101-8 Correlation of Middle Devonian (Eifelian) Sequences and Unconformities in Ohio-Indiana: Implications for Sequence Stratigraphy and Bioevents

Session: Paleontology, Biogeography/Biostratigraphy & Phylogenetic/Morphological Patterns

Presenting Author:

Thomas Van Tassel

Authors:

Van Tassel, Thomas Robert¹, Brett, Carlton E.², Dattilo, Benjamin F.³, Welych-Flanagan, Martin Andrew⁴, Danielsen, Erika M.⁵, Waid, Christopher T.⁶

Abstract:

Middle Devonian strata of the Appalachian foreland basin (AFB) preserve a detailed record of high-order (3^rd and 4^th order) sequences and bioevents. However, in northern Ohio and northeast Indiana, correlations are obscured by differences in terminology, truncation of units by subtle unconformities, and variations in unit thickness/facies. A study of 20 outcrops and 10 cores, from Delaware to Sandusky, Ohio, and drill cores from northeast Indiana, reveals a consistent regional framework of Eifelian to earliest Givetian sequences from this area into the Appalachian, Michigan (MB), and Illinois (IB) basins. Lower Eifelian, Eif-1: (Columbus Limestone), rests unconformably on the Silurian and displays a consistent, retrogradational suite of a) coral-rich (dolo)grainstones/rudstones into b) white chert in fined-grained limestone, and c) bioturbated, fossiliferous wacke- to packstones with two persistent dark shale seams, possibly correlating to the Nedrow “black beds” (Choteč bioevent). Overlying regressive grainstones grade northward into peritidal stromatolitic-thrombolitic facies of the Detroit River Formation.  The second Eifelian sequence boundary (Eif-2) is marked in northern localities by a breccia zone, sharply overlain by a) highly fossiliferous crinoidal grainstone (H, with classic “Columbus fauna”) followed by b) brownish argillaceous limestone to c) shale and brownish gray, cherty wackestones (Delaware Fm) forming the Eif-2 highstand; it persists into the eastern Illinois and  Michigan basins, where it is mapped as lower part of the Dundee Formation and passes eastward into the lower Marcellus shale of the AFB. An upper crinoidal- coral-rich grainstone (Lewis Center Beds) with a diverse “recurrent Columbus fauna” extends from Delaware, Ohio, northwestward, where it forms the upper beds of the Dundee. It represents the basal portion of a previously unrecognized 4^th order sequence, the upper part of which (Rogers City Fm with distinctive “Stony Hollow fauna” in MB) is absent in nearly all locations at the approximate Eifelian-Givetian sequence boundary. This disconformity is marked in central Ohio by a persistent, thin crinoidal transgressive lag, rich in the small discoidal rugose coral Hadrophyllum dorbignyi. It is represented in the Fort Wayne (IN) core by a phosphatic grainstone with reworked limestone clasts at the base of the Traverse Group directly overlying the Lewis Center/top Dundee grainstone. Evidence of the late Eifelian Stony Hollow event has been removed at this boundary, which locally cuts into the Delaware Formation.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-7137

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