c a rb o n a te s, san d sto n e s, and s h a le s u n t i l L ate A p tia l tim e (H ayes, a). D uring th e maximum tr a n s g r e s s io n o f th e E a rly A lb ian, th e mass iv e lim e sto n es of th e Upper M ural w ere d e p o site d. These h ig h ly f o s s i - lif e r o u s lim e sto n e s a re r e s t r i c t e d to th e s o u th e a s te rn c o rn e r in A rizona, b u t co n tin u e so u th in to Mexico and Texas and e a s t in to New Mexico (Hayes, a). The M iddle A lbian was a tim e o f re g re s s io n, and th e C in tu ra re p r e s e n ts a c l a s t i c sequence of d e l t a i c o r ig in s s im ila r to th e M o rita. This r e g re s s io n i s a t t r i b u t e d to th e n o rth e a stw a rd t i l t i n g of th e r e g io n r a th e r th an th e low ering o f th e sea le v e l (Hayes, a). E vidence of t h i s i s th e p re sen c e o f th ic k e r lim e sto n es and l a t e M iddle A lb ian f o s s i l assem blages in so u th w est New Mexico and T exas, p ro o f th a t th e n o rth e rn e x te n sio n of th e Chihuahua Trough had n o t r e tr e a te d to th e so u th.

19 mountains foothills coastal I owl and plain A) LATE NEOCOMIAN B) EARLY APTIAN lowland low plain \ - A b j 8 C k l s t C = sf lood\deltalo / V jaijix plau sr^ 0 nearshorj clast Ija^ C) EARLY ALBIAN D) MIDDLE ALBIAN F ig u re 5. P aleo g eo g rap h ic Maps o f S o u th east A rizona (Hayes, 1970a). H to

20 CHAPTER 2 FACIES DESCRIPTION F a c ie s o f th e r e e f s were determ ined by th e r e l a t i v e abundance of s p e c ie s, th e d iv e r s ity of th e s p e c ie s, and th e lith o lo g y. The b a s is o f th e se d e te rm in a tio n s a re th e sam ple q u a d ra t d a ta (Appendix A) and th e p e e ls and p o lish e d s la b s (Appendix B). From th e f i e l d o b s e rv a tio n s, d iffe r e n c e s w ith in th e r e e f were recognized and th e d i s t r i b u t i o n of th e d if f e r e n t f a c ie s was d eterm ined. L ith o lo g ic d e s c r ip tio n s o f th e f a c ie s a re based on a c l a s s i f i c a tio n scheme d e v ise d by Embry and Klovan (1971). T his c l a s s i f i c a t i o n i s based on th a t o f Dunham (1962) which em phasizes th e d e p o s itio n a l te x tu r e of c a rb o n a te s. Embry and K lovan*s scheme in tro d u c e s some p a le o - e c o lo g ic a l s ig n if ic a n c e to th e way in w hich th e lith o l o g i c components a re bound to g e th e r. F u rth e r d e s c r ip tio n of th e ro c k i s g iv en by u sin g th e rock names a s t e x t u r a l m o d if ie r s ; f o r exam ple, a c o r a l b a f f le s to n e w ith w ackestone m a trix i s a co ra l-d o m in a te d ro c k w ith th e organism s actr- in g as b a f f le s surrounded by a m ud-supported m a trix w ith more th an 10 p e rc e n t g ra in s. By u sin g t h i s scheme, th e name in d ic a te s th e r o le of th e f o s s i l s in th e te x tu r a l make-up of th e ro ck (F ig u re 6 ). Four f a c ie s have been d e fin e d on th e b a se s m entioned above. W ithin th e se g e n e ra l f a c ie s, d if f e r e n c e s do e x i s t and t r a n s i t i o n a l a re a s occur betw een th e f a c ie s. The fo u r f a c ie s a r e : m olluscan d e b r is, c o r a l, M icro so lena-s tr o m a to lite. and r u d i s t. These f a c ie s a re shown on th e to p o g rap h ic map of th e a re a (F ig u re 7 ). 13

21 Allochthonous Limestone A u t o c h t h o n o u s Limestone Origins! Com ponents not O rg e n lc e lly Bound Original Com ponents Orgenlcally During D e p o s itio n Bound During D e p o s i ti o n L e ss th a n 10% i 2 mm components G reeter t h a n 10% > 2 m m com ponents no.con t e 1 n s lime mud lime («. 03 mm By By By O r g a n is m s O r g a n i s m s Org a n lam e M ud W h ic h W h ic h W hich S u p p o r t e d» 2 m m - G re 1 n M a t r i x act E n c ru s t B u ild S u p p o r t e d S u p p o r t e d C o m p o n e n t as and a L ess Sup p o r t e d then Greater B a f f l e s Bind R igid 10% then g reins 10% F r a me work 1 >.03mm grains <2 mm Mudstone Weeks Peckstone Grain Floats tone Rude tone Ba ffleetone B 1n d stone Fr amestone stone stone F ig u re 6. Rock C la s s if ic a tio n C hart (Embry and Klovan, 1971)

22 1 15

23 16 D eb ris F a c ie s T his f a c ie s c o n s is ts of a l i g h t grey m olluscan d e b ris p ack sto n e. In th e d e b ris f a c ie s th e ro ck i s made up of subrounded to su b an g u lar carb o n ate m a te r ia l o f c o a rse to f in e sand s iz e. The p a r t i c l e s a re o v erw helm ingly m ollu scan s h e l l frag m e n ts. M inor c o n s titu e n ts a re fragm ents of d asy clad acean a lg a e, o o l i t e s, and m ic r ite and m icro sp ar c l a s t s (F igure B -1 2 ). The ro c k i s g ra in -s u p p o rte d, and mud i s a m inor compon e n t. The g ra in s a r e n o t p r e f e r e n t i a l l y o rie n te d. The d e b ris f a c ie s cro p s o u t in th e n o rth w e st, s o u th e a s t, and w est s id e of th e k n o ll (F ig u re 7 ). The n o rth w est a re a i s th e m ost exte n s iv e and re p re s e n ts a d r a s t i c change in lith o lo g y from th e o th e r r e e f f a c ie s. T o p o g rap h ically th e ro c k s u rfa c e becomes f l a t t e r and d ip s n o rth ward a t a low a n g le away from th e c o re. T h is a re a ex ten d s from th e core and from th e c l i f f on th e e a s t s id e o f th e k n o ll to th e w e ste rn edge of th e o u tc ro p. D eb ris in th e s o u th e a s te r n a re a ex ten d s from th e f a u l t on th e so u th ern edge of th e o u tcro p n o rth and w est in to th e c o ra l and M icro so lena-s tr o m a to lite f a c ie s and e a s t to th e edge o f th e c l i f f. T his a re a i s a ls o f l a t and shows a low to p o g ra p h ic r e l i e f. The w estern a re a i s th e s m a lle s t d e b ris a re a exposed. T h is l i t h o f a c i e s i s re m in is c e n t of th e h a lo o f d e b ris seen around many R ecent p a tc h r e e f s (G a rre tt and o th e rs, 1971). C oral F a c ie s The m a trix in th e c o r a l f a c ie s i s dom inated by m i c r i t i c mud w ith p atch es of s h e l l d e b r is. A ccording to Embry and K lo v an's (1971) c l a s s i f ic a tio n o f re e f m a te r ia l, t h i s f a c ie s i s a medium g rey to brow n-grey

24 17 c o ra l b a f f le s to n e to fram estone w ith a m udstone to w ackestone m a trix (F ig u re 8 ). C o rals dom inate th e fauna in t h i s f a c ie s. M a ssiv e -c o ra ls a re most abundant in th e f a c i e s, alth o u g h b ran ch in g c o r a ls a r e a ls o im porta n t. The m assive c o r a ls found h e re in c lu d e th e th a m n a ste ro id s, M icro- so len a texan a and T ham nasterea s p., and a c e ro id c o r a l, A c tin a s tre a sp. M y rio p h y llia s p., a g lo b u la r m eandroid c o r a l, i s a lso p re s e n t in a few p la c e s. The b ran ch in g c o r a ls a re dom inated by a sm all p h a celo id c o r a l, C la d o p h y llia s p., and a la r g e r p h a c e lo id, C alam ophyllia sp. A few o th e r r a r e u n id e n tif ie d b ran ch in g c o r a ls a re a ls o p re s e n t. P e p lo sm ilia s p., a s o l i t a r y c o r a l, a ls o o ccu rs c o n s is te n tly th ro u g h o u t t h i s f a c ie s. A ll of th e c o r a ls a r e r e c r y s t a l l i z e d to m icro sp ar o r s p a rry c a l c i t e (F ig u re 9 ). Minor c o n s titu e n ts o f th e c o r a l f a c ie s in c lu d e th e r u d i s t s, P e ta lo d o n tia sp. and Coalcomana ram osa, b iv a lv e s w hich a r e dom inant in o th e r f a c i e s. E n c ru stin g b ry o zo an s, e c h in o id s, sm all b ra c h io p o d s, and b iv a lv e s a re a ls o common. Red c o r a llin e a lg a e, o s tra c o d s, trochoform g a stro p o d s, and fo ra m in ife ra a re p re s e n t b u t r a r e. B oring i s e v id e n t in most o f th e m assive c o ra ls and in th e r u d i s t s. The c o r a l f a c ie s cro p s o u t in th e so u th e rn a re a of th e k n o ll and form s a c re sc e n t-sh a p e d zone (F ig u re 7 ). The c o ra l f a c ie s may n o t be p re s e n t on th e e a s t s id e of th e r e e f becau se o f f a u ltin g in th e a r e a. The c o r a l f a c ie s g rades in to th e m o llu scan d e b ris f a c ie s and in to th e u n d e rly in g foram d e b r is. On th e so u th w estern edge o f th e c o r a l f a c i e s, c o r a l i s in te r s p e r s e d w ith T o u casia sp. and o y s te r s. T here i s l i t t l e

