Stratigraphy and Conodont Paleontology of the Brassfield (Silurian) in the Cincinnati Arch Area

Indiana Geological Survey 36Abstract Conodonts were collected from 49 sections of the Brassfield Formation (Brassfield Limestone) in its outcrop belt around the Cincinnati Arch in Indiana, Kentucky, and Ohio. Thirty-four indigenous species represent the genera Acodus, Ambalodus, Distomodus, Drepanodus?, Euprioniodina, Icriodina, Ligonodina, Lonchodina, Neoprioniodus, Ozarkodina, Paltodus, Panderodus, Plectospathodus, Spathogna thodus, Synprioniodina, Trichonodella, and a generic group that includes species variously referred to Keislognathus?, Rhynchognathodus?, Roundya, and Trichonodella. Seven new species named herein are Icriodina stenolophata, Ligonodina? extrorsa, Paltodus costulatus, P. debolti, P. dyscritus, P. migratus, and Spathognathodus oldhamensis. The new subspecies Panderodus unicostatus serratus is also named. Conodonts show that the Brassfield Limestone as it is now recognized belongs in the upper part of Bereich I of the European conodont zonation. Younger strata, which overlie the Brassfield from Jefferson County, Ind., into Bullitt County, Ky., possibly should be placed within the Brassfield, and if they were included, the formation in this area would include beds belonging in the celloni-Zone. The Brassfield correlates with the Kankakee Dolomite and the Sexton Creek Limestone of the Alexandrian Series in Illinois. Conodonts support the evidence based on brachiopods that the upper part of the Brassfield is younger west and north of the type area than in the type area of central Kentucky. From about 5 miles southeast of Stanford, Ky., northeastward to northern Adams County, Ohio, the Brassfield Formation is overlain conformably or with slight unconformity by the Noland Formation, which also contains Bereich I conodonts. From Adams County north to Piqua, Ohio, the formation is unconformably overlain by the Dayton Limestone. In Indiana and Kentucky on the west side of the Cincinnati Arch, the Osgood Member of the Salamonie Dolomite or its equivalents overlie the Brassfield with major unconformity except where strata intermediate in age are present from Jefferson County, Ind., into Bullitt County, Ky. The Brassfield unconformably overlies Ordovician strata throughout the Cincinnati Arch area. Tie Ripley Island positive area of southeastern Indiana was the only active structure influencing Brassfield sedimentation in the area studied.Indiana Department of Natural Resource

Stratigraphy and Conodont Paleontology of the Salamonie Dolomite and Lee Creek Member of the Brassfield Limestone (Silurian) In Southeastern Indiana and Adjacent Kentucky

Indiana Geological Survey Bulletin 40Zonation established by study of the conodont faunas of the Lee Creek Member (new member) of the Brassfield Limestone and of the Salamonie Dolomite, both of Silurian age, from 42 sections in southeastern Indiana and north-central Kentucky differs from the conodont zonation established by O. H. Walliser in 1964 for the lower Silurian and lower part of the middle Silurian rocks of the Carnic Alps of Europe. Three conodont assemblage zones are named. In ascending order these are the Icriodina irregularis Assemblage Zone, the Neospathognathodus celloni Assemblage Zone, and the Pterospathodus amorphognathoides-Spathognathodus ranuliformis Assemblage Zone. These zones correspond in general with the upper part of Walliser’s Bereich I and with his celloni-and amorphognathoides-Zones. The new name Lee Creek Member is applied to a thin dolomite unit at the top of the Brassfield Limestone. Fifty-nine named species, 16 of them new, belonging to 22 genera, two of them new, were identified from about 8,900 specimens obtained in this study. The new taxa include the genera Diadelognathus and Neospathognathodus and the species Diadelognathus compressus, D. excertus, D. primus, Drepanodus aduncus, Ligonodina petila, Neospathognathodus bullatus, N. ceratoides, N. latus, Ozarkodina hanoverensis, 0. neogaertneri, Spathognathodus hadros, S. polinclinatus, Synprioniodina? variabilis, Trichonodella asymmetrica, T.? expansa, and T. papilio. Two species each of Diadelognathus and of Paltodus, and one each of Carniodus, Distacodus?, and Trichonodella are described but not named.Indiana Department of Natural Resource

