DEPARTMENT OF THE INTERIOR UNITED STATES GEOLOGICAL SURVEY GEOLOGIC MAPS OF THE JACKSON PURCHASE REGION, KENTUCKY By Wilds W. Olive Prepared in cooperation with the KENTUCKY GEOLOGICAL SURVEY MISCELLANEOUS INVESTIGATIONS SERIES Published by the U.S. Geological Survey, 1980 G DEPARTMENT OF THE INTERIOR TO ACCOMPANY MAP 1-1217 UNITED STATES GEOLOGICAL SURVEY GEOLOGIC MAPS OF THE JACKSON PURCHASE REGION, KENTUCKY By Wilds W. Olive INTRODUCTION STRATIGRAPHY AND ENVIRONMENT The Jackson Purchase region, that part of Kentucky west of the CRETACEOUS Tennessee River, is in the northeastern part of the Mississippi em­ UPPER CRETACEOUS bayment, a broad south-plunging structural downwarp whose axis Tuscaloosa Formation approximately coincides with the east valley waU of the Mississippi The Tuscaloosa Formation in the Jackson Purchase region was first River. Rocks exposed in the region range in age from Devonian to recognized by Roberts, Gildersleeve, and Freeman ( 1945, p. 38-41), Holocene. Those of post-Paleozoic age are the principal subject of this report. The post-Paleozoic rocks consist entirely of clastic conti­ although a chert-gravel deposit, designated as Tuscaloosa by Wade nental and marine sediments, the oldest of which are Late Cretaceous (1917), had earlier been reported to extend from Tennessee into an in age. Although the Late Cretaceous stratigraphic record contains area of Kentucky now known as the Land-Between-the-Lakes­ gaps due to erosion and nondeposition, strata representing most bordered by Kentucky Lake on the west and by Lake Barkley on the stages of the Tertiary are present. Post-Paleozoic sediments attain a east. Wade's identification resulted from his tracing of discontinuous outcrops from Wayne County in southern Tennessee, where Miser maximum thickness of about 2,050 feet near the embayment axis at (1917, p. 200) had reported gravel of the Tuscaloosa Formation the Kentucky-Tennessee State line. beneath the Eutaw Formation. According to Christopher (in press), Prior to investigations made for this report, knowledge of the areal the Tuscaloosa in Alabama is middle Eaglefordian in age. This age geology of the Jackson Purchase region was based in large measure assignment is based on palynologic correlation of the Tuscaloosa of on investigations by Loughridge (1888), Glenn (1906), and Roberts, Alabama with the Eagle Ford Group of Texas. GUdersleeve, and Freeman (1945), which were of reconnaissance Palynomorph assemblages from localities 03142 and 03331 (Map type. Owing to the scarcity or absence of fossil fauna and to the B) in northeast Marshall and southeast Calloway Counties indicate general lack of key beds, identification of most stratigraphic units was that the Tuscaloosa of Kentucky is equivalent in age to the Eutaw by homotaxlal correlation with type sections, all of which were 100 Formation (Austinian Stage) of Alabama and thus is considerably miles or more south of Kentucky. Berry (1915, 1916, 1924, 1930, younger than it is in the type area. The difference in age indicates that 1941) used fossil leaves and fruits for correlation and age determina­ the formation is a time-transgressive unit that becomes progressively tions of Eocene units, but partly because of errors in the stratigraphy younger northward from its type locality. The formation in the of some of the type areas used for base control, many of Berry's correlations are invalid. Jackson Purchase region is equivalent to the nonmarine western The ages and correlation of stratigraphic units of this report have facies of the Tuscaloosa of Marcher and Stearns ( 1962, p. 1371-1374). been determined largely through systematic palynological investiga­ tions by R. H. Tschudy and collaborators. The results of these investi­ gations are contained in several published reports (Tschudy, 1966a, McNairy Formation 1970a, b, 1973a, b, 1975; Herrick and Tschudy, 1967; Tschudy and The McNairy Formation is correlated on the basis of palynology Pakiser, 1967; Tschudy and Van Loenen, 1970) and in the open-file with the McNairy Sand at its type locality in McNairy County, Tenn. reports referred to on Map B. Additionally, the palynological investi­ where it was originally defined by Stephenson ( 1914, p. 17, 18) as a gations have provided much new data that indicate environments of member of the Ripley Formation. Subsequently, Russell (1966) deposition. raised the unit in Tennessee to the rank of fonnation. It is designated as McNairy Formation in Kentucky because in the northern part of the Purchaseregionitisdominantlyclay. Steams (1957, p. 1092, fig. 12), Pryor (1960, p. 1476,fig. 2),and Russell (1975, p. All, fig. 4) showed the McNairy to be intergradational with rocks of Tayloran and early Navarroan ~· However, in Kentucky, palynological data indicate that this is not true, at least in the area of outcrop, and that sediments ofTayloran and early Navarroan Age are missing, probably because of ACKNO~EDGEMENTS nondeposition. In the subsurface throughout the Jackson Purchase This report is based largely on all or parts of forty-seven 7%-minute r~n, Cretaceous sediments for the most part are lithologically