25 18 F ig u r e 8. C oral F a c ie s

26 19 Figure 9. Recrystallization of Corals

27 20 to p o g raphic r e l i e f in th e c o ra l f a c ie s, and i t i s covered by s o i l and ru b b le in some a r e a s. Thus, th e t o t a l g eo g raphic e x te n t of t h i s f a c ie s i s n o t known. M icro so len a-s tr o m a to lite F a c ie s The m a trix of th e M icro so le n a -s tr o m a to lite f a c ie s i s dom inated by f in e s tr o m a to litic muds. The ro c k i s a medium to l i g h t g rey M icro- so len a texan a b in d sto n e w ith a s tr o m a to litic m udstone m a trix. The amount o f c o a rse d e b ris m a te r ia l in th e m a trix i s a m inor p a r t of th e lith o lo g y. Some c o a rse f o s s i l d e b ris i s p re s e n t in th e m ic r ite m a trix in th e n o rth e rn i n t e r i o r of th e M icro so len a-s tr o m a to lite f a c ie s. A la r g e p o r tio n, a v erag in g 50 p e rc e n t of th e e n t i r e ro c k, i s s tr o m a to litic muds. The f a c ie s i s dom inated by M icrosolena te x a n a. so len a i s u n d e rla in by a th in s h e e t o f sandy m a te r ia l. G e n era lly M icro The grow th h a b it v a r ie s ; i t may be lam in ar and f l a t, v e r t i c a l l y o r ie n te d, o r cup-shaped (F ig u re 1 0 ). T hick n esses o f th e c o r a l may v a ry from 0.6 to 2.5 cm (0.25 to 1 in c h ). M icrosolena te x an a commonly i s e n c ru ste d by a lg a e a n d /o r bored by organism s b eneath th e s tr o m a to litic muds. The stro m a to l i t e s ta k e on two grow th form s w ith in th e M icro so le n a -s tr o m a to lite fram ework. M icro so lena. The h em isp h ero id al form s grow up from th e s u rfa c e o f th e T his upward grow th may be h a lte d by th e p re sen c e of ano th e r c o r a l o r by p a tch e s of d e b r is. I r r e g u la r grow th form s a r e more common in t h i s framework. space betw een th e c o r a ls. These ir r e g u l a r form s f i l l in th e a v a ila b le The s tr o m a to lite s a re made up o f th in a lg a l la m in a tio n s w ith th ic k e r la y e r s of tra p p e d c a rb o n a te muds in betw een

28 21 F ig u r e 10. Growth Form o f M ic r o so le n a in th e M ic r o s o le n a - s t r o m a t o lit e F a c ie s.

29 22 and e x h ib it as much a s two in c h es in r e l i e f (F ig u res 11 and 1 2 ). Hemis- p h e ro id a l and i r r e g u l a r form s o f s tr o m a to lite s a ls o a re seen in v e r t i c a l b u ild -u p s w ith hydrozoa in th e Lower C retaceous James Reef complex in Texas (Achauer and Johnson, 1969). The s o l i t a r y P e p lo sm ilia sp. and th e la r g e r b ranchin g c o r a l C alam ophyllia sp. a re common. Large bouquets of C alam ophyllia sp. occur s p o r a d ic a lly. O ther f o s s i l c o n s titu e n ts and r u d is ts a r e r a r e. The M ic ro so le n a -s tr o m a to lite f a c ie s makes up a la r g e a re a o f th e k n o ll. I t o c cu rs to th e n o rth o f th e c o ra l f a c ie s and g rades r a p id ly in to a d ja c e n t f a c i e s. T his f a c ie s a ls o o ccu rs on th e s o u th e a s te rn s id e of th e k n o ll n o rth o f th e c o r a l f a c ie s and co n tin u e s in to th e m id d le a re a of th e k n o ll behind th e P e ta lo d o n tia f a c ie s (F ig u re 7 ). The exposu re s of t h i s f a c ie s commonly show v e r t i c a l or h ig h r e l i e f b ecau se th e w eath erin g of th e M icro so len a-s tr o m a to lite sequence makes f o r hummocky topography. T h is f a c ie s i s th e m ost e x te n s iv e on th e r e e f. Some a re a s c o n ta in e x c lu s iv e ly M icro so len a texan a and s tr o m a to litic m a te r ia l, and la rg e buildr-ups of th e se two components a re common. lim ite d to th e a re a s which b o rd e r th e c o r a l f a c ie s. Such b u ild -u p s a re Behind th e s e mounds th e re is g r e a te r v a r i a t i o n and some of th e c o ra ls from th e c o r a l f a c i e s, along w ith a few r u d i s t s, a r e in te rm in g le d w ith th e m ajor c o n s titu e n ts of th e M icro so le n a -s tr o m a to lite f a c i e s. R u d ist F a c ie s In th e r u d i s t f a c ie s th e m a trix i s c o a rse, and m olluscan f r a g m ents a r e an im p o rta n t p a r t o f th e m a trix. The r u d i s t f a c ie s lith o lo g y v a rie s from a medium brown g re y m udstone to w ackestone and r e p r e s e n ts a

30 STROMATOLITE DEBRIS MICROSOLENA Figure 11. Sketch of Microsolena-stromatolite Association

31 MICRITIC MUD SPARRY CALCITE STROMATOLITES MICROSOLENA DEBRIS 2 cm Figure 12. Sketch of Microsolena-stromatolite Growth Forms

32 25 b a f f le s to n e fram ework acco rd in g to Embry and K lo v an 's (1971) c l a s s i f i c a tio n of r e e f lim e sto n e s. The fragm ents a re th o se o f th e predom inant r u d is t in th e a re a. P e ta lo d o n tia, u p rig h t to r e c lin in g r u d i s t s, commonly show g e o p e ta l s tr u c tu r e s. G en erally th e m an tle c a v ity h as been f i l l e d w ith f in e m ic r ite muds (F ig u re 1 3 ). The c a p r in id s a r e a ls o f i l l e d w ith m ic r ite, and th e p a l l i a l c a n a ls show th e same ty p e o f f i l l in g a lth o u g h m ic ro sp ar a ls o i s p re s e n t (F ig u re 14). Two a re a s a r e dom inated by r u d i s t s : one by P e ta lo d o n tia s p., th e o th e r by c a p r in id s. The most e x te n s iv e r u d i s t a re a i s dom inated by a th ic k - s h e lle d m onopleurid, P e ta lo d o n tia sp. These r u d i s t s a r e c lo s e ly c lu s te r e d to g e th e r and a re p redom inantly in l i f e p o s itio n (F ig u re 1 5 ). Many a r e bored and g e n e ra lly only th e a tta c h e d v a lv e i s p re s e n t. C a p rin id s, along w ith M icrosolena tex an a and th e s o l i t a r y c o r a l P e p lo - s m ilia s p., a re m inor c o n s titu e n ts. These acco u n t fo r 16 p e rc e n t of th e t o t a l 36 p e rc e n t of th e ro c k re p re se n te d by f o s s i l m a te r ia l. The cap rin id -d o m in a te d a re a has le s s f o s s i l m a te r ia l th a n th e P e ta lo d o n tia s u b fa c ie s. The m a jo rity of th e c a p r in id s p r e s e n t a r e C o al- comana ram osa, a lth o u g h th e r e a re a few C ap rin u lo id e a sp. The c a p r in id s a re n o t as c lo s e ly packed to g e th e r a s th e P e ta lo d o n tia sp. and tend to be more d is p la c e d th a n th e m onopleurids (F ig u re 1 6 ). P e ta lo d o n tid s may be c lo s e r to g e th e r b ecau se th ey w ere a tta c h e d to one a n o th e r as ju v e n i l e s (R. W. S c o tt, p e rs o n a l com m unication, 1978) and b ecau se t h e i r u p rig h t c o n ic a l p o s itio n in l a t e r l i f e allo w s f o r c lo s e packing (Kauffman and S ohl, 1974). M icro so len a tex an a and P e p lo sm ilia sp. occ u r in g r e a te r amounts w ith th e c a p r in id s th a n in th e o th e r

33 26 Figure 13. Fine Mud in Rudist Mantle Cavity. Geopetal s tru c tu re in R udist, negative of peel. Figure 14. Pallial Canal Filling in a Caprinid. Negative of peel.

34 27 Figure 15. P etalo d o n tia Subfacies. Western edge of D tra n s e c t. Figure 16. Caprinid Subfacies. Quadrat F 1*

35 28 ru d ist-d o m in a te d a re a. P e ta lo d o n tid s a ls o a r e an im p o rtan t c o n s titu e n t in th e c a p r in id f a c ie s. The P e ta lo d o n tia s u b fa c ie s i s exposed in th e so u th w estern p o r tio n of th e k n o ll behind th e M icro so len a-s tr o m a to lite f a c ie s (F ig u re 7 ). This a re a i s p a r tly surrounded by a t r a n s i t i o n a l a re a th a t c o n ta in s c o ra ls and s tr o m a to litic muds. Topographic r e l i e f i s m o d erate, ap p ro x - m ately 20 f t, and th e a re a i s le s s hummocky th a n th e M icro so le n a - s tr o m a to lite f a c ie s. N o rth e a st of th e P e ta lo d o n tia s u b fa c ie s i s th e c a p rin id s u b fa c ie s, which i s a ls o surrounded by a t r a n s i t i o n a l a re a. T his i s a sm a lle r a re a :than th e P e ta lo d o n tia s u b fa c ie s and i s lo c a te d on th e h ig h e s t a re a of th e k n o ll. The a re a i s f l a t w ith a r e l i e f of only 5 f t (F ig u re 7 ). T r a n s itio n a l A reas. Not a l l of th e f a c ie s w ith in th e r e e f change a b ru p tly from one to a n o th e r. G radual changes from one f a c ie s to a n o th e r make i t d i f f i c u lt to d eterm in e where a f a c ie s te rm in a te s. T r a n s itio n a l a re a s a re common in th e a re a n o rth of th e i n i t i a l b u ild -u p of th e M icro so lena- s tr o m a to lite f a c ie s and su rro u n d in g th e two r u d i s t s u b fa c ie s. These a re a s a r e n o t dom inated by one s p e c ie s o r by a group o f s p e c ie s. In th e a re a su rro u n d in g th e P e ta lo d o n tia s u b fa c ie s, m assive c o r a ls, stro m a to l i t i c muds, and c a p rin id s a r e p re s e n t alo n g w ith th e m onopleurid. C a la - m o p h y llia sp. and P e p lo sm ilia sp. a re a ls o p re s e n t in p a tc h e s in t h i s a re a. T h is same ty p e of t r a n s i t i o n a l a re a i s p re s e n t su rro u n d in g th e c a p rin id f a c ie s, alth o u g h th e p e rc e n ta g e of th e c o r a ls i s low er.

