TULANE STUDIES IN GEOLOGY AND PALEONTOLOGY Volume 19, Number 1 July 31, 1986 THECALCAREOUSNANNOPLANKTONOFTHE MIDWAY GROUP (PALEOCENE ) OF ALABAMA DAVID D. REIMERS REIMERS RESEARCH HOUSTON , TEXAS CONTENTS I. ABSTRACT . 1 II. INTRODUCTION . 1 III . P REVIOUS STUDIES . 7 IV. L OCATION OF SAMPLED SECTIONS . 11 V. T ECHNIQUES AND PROCEDURES . 12 VI. R ESULTS AND CONCLUSIONS . 13 VIL A CKNOWLEDGMENTS . 18 VIII. S YSTEMATIC PALEONTOLOGY . 18 IX. REFERENCES ..... ... .. .. ... .. ......... ...... .. 46 ILLUSTRATIONS PLATES 1-14 beginning on p. 19 I. ABSTRACT IL INTRODUCTION The calcareous nannoplankton in sam­ The Midway Group of Alabama consists ples fr om the Paleocene Midway group of of three formations (figure 1 ). These are , in Alaba ma were examined and photo­ order of stratigraphic sequence: (1) the graph ed using both a light misroscope and Clayton Formation, which in central a scan ning electron miscroscope . Twenty­ Alabama is divided into the lower Pine seven species were identified, two of Barren Member and the upper McBryde which are described as new. The nanno­ Limestone Member ; (2) the Porters Creek plank ton distribution was used to correlate Clay, present only in western Alabama , the Alabama Midway Group with standard with the Matthews Landing Marl Member Paleocene nannoplankton zonations re­ at the top ; and (3) the Naheola Formation , sulting in the Pine Barren and McBryde present only in central and western memb ers of the Clayton Formation being Alabama , divided into the lower Oak Hill assigned to the Cruciplacolithus tenuis Member and the upper Coal Bluff Marl zone, and the Porters Creek Clay and the Member. Matth ews Landing Member being as­ Smith (1886) first used the term "Mid­ signe d to the Cyclococcolithina robusta way " in describing the strata exposed at zone. The nannoplankton distribution and Midway Landing on the Alabama River in abunda nces are related to the lithology Wilcox County , Alabama (figures 2, 3 ·and and depositional environments of the Mid­ 4). This section at Midway Landing was way u nits. The Clayton and Porter s Creek described by Smith as having a few feet of units contain certain species that are con­ black clay, which seemed equivalent to fined to or are more abundant in , particu­ that at Black Bluff on the Tombigbee River lar lithologic facies . The very shallow­ (Porters Creek Clay ), overlying about ten water deposits of the Naheola Formation feet of gray , argillaceous lime stone (the are barren of nannoplankton . McBryde Limestone ) with the nautiloid EDITORIAL COMMITTEE FOR THIS PAPER: DAVID T . DOCKERY , III, Missis sippi Geological Survey, Jackson , Mississippi WILLIAM W. HAY, University of Colorado, Boulder, Colorado CHARLES C . SMITH , Tenneco Oil , Houston , Texas 1 2 Tulane Studies in Geology and Paleontology Western Alabama Central Alabama Eastern Coal Bluff Marl --Member- Naheo1a a I e t formation 0ak Hill Member Porters Creek Clay Clayton Pormatian McBrycleLimestone Member Pine Barren Member Figure 1- Formations and Members of the Midway Group in Alabama Enclimatoceras. LaMoreaux and Toulmin Highway 21 in Wilcox County (figures (1953) described this Midway section as and 4). In the upper part of this member· part of the McBryde Limestone Member of the "Turritella rock" of Smith (1894 the Clayton Formation, consisting of four which consists of a sandy yellow , cryst hard calcareous claystone ledges interbed­ line limestone containing Turritel ded with gray marl. Since the Alabama alabamensis. The lower part of the me River has been dammed, only the upper­ her is a gray calcareous silt with indurat most claystone ledge is exposed. ledges. In Wilcox County the Pine Barre The Clayton Formation was named for Member has an estimated thickness of 1 exposures near Clayton, Barbour County, feet (LaMoreaux and Toulmin, 1953) . Alabama by Smith (1892) . Exposures at the The McBryde Limestone Member w type locality, in a Central of Georgia Rail­ named by MacNeil (1946) for exposures · road-cut one mile east of Clayton, consist roadcuts along Alabama Highway 21 · of approximately 12 feet of dense, crystal­ Wilcox County, approximately three mil line, gray limestone underlain by a tan, west of McBryde Station. The station clayey sand (figures 2 and 5). LaMoreaux longer exists but exposures can be fou and Toulmin (1953) described the Clayton along Highway 21 at a locality 0.2 m· in Wilcox County, Alabama, as consisting south of the intersection of Highway 21 of about 140 feet of massive limestone with Highway 28 in Wilcox County (figures some basal sand. In extreme western and 4). At this locality the strata consist Alabama the Clayton Formation consists of approximately ten feet of light gray Jim less than 20 feet oflimestone. stone, lying directly on the "Turritel The Pine Barren Member of the Clayton rock" of the Pine Barren Member . T Formation was named by MacNeil (1946) McBryde