TIJLANE STIJDIES IN GEOLOGY

Volume 4, Number 2 May 27, 1966

STRATIGRAPHY OF THE UPPER MIOCENE DEPOSITS IN SARASOTA COUNTY, FLORIDA HERBERT C. EPPERT . .TR . JJEPAH'l'JfEN'l' OF' GEOLOGY 'ITL.1 N£' UNII'b'RSJ'JT

CONTENTS Page I. ABSTRACT ______49 11. INTROD UCTION 50 III. ACKNOWLEDGMENTS 50 IV. PROCEDURE 50 V. STRATIGRAPHY 52 VI. MINERAL ANALYSIS OF THE AQUICLUDE 60 VII. SUMMARY ______60 VIII. LITERATURE CITED 61

I. ABSTRACT one ttlocyma, Ostrea cf. 0. tamiamiensis, The presence of undisputed Upper Mio­ Ostrea tamiamiensis monroensis, and En­ cene sediments in Sarasota County, Florida, cope macrophora tamiamiensis. has nor been widely known. Most authors Within the Upper Miocene deposits exists have stared that the Middle Miocene Haw­ an impermeable bur porous bed character­ thorn Formation is overlain by Pliocene to ized by a decrease in radioactivity and elec­ Recent deposits. The Upper Miocene is rep­ trical resistivity. These characteristics are resented in southern Florida by the Tamiami indicative of clay and the interpretation of Formation. The Upper Miocene age deter­ x-ray diffraCtion patterns verified the pre­ mination is based on the characteristic faunal dominance of clay minerals in rhe aquiclude. assemblage, Ostrea disparalis, Chione ?t!o­ Montmorillonite was the dominant clay min­ cyma, and Ecphora qttadricostata tnnbilicata. eral with lesser amounts of attapulgire and Fossil mollusks, echinoderms, and bryozoans alpha sepiolite. collected from ourcrops, quarries, and sink­ holes in this area definitely confirm the Based on evidence presented in this paper, presence of Upper Miocene sediments in the Upper Miocene deposits occurring in Sarasota County. Typical Upper Miocene Sarasota County are considered to be a species include Anadara cf. A. idonea, Chi- lithosome of rhe Tamiami Formation.

EDITOIUAL COMMITTEE FOR THIS PAPER: H. K. BROOKS, University of Florida, Gainesville, Florida ROBERT 0. VERNON, Florida Geological Survey, Tallahassee, Florida

HAROLD E. VOKES, Tulane University, New Orleans, Louisiana

49 50 Tulane Studies in Geology Vol. 4

II. INTRODUCTION Ill. ACKNOWLEDGMENTS Undisputed Upper Miocene deposits 1 pre­ The author wishes w express his gratitude viously have not been recognized in Sara­ to Dr. H. K. Brooks for his helpful advice, sota County, Florida. It generally has been sincere interest, and willing assistance in assumed that "Pliocene" to Recent sa nds n1any matters which made the completion overlie the Middle Miocene Hawthorn For· of this study possible. Particular thanks are marion. Fossil mollusks from quarr ies in due tO Dr. Robert 0. Vernon for his sug­ Sarasota County and souther n Manatee gestion of the problem and for furnishing County definitely confirm the presence of all well samples, electric and radioactive Upper Miocene strata overlying the recog­ logs, and his helpful comments. nized Middle Miocene H awthorn Formation. The author appreciates the helpful sug· It is within these deposits that the confin­ gestions of the following persons, who criti­ ing bed, described below, occurs. These de­ cally read the manuscript: Dr. H. K. Brooks, posits are here referred stratigraphically to Dr. Hubert C. Skinner, Dr. Harold E. Vokes, a lithosome of the upper part of the Tami­ Dr. Robert 0 Vernon, and Arnold Ross. ami Formation. The author appreciates the assistance and During the summer of 1962, the United helpful suggestions of the following persons, States Geological Survey, in co-operation who verified the author's identification of with the Florida Geological Survey, con· the fauna: Dr. H. K. Brooks, Arnold Ross, ducted a pumping test on the well field of and Reginald Scolaro. The author is in­ Venice, Sarasota County, Florida, to deter­ debted to Clifton T. Mansfield and Dr. mine the probable effects of salt water Guerry H. McClellan for their assistance in from the proposed intercoastal waterway on preparation and interpretation of the x-ray the city's water supply. The author served diffraction patterns. as a member of the field party (Florida This paper would not have gone tO press Geological Survey) . without the insistence, encouragement, and Prior to the rests, electric and gamma-ray editorial guidance of Dr. Hubert C. Skinner logs were obtained for as many wells as pos­ of Tulane University. sible. These logs revealed the presence in each well of an impermeable bed character­ JV. PROCEDURE ized by a pronounced decrease in electrical Outcrop samples, well cuttings, and elec­ resistivity and radioactivity (see Figure l). trical and radioactivity logs were studied. Data from wells in other portions of Sara­ The outcrops in Sarasota County are limited sora and adjoining counties also were used to a few dolomite quarries located in the in . delimitation of the confining lithologic northern part of the county and one dolo­ unu. mire quarry in the southern portion. In All known Neogene exposures were ex­ these quarries there is rarely more than 30 amined, measured, and mapped. Informa­ feet of rock exposed, of which approximate­ tion obtained from the field during 1962- ly lO feet are termed "Pliocene" tO Recent 1963 was supplemented from the paleon­ sands. In the southern part of the county tological and petrological coll ections of the at least 200 feet are exposed in Warm Min­ Florida Geological Survey and the Florida eral Springs. State Museum. The limited exposures in Sarasota County required special emphasis ro be placed on 1 It may be noted that Puri a.nd Vernon well cuttings and geophysical logs. The (1959, revised 1964 ), in their "Geologic Map latter were used ro rrace the vertical and of Florida," show the Bone Valley Fonna­ tion extending into extreme northeastern horizontal extent of the confining bed. Well Sarasota County, Florida. This diachro­ cuttings were used ro verify the identifica­ nous formation is assigned variously to tion of this bed in each well , tO provide the "Alum Bl'uff Stage," "Choctawhatchee stratigraphic information concerning the age Stage," or "Alum Bluff and Choctawhat­ chce Stages" in different portions of their of chis unit, and for the mineralogical analy ­ reports, but evidently (Vernon, personal ses of the aquiclude. commun ication, 1966) co nsidered it to be Sampling and study of the section at Upper Miocene age in Sarasota County, Warm Mineral Springs were accomplished Florida. This writer believes the evidence upon which this age assignment is based with the aid of self-comained underwater to be inconclusive. breathing apparatus. \0 llN \IS 12N 145 !SE •20 - ~ - ';i:f_ , ;,;.:; 19(: ;:.~