36 29 A nother t r a n s i t i o n a l a re a o ccurs along th e r e e f edge. F a c ies along th e edges of th e re e f show an in te rm in g lin g w ith m olluscan d e b ris m a te ria l, such a s th e c o r a l f a c ie s, a t th e r e e f f r o n t. The d e b ris i s in p atch es t h a t a r e is o la te d from th e c le a n m a trix of th e c o r a l f a c ie s. Some sam ples show p a tc h e s of d e b ris and mud m a trix in te rm in g le d w ith th e c o ra ls (F ig u re 1 7 ). Along th e s o u th e a s t edge of th e o u tc ro p, d e b r is occurs in ch an n els w ith in th e M icro so lena-s tr o m a to lite m a te r ia l. In th e a re a on th e n o rth e rn edge of th e r u d i s t f a c ie s, a n o th er p a tc h of d e b ris m a te ria l i s in te rm in g le d w ith th e r u d is t f a c ie s. T his m a te r ia l becomes in c re a s in g ly dom inant to th e n o rth and w est, away from th e c e n te r of th e c a p rin id f a c ie s. F in a lly, a l l resem blance to th e r u d i s t f a c ie s i s l o s t and th e ro c k i s composed e x c lu s iv e ly of d e b ris m a te r ia l (F ig u re 1 8 ). Below th e d e b ris m a te r ia l in th e c l i f f i s a fin e -g r a in e d carb o n a te mud. T his ro c k has s i l i c i f i e d b o rin g s w ith l i t t l e ev id en ce o f o th e r o rg an ic a c t i v i t y. Below t h i s bed of m ic r itic m a te r ia l a r e th e in te r b e d - ded lim e sto n es and c a lc a re o u s s h a le s o f th e Lower M ural. R id in g 's (1977) C la s s if ic a tio n of Reef F a c ies R iding (1977) proposed a s e t of concep ts to b e t t e r d e s c rib e and u n d erstan d r e e f f a c ie s. He based h is c l a s s i f i c a t i o n of r e e f f a b r ic s on th re e m ajor com ponents: in - p la c e org an ism s, lo o s e m a trix, and c a v ity. These th r e e end members a r e used to form a tr i a n g u la r diagram in w hich sam ple p e rc e n ta g e s can be p lo tte d. The p ro p o rtio n s o f th e components a re r e la te d to th e volum e, shape, and m utual r e la tio n s h ip s o f th e o rg a nism s. In h is scheme. R iding (1977) d e fin e d fo u r ty p e s of d e p o s its :

37 30 Figure 17. T ra n sitio n a l Area.

38 Figure 18. Debris F acies. Tape ~ 1% x 1 V \ so u th east edge of reef near easte rn end of tra n s e c t C.

39 32 1) s o lid, alm o st e n tir e ly made up of o rg a n ic s k e le to n ; 2) fram e, organisms in c o n ta c t b u t w ith sp ace f o r m a trix a n d /o r c a v ity ; 3) d e n se, o r ganism s in p ro x im ity to one a n o th e r (allo w in g fo r la r g e r amounts of c a v ity or m a tr ix ) ; and 4) s p a rs e, w ith even g r e a te r space betw een organisms (F ig u re 1 9 ). R iding (1977) f e l t th a t th e lim itin g c o n d itio n s of s u b s tr a te, w a ter movement, and sed im en ta tio n a r e r e f le c te d in th e d i s t r i b u tio n o f th e s e d e p o s its. R iding d id n o t, how ever, ap p ly h is c l a s s i f i c a t i o n to a p a r t i c u l a r r e e f. T his c l a s s i f i c a t i o n i s u t i l i z e d h e re to t e s t th e a p p l i c a b i l i t y of h is co n cep tu a l scheme. The c o r a l f a c ie s c o n ta in s th e m ost d iv e r s e sh ap es. Shapes in clu d e m assiv e, g lo b u la r, b ra n c h in g, la m in a r, and in some c a se s c o n ic a l. The c o r a ls a r e in c o n ta c t w ith one a n o th e r, b u t th e com plexity of th e grow th form s a llo w s f o r c a v ity sp ace. T his f a c ie s r e p r e s e n ts a fram e s tr u c tu r e acco rd in g to R id in g s c l a s s i f i c a t i o n (1977) due to th e low d eg ree of packing and th e sm all p ro p o rtio n o f th e e n t i r e ro c k occupied by organism s (F ig u re 20). The M ic ro so le n a -s tr o m a to lite f a c ie s i s dom inated by lam in ar and e n c ru stin g fo rm s. A ccording to R iding (1977), th e s e form s u t i l i z e space m ost e f f i c i e n t l y b ecau se th e shapes conform to th e topography and le a v e l i t t l e open sp ace. The two dom inant l i f e form s seem to be in co m p etitio n w ith one a n o th e r. M icro so len a developed on a d e b ris la y e r o f m a te r ia l and may ta k e on a h o r iz o n ta l o r cup-shaped grow th h a b it. When M icro so len a tex an a appeared to d ie in one a re a and became o v e rla in w ith s tr o m a to litic m a te r ia l, a liv in g p a r t of th e same c o r a l grew v e r t i c a l l y. The p ro c e ss s t a r t e d over a g a in w ith th e M icro so len a

40 ORGANIC-SKELETON So Solid F Frame Dense % organic Sparse MATRIX m/c ratio CAVITY F ig u re 19. R id in g 's Three-com ponent Diagram.

41 34 CO Cora I P.. Petalodontia CA C a p r i n i d M /s Microsolena / St roma tol i te F ig u re 20. F a c ie s P lo tte d on R id in g fs Three-com ponent Diagram. m /s may ap p ear as a dense or s o lid framework.

42 e n c ru stin g on a th in la y e r of c o a rse m a te r ia l, alth o u g h lo c a l ly th e c o r 35 a l grew d i r e c t l y over th e s tr o m a to litic mud. T his p ro c e ss formed a s ta b le v e r t i c a l fram ew ork. A ccording to R id in g 's system, a s o lid s tr u c tu r e i s id e a l ly m o n o sp ecific. A lthough h e would c la s s if y s tr o m a to litic muds w ith th e m a trix in s te a d of f o s s i l m a te r ia l, th e s tr o m a to lite s a r e c le a r ly r e p r e s e n ta tiv e of a l i f e form. T h is f a c ie s shows m assiv e v e r t i c a l grow th of lam in ar and e n c ru stin g form s t h a t form a s o lid to sem i s o lid s tr u c tu r e. P e ta lo d o n tia sp. a r e th ic k - s h e lle d c o n ic a l, u p rig h t r u d i s t s th a t a r e u s u a lly found in l i f e p o s itio n. They form a t i g h t l y packed netw ork. In p a r ts o f th e P e ta lo d o n tia s u b fa c ie s la r g e bouquets of b ran ch in g c o r a l cau se packing th a t i s n o t a s t i g h t a s w ith in th e c lu s t e r s o f r u d i s t s. O v e ra ll, th e s t r u c t u r e of t h i s s u b fa c ie s would be c l a s s i f i e d a s d en se. In a dense fram ework th e organism s a c t as a b a f f le to th e c u r r e n ts. The b a f f le e f f e c t allo w s sed im en ts to s e t t l e in betw een in d iv id u a l organism s. The c a p r in id s u b fa c ie s i s a m arg in al s tr u c tu r e, acco rd in g to R id in g 's c l a s s i f i c a t i o n. The r u d i s t s in t h i s a re a a r e n o t a s c lo s e ly grouped to g e th e r a s in th e P e ta lo d o n tia s u b fa c ie s. The same shape domin a te s t h i s s u b fa c ie s, b u t few er in d iv id u a ls a r e in l i f e p o s itio n and more broken m a te r ia l i s p r e s e n t. T here i s le s s chance o f th e c a p r in id s a c tin g a s a se d im e n t-tra p p in g fram ew ork b ecau se of th e la r g e r amount o f space betw een in d iv id u a l o rganism s. T his s u b fa c ie s would be co n sid e re d a s p a rse fram ework. The co n cep ts p re se n te d by R iding (1977) work w e ll in d e s c rib in g th e s tr u c tu r e o f th e r e e f f a c ie s, a lth o u g h th e r e i s a problem w ith

43 36 c la s s if y in g s tr o m a to lite s. S ince th ey a re n o n - s k e le ta l m a te r ia l, th ey would appear c lo s e r to th e m a trix " p o le of th e tr ia n g u la r diagram p ro posed by R iding (1977) (F ig u re 2 0 ). The s t r u c t u r a l p a tte r n formed by th e s tr o m a to lite s su g g e sts p la c in g them c lo s e r to o rg a n ic m a te r ia l. C la ssify in g s tr o m a to lite s a s a m a trix o r o rg a n ic m a te r ia l would le ad to d i f f e r e n t c o n c lu sio n s a s to th e s tr u c tu r e of th e f a c ie s. The f a c ie s could be c l a s s i f i e d e i t h e r a s a s o lid s tr u c tu r e ( i f s tr o m a to lite s w ere co n sid ered p a r t o f th e m a tr ix ). T h is would have an in flu e n c e on th e en v ironm ental i n t e r p r e t a t i o n of th e M icro so le n a -s tr o m a to lite f a c ie s. The en v iro n m ental i n te r p r e ta tio n s of r e e f f a c ie s may be i n f l u enced by R id in g s d e s c r ip tiv e c l a s s i f i c a t i o n. D e sc rib in g f a c ie s in t h i s way c r e a te s an aw areness o f grow th m orphology and th e r e la tio n s h ip o f th e o rg an ic m a te r ia l to m a trix and c a v ity sp ace. T his s e rv e s a s a b a s is f o r th e a n a ly s is of en v iro n m ental f a c to r s a f f e c tin g th e r e e f f a c ie s. R id in g s c l a s s i f i c a t i o n o n ly a c ts as a v e h ic le f o r f u r th e r d e s c r ip tio n of th e f a c ie s, n o t as an i n t e r p r e t e r of th e f a c ie s. D e n sity and D iv e rs ity D en sity and d i v e r s i t y w ere a ls o used to d e term in e f a c ie s w ith in th e r e e f. D ensity r e f e r s to th e r e l a t i v e p ro p o rtio n o f f o s s i l m a te r ia l and m a trix m a te r ia l. D iv e rs ity c o n sid e rs th e number o f s p e c ie s, t h e i r r e l a t i v e abundance, and th e v a r ie ty of grow th m o rp h o lo g ies. F o s s il m a te r ia l in th e c o r a l f a c ie s r e p r e s e n ts 34 p e rc e n t o f th e t o t a l ro ck. D iv e r s ity i s h ig h, w ith as many a s 11 g enera p r e s e n t. N ine g enera a re ab u n d an t. M o rp h o lo g ic ally, 4 m assiv e c o r a ls, 2 common b ran ch in g c o r a ls, 1 s o l i t a r y c o r a l, and 2 c o n ic a l r u d i s t s a r e