geologic quadrangle maps (see index map) resulting from investiga­ similar to and have about the same thickness as the McNairy in the tions conducted by 15 geologists from 1960 to 1977, as pa.rt of a area of outcrop. No paleontologic data are available to indicate the cooperative mapping program by the Kentucky Geological Survey age of the complete subsurface Cretaceous sequence, but these and the U.S. Geological Survey. Most of the information presented deposits are considered to be of McNairy age except for a thin here is a summary of that presented on the individual geologic sequence of younger sediments at one locality that is equivalent in quadrangle maps; however, data accumulated during the late stages age to the Owl Creek Formation. of the mapping program have indicated a need for refin'ement and As Illustrated by Steams (1957, p. 1086), "deeper marine" sedi­ revision of some of the earlier Interpretations. Most revisions are of ments \o\ledge out against overlying McNairy Sand in the subsurface this category; however, some, ~rticularly those relating to faulting near the Mississippi River, about 20 miles south of the Kentucky­ and to the delineation of concealed boundaries of Eocene formations, Tennessee State line. The "deeper marine" sediments, as here inter­ are based on opinions derived from a knowledge of the regional preted, are equivalent in age to the Coon Creek Formation and geology after the mapping was completed. Such revisions, though Coffee Sand and are overlapped by the McNairy in northern Tennes­ consistent with available data, do not necessarily indicate that previ­ see. ous interpretations were incorrect, they merely indicate the prefer­ Paleontologic evidence indicates that the depositional environ­ ence of the present author. ment of the McNairy was marine to freshwater deltaic. The area was Ernest E. Russell and Warren I. Finch reviewed the report, and Paul occupied by a shallow marine body of water bordered by bays, E. Potter, Wayne A. Pryor, and H. B. Willman were consulted during lagoons, and saltwater marshes that merged landward with freshwa­ various stages of the investigation. All contributed knowledgeable ter swamps between levees of distributaries. The climate was warm council and made many helpful criticisms and suggestions. temperate to subtropical. 1 Owl Creek Formation Sims (1972), who conducted a petr~hic investigation of the The Owl Creek Formation, the youngest of the Cretaceous forma­ Porters Creek Oay in the Jackson Pm:chase region, has presented tions in the northern Mississippi embayment, is not exposed in the evidence to demonstrate that sediments of the formation are of Jackson Purchase region and is known in the subsurface only from volcanic origin in part. Although he considered possible source areas one drill hole, at locality 04079 in north-central Carlisle County, in Texas, Louisiana, Arkansas, and Mississippi, he acknowledged a where it was identified by a comparison of its pollen content with lack of evidence for Paleocene volcanism in these areas. Unknown pollen from the type locality in northern Mississippi. The unit in to Sims, igneous rocks were reported in 1941 by Mrs. Mary H. Kentucky consists of about 60 feet of glauconitic sandy clay. The O.Vl McCrackerf from an oil test near New Madrid, Mo., 22 miles west of Creek may intergrade with nonmarine sediments of the McNairy Hickman. The section containing the igneous rocks is desaibed as Formation, but evidence to indicate an intergradation is lacking. "red siderite, porphyry, magnetite," and occurs at the contact bet­ Tschudy (written commun., 1977) stated: "With the exception of ween the Porters Creek Clay and the Wilcox Formation between samples from Owl Creek marine deposits I am at present unable to depths of 800 and 810 feet This occurrence suggest the ~ibility of distinguish palynologically, upper McNairy samples from those of volcanic activity during the Paleocene and Eocene and a nearby Owl Creek age." Hence, because of concealment and because the source of volcanic material during deposition of the Porters Creek. two units cannot be distinguished from one another in areas where the O.Vl Creek may be nonmarine, the interrelation of the two units in EOCENE AND OLIGOCENE ROCKS the Jackson Purchase was not determined. In northern Mississippi Eocene rocks of the Jackson Purchase include a sedimentary (Stephenson and Monroe, 1937), the area of its type locality, and in sequence equivalent in age to the Wilcox, Claiborne, and Jackson southwestern Tennessee (Russell, 1975, p. A46-A47), the Owl Groups of the Gulf Coastal States (Tschudy, 1973a), where each Creek rests unconformably on the McNairy Sand. group is represented by two to as many as six formations. Northward TERTIARY across Mississippi, the exposed formations of each group lose their PALEOCENE lithologic identity, and near the Mississippi-Tennessee State line, they Midway Group merge into a sedimentary sequence within which only the boundaries Clayton Formation corresponding to group boundaries farther south can be defined on the basis of compositional and paleontological differences.