0 s~=·~EL

-2 0 - -

- 40 - -

- _- ..>

- 60 - -

- 80 - - -_ --_-_..,

-100 - -

['2]1 -120 -- E£:3 CALCILU11TE

5:9 DOLO/IIITE . 140 ...!:_t:,E.I._ ~ CLAY

~ PIIOSPIIOHITE --- ELECTIHC LOGS

~SHELLS __ ---GAMMA-IlA Y LOGS

figure 1. ELECTHIC GAMMA-LOGS DEFINING TilE AQUICLUDE IN THE VENICE WELL FIELO 52 Tulane Studies ;,. Geolon VoL 4

V. STRATIGRAPHY Tamiami Formation in certain localities and Upper Miocene deposits of Florida are unconformably in ochers. Further work may li mited mainly to rwo areas, the panhandle establish whether these beds are Upper Mio­ and the southern peninsula. According to cene or Pliocene. Langdon ( 1889, p. 323 ) the Carolinian A long the west coast of Florida (between Miocene of Heilprin ( 1887, p. 12 7) is rep­ the panhandle and the southern tip of the resented in the Florida panhandle by the stare) , the presence of Upper Miocene sedi­ uppermost bed at Alum Bluff, Liberty Coun­ ments has not been widely known. How­ ty, Florida. This age determination was ever, as early as 1887 ( Heilprin, p. 13 ), rhe based on the presence of the characrerisric probable equivalence of the fossiliferous Upper Miocene gastropod Ecphora quadri­ limestones exposed at Rocky Bluff, Manatee costata mnbilicata. Puri (1953, p. 27 ) rec· County, Florida, ro the Carolinian Miocene ognized the fou r faunal zones, ''Yoldia." was recognized. In addition, material ''Area," "Ecphora," and ''Caucellaria" of dredged from Tampa Bay was referred to rhe Cooke and Mossom ( 1929 ) and Mansfield Upper Miocene by Mansfield (Cooke and and Ponton ( 1932) as biozones at Alum Mosson1, 1929, p. 148 ) . Aside from these Bluff. He referred this formation, a strati· two localities, no sediments in west central graphic unit, to the ra nk of stage, a rime­ Florida have been assigned an Upper Mio­ stratigraphic uni t ( Puri, 1953, p. 28 ) ." The cene age. "Choctawharchee Stage·· as defined by Puri Biostratigraphic studies of the Upper Mio­ includes all Miocene sed iments of post-Alum cene of Sarasma and Manatee Counties are Bluff age in northwestern Florida. presently being made under the direction of DuBar and Beardsley ( 196 1, p. 160 ) Dr. H. K. Brooks. His results earlier sug· recognized the fact that Puri had changed gesred the presence of Upper Miocene de· the rank of the Choctaw hatchee from forma­ posits in Sarasota County. The present study tion tO that of stage "without a stared rea­ was undertaken as a pan of this project. son."' They re fer to the Late Miocene rocks Study of the impermeable lithologic unit of rhe Flori da panhandle as the "Choctaw­ in the supply wells of Venice, Sarasota Coun­ harchee deposits" and ''as a marter of con­ ty, raised the question of the age of the venience for reference have temporaril y re­ bounding strata. This problem and that of tai ned Puri 's fac ies nomenclature for all bur determining the mineralogic composition of the expos ures at Alum Bluff and Jackson the unit are ueated herein. Bluff." T he Tamia mi Form ation as redescribed by THB AQUICLUDE IN SARASOTA COUNTY Parker ( 195 1, p. 823) includes all deposits This confining layer acts as an aquiclude of Upper Miocene age in southern Florida. between the aquifers above and below. All His formation includes the Tamiami Lime­ subsurface logs available from Sarasota stone and Buckingham Limestone of Mans· County and many of those from the border­ fie ld ( 1939, p. 8), which were desi gnated ing counties were examined w determine facies by Parker. Based on the chara cteristic the horizontal extent of this bed. faunal assemblage, Ostrea disparalis. Chio11 e ulocpna, and Ecphora quadricostata umb:li­ Three separate cross sections were plotted: cata, the deposits were referred to as the one, from west to east, across the northern Upper Miocene (Parker, p. 823). part of the county (wells 36-17-13-3, W- Olsson and Petit ( 1964, p. 516) proposed 5966, W-5974, 36-18-24-1, 19-36-22-2, the name "Pinecrest beds" for cenain strata W-938, 20-36-3-1 , and the Kaimee Ranch in the region of 40-mile Bend on the Tami­ rest well ); the second, from north to south ami Trial. This exposure extends from west­ along the Gulf coast ( wells 36-17-13·3, W-61 3 1, W-4947, and W-1917); and the ern Dade County into Collier County. These late Neogene beds lie conformably on the third, from northwest to southeast along the southern part of the county ( wells 9 N , W- 2 Dr. R. 0 . Vernon (personal communica­ 542 1, SA-90, C-46, and the section from tion, January 27, 1966) suggests, 14 Dr. Puri W arm Mineral Springs ) . The three sec­ chose as a means of conveni ence, so as not tions \vere connected to construct the fence to complicate the literatu re further, to refer to these formations as stages rather than as diagram ( Figure 2) . Data available were stratigTaphic units." insufficient to prepare an isopach or srruc- No. 2 Upper Miocene deposits, Sarasottt Comlt), Florida 53