44 37 p re v a le n t in t h i s f a c ie s. A ccessory f o s s i l s a re abundant and d iv e rs e. T his f a c ie s does n o t show th e d e f i n i t i v e dominance e v id e n t in o th e r f a c ie s w ith in th e r e e f. The M ic ro so le n a -s tr o m a to lite f a c ie s i s d e c e iv in g because o n ly 30 p e rc e n t o f th e ro c k i s made up of o rg a n ic s k e le ta l m a te r ia l. T his f ig u r e, how ever, does n o t in c lu d e th e s tr o m a to litic muds th a t make up 50 p e rc e n t o f th e t o t a l ro ck. In c lu d in g th e s tr o m a to litic muds means 80 p e rc e n t o f th e ro c k was c re a te d by o rg a n ic a c t i v i t y. Looking a t th e s tr o m a to lite s in t h i s way makes t h i s f a c ie s th e m ost dense in th e r e e f. The d e n s ity in th e M icro so le n a -s tr o m a to lite f a c ie s i s a p ro d u c t of th e lam inar and e n c ru s tin g form s of th e organism s in v o lv e d. D iv e rs ity i s low, and M icro so lena tex an a i s dom inant (ex clu d in g th e s tr o m a to litic mat e r i a l ). S o lita r y c o r a ls and a few b ran ch in g c o r a ls a r e p re s e n t in minor amounts in some a re a s of th e f a c ie s. A ccessory fauna a r e few; b o re rs and e n c ru s tin g a lg a e a r e th e m ost p re v a le n t. The P e ta lo d o n tia s u b fa c ie s shows one of th e h ig h e s t d e n s itie s in th e r e e f ; 38 p e rc e n t of th e t o t a l ro ck i s composed of f o s s i l s. The reaso n f o r t h i s i s th e dom inance o f one m orphology and th e c lo se n e ss o f th e f o s s i l s to one a n o th e r. The c a p rin id s u b fa c ie s on th e av erag e conta in s o n ly 30 p e rc e n t f o s s i l m a te r ia l. Even though one m orphologic ty p e d o m inates, th e p e rc e n ta g e in t h i s a re a i s a f f e c te d by th e la c k of c lo s e c lu s te r in g o f th e r u d i s t s th a t i s p re s e n t in th e o th e r r u d i s t s u b fa c ie s. In th e P e ta lo d o n tia s u b fa c ie s, P e ta lo d o n tia sp. i s subdom inant. D iv e r s i t y i s low in b o th a r e a s, a lth o u g h th e r e a r e a few o th e r f o s s i l s such

45 38 as a s o l i t a r y c o r a l and is o la te d m assiv e c o r a ls. A ccessory fau n a and f lo r a a r e lim ite d to a few b o re rs and d asy cladacean a lg a e. The f a c ie s m entioned above r e p re s e n t e s s e n t i a l l y in - p la c e f o s s i l m a te ria l. The d e b ris f a c ie s i s composed of tra n s p o rte d m a te r ia l from th e r e e f and c o n s is t of broken f o s s i l m a te r ia l; m o llu sc s, d asy clad acean a lg a e, f o r a m in ife r a, and su ch m inor elem ents as sm all b iv a lv e s and g a s tro p o d s. The mud p e rc e n ta g e i s low, much le s s th an in any of th e m ain re e f f a c ie s. A sm all p e rc e n ta g e o f th e t o t a l ro c k (19 p e rc e n t) i s fo s s i l m a te r ia l and p ro b ab ly does n o t re p r e s e n t in - p la c e f o s s i l s. C lu s te r A n aly sis A com puterized c l u s t e r a n a ly s is was done u sin g d a ta from th e q u a d ra ts. N ine v a r ia b le s M icro so le n a, C alam o p h y llia, C la d o p h y llia, P e p lo s m ilia,. o th e r b ran ch in g c o r a ls, c a p r in id s, P e ta lo d o n tia, A c tin a s - tr e a, and o th e r u n id e n tif ie d c o r a ls were s e le c te d. A nalyses on b o th r e l a t i v e abundance and p re sen c e -a b se n c e d a ta were done. The r e l a t i v e abundance d a ta w ere c a lc u la te d w ith e u c lid ia n squared s i m i l a r i t y c o e f f i c i e n t and a n e a r e s t n eig h b o r and av erag e g ro u p in g. The b e s t c l u s t e r ing was w ith averag e g ro u p in g. The dendrogram r e s u ltin g from t h i s a n a ly s is (F ig u re 21) shows a t i g h t c lu s te r in g of M icro so le n a -s tr o m a to lite sam ples. A nother c lu s t e r shows th e r u d i s t sam ples to have a h ig h d egree of s im ila r ity. A th ir d c l u s t e r (la b e le d T) h as no r e a l g eo g rap h ic exp re s sio n. f a c ie s. T h is c l u s t e r seems to r e p r e s e n t a re a s o f t r a n s i t i o n betw een The l a r g e s t d iscre p a n c y betw een q u a l i t a t i v e l y d e fin e d f a c ie s p a tte r n s and th e s t a t i s t i c a l r e s u l t s i s th e c o r a l f a c ie s. T here a re two p o s s i b i l i t i e s why c lu s t e r i n g does n o t occu r in th e c o r a l sam ples:

46 R RUDIST C COR AL T t r a n s i t i o n a l M/S-MlCROSOLENA-STROM» o ir c r o o e* O' ar try cr o* ar N m m N N -A F ig u re 21. C lu ste r A n aly sis Dendrogram (jj VO

47 1) th e la c k o f dominance by any one organism ; and 2) th e p a tc h in e s s o f o th e f o s s i l s, making a i m q u a d ra t in a d e q u a te fo r t h i s a re a. The c o r a l sam ples g e n e ra lly d id n o t group w ith any o f th e o th e r f a c ie s t h a t d id c l u s t e r, and s e v e ra l a r e found to g e th e r in th e dendrogram, b u t th e se 40 c lu s t e r a t a v e ry low le v e l. The c o r a l f a c ie s i s s t i l l co n sid e re d a v a lid grouping b ecau se th ey a r e s e t a p a r t s t a t i s t i c a l l y from th e o th e r f a c ie s and because o f t h e i r d if f e r e n c e s in f i e l d o b s e rv a tio n s. A nother grouping la b e le d D r e p r e s e n ts a few sam ples th a t a r e along th e edge o f th e re e f c o re. These sam ples r e p r e s e n t a t r a n s i t i o n from d e b r is and i n t e r - r e e f f a c ie s in th e n o rth e rn and so u th e rn edges o f th e r e e f - t o - re e f c o re environm ents. A summary o f c h a r a c t e r i s t i c s o f th e f a c ie s th a t group to g e th e r in th e c l u s t e r a n a ly s is i s seen in F ig u re 22.

48 FACIES-* TRAITS 4. DEBRIS CORAL MICRO/STROM RUDIST " POSITION Fore reef Reef front Reef crest Reef flat ( back reef) TOPOGRAPHIC RELIEF Low relief Low relief High relief Moderate to low relief DOMINANCE n/a None Mlcrosolena Petolodontla or Coalcomona DIVERSITY n/a High Low Low to moderate PRESERVATION n/a In place fossil recrystaii Ized In place fossil recrystallized 1n place and broken, recrystallized MINOR FAUNA Oolites, Oasycladacean. algae fragments BrachlopodS'Rud ists, Bryozoa ns. Bivalves, Echlno!ds,Coralllne algae,gastropods Boring organ Isms Coralline algae Boring organisms Dasyclad algae Sand size Fine muds, Fine grained Molluscan MATRIX Subrounded Molluscan fragments patches of coarse material stromatolltic muds frag ments in fine grained muds ROCK NAME Wackestone Gralnstone F ramestone Blndstone Bafflestone F ig u re 22. Summary of F a c ies C h a r a c te r is tic s

49 CHAPTER 3 ENVIRONMENTAL INTERPRETATION The r e e f d e sc rib e d h e re i s a sm all p a tc h r e e f t h a t i s in a s e r i e s of e s s e n tia l ly n o rth - tre n d in g r e e f s. The r e e f developed on a sh o aled a re a of m o lluscan-foram d e b ris m a te r ia l (S c o tt and B ren ck le, 1977). T his gave th e c o r a ls a p ack sto n e to g ra in s to n e s u b s tr a te to a tta c h to and b u ild upon., When r e e f - b u ild in g organism s develop a s tr u c tu r e h ig h e r th an th e su rro u n d in g a r e a s, w a ter c ir c u la t io n i s a f f e c te d. With w a ter c u r r e n ts a f f e c te d, th e se d im e n ta tio n p a tte r n s a l t e r and z o n a tio n o fte n ta k es p la c e w ith in th e r e e f and in th e su rro u n d in g a r e a s. A r e e f i s o fte n d iv id e d in to f iv e zones: 1) f o r e - r e e f, an a re a of s k e l e t a l deb r i s ; 2) r e e f f r o n t, an a re a of abundant s k e l e t a l grow th; 3) r e e f c r e s t, th e h ig h e s t p a r t of th e r e e f and s u b je c t to th e m ost wave energy 4) th e r e e f f l a t, a p ro te c te d a re a behind th e c r e s t ; and 5) th e back r e e f, a m ud-rich a re a w ith mud- and sand-p ro d u cin g fauna (Jam es, 1978). F ore Reef The h a lo o f m olluscan d e b ris r e p r e s e n ts th e f o r e r e e f. The l ith o lo g i c change from th e r e e f c o re to f o r e r e e f i s g ra d u a l on th e n o rth s id e of th e r e e f and a b ru p t on th e w est, and s o u th e a s t s id e s. The n o rth e rn p a r t o f th e f o r e r e e f c o n ta in s b lo c k s of s k e l e t a l d e b r is from th e r e e f c o re. A ll of th e d e b ris m a te r ia l i s subrounded s a n d -siz e d p a r t i c l e s th a t su g g est h ig h w ater energy. T h is f a c i e s i s p ro b ably a 42