Geology as a Contribution to Land Use Planning in LaPorte County, Indiana

LaPorte County, in northwestern Indiana, is in a geologically complex region underlain at shallow depths by depositional sequences of glacial till, 1 outwash sand and gravel, and lacustrine silt and clay. The combined agents of ice, wind, and water have sculptured these deposits into a topographically varied landscape ranging from sandy flats of the Kankakee Outwash and Lacustrine Plain to partly wooded hilly uplands on the Valparaiso Moraine. Beneath the glacial materials, which range from 25 to 350 feet in thickness, is a sequence of Paleozoic rocks that is about 4,000 feet thick. Limestone, dolomite, sandstone, and shale, complexly interlayered and varying in thickness, make up the bedrock units, which provide ground water potential and contain potentially commercial deposits of gypsum near LaPorte

Excursions in Indiana Geology

Indiana Geological Survey Guidebook 12Indiana lies wholly within the Central Lowland Province and thus calls to mind widespread, thin, nearly flat-lying Paleozoic rocks, major unconformities, and extensive plains. These features express epeirogenic submergences of the central part of the continent, long periods of general stability, and, nevertheless, repeatedly interrupted episodes of sedimentation and landform sculpture. Outstanding among these episodes was continental glaciation that carried to the Ohio River. Receiving ice from two principal directions the State's surface nearly everywhere attests to its latest experience, most obviously in the form of a great till plain that is interrupted in its gross appearance by end moraines, valley trains, and ice-contact deposits. Structurally, the State lies athwart a broad crestal area, the Cincinnati Arch, which separates the Michigan Basin on the north from the Illinois Basin on the southwest. Some structural instability, manifest as long ago as Precambrian time, is evident in such sedimentational or second-rank structural features as lithofacies, Silurian-Devonian and Mississippian-Pennsylvanian unconformities that change both locally and regionally in magnitude, and faulting. The more recent erosional record reflects structural history as well, and Paleozoic rocks from middle Ordovician to middle Pennsylvanian in age crop out at the bedrock surface according to their order of superposition. The Paleozoic units west and south of the Cincinnati Arch have special interest on these excursions. Their truncated edges, having differing resistances, are expressed alternately by open vales of gentle relief and uplands consisting of partly dissected westward-facing dip slopes and rugged forested scarps. Within easy range of Bloomington we can demonstrate much of the variety of geologic form characteristic of the State. Crossing the regional strike and the boundary between driftless and glaciated areas, the first day's excursion (inside front cover) is generally eastward to traverse bedrock of Mississippian to Silurian age and drifts assigned to the Kansan, Illinoian, and Wisconsin Stages. It emphasizes the State's most widely known natural product, the Indiana Limestone, and relationships of physiography to bedrock and drift. The second day's excursion (inside back cover) is northwestward from Bloomington and crosses younger bedrock (to middle Pennsylvanian in age). It emphasizes the Mississippian-Pennsylvanian unconformity, stratigraphic relationships of drifts, and some of the newest methods of coal mining and land reclamation.Indiana Geological Survey Indiana Department of Natural Resources American Association of State Geologist

Excursions in Indiana Geology

Our purpose on these excursions arranged for the 58th meeting of the Association of American State Ge ologists is to bring about an awareness of Indiana geology and its attraction. Although our State lacks a Grand Canyon and production of glamour metals, features which in themselves would assure success of a field trip, it nevertheless offers many geologic challenges--challenges that we shall in part take up during these two days

Conodonts from the Keokuk, Warsaw, and Salem formations (Mississippian) of Illinois

Cover title.Bibliography: p. 25-26

Six charts showing biostratigraphic zones, and correlations based on conodonts from the Devonian and Mississippian rocks of the Upper Mississippi Valley

Bibliography: p. 28-32

Condonts from the Louisville Limestone and the Wabash Formation (Silurian) in Clark County, Indiana and Jefferson County, Kentucky

Ten multielement species of conodonts representing the Kockelella variabilis Zone are described from samples from 10 locations in the Louisville Limestone and in the lower part of the Wabash Formation in the type area of the former. The conodonts have moderately long stratigraphic ranges, but their association is compatible with a late Wenlockian-early Ludlovian age assignment for the two stratigraphic units. Genera recorded include Kockelella, Ozarkodina, Dapsilodus, Decoriconus, Panderodus, and Walliserodus. A new subspecies of Ozarkodina confiuens is recognized but not named