SARASOTA COUNTY

Figure 2. Fence diagram indicating the relative position of the aquiclude in Sarasota County, Florida.

rural comour map, largely due to the vari­ clay bed was nor penetrated. The unit thins ation in thickness from well ro welL to the north and northeast (in wells W -4947 The recorded decrease in electrical re­ and W -613 I ) tO a point no more than two sistivity of this unit indicates the increase in miles from the Gulf of Mexico. In well porosity and decrease in permeability char­ W-5 11 8, southwest of well W-4917, the acteristic of clays. Most clays are porous confining bed is nor present. Eastward from and contain warer bur are nor permeable. the coast the clay bed again thickens (well The x-ray diffraction patterns confirmed the W-5966) to 18 feet in the northern part of identification of clay rninerals. the county. In well W -938 in the northeast The clay is thickest in the Venice area corner of the coumy the bed is approximate­ (see figure 2), where ir reaches rhe maxi­ ly eight feet thick, the same as in well mum thickness of 28 feet. Southeastward 20-36-36- I, the control well in the north­ it thins ro eight feet in well C-46 in Char­ eastern parr of rhe councy. lotte County. North of well C-46 (in the The areal extent of the confining bed is NW 4, NW '4 sec. 30, T38S, R22E) the determined from the following control 54 Tulane StudieJ in Geology Vol. 4

wells: 36-17-13-3, 20-36-36-1, W-938, ley, and Calooshatchee. Puri and Vernon W-1917, and C-46, which occur respectively (1959, 1964), in the most recently published in the northwest, northeast, north, south­ studies on the geology of Florida, also re­ west, and southeast sections of the county. ferred to the geology of Sarasota County. The available information from subsurface Lower Neogene srrara crop our in a few logs and lithologic samples indicates that drainage ditches, along the banks of creeks, this clay bed strikes parallel tO the coast to and along the shore of Sarasota Bay. Seldom the city limits of Sarasota along the main­ is more than a few feet of rock exposed. land side of Sarasota Bay. It is thickest in The most extensive exposures occur in quar­ a belt extending from the eastern portion of ries near the Sarasota-Manatee County line Range IS in the north through all of Range and east of Venice. The available thickness 19 in the southern part of the county. The of these exposures depends upon the level bed is thinner in the southeastern section of the water table. Under dry conditions no (Range 22) and in the northeastern section more rhan 20 feet is exposed, a portion of (Range 21) of the county. which is Quaternary sand. Nearly all the geological information available is obtained UPPER MIOCENE DEPOSITS OF from well cuttings. A stratigraphic section SARASOTA COUNTY at Warm Mineral Springs (from approxi­ Introduction mately eight feet above to about 80 feet be­ low mean sea level) is presented below. It generally has been assumed that the aquiclude studied is a member of the Haw­ Previous studies of Sarasota County well thorn Formation (Dall, 1892). The Haw­ logs and the sections described reveal that thorn is extremely variable in lithology and the Pliocene to Recent sediments supposed­ consists of from 60 to several hundred feet ly rest directly upon the Middle Miocene of interbedded clays, sands, sandy lime­ Hawthorn Formation, thus excluding Upper stones, dolomites, and marls. In Sarasota Miocene deposits in most parrs of the County, a sandy dolomite containing brown county. The dolomites and limestOnes quar­ phosphorite grains is the predominant com­ ried in southern Manatee and northern ponent. Sarasota Counties are referred to the Haw­ The only extensive geological investiga­ thorn Formation by Cooke and Mossom tion in Sarasota County was that of V. T. ( 1926), Stringfield (1933), Cooke ( 1945), Stringfield (1933, p. 121-227), in which Peek (1958), and Puri and Vernon (1959, he described the geology and existing ground 1964). In all quarries visited by the writer water conditions. Previously, the geology it was possible to collect fossils. Many and ground water of Sarasota County were specimens recovered are pseudomorphs; mentioned only in several reports of the some are well preserved mollusks and bryo­ United States Geological Survey and the zoans. Identification of the fossils collected Florida Geological Survey (Matson, 1913; confirms the existence of Upper Miocene Sellards and Gunter, 1913; Mossom, 1926; faunas in beds overlying the Hawthorn and Cooke and Mossom, 1929). Marson Forn1ation. (1913, p. 319, 362-364) briefly described The Tamiami Formation, as described by the geology of Manatee County and part of Parker ( 1951, p. 823), includes all the de­ Sarasota County. Sellards and Gunter (1913, posits of Late Miocene age in southern p. 269) mentioned only the wells in Sara­ Florida. Both the Tamiami LimestOne and sota County. Mossom (1926, p. 171-268) the Buckingham Limestone of Mansfield described the general geological structure of (1939, p. 8 ) are included in Parker's defi­ Florida. The most detailed study prior to nition. Parker based this correlation on his Stringfield's report was that of Cooke and discovery of Ecphora qttadricostata ttnzbili­ Mossom ( 1929, p. 29), who described the cata (W agner ) in the marl along the Ca­ general stratigraphy of Florida and included loosahatchee River, at Banana Creek. This a geologic map showing the areal extent of index fossil established the Tamiami Forma­ the formation at or near the surface. Cooke tion as Upper Miocene age. Other key mol­ ( 1945) described the geology of Florida lusks were identified from Alligator Creek and mentioned the formations exposed in in Charlotte County, including Ostrea dis­ Sarasota County: the Hawthorn, Bone Val- para/is, Chione rdocyma. and Tttrritella pon- No. 2 Upper Miocene deposits, Sarasota County, Florida 55 t01zi. These are diagnostic Upper Miocene Duplin Marl. Puri ( 1953), however, as­ species. Specimens of Ecphora quadricostata signed all four of these biofacies to his umbilicata (Wagner) from near Fort Myers "Choctawhatchee Stage," in which he in­ and near Buckingham, Lee County, Florida cluded all Miocene sediments of post-Alum ( in the Florida State Museum collection, Bluff age in the Florida panhandle and their University of Florida) further support the equivalents in the central and western Gulf Upper Miocene age of the Tamiami Forma­ srates. tion (Brooks, Ross, and Eppert, 1963). Heilprin (1887, p. 13) described an out­ The lithology of the Tamiami Formation crop at Rocky Bluff, Manatee County, one is extremely variable. As described by Mans­ mile easr of Ellenron on rhe Manatee River, field (1939), the Tamiami Limesrone con­ consisting of a fossiliferous basal white sists of calcareous sandstOne, sandy lime· marl and yellow sandstone and an overlying stone, and beds and pockets of quartz sand; barren siliceous conglomerate. He believed and, the Buckingham Limeswne consists of the fauna identified from the basal unit to creamy white to green calcareous clay. be distinctly of Upper Miocene age. Mans­ Where exposed to weathering, the Bucking­ field (Cooke and Mossom, 1929, p. 136- ham limestone has been case-hardened, 137) recognized the deposit as Miocene, stained a light brown, and riddled by solu­ bur believed it to be older than had been tion holes. It also comains considerable indicated by Heilprin. Cooke ( 1945, p. amounts of phosphoritic particles ranging 158) referred the clayey sand and yellow in size from sand to pebbles. phosphatic marl near Ellenton to the Haw­ Exposures of the Tamiami Formation thorn Formation. He included in the Haw­ south of Sarasota County extends in a belt thorn a white sandstone exposed in a ditch from north of Adine in Chat!otte County, on U.S. Highway 41, two miles south of eastward tO Denaud, in Hendry County. Bradenton. Though the fauna from these Along the west coast, it extends from nonh localities has been noted in the Upper Mio­ of Adine south to Fort Myers Beach and ro cene of other areas, there still is some ques­ the coast at Bonita Spring~, in Lee County. tion as to whether these deposits are upper Middle Miocene or lower Upper Miocene. Upper Miocene deposits north of Sara­ Both paleontological and stratigraphical evi­ sora County consist solely of a sandy phos­ dence from the present investigation con­ phoritic limestOne dredged from Tampa Bay firm the existence of Upper Miocene de­ in the vicinity of Sr. Petersburg, Pinellas posits in Sarasota County. County. The age assignment of these de­ posits is based on the fauna identified by Discussion Mansfield (Cooke and Mossom, 1929, p. All of southern Florida (including Sara­ 148), apparently from the same horizon as sota County) is underlain by the Hawthorn Puri's Choctawhatchee Stage ( 1953, p. Formation. The boundary between the in­ 27-67). terbedded clay, sand and sandy limestone, The Choctawhatchee Marl, as defined by dolomite, and marl of the Hawthorn For­ Matson and Clapp (1909, p. 114), consisted marion and the silty, sandy clays and lime­ of the "Ecphora bed" and aluminous "clay" stones of the overlying Tamiami Formation of Dall ( Dall and Stanley-Brown, 1894, p. is transitional and difficult tO recognize. 168-169). Cooke and Mossom (1929, p. Stratigraphic data obtained from quarries, 138) elevated the mat! tO formational rank. well samples, and Warm Mineral Springs Mansfield (Cooke and Mossom, 1929, p. demonstrate that the upper 130 feet of the 140) recognized three faunizones, the strata in Sarasota County consist essentially ''Area," 0 Ecphora," and "Cancellaria," in of phosphoritic dolomite and limestone with the Chocrawharchee Formation. Later, Mans­ interbedded layers of clay. There is Jess field and Ponton ( 1932, p. 84-88) added lithologic variation in the sediments than a fourth zone, the "Yoldia." Cooke (1945) in rhe typical Hawthorn or Tamiami for­ discarded the term Choctawharchee and mations. placed the rwo lower faunizones, 11Arca'1 In rhe area smdied, the lithology of the and "Yoldia,11 in the Shoal River Formarion rocks is similar; however, color variation of Upper Middle Miocene, and the upper proved valid for local correlation. The color rwo, rrcancellar·ia, and ,,Ecphora," in the variations in the sections studied ranged 56 Tulane Studies in Geology Vol. 4