50 r e s u l t of wave energy and b io g e n ic a c t i v i t y. Some m a te r ia l in t h i s f a c ie s i s d e riv e d from o th e r p a r ts o f th e r e e f. 43 Reef F ro n t The c o r a l f a c ie s r e p r e s e n ts th e r e e f f r o n t a re a. The d iv e rs e fauna of v a rio u s m orphologies in d ic a te a m oderate wave energy (Jam es, 1978). Because liv in g c o r a ls a re i n t o le r a n t of se d im e n ta tio n, th e c o r a l f a c ie s m ust have been in an a re a o f low se d im e n ta tio n. The p re sen c e of c o ra ls in th e r e e f i s a ls o ev id en ce of a norm al s a l i n i t y. T ra n s p o rta tio n or d is tu rb a n c e of th e f o s s i l s i s s l i g h t on th e r e e f f r o n t, b u t some of th e b ran ch in g c o r a ls a r e on t h e i r s id e s, presum ably d is p la c e d by storm waves. R eef C re st The M ic ro so le n a -s tr o m a to lite f a c ie s re p re s e n ts th e r e e f c r e s t zone. The c r e s t a re a shows a ra p id b u ild -u p of la y e re d m a te r ia l and an in c re a s e in to p o g ra p h ic a l r e l i e f. The M icro so le n a -s tr o m a to lite f a c ie s co n tin u e s behind th e i n i t i a l v e r t i c a l b u ild -u p. The r e e f c r e s t i s b e hind th e c o r a l f a c ie s. The la m in a r and e n c ru stin g grow th m orphology can w ith sta n d g r e a t p h y s ic a l s t r e s s and i s ev id en ce o f a h ig h -e n e rg y e n v i ronment.. The p o s itio n of th e c r e s t su g g e sts s tro n g c u r r e n ts from th e s o u th e a s t, becau se th e c r e s t would form w here th e c u r r e n ts a re s tr o n g e s t. Reef F la t The re e f f l a t a re a h as a v a r ie ty o f f a c ie s in d ic a tin g th e d i f f e r e n t environm ents c re a te d behind th e r e e f c r e s t. The f l a t i s dom inated by th e two r u d i s t f a c i e s. T r a n s itio n a l a re a s a r e common in th e r e e f

51 f l a t, e s p e c ia lly around th e ru d ist-d o m in a te d a r e a s. A reas of ru b b le a re s c a tte r e d th ro u g h o u t th e r e e f f l a t w ith sm all mounds o f M icro so le n a - s tr o m a to lite m a te r ia l. The r u d i s t s occur in a re a s of low er energy behind th e r e e f c r e s t and w ere s u b je c t to in f lu x of r e e f d e b ris from th e r e e f f r o n t. The deb r i s was b ro u g h t over th e r e e f c r e s t by wave energy and dumped in th e calm er a re a s of th e r e e f f l a t. A low er energy, p ro te c te d environm ent i s in d ic a te d by th e p o s itio n of th e r u d i s t f a c ie s w ith r e l a t i o n to th e r e e f c r e s t. The p e ta lo d o n tid ' s u p rig h t c o n ic a l p o s itio n e le v a te s th e commissu re above th e sedim ent w a ter in te r f a c e. The c o n ic a l shape gave th e b i v a lv e th e a b i l i t y to crowd c lo s e ly to g e th e r and th u s added s t a b i l i t y to th e o th e rw ise u n s ta b le p o s itio n. The c a p r in id s a r e th in n e r and have curved tu b u la r shape allo w in g fo r a la r g e r atta ch m e n t a re a on th e subs t r a t e. The c a p r in id shape does n o t allo w f o r th e c lo s e c lu s te r in g seen in th e P e ta lo d o n tia s u b fa c ie s (Kauffman and S ohl, 1974). P e ta lo d o n tid c lu s t e r s show l e s s d is tu rb a n c e and le s s borken m a te r ia l th a n th e c a p r i n id s u b fa c ie s. Surges in wave energy p ro b ab ly caused th e d is tu rb a n c e s in th e r u d i s t s u b fa c ie s and seems to have had a g r e a te r e f f e c t on th e c a p r in id s. D asycladacean a lg a e a r e a ls o p re s e n t in p o rtio n s of th e r e e f f l a t and a re ev id en ce o f a low -energy, sh allo w -w ate r environm ent (Wray, 1977). The sam ples c o n ta in in g th e a lg a e a r e in th e c a p rin id f a c ie s and th e su rro u n d in g t r a n s i t i o n a l a re a. The M ic ro so le n a -s tr o m a to lite m a te r ia l in th e r e e f f l a t i s s c a t te re d and c o n ta in s many c o r a ls p re s e n t in th e c o r a l f a c i e s. These sm all

52 a re a s p ro b ably re p r e s e n t sh allo w -w ater w ave-sw ept a re a s in th e r e e f f l a t (Jam es, 1978). 45 Back Reef A back r e e f zone i s n o t e a s ily recognized in t h i s p a tc h r e e f and i s p ro b ab ly p a r t of what has been c a lle d th e r e e f f l a t. The back r e e f i s ty p ic a lly re p re s e n te d in r e e f s by b ra c h io p o d s, o s tra c e d s, c r in o id s, and o th e r mud- and sand-p ro d u cin g fauna. Stubby d en d ro id and bushy knobby c o r a l grow th h a b its, m orphologies t h a t can w ith sta n d a g ita tio n and q u ie t muddy p e rio d s, a r e common in th e back r e e f (Jam es, ).. I su sp e c t t h a t th e c a p rin id s u b fa c ie s and a re a s w est of t h i s in th e M icro so le n a -s tr o m a to lite f a c ie s and th e anomalous c o r a l f a c ie s a re a a re in th e back r e e f zone. The c a p rin id h a b ita t i s im ita tiv e of s o l i t a r y c o r a ls, and th e re i s an in c re a s e o f s o l i t a r y and b ran ch in g c o r a ls in th e n o rth e rn p a r t of th e re e f th a t could cope w ith c o n d itio n s o f th e back r e e f. The zo n atio n seen in t h i s sm all p a tc h r e e f i s asy m m etrical. The r e e f c o re (th e r e e f c r e s t, r e e f f l a t, and back r e e f ) i s e lo n g ated and covers a la r g e p o rtio n o f th e r e e f. The o n ly h a lo e f f e c t seen i s p atch y and re p re s e n te d by th e fo r e r e e f. P atch r e e f s commonly show a h a lo on th e r e e f f r o n t a ls o, b u t t h i s i s n o t e v id e n t from what i s seen in th e o u tcro p (Jam es, 1978). The r e e f p ro b ably had a v e ry hummocky topography when a l i v e. The r e e f c r e s t was th e h ig h e s t p a r t of th e r e e f. The v e r t i c a l r i s e from th e r e e f f r o n t to th e c r e s t was p ro b ab ly q u ite a b ru p t, b u t behind th e c r e s t th e slo p e a p p ears to have been g ra d u a l away from th e c r e s t. The d e e p e st a re a of th e r e e f i s th e r e e f f r o n t. The

53 46 re e f c r e s t was in sh allo w e r w a ter. A d e p o s itio n a l model o f th e d i f f e r ent f a c ie s i s shown in F ig u re 23. Below th e d e b ris m a te r ia l in th e c l i f f a re a th e r e i s a c o n tin u ous la y e r of v e ry f in e g ra in e d c a rb o n a te m a te ria l p re s e n t. T his s e c tio n i s alm ost co m p letely devoid of f o s s i l m a te r ia l; only s i l i c i f i e d b o rin g s, ap p ro x im ately 0.5 in c h e s in d ia m e te r, su g g est b io g e n ic a c t i v i t y. The m a te ria l i s such f in e - g r a in e d lim e mud th a t th e s u b s tr a te was p ro b ab ly too s o f t to su p p o rt any r e e f fauna. The d e p o s it would in d ic a te a sh allo w -w ater, low -energy environm ent th a t allow ed fin e -g r a in e d m a te r ia l to drop o u t of su sp e n sio n. Below t h i s f a c ie s, th e topography and l i t h o l ogy change to th e g e n tle slo p in g sh ale y c a rb o n a te s o f th e low er member of th e M ural L im estone.

54 DEBRIS CAPRINID PETA LODONTI A MICROS. NA /STROM CORALS DEBRIS C u rren ti MASSIVE CORALS I Microsolene) SOLITARY CORALS BRANCHING CORALS CAPRINIDS PETALODONTIDS Q Percent reletive abundance F ig u re 23. D e p o sitio n a l Model of R eef.

