Lower to middle Paleozoic sequence stratigraphy and paleontology in the greater Louisville, Kentucky, area

Abstract

The Cincinnati Arch region of Ohio, Kentucky, and Indiana is an icon of North American Paleozoic stratigraphy, as it exposes strata ranging from Ordovician to Pennsylvanian in age. In particular, the highly fossiliferous Ordovician, Silurian, and Middle Devonian successions have been extensively studied since the nineteenth century, and continue to serve as a crucial proving ground for new methods and models of biostratigraphy, chemostratigraphy, and sequence stratigraphy in mixed clasticcarbonate depositional settings. These strata are locally capped by Middle Devonian limestones with their own diverse fauna and unique depositional history. Outcrops near Louisville, Kentucky, provide an excellent opportunity to examine these strata firsthand and discuss sequence stratigraphy, chemostratigraphy, sedimentary environments, and paleoecology. A series of new roadcuts south of Mount Washington, Kentucky, exposes the lower to middle Richmondian Stage (Upper Ordovician, Cincinnatian) and presents a diverse suite of marine facies, from peritidal mudstones to offshore shoals, coral biostromes, and subtidal shales. These exposures are well suited for highlighting the revised sequence stratigraphy of the Cincinnatian Series, presented herein. Nearby outcrops also include much of the local Silurian succession, allowing an in-depth observation of Llandovery and Wenlock strata, including several chemostratigraphically important intervals that have improved regional and international correlation. Supplementary exposures east and north of Louisville provide context for subjacent and superjacent Ordovician-Silurian strata, as well as examples of lateral facies changes and unconformities. Additionally, the Falls of the Ohio at Clarksville, Indiana, features an exceptional outcrop of the overlying Middle Devonian succession, including an extensive and well-preserved biostrome of corals, sponges, and other marine fauna. These fossil beds, coupled with significant exposures in local quarries, are critical for understanding the paleoecology and stratigraphy of