Limestone thickens to about for strata exposed in roadcuts on the south feet in eastern Wilcox County and Butl side of Pine Barren Creek, along Alabama County (LaMoreaux and Toulmin, 19 No. 1 Midway Calcareous Nannoplankton 3 F rther west it becomes more clayey and Sucarnoochee Creek in Sumter County , in~ertongues with the lower part of the Alabama . The type locality of the Sucar­ Port ers Cre ek Clay. noochee Clay is Black Bluff on the Tom­ The Port er 's Creek Clay was named by bigbee River below its confluence with Safford (1864) for exposures west of Mid­ Sucarnoochee Creek (figures 2 and 6 ). In dleton , Te nnessee . The e~':1ivalent de­ western Alabama , the Porters Creek Clay posits in Alabama were origmally called consists of 350 feet of black , jointed clay the Sucarno ochee Clay by Smith (in Smith with some limonitic concretions. Approxi­ and Johnso n, 1887 ) from exposures along mately 5 feet of glauconitic sand is present Figure 2 - Counties containing type se.ction s of the Midway Group in Alabama 4 Tulane Studies in Geology and Pal eontology Vol. 19 Figure 3- Outcrop of the Midway Group in Alabama at the top in the Matthews Landing Mem­ County. The dam on the Tombigbee Riv ber . In central Alabama the Porters Creek has resulted in most of the exposures Clay thins to about 100 feet and is more cal­ this locality being covered by water careous and fossiliferous. In this area , it river sediments. Only five feet of tan-gra contains some claystone and sandstone blocky clay underlain by five feet of blac ledges . Farther eastward, beds correlative blocky clay are now exposed during lo with the Porters Creek are included in the water . Clayton Formation (MacNeil , 1946). In western Alabama the Naheola Fo The Matthews Landing Member was mation is divided into the lower Oak named by Smith (in Smith and Langdqn , Member and the upper Coal Bluff Me 1894) for exposures at Matthews Landing her . The Oak Hill Member was named on the Alabama River in Wilcox County , Toulmin, LaMoreaux and Lanphere (195 Alabama (figures 2 and 4 ). Here the Matth­ for exposures in roadcuts near the town ews Landing Member is a gray-green , Oak Hill in Wilcox County , Alabama (fl sandy marl approximately 20 feet thick. ures 2 and 4 ). At this locality the Oak The marl thins westward to about five feet consists of approximately 51 feet of gra in Choctaw County . Due to the dam on the tan , laminated sandy and silty clay wi Alabama River only about ten feet of the carbonaceous layers. A thin bed of ligni Matthews Landing Member is exposed at marks the top of the Oak Hill Member. T present. Coal Bluff Marl Member was named The Naheola Formation was named by Toulmin (1944) for exposures at Coal Bl Smith (in Smith and Johnson , 1887) for ex­ on the Alabama River in Wilcox Coun posures at Naheola Landing on the Tom­ Toulmin described the section as ·consis bigbee River in Choctaw County, Alabama ing of gray , glauconitic, micaceous s (figures 2 and 7 ). LaMoreaux and Toulmin and clay · at the top , with large glauconiti (1953) described the exposures at this local­ sandstone concretions in a green san ity as consisting of 16 feet of tan to gray, marl at the base. The section is now e sandy clay with indurated ledges overlying tirely under water . The Coal Bluff Me approximately four feet of black , sandy, her is exposed at the type locality of blocky clay. The Naheola Formation thins Oak Hill Member and at Shoal Creek · eastward until it disappears east of Wilcox Wilcox County (figures i and 4) . No. 1 Midway Calcareous Nannoplankton 5 ••••ou11 cou11n Figure 4 - Locat ion of the sampled section s in Wilcox County . A - Midway Landing B - Sec onda ry McBryde section C - Matt hews Landing D - Seco nda ry Coal Bluff section E - Pine Bar ren section Figure 5 - Location of sampled section o F - McBryde section f the Clayton Formation in Barbour G - Oak Hill and Coal Bluff sections Count y , Alabama N 1 CHOCTAW COUNTY +---I.... 1------i I"''· Figur e 6 - Loca tion of sampled section of Fi gure 7 - Location of sampled section of the P orters C ree k Formation in Sumt e r the Naheola F ormation m Chocta w Count y, Alaba ma County , Alabama 6 Tulane Stud ies in Geology and Paleontology All of the Paleocene Midway units ex ­ the Naheola Formation . posed in Alabama represent marine envi­ NacNeil (1946) stated that the Tertiary ronments , as indicated by the paleontology deposits of central and western Alabam (Toulmin , 1946) and the lithology (Murray , are composed of deeper water facie s tha 1947). Bornhauser (1947) considered the those of eastern Alabama. This is rep calcareous deposits of the Lower Tertiary resented in the Paleocene Midway Grou of Alabama and Mississippi to be trans­ by the occurrence of a basal sand an gressive deposits ; with the shales and clays sandy limestone in the Clayton Formatio to be open marine inundative deposits and in easternmost Alabama .