55 CHAPTER 4 COMPARISON TO CONTEMPORANEOUS REEFS IN TEXAS The M ural L im esto n e i s contem poraneous w ith th e G len Rose Formatio n of th e T r in ity D iv isio n of c e n tr a l Texas. The Glen Rose c o n ta in s s e v e ra l re e f zones of v a rio u s a g e s. A low er M iddle A lbian r e e f zone in th e Glen Rose (P e rk in s, 1974) p ro v id e s an o p p o rtu n ity f o r com parison w ith th e M ural r e e f analy zed h e re. The r e e f s in th e a re a s tu d ie d by P e rk in s a r e dom inated by c a p - r in i d s. The r e e f s a r e made up of th r e e c o n s titu e n ts : 1) c a p r in id s in p la c e, a c tin g as a sed im en t-b in d in g fram ework; 2) broken c a p r in id s and lith o c a s t s ; and 3) la y e r s of p a le o c a lic h e, w eathered ro c k, and o th e r evidence of p e rio d ic s u b a e r ia l exposure. The lith o lo g y of th e ro c k i s p ackstone except fo r th e m udstone th a t f i l l s th e m an tle c a v i t i e s of th e c a p rin id s. Behind th e r e e f a re a a re m onopleurid b io stro m e s, o y s te r b io - stro m es, and a t r a n s i t i o n a l a re a betw een th e se two b io stro m a l a r e a s. These a re a s have a la r g e amount of c l a s t i c m a te r ia l and a r e co n sid e re d w ackestone to m udstone (P e rk in s, 1974). The b io stro m es and th e r e e f s ru n p a r a l l e l to th e s h o r e lin e, w ith th e o y s te r b io stro m es c lo s e s t to th e s h o re lin e. The Texas and Arizona re e fs d iffe r in the faunal c o n stitu e n ts th a t play an im portant r o le in th e development of th e re e f s. The caprin id s a ct as a tra p fo r sediment and are a dominant p a rt of the re e f in the Glen Rose, whereas th e Mural re e f i s dependent on c o ra ls and 48

56 49 s tr o m a to lite s, a s w e ll as r u d i s t s, f o r r e e f developm ent. A lthough P erk in s (1974) does m ention c o ra ls in th e Texas r e e f s, th e y do n o t seem to p lay a m ajor r o le. P e rk in s p o s tu la te s t h a t th e su b o rd in an ce of c o r a l s i s due to s a l i n i t y. P e rk in s s t a t e s th a t norm al m arin e w a te rs were brought w estw ard a c ro ss th e broad s h e l f, and s a l i n i t y was a lte r e d by e v ap o ratio n and ru n o ff from th e Llano u p l i f t. The in s ig n if ic a n c e of th e c o r a ls in com parison to th e r u d is ts in developm ent of th e Texas r e e f s may be in d ic a tiv e of l e s s th an norm al m arine c o n d itio n s in th e Glen Rose. R. W. S c o tt (p e rso n a l com m unication, 1978), how ever, su g g ested c o r a ls may be abundant in th e s u b su rfa c e, seaward of th e a re a s tu d ie d by P erk in s on th e o th e r s id e of th e B alcones F a u lt. The ev id en ce o f exposure a t s e v e ra l s ta g e s th ro u g h o u t th e d e v e l opment of th e r e e f s i s a n o th e r im p o rtan t d if f e r e n c e in th e Glen Rose and th e M ural r e e f s. E vidence fo r s u b a e r ia l exposure i s n o t p re s e n t in th e M ural. P e rk in s (1974) b e lie v e d th e Glen Rose r e e f s to be w ith in 50 m ile s of s h o re lin e. In th e m onopleurid b io stro m e s, 5-10 m ile s behind th e r e e f s, d in o sau r tra c k s a r e p re se rv e d. T his in d ic a te s a sh a llo w -w a te r, n e arsh o re environm ent. P e rk in s (1974) d e s c rib e s t h i s a re a as a f e a tu r e le s s s h e lf w ith a g e n tle slo p e away from th e s h o re lin e. Bay (1977) conc u rs w ith P e rk in s and r e f e r s to th e Glen Rose s h e lf a s a ramp. S ubsurface and s u rfa c e s tu d ie s (Bay, 1977) in d ic a te th a t a marked b re a k in slo p e did n o t e x is t in e a r ly Glen Rose tim e. T h e re fo re, th e r e e f s of c e n tr a l Texas r e p r e s e n t th e h ig h e s t energy, sh allo w -w ate r sed im e n ta tio n th a t o ccu rred d u rin g t h i s tim e. The f a c t t h a t r e e f s w ere exposed se v e r a l tim es d u rin g t h e i r developm ent i s f u r th e r ev idence of a v e ry g e n tle

57 50 slo p e. The f la tn e s s of th e a re a had a g r e a t e f f e c t on environm ents whenever th e r e was a s l i g h t change in sea le v e l. The M ural r e e f s app ear to have developed on a h ig h e r a n g le s lo p e because th e r e i s no e v i dence of ra p id changes in en v iro n m en tal c o n d itio n s. F u rth e r evidence of th e M ural r e e f s bein g on a g r e a te r slo p e i s th e in c re a se d p resen ce of c a p r in id s and m onopleurids in th e north ern m o st r e e f s of th e M ural (R. W. S c o tt, p e rso n a l com m unication, 1978). In th e se n o rth e rn r e e f s, th e c o r a ls seem to be le s s im p o rtan t in th e f o r m ation of th e r e e f s. C o rals appear to dom inate in d eep er w ater e n v iro n m ents o f norm al s a l i n i t y, w h ile r u d i s t s dom inate in sh allo w er w ater environm ents of abnorm al s a l i n i t y o r h ig h e r sedim ent in f lu x. The M ural p atch r e e f s tu d ie d r e p re s e n ts a sm all r e e f in w hich r u d i s t s, th e m ain component of many o th e r r e e f s of th e Lower C retaceo u s, a r e n o t th e m ajor r e e f - b u ild e r s. Herm atypic c o r a ls bound to g e th e r by b lu e -g re e n a lg a l s tr o m a to lite s c o n stru c te d a r e s i s t a n t fram ework, th e b a s is o f th e r e e f. The r u d i s t s a r e secondary and a r e p ro te c te d by th e c o ra l b a r r i e r. The dom inance of c o r a ls d is tin g u is h e s th e M ural r e e f s from o th e rs in th e Lower C retaceo u s in Texas and Mexico (P e rk in s, 1974; Smith and Bloxsom, 1974). T his i s n o t to say th a t c o r a ls do n o t occur in o th e r r e e f s w ith r u d i s t s o r do n o t form r e e f s tr u c tu r e s in th e Cretaceo u s (W ells, 1932; Lozo and S tr i c k l i n, 1956; S t r i c k l i n, Sm ith, and Lozo, 1971). C o rals commonly a re secondary components of r u d i s t - dom inated r e e f s. Exposures and docum entation a r e la c k in g on c o r a l- dom inated r e e f s o f th e Lower C retaceo u s in th e G ulf C oast. The e x te n s iv e exposure of th e M ural r e e f s makes t h i s stu d y im p o rtan t a s a. p o s s ib le model fo r su b su rfa c e m a te r ia l.

58 51 The dominance of c o r a l in th e M ural r e e f s seems to in d ic a te a h ig h er a n g le slo p e p o s itio n of th e r e e f s th a n th o se dom inated by ru d - i s t s. F u rth e r evid en ce of t h i s i s th e predom inance of r u d i s t s in th e M ural r e e f s c lo s e r to th e s h o re lin e n o rth of th e stu d y a re a. T his l i n e of r e e f s ru n n in g in a n o rth e rly, d ir e c tio n seems to be contem poraneous and shows shorew ard p ro g re s sio n p a r a l l e l to c u r r e n t d ir e c tio n. The same fa u n a l change from c o r a l to r u d i s t th a t i s seen on t h i s la r g e s c a le i s r e f le c te d in th e z o n a tio n of th e p atch r e e f d e sc rib e d in t h i s stu d y.

59 CHAPTER 5 CONCLUSIONS The M ural p a tc h r e e f s tu d ie d c o n ta in s fo u r m ajor r e e f f a c ie s. These f a c ie s a r e : 1) The c o r a l f a c ie s, a d iv e rs e a re a dom inated by a v a r ie ty of c o r a l s. The c o r a ls a c te d as a b a f f le to th e waves and c re a te d m ic ro h a b ita ts in which o th e r org an ism s, such as th e r u d i s t s, could l i v e. 2) The M ic ro so le n a -s tr o m a to lite f a c ie s, a s o lid v e r t i c a l framework o f lim ite d d iv e r s ity. 3) The two r u d i s t s u b fa c ie s, P e ta lo d o n tia and c a p r in id, dom inated by t h e i r r e s p e c tiv e r u d i s t s. These form th ic k e ts behind th e M ic ro so le n a -s tr o m a to lite f a c ie s. 4) The d e b r is f a c ie s, sem i-rounded m olluscan d e b r is. T h is f a c ie s i s p re s e n t on alm ost every s id e of th e r e e f c o re and i s deriv e d from th e r e e f c o re. D iv e rs ity i s h ig h e s t a t th e f r o n t of th e re e f in th e c o r a l f a c ie s ; no s in g le tax o n dom inates t h i s f a c ie s. O ther f a c ie s c o n ta in d i s t i n c t l y dom inant s p e c ie s. The m ost dense f a c ie s i s th e P e ta lo d o n tia f a c ie s w here th e r u d i s t s a r e t i g h t l y c lu s te r e d to g e th e r. The M icro so le n a -s tr o m a to lite f a c ie s a ls o h as a h ig h d e n s ity o f s k e le ta l m a te ria l and would be g r e a te r i f a l l of th e m a te r ia l formed by o rg a n ic a c t i v i t y i s taken in to c o n s id e ra tio n. 52

60 53 The p a tch r e e f formed in a norm al m arine environm ent. The c o ra l f a c ie s a t th e r e e f f r o n t formed in a m oderate wave energy a t medium to shallow d e p th s. The v e r t i c a l grow th o f th e M icro so le n a -s tr o m a to lite f a c ie s behind th e c o r a ls formed th e r e e f c r e s t in a sh allo w h ig h -e n e rg y environm ent. The c r e s t a c te d as a energy b a r r i e r and allow ed th e grow th o f th e r u d i s t c l u s t e r s in a sh allo w, p ro te c te d environm ent. The subrounded s a n d -siz e d f o s s i l d e b ris of th e d e b ris f a c ie s in d ic a te s th a t wave a c tio n and b io g e n ic a c t i v i t y to o k i t s t o l l on th e re e f organism s. Compared to th e r u d i s t r e e f s of e q u iv a le n t age in Texas, th e M ural r e e f, b ecau se o f th e p re sen c e of c o r a ls, in d ic a te s a more norm al m arine environm ent. The Texas r e e f s developed on a b ro ad, g e n tle s lo p ing s h e lf s o u th e a s t of th e Llano u p l i f t from which sedim ents w ere s t i l l bein g d e p o site d in to th e b a s in. had an a f f e c t on th e s a l i n i t y. R unoff from t h i s u p l i f t may have a ls o The slo p e of th e p la tfo rm made th e r e e f s s u s c e p tib le to d r a s t i c en v iro n m en tal changes, such a s s u b a e r ia l exposure. Both th e d r a s t i c en v iro n m en tal changes and sedim ent in f lu x do n o t ap p ear to be f a c to r s in v o lv ed in th e fo rm atio n of th e M ural r e e f. T his may in d ic a te th a t th e M ural r e e f s w ere on a h ig h e r an gled c a rb o n a te p la tfo rm. The r e e f s n o rth of th e r e e f s tu d ie d show an in c re a s in g dominance of r u d i s t s, which may in d ic a te g r e a te r sedim ent in f lu x and low er energy environm ents th e r e.