from whire w pale orange w yellowish gray Bluff on rhe Manaree River, about one mile w olive gray. Some of the clays encoumered east of Ellenron. This is rhe ourcrop from showed a slighr bluish color, especially when which Heilprin (1887, p. 63) described rhe wer. An abrupr color change from pale first late Miocene fauna reponed from orange w pale olive was nored in rhe dolo­ sourhern Florida. mire from the quarry at Oneco, M3naree Counry, Florida. This general color change Section at Rocky BINff, Mcmat ee County is also present in the Manatee Rock Com· Bed Thickness pany Quarry locared I. 7 miles norrh of rhe Quaternary city limits of Samoser, Manatee County, -! Loam, sandy, light and Florida. dark 1 foot Many of rhe dolomires being mined in Loam, black, clayey with northern Sarasora and southern Manatee bone fragments 1 foot Counties are case-hardened. Below rhe case­ Miocene 2 Fuller's earth, light hardened layer is a sofr marly dolomire. gray 2-3 feet Alrernarion of sofr marly and lirhified dolo­ Limestone, light gray mires occurs rhroughour a 20- w 30-foor to pale yellow, impure, section in the aforementioned quarries. In fossiliferous; extend­ ing at least nine feet well samples from Sarasora Coumy rhis al­ below the water level 13 feet ternating characreriscic was observed. At grearer deprhs crystalline dolomires also are The firsr reporr of Upper Miocene fauna imerbedded. south of the Manaree River was from the The upper 40 feet of sedimenrs are poorly Manaree Rock Company Quarry, locared 1.7 fossiliferous. This is, in parr, due to the miles north of the city limits of Samoset, leaching acrion of ground warer. Florida (NE 4, SW 4, sec. 32, T34S, X-ray diffraction parrerns were obrained RISE); an Upper Miocene fauna was col­ from numerous samples to determine the leered. Berween beds 2 and 3 are voids rep­ minerals present. The dominant mineral in resenting solution channels trending east­ each sample was dolomite, with lesser west. amounts of quartz, calcite, and phosphorite. The color changes abruprly from pale Similar resulrs were obrained by Pirrsburg orange to pale olive in the dolomite section Testing Laborarories analyzing rock samples ar Oneco Quarry, Manaree Counry, Florida for rhe Manaree Rock Company while de­ veloping rhe quarry. Secti~u at Mcmtltee Rock Company Qlfarry The amount and size of rhe phosphorite Bed Thickness grains vary verrically in nearly al l of rhe sec­ Quaternary rions srudied. Well 16, locared in rhe Venice 6 Sand, fine quartz, angu- well field, is rypical. A sample collecred lar with abundance from 34-43 feer below rhe su rface conrained of Chione cancellata 10 feet very small amounrs of fine phosphorire Miocene grains. The sample from 43-50 feer con­ Clay, gTcenish gtay, blocky, sandy 2 feet tained pebble-size grai ns of phosphorire and Dolomite, very pale rhe sample from 50-60 feer conrained very orange, case-hardened, slight amounts of fine grains. The variation phosphoritic, few muJ­ in rhe size of rhe phosphorire grains also lusk impressions; val'Y­ proved useful for local correlarion. ing in thickness from two to five feet 5 feet The aquiclude illusrrared in rhe fence dia­ Dolomite, pale orange, gram is the only continuous clay layer in the soft, very fossiliferous, phosphoritic 5 feet upper 130 feet of rhe srrarigraphic secrion Dolomite, pale orange, of Sarasota County. ln the northeastern and hard, phosphol'itic 5 feet nonhero pan of the county and in Sarasota Dolomite, pale orange to Bay, thin silr and clay beds are inrerbedded pale olive hard to soft, wirh sand and limesrone in rhe upper 35 phosphoritic with few fossil impressions; thick­ feet of the stratigraphic seoion. ness greater than 10 The following secrion is exposed ar Rocky feet 10 feet No.2 Upper Miocene deposits. Sarasota Co11111}. Florida 57