61 APPENDIX A QUADRAT DATA The n o te s below p ro v id e e x p la n a tio n fo r th e d a ta th a t fo llo w. A1-J5 Q uadrats m easured as seen on to p o g raphic map and f a c ie s map (F ig u res 3 and 7 ). M icro so len a; P e p lo s m ilia : C alam o p h y llia: C la d o p h y llia : m assiv e a n d /o r lam in ar th am n astero id c o r a l s o l i t a r y c o ra l la r g e (0.5 inch d ia m e ter) p h a celo id c o r a l sm all (0.2 in c h d iam eter) p h a celo id c o ra l Sm all b ran ch in g c o r a l: r a r e u n id e n tif ie d b ranch in g c o r a l T e x a s tre a : m assiv e m eandroid c o ra l A c tin a s tr e a : m assive c e ro id c o ra l C a p rin id : tu b u la r shaped r u d i s t g e n e ra lly Coalcom na ram osa, r a r e ly C ap rin u lo id e a sp. M onopleurid: c o n ic a l shaped r u d i s t, g e n e ra lly P e ta lo d o n tia s p., r a r e ly sm all u n id e n tif ie d M onopleurids T o u c a sia : m inor r u d i s t (piano s p i r a l ) (W ackestone): in d ic a tin g dom inant m a trix S izes r e f e r r e d to in r u d i s t d e s c r ip tio n : Sm all in c h in d iam eter Medium in c h e s in d iam eter Large - g r e a te r th a n 2 and up to 3.5 in c h e s in d ia m e te r. 54

62 Q u ad rats A1 A2 A3 A4 M icrosolena 10% m assive 15% m assive 15% 35% m assive P e p lo stn ilia 5% C alam ophyllia 25% 20% p re s e n t Sm all Branching C oral 5% C aprinid 6, 2 u p rig h t 9 u p rig h t and fragm ents M onopleurid ' 13% u p rig h t and fragm ents 3 sm all 10 u p rig h t medium s iz e 3 sm all 12 M atrix F in e 60% 18% 5% s t r o m a to litic - 18% C oarse 42% 45% 42% Minor Fauna, e tc. 3% hash, e ch in o id, g a stro p o d, bryozoan o y s te r, ech in o id, g astro p o d b o rin g (w ackestone) la r g e amounts of boring (m udstone)

63 Q uadrats A5 A6 B1 B2 B3 M icrosolena 15% lam in ar 10% 2% 2% 28% in c lu d e s o th e r m assive P e p lo sm ilia 2% 5% 8.5% 5% 2% C alam ophyllia 5% 8% 63% Sm all B ranch- Ing C o ra l 8% 2% 3.5% C ap rin id 1 1 sm all 1 w hole, fragm ents M onopleurid 1 A c tln a s tre a 7.5% M atrix F in e s tr o m a to litic, 35% s tr o m a to litic, 65% 9% s tr o m a to litic. f i n e, 35% 30% f in e, 45% C oarse 10% 21% ' 63% Minor Fauna b rach io p o d s, b o rin g, brachiopods e n c ru stin g a lg a e, ech in o id s e tc. d asy clad a lg a e, m ol- g a stro p o d s, b ra c h i lu scan d e b ris opods, sm all (w ackestone) amounts o f b o rin g (m udstone)

64 B4 B5 B6 B7 B8 M icrosolena 40% in c lu d e s o th e r m assive 12% 6% 3% m assive P e p lo s m illa. 2.5% 2 % 2% 2% C alam ophyllia 12% Sm all B ranching C oral 2.5% C ap rin id 5 u p rig h t few fragm ents 5 sm all 32 most u p rig h t 10 M onopleurid 1 broken 28%, h upr i g h t, h d isp la c e d 13 u p rig h t medium to la rg e M atrix F in e 5% 30% 6% C oarse 45% f o s s i l fragm ents 70% medium c o a rse 60% s i l t y to c o arse 30% medium to c o a rse 54% Minor Fauna e tc. e n c ru stin g a lg a e bryozoan, ech in o id (mudstone to w ackestone) b o rin g (w ackestone) gastropod ( T u rrit e l l a? ) la rg e amounts of r u d i s t fragm ents

65 Q u ad rats B9 Cl C2 C3 C4_ M icrosolena 3% 17.5% 6% 10% 15% P e p lo sm ilia 2% 2% 5% C alam ophyllla 7% Sm all B ranchin g C oral C aprinid 14 u p rig h t sm all to medium 3.5% 2% 5 5 fragm ented 6 1 fragm ent M onopleurld 22% on s id e 40% medium to la rg e 28% most in l i f e p o s itio n u p rig h t sm all to medium M atrix F in e 58.5% 58.5% 12% C oarse s a n d -siz e 65% 6.5% 60% medium to c o a rse 48% medium to c o a rse 70% medium to c o a rse Minor Fauna e tc. "ech in o id s, borin g e n c ru stin g a lg a e, b r a c h i- opods, e c h i n o id s (w ackestone) (mudstone to wackesto n e)

66 Q uadrats C5 C6 C7 D1 D2 M icrosolena 20% m assive and lam in ar 20% 16.5% lam inar 10% lam in ar P e p lo sm ilia. 4% C alam ophyllia 4.5% Sm all B ranching C oral T ex a strea 4%.3% 5% 1%. 2% C ap rin id 2 sm all 4 1 medium M onopleurid M atrix F in e 66% s tr o m a to lltlc, 30% C oarse 3.5% 45% 100% s h e ll d e b ris s t r o m a t o l l t l c, 30% 45% s t r o m a t o l i t i c, 56% 24% Minor Fauna e t c. e n c ru stin g a lg a e b o rin g e n c ru stin g a l gae O rb ito lin a sp. ech in o id (packestone) d asy clad a lg a e, e c h in o id s, b o r ing (w ackestone) b o rin g p re s e n t (m udstone) U i vo

67 Q uadrats D3 D4 D5 D6 El M lcrosolena 24% 16% 7.5% 7.5% 8% P e p lo sm ilia 4% 2% 6% 3% C alam ophyllia 4% 3% 8% C lad o p h y llia 1% 6% 12% Sm all B ranching C oral 4% 3% T ex astrea 2% 8% C ap rin id 4 M onopleurid M atrix F in e C oarse 2% most u p rig h t u p rig h t 9% s tr o m a to litic 8% s ilty - s a n d y 51% 72% 2 16 fragm ented s tr o m a to litic, 14% s t r o m a to litic, 56% 60% 14% 56% Minor Fauna e tc. b o rin g b iv a lv e s, (mudstone to w ackestone) b rach io p o d s, e c h in o id s, o y s te rs b rachio p o d s, b i - T oucasia, b i v a lv e s, red a lg a e, v a lv e s, o s tra c o d s, d asy clad a lg a e, frag m ents, (mude c h in o id s, g a s tr o - sto n e) pods ON o

68 Q uadrats E2 E3 E4 E5 E6 M icrosolena 34% lam inar 21% lam in ar 4% 19% lam in ar P e p lp sm ilia 4% 3% 5% 4% C la d o p h y llia 6% 2% C ap rin id +25 many on s id e M onopleurid 6 sm all 12 M atrix F in e s tr o m a to litic, 34% s t r o m a t o l i t i c, 63% 7% s t r o m a to litic, 56% C oarse 100% c o a rse d e b ris 6% 7% c o a rse to s i l t y, 63% 19% Minor Fauna e tc. b rach io p o d s, e c h in o id s, la r g e amounts of b o rin g e c h in o id s, b rachiopods (m udstone) e c h in o id s, b ra c h io p o d s, e n c r u s t in g a lg a e

69 Q uadrats FI F2 F3 F4 F5 M icrosolena 2% m assive 12% 23% 16% 9% P e p lo sm ilia 2% 3% 1% 1% C alam ophyllia 3% C la d o p h y llia 2% T e x a strea 10% C ap rin id few u p rig h t 6 1 u p rig h t 2 M onopleurid 14 6 u p rig h t medium s iz e 4 6 M atrix F in e 7% 52% s tr o m a to litic 66% s tr o m a to litic, 24$ 9% C oarse s i l t y 63% 23% 4% 52% 81% Minor Fauna e tc. d asy clad a lg a e b o rin g (wackesto n e) b rach io p o d, b i v a lv e, g astro p o d (m udstone) (m udstone) e c h in o id s, b o rin g (p ack sto n e) o y s te rs

70 Q u ad rats F6 Gla Gib G2 G3 M icrosolena 24% 8% 8% 8% 11% lam in ar P e p lo sm ilia 6% 1% 1% 3% 5% C alam ophyllia 30% 5% C la d o p h y llia 6% 5% T e x a strea 8% C ap rin id 6 1 C ap rin u - lo id e a M atrix F in e 24% 76% l s i l t y 56% s i l t y 60% C oarse 16% 90% d e b ris 4% d e b ris 24% d e b r is 15% Minor Fauna e tc. g a stro p o d, ech in o id some b o rin g g a stro p o d s, b ra c h io - pods, e c h in o id s, o y s te r s, dasy clad a lg a e (p ack sto n e to g ra in s to n e ) g a stro p o d, b rach io p o d, e c h in o id s, o y s te r s, d asy clad a l g a e, (p ack - sto n e to g ra in s to n e ) b o rin g (w ackestone)

71 Q uadrats G4 HI H2 H3 H4 M icrosolena 9% lam in ar and m assive 18% lam inar 10% 15% 3% P e p lo sm ilia 4% 3% C alam ophyllia 1% C la d o p h y llia 5% 6% T e x a strea C ap rin id 2 4% 2% 7.5% 24% 1% 1.5% 3% 4 u p rig h t M onopleurid 7 medium s iz e M atrix F in e 16% s tr o m a to litic, 21% 12% s tr o m a to litic, 60% s tr o m a to litic 4% C oarse 64% 49% 48% d e t r i t a l 20% 76% Minor Fauna e tc. o y s te rs 1% T o u casia, b rachip p o d s, e ch in o id s b rach io p o d s, e c h i n o id s, e n c ru stin g a lg a e b rach io p o d s, e c h in o id s b rachio p o d s, b o rin g e c h in o id s, o y s te r s, T u r r i t e l l a \ o> 4>

72 Q uadrats H M icrosolena 8% 16% 10% lam inar 14% 20% m assive P e p lo sm ilia 6% 6% 5% 6% C alam ophyllia 8% 4% 16% C lad o p h y llia 16% 1% 1% T e x a stre a 2% C ap rin id 5 2 M onopleurid 4 sm all 10 la rg e M atrix F in e 36% s tr o m a t o l i t i c, 49% s tr o m a to litic, 45% 16% s tr o m a to litic 60% C oarse 24% 21% 30% 64% Minor Fauna e tc. e n c ru stin g a lg a e b o rin g b o rin g b ra c h io p o d, T u r r i t e l l a ech in o id s

73 Q uadrats J1 J2 M icros olena 12% 6% P e p lo sm ilia 6% 6% C alam ophyllia 7.5% C la d o p h y llia 6% Sm all B ranch- 6% Ing C oral A c tln a s tre a 3% J3 J4_ J5 16% lam in ar 9% 7% 6% 3% 1% 4% 15% 6% 12% 6% 6% C aprlnld M onopleurld 6 on s id e 1 10 m ost u p rig h t 3 la rg e s e v e ra l broken M atrix F in e 42% s tr o m a to litic, 56% C oarse 28% patch y 14% 54% 49% s tr o m a to litic 56% 6% 21% 14% Minor Fauna b iv a lv e s, b rach io p o d s, e c h i e tc. b ry o zo an s, n o id s, bryozoan e ch in o id s b ra c h io p o d s, e c h in o id s b rachio p o d s, Toucasia T u r r i t e l l a, b ra c h io p o d s, e c h in o id s, b o rin g o> o \

74 APPENDIX B PEEL NEGATIVES N ote: The s c a le on th e fo llo w in g photographs i s 1 to

75 68 F ig u r e B -2. F ^ -C a la m o p h y llia, Sm all M onopleura.

76 69 F ig u r e B -4. Sm all C o r a ls, M a ssiv e C o r a ls, O str a c o d s, B ryozoan F ragm en ts, B o rin g.

77 70 F ig u r e B -5. B^-M ic r o so le n a on S id e. Figure B-6. C^-Caprinid on Side Showing Pallial Canal Filling.

78 Figure B-8. -Laminar Microsolena and Stromatolitic Muds. 71

79 72

80 73 Figure B-12. NE-Debris Facies, Subangular to Subrounded Material.

81 REFERENCES CITED A chauer, C. W. and Johnson, J. H., 1969, A lg al s tr o m a to lite s in th e James Reef Complex (Lower C retaceo u s, Fairw ay F ie ld, T e x a s): J o u r. Sed. P e t r o l., v. 39, p Bay, T. A., J r., 1977, Lower C retaceous s tr a tig r a p h ic m odels from Texas and M exico, in C retaceous C arbonates of Texas and M exico, A p p lic a tio n s to S u b surface E x p lo ra tio n, B ebout, D. G. and Loucks, R. G. ( e d s.) : Bureau of Economic Geology, U niv. o f T exas, A u stin, R eport of In v e s t. 89, p C oates, A. G., 1973, C retaceous Tethyan c o r a l - r u d i s t biogeography r e la te d to e v o lu tio n of th e A tla n tic Ocean: Spec. Pap. P a la eo n to lo g y, v. 12, p Coogan, A. H., 1977, E a rly and M iddle C retaceous H ip p u rita c e a ( r u d is ts ) of th e G ulf C oast, in C retaceo u s C arbonates of Texas and M exico, A p p lic a tio n s to S u b su rface E x p lo ra tio n, Bebout, D. G. and Loucks, R. G. ( e d s.) : Bureau of Economic Geology, Univ. of T exas, A u stin, R eport of I n v e s t..89, p. 38. Sm ithson Cooper, G. A., 1955, New C retaceo u s B rachiopoda from A rizona: ia n M isc. C o ll., v. 131, no. 4, 18 p. Cooper, J. R., 1959, R econnaissance g e o lo g ic map of s o u th e a s t C ochise County, A rizona: U. S. G eol. Survey M in eral In v. Map, MF-213. Dunham, R. J., 1962, C la s s if ic a tio n o f c a rb o n a te ro cks accord in g to depos i t i o n a l te x tu r e : Am. A ssoc. P e tr o l. G eol. B u l l., Memoir 1, p Embry, A. F. and Klovan, J. E., 1971, A L ate Devonian r e e f t r a c t on n o r th e a s te r n Banks I s la n d, N.W.T.: B u ll. Can. P e tr o l. G e o l., v. 19, p G a rre tt, P., Sm ith, D. L., W ilson, A. 0., and P a tr iq u in, D., 1971, Physio g ra p h y, ecology, and sed im en ts of two Bermuda p a tc h r e e f s : Jo u r. G e o l., v. 79, p Gordon, W. A., 1973, M arine l i f e and ocean s u rfa c e c u r r e n ts in th e C reta c e o u s: Jo u r. G e o l., v. 81, no. 3, p Grocock, G. R., 1975, S tra tig ra p h y and p e tro g raphy of th e Upper Member of th e M ural Lim estone in s o u th e a s t C ochise County, A rizona: U npublished M.S. T h e s is, Univ. of C olorado, B oulder, 125 p. 74

82 Hayes, P. T., 1970a, C retaceous paleogeography of s o u th e a s te rn A rizona and a d ja c e n t a re a : U. S. G eol. Survey P ro f. P aper 658-B, 42 p., 1970b, M esozoic s tr a tig r a p h y o f th e Mule and Huachuca Mount a i n s, A rizona: U. S. G eol. Survey P ro f. P aper 658-A, 28 p. H eckel, P. H., 1974, C arbonate b u ild u p s in th e g e o lo g ic re c o rd : a r e view, in R eefs in Time and Space, L a p o rte, L. F. ( e d.) : Soc. Econ. P a le o n t. and M in eral. Spec. Pub. 18, p. 90. H endricks, L., e d., 1967, Commanchean (Lower C retaceo u s) s tr a tig r a p h y and p a leo n to lo g y of Texas: Soc. Econ. P a le o n t. and M in eral. Perm ian B asin S e c tio n, Pub. No , 410 p. Jam es, N. P., 1978, F a c ie s m odels 10. r e e f s : G eoscience Canada, v. 5, p Kauffman, E. G. and S ohl, N. F., 1974, S tr u c tu re and e v o lu tio n of A n tille a n C retaceo u s r u d i s t fram ew orks: F e s t s c h r i f t f u r Hans K ugler. V erhandl. N a tu rf. Ges. B a se l, v. 84, p Lozo, F. E. and S t r ic k lin, F. L., J r., 1956, S tr a tig r a p h ic n o te s on th e o u tcro p o f b a s a l C retaceo u s, c e n tr a l Texas: G ulf C oast A ssoc. G eol. T r a n s., v. 6, p P e rk in s, B. F., 1974, P aleoecology of a r u d i s t r e e f complex in th e Comanche C retaceous Glen Rose Lim estone of c e n tr a l Texas, A spects of T r in ity D iv isio n Geology: G eoscience and Man, v. 8, p Ransome, F. L., 1904, The geology and o re d e p o s its o f th e B isbee quadr a n g le, A rizona: U. S. G eol. Survey P ro f. Paper 21, 168 p. R id in g, R., 1977, Reef c o n cepts: P ro c. T hird I n t. C o ral Reef Symp., Univ. Miami, R o se n tie l School Mar. and Atmos. S c i., v. 2, p S c o tt, R. W., in p re s s, D e p o sitio n a l model of E a rly C retaceo u s c o r a l- a l g a l - r u d i s t r e e f s, A rizona: Am. A ssoc. P e tr o l. G eol. S c o tt, R. W. and B renckle, P. L., 1977, B io tic z o n a tio n of a Lower Creta ceous c o r a l - a l g a l - r u d i s t r e e f, A rizona P ro c. T hird I n t. C oral Reef Symp., Univ. Miami, R o se n tie l School Mar. and Atmos. S c i., v. 2, p Sm ith, C. I. and Bloxsom, W. E., 1974, The T r in ity D iv is io n and equiv a l e n t s o f n o rth e rn C o ah u ila, M exico; A spects o f T r in ity D iv isio n G eology; G eoscience and Man, v. 8, p Stoyanow, A., 1949, Lower C retaceous s tr a tig r a p h y in s o u th e a s t A rizona: G eol. Soc. America Memoir 38, 169. p. 75

83 S t r ic k lin, F. L., J r., Sm ith, C. I., and Lozo, F. E., 1971, S tra tig ra p h y of Lower C retaceous T r in ity d e p o s its of c e n tr a l Texas: Univ. Texas, A u stin, Bureau of Economic Geology, R eport o f I n v e s t., 71, 63 p. T ucker, D. R., 1962, S ubsurface Lower C retaceous s tr a tig r a p h y, c e n tr a l Texas: c o n tr ib u tio n s to th e geology of South T exas, San A ntonio: South Texas G eol. S o c., p W arzeski, R. E., in p r e p., Sedim entology and p e tro lo g y of th e Lower Cretaceous c a rb o n a te s h e lf in s o u th e a s te rn A rizona and n o rth e rn Sonora, Mexico: Ph.D. D is s e r ta tio n, SUNY Binghamton. W ells, J. W., 1932, C o rals of th e T r in ity Group o f th e Comanchean of c e n tr a l Texas: Jo u r. P a le o., v. 6, no. 3, p Wray, J. L., 1977, C alcareous A lgae: E ls e v ie r, New York, p

84