( west central part of sec. 7, T 35S, RISE ). in the abandoned dolomite quarry. A spring Approximately three feet of rock are ex­ line between beds 3 and 4 is visible. posed above average water level in this quarry, bm no fossils were collected here. Section at West Coast Dolomite Com pan) Sectio11 ttl Oneco Qllttrry Q11arr) Bed Thickness Bed Thickness Quaternary Quaternary 5 Sand, fine to medium, sub- 4 Sand, fine quartz, angu- angular to rounded; lar, with abundance of very few shell fragments 8 feet Chione cancellata. 12 feet Miocene .Miocene 4 Dolomite, finely phos- 3 Dolomite, pal e orange, phoritic, pale orange, soft, phosphoritic 4 feet case-hardened, fossili· Dolom ite, pho sphoritic, ferous :> feet pa!P orange, case­ Mad finely phosphoritic, hardened 4 feet pale orange, dolomite, Dolomite, phosphoritic, few fossil im pressions 3 feet pale ol ive, case­ 2 Dolomite, finely phospho- hardened 2 f eet ritic, pale orange, case­ hardened, very fossili- An abandoned dolomite quarry, one mile ferous 1 feet east of the Sarasora-Bradenron Airpon Water level (N '2, sec. 6, T 36S, R 18E ) was visited dur­ Dolcmite, finely phospho­ ritic, grayish green, ing the fall of 1962. Fill material excavated crystalline, very fos. from the center ponion of the quarry ex­ siliferous 3 feet posed a 24-foot section. At the base is a dense dark clay. Above the clay is a thin Warm Mineral Springs is located in the bed of fossiliferous dolomite, from which southern part of Sarasota County (NW '4, well preserved mollusks were collected. NW 4, sec. 25, T39S, R 20E). Bed lO is represented in the fence diagram as the aqui­ Section at Abandoned Dolomite Q11arry clude. Poorly preserved mollusk impressions Bed Thickness are recognizable throughout the section. The sa mple from the clay bed was collected in Quaternary 1961 by Dr. H . K. Brooks. 7 Sand, fine angular quartz; Heilprin ( 1887, p. 63) recognized several abundance of Chione cancellata 2 feet mollusks from Rocky Bluff which are dis­ Miocene tinctive of the Upper Miocene formations 6 Dolomite, pale orange, in the northeastern United Scates. The spe­ ca se-hardened, with fine cies, identified from casts and impressions, phosphorite grains 8 feet included Pecten nzadiso1lius, P. jeffersonius, Claystone, greenish g ray, pure 4 feet PenM maxi/lata, Venus alveata, and Area 4 Dolomite, very light gray ido1m1 ('). H eilprin believed these indi­ to yellowish gray, hard, cative of an Upper Miocene fauna. fossiliferous 2 feet A locality near the north end of Little Clay, light gray to yellow gray, mottled with Sarasota Bay known as White Beach was nodules of dolomite 1 foot described by Heilprin ( 1887, p. 64-65) and Clay, yellowish gray to Dall ( 1892, p. 114-115). The exposure li g ht green 1 foot consists of a yell owish limestone, badly Clay, dark greenish g ray, dense 6 feet waterworn and covered in places with a thin veneer of Recent sediments. The rock con­ The following section is exposed in the ta in s distorted molds of many species which West Coast Dolomite Company Quarry east cannot be identified, but in some places of Venice, Sarasota County, Florida (SW ·4, these molds have become filled with pseudo­ NE 4, sec. 6, T 39S, R 20E ). The quarry is morphs of the original shells. The speci­ located in an old river valley and most of mens resemble closely the following species: the fossils are leached out of the upper Pee/en jeffersonius, P. madisonius, and Ve ­ sa nds. The lithology is not as var iable as Il/IS alz •eata. 58 Tulane StudieJ in Geology Vol. 4

Section from Warm Mineral SpringJ On the banks of Phillippi Creek, which flows into Sarasota Bay, Heilprin ( 1887, p. Bed Thickness 16) found casts of Pecten jeffenonim, P. Quaternary madisonius, and Area idonea, and orhers 17 Sand, fine, angular 6 feet which appeared identical to those described 16 Sand, light olive gray, from Rocky Bluff. a-ngular, fine-grain quartz, calcareous, Dall ( 1892, p. 126) reported a specimen abundance of Chione of Ecphora quadricoJtata ttmbilicata colleCt­ cancellata 5 feet ed from the beach of Long Key in Manatee Miocene and Sarasota Counties. This waterworn shell 15 Limestone, whitish gray, probably washed ashore from a more west­ fine grain, dolomitic, sandy, hard, fine phos- erly submerged stratum. phoritic grains 8 feet The fauna collected from the Manatee 14 Dolomite, very pale orange, Rock Company Quarry by Dr. H. K. Brooks fairly hard, sandy, fine and rhe wrirer was very poorly preserved. phosphorite grains; outer layer of travertine 7 feet Mosr specimens were impressions of pseudo­ 13 Limestone, yellowish gray, morphs of the original shells. One ectoproc­ fairly hard, sandy dolo­ tous bryozoan was found, Cttpttladria ca­ mitic, fine phosphorite nariensis. This species ranges from lower grains; outer layer of travertine 10 feet Middle Miocene (Chipola Formation) to 12 Dolomite, yellowish gray, Recent. The following species were identi­ hard, calcareous, fine fied from the quarry: phosphorite grains, fossil impressions; outer Bryozoa layer of travertine 4 feet Cttpttlrulria ca11ariemiJ Busk 11 Limestone, pale greenish Echinodermata yellow, fairly hard, fine Encope tmniamie11sis Mansfield phosphorite grains 10 feet Gastropoda 10 Silt, greenish gray 6 feet Cypraea sp. Dolomite, very pale Coni/J sp. orange, hard, phospho- rite grains, fossil im­ Lyrift cf. L. PJ'C11op!ettra Gardner pressions; outer layer Pelecypoda of travertine 3 feet Anadara cf. A. ido11ea (Conrad ) 8 Siltstone, pale greenish Venericardia sp. yellow, chalky, dolo- mitic, phosphorite Chio1te cf. C. cancel lata (Linnaeus) grains 3 feet Mercenaria cf. M. prodrama (Gardner) Dolomite, yellowish gray, hard, cal'careous, phos- Two species, Lyria cf. L. pywoplettra and phorite grains, fossil Mercenaria cf. M. prodrama, commonly are impressions; outer layer reported from horizons of Middle Miocene of travertine 9 feet 6 Limestone, yellowish gray, age in northern Florida. Chiom cancellata sandy, fairly hard, dolo­ ranges from Upper Miocene to Recent. mitic 5 feet Anadara cf. A. idonea is a characrerisri c 5 Limestone, yellowish gray, Upper Miocene species reponed from the porous to indurated; outer layer of travertine 6 feet "Ecphora zone" of the "Choctawhatchee Dolomite, yellowish gray, Srage" and from rhe Tamiami Formarion on chalky to indurated, Banana Creek, Hendry County, Florida. En­ phosphorite grains, fos­ cope tamiamiensis is characrerisric of rhe sil impressions 3 feet Dolomite, yellowish gray, Tamiami Formation. Chlamys cf. C. madi­ hard, fossil impressions 3 feet sonia is synonymous wirh Pecten madisonitts 2 Limestone, grayish yellow, reponed from the Upper Miocene Calvert hard, phosphorite grains 3 feet and Choptank formations in Virginia and Dolomite, yellowish gray, Maryland. hard, phosphorite grains, fossil impressions 2 feet The fauna identified from the old dolo­ mite quarry east of the Sarasota-Bradenton M odi{ied f1'om unpubli8hed section measured by H. K. Brookll, 1959. Airport (see below ) contained only two species found in the quarry just mentioned. No.2 Upper Miocene deposits, Sarasota Comuy, Florida 59

The matrix in which they occurred is located Petaloconchus sculptJtratm ranges from below the pale orange dolomite occurring in Lower Middle Miocene ( Chipola Forma­ the Manatee Rock Company Quarry. The tion) to Upper Miocene. Both Ostrea meri­ bed is very thin and consists of light gray, diana/is and Ostrea tamiamiensis were origi­ hard, clayey dolomite. The preservation of nally described from the Tamiami Forma­ the fossils here is much better, especially the don. Chione ulocyma occurs in deposits no oysters, which still possess part of their origi­ younger than Upper Miocene; Chione lati­ nal shell. lerata athleta ranges from Upper Miocene The following is a list of species identified co Recent. from this quarry: The West Coast D olomite Company Bryozoa Quarry is the most southerly exposure in Cupuladria canariewis Busk Sarasota County from which fossils were Trigonopora arimlatum ( Canu and collected. Bassler ) The Florida State Museum collections, at Gastropoda the University of Florida, contain specin1ens Polinices jttdsoni (Maury) of Ostrea tamiamiensis 1rtonroensis dredged Conus cf. C. dauctts H wass from lower Sarasota Bay, approximately Tttrbinella cf. T. regina Heilprin eight miles south of Sarasota. Oslrea tami­ Pelecypoda amiensis m.o11roensis is extremely abundant O.rtrea tamiarniensis Mansfield in the Tamiami Formation and generally Pecten sp. exhibits an excellent stare of preservation. Chlamys condylomatm Dall Lima ( Mantellum) carolinemis Dall Stratigraphic Conclmiom V enericardia sp. Lithologically, it is impossible to distin­ Echinochama sp. guish the boundary between the upper Mio­ Chione cf. C. cancellata ( Linnaeus ) cene and Middle Miocene. There is grada­ There are three distinct Upper Miocene tional change with no clear lithologic bound­ species in this quarry, Lima carolinensis, ary. It is possible to trace the pale orange, Ostrf::'a tamiamJensis, and Cupuladria cana· fossiliferous dolomite from the Manatee riensis. Lima carolinensis has been described Rock Company Quarry all the way to Warm from both the "Cancellaria zone" of the Mineral Springs. In some sections this dolo­ "Choctawhatchee Stage" and the Bucking­ mire is more fossiliferous than in others. ham limestone facies of the Tamiam i For· Heilprin ( 1887) and Dall (1892) described marion. Ostrea tamiamiensis is one of the this fossiliferous dolomite also from Rocky most abundant mollusks found in the Tami­ Bluff on the Manatee River and Phillippi ami Formation. Creek, south of Sarasota. The section exposed in the W est Coast The fauna listed from the outcrops, quar­ Dolomite Quarry east of Venice, Sarasota ries and from Sarasota Bay correlate with de­ County, Florida, consists of at least 12 feet posits herein considered Upper Miocene. of fossiliferous dolomite. Fossils are well Four species were identified rhar are known preserved as casts and impressions. Several to occur in Middle Miocene deposits. Four of the species retain their original shell ma­ species range from Middle Miocene to Up­ terial. The dolomite is "dense" throughout per Miocene and six have been reported the whole section. The following species only from the Upper Miocene. Two are were identified from the quarry: known ro range from Upper Miocene to Gastropoda Recent and rwo from Pliocene ro Recenr. Petaloconclms swlpt~tratm Lea One species ranges from Lower Miocene to Pelecypod a Upper Miocene. Ostrea meridionalis H eilprin Based on the evidence presented in this Ostrea tamiamiensis Mansfield paper, Upper Miocene deposits definitely Lima ( Mantellum) carolinemis Dall exist in Sarasota County. The deposits are V enerica·rdia sp. referable to a lithosome of the Tamiami Chione cf. C. cancellata ( Linnaeus) Formation of southern Flori da. The total Chi one latilirata athleta ( Conrad) thickness of the Upper Miocene Sarasota Chione ulocyma Dall County deposits here described is not known. 60 Tulane Studies in Geology Vol. 4

VI. MINERAL ANALYSIS OF THE Vll. SUMMARY AQUICLUDE The geologic investigation of an aqu i­ The mineralogic composition of the litho­ clude (see Figure 2) in Sarasota County re­ logic unit presented in Figure 2 is based on su lted in a stratigraphic study of the adjoin­ the interpretation of x-ray diffraction pat­ ing strata. Fossils were collected from three terns. The outcrop of the confining bed in quarries, one in southern Manatee County Warm Mineral Springs provided the only and the others in Sarasota County. The age uncontaminated sample. The final results of the specimens identified ranges from of the mineralogical study were based on Lower Miocene to Recent. Typical Upper the analysis of the Warm Mineral Springs Miocene species included Anadara cf. A. sample. idonea. Chioue latilerata athleta, Chioue ttlo­ Samples from cable and rotary tools are cyma, Lima (i\1antelltmz ) carolinensis, Os­ rarely satisfactory for percentage determina­ trea cf. 0. tamiamien.ris, O.rt rea cf. 0. meri­ tions unless the caving intervals have been tlionalis. Ostrea ta.miamiensis 1nonroensis. cased. The contamination from overlying and Encope nwcrophora. tarniamiensis. Two debris obscures diagnostic features and of these, Ostrea tamiamieusi.r and Ostrea makes uncertain the identification of in­ tamiamiensis monroensis, are the most com­ digenous fine clastic materiaL mon mollusks in the Upper Miocene Tami­ ami Form ation of southern Florida. En. co pe The samples analyzed were obtained from macrophora tamiarniensis is considered an wells W-4476, W-4477, W-4488, W-5974, index foss il for the Upper Miocene in south­ and the outcrop sample from Warm Mineral ern Florida. Thus, paleontological evidence Springs. The samples were taken from the definitely places these strata from Sarasota central interval of the confining bed at each County in the Upper Miocene. station. The clay minerals identified from the The occurrence of Upper Miocene depos­ its in Sarasota County was first reported by aforementioned wells consist of predomi­ Heilprin (1887, p. 127) . Heilprin reponed nantly montmorillonite and attapulgire wirh several species of mollusks (Pecten jeffer­ a minor amount of alpha sepiolite. The in­ tensity of the reflections from montmoril­ sonitt.r1 Pecten madisouius, and Venus alve­ lonite surpassed both attapulgire and alpha ata) collected from a yellow arenaceous sepiolite in all the samples, indicating that limestone near the mouth of Phillippi Creek. The specimens were in a poor srate of pres­ montmorillonite is the dominant clay mineral. ervation, but were similar to species col­ The patterns indicate that the clay min­ leered from an outcrop at Rocky Bluff, erals are poorly crystalline, especially the Manatee County. Heilprin's specimens were montmorillonite. It is believed that the characteristic Upper Miocene species origi­ poorly crystalline nature of all the clays rully described from the Upper Miocene would indicate a detriral origin with a short deposits of Maryland and New Jersey. distance of transportation. If the m aterial Mansfield (Cooke and Mossom, 1929, p. had been transported very far, the attapulgire 136-1 37) visited these same localities and would likely have been destroyed. Weather­ suggested that the deposits were somewhat ing causes attapulgire to brea k down to old er than indicated by H e ilprin. Prior ro form montmorill onite. This has not been the present study, it had been assumed that demonstrated conclusively, though structur­ "Pliocene" ro Recent sands unconformably ally the idea is quire permissible. Ralph E. overlie the Middle Mi ocene Hawthorn for­ Grim (McClellan, 1962) has indicated that, marion in Sarasota County. in his opinion, this transition is possible. The deposits here are referred ro a litho­ The impurities identified in the sed i­ some of the Tamiami Formation. The exact mented and glycolared sa m pies are quartz, thickness is not known. The boundary be­ calcite, and dolomite. tween the H awthorn Formation and the The confining bed was presumed to con­ overlying Tamiami Formation is transitional sist essentially of clay, based on the char­ and it can not be differentiated lirhologically acteristic decrease in electrical resistivity in­ or faunally. The stratigraphic section ex­ dicating a porous but imperm eable stratum. posed at Warm Mineral Springs contains This was verified by x-ray analysis. approximately 120 fee t of phosphoritic dolo- No.2 Upper Miocene deposits, Sarasota Coumy, Florida 61

mire and clay. The upper 90 feer of rhis MANSFIELD, W. C., 1939, Notes on the Upper section conrain mollusk impressions so poor­ Tertiary and Pleistocene mo1lusks of pen­ insular Florida: Florida Geol. Survey, ly preserved as co prevent idenrificarion. Bull. 18, 75 p., 3 pis., 1 fig. The aquiclude srudied is a lirhologic unir MANSFIELD, W. C., and C. M. PONTON, 1932, within the Tamiami Formation of Upper Faunal zones in the Miocene Choctawhat­ Miocene age in Sarasora Counry, Florida. chee Formation of Florida : Washington Acad. Sci. Jour., v. 22, no. 4, p. 84-88, This aquiclude separates rwo aquifers in rhe 1 fig. Venice area. It was traced throughout the MATSON, G. C., and F. G. CLAPP, 1909, A coumy by electric and gamma-ray logs of preliminary re-port on the geology of water wells. The correlations were con­ Florida with special' reference to the firmed by analysis of well currings. X-ray stratigraphy: Florida G€ol. Survey, 2nd Ann. Rept., p. 25-173, map. diffraCtion patterns were run on samples of rhe aquiclude and rhe results indicare rhar MATSON, G. C., and SAMUEL SANFORD, 1913, Geology and ground waters of Florida: montmorillonite is the dominant clay min­ U. S. Geol. Survey, Wate1· Supply Paper eral, with lesser amounts of anapulgire and 319, p. 362-364. alpha sepiolite. The parrerns also showed McCLELLAN, G. H., 1962, Identification of minor amounrs of dolomire, quartz, and cal­ Clay Minerals from the Hawthorne For­ eire. The dolom ire and calc ire are believed mation, Devil's Mill Hopper, Alachua County, Florida: Unpublished M.S. The­ ro be contamination from collapse material sis, University of Florida, 38 p. in rhe course of drilling and sampling of rhe MossOM, D. S., 1926, A review of the struc­ wells. ture and stratigraphy of Florida, with special reference to the petroleum pos­ Vlll. LITERATURE CITED sibilities: Florida Geol. Survey, 17th Ann. Rept., p. 169-275. BROOKS, H. K., ARNOLD Ross, and H. C. EPPERT, JR., 1963, An unusual occurrence OLSSON, A. A., and R. E. PETJT, 1964, Some of a Miocene pelecypod burrow: Florida Neogene Mollusca from Florida and the Acad. Sci., Quart. Jour., v. 26, no. 1, p. Carolinas: Bull. Ame1·. Paleontology, v. 47-52, 1 fig. 47, no. 217, p. 516-518. COOKE, C. W., and D. S. MossOM, 1929, Ge­ PARKER, G. G., 1951, Geologic and hydro­ ology of F lorida: F lorida Geol. Survey, logic factors in the perennial yield of the 20th Ann. Rept., p. 29-277, 29 pis., incl. Biscayne aquifer: Amer. Water Works geol. map. Assoc. Jour., v. 43, no. 10, p. 817-833. COOKE, C. W., 1945, Geology of Florida: PEEK, H. M., 1958, Ground-Water Resources Florida Geol". Survey, Bull. 29, 339 p. of Manatee County, Florida: Florida DALL, W. H., 1890-1903, Contributions to Geol. Sm·vey, Rept. Investigation 18, 99 p. the Tertiary fauna of Florida: Wagner PURl, H. S., 1953, Contributions to the Study Free Inst. Sci. Trans., v. 3, pts. 1-6, p. 1- of the Miocene of the Florida Panhandle: 1654. Flol"ida Geol. Survey, Bull. 36, 345 p. DALL, W. H., 1892, The Miocene of North America: U. S. Ceo!. Survey, Bull. 84, PURl, H. S ., and R. 0. VERNON, 1959, Sum­ 349 p. mary of the Geology of Florida and a Guidebook to the Classic Exposures: DALL, W. H., and JOSEPH STANLEY-BROWN, Florida Geol. Survey, Spec. Pub!. 5, 255 p. 1894, Cenozoic geology along the Apal"achi­ cola River: Geol. Soc. America Bull., v. PURl, H . S., and R. 0. VEHNON, 1964, Sum­ 5, p. 147-170. mary of the Geology of Florida and a DuBAR, J. R., and D. W. BEARDSLEY, 1961, Guidebook to the Classic Exposures: Paleoecology of the Choctawhatchee de­ Florida Geol. Survey, Spec. Pub!. 5 (re­ posits (Late Miocene) at Alum Bluff, vised) , 312 p. Florida: Southeastern Geology, v. 2, no. SELLAlWS, E. H., and HERMAN GUNTER, 1913, 3, p. 155-189. The artesian water supply of eastern GlllM, R. E., 1953, Clay Minerology: Mc­ and southern Florida: Florida Geol. Sur­ Graw-Hill Book Company, New York, vey, 5tll Ann. Rept., p. 269. N . Y., 384 p. STRINGFIE-LD, V. T., 1933, Ground-water re­ HEJLPRIN, ANGELO, 1887, Exploration of the sources of Sarasota County, Florida: west coast of Florida and in the Okeecho­ Fl"orida Geol. Survey, 23rd-24th Ann. bee wil'derness: Wagner Free Inst. Sci. Rept., p. 121-194. Trans., v. 1, p. 1-134. STRINGF IELD, V. T., 1933, Exploration of LA NGDON, D. W., 1889, Some Florida Mio­ artesia.n wells in Sarasota County, Flori­ cene: American Jom·. Sci., ser. 3, v. 38, p. da: Florida Geol. Survey, 23rd-24th 322-324. Ann. Rept., p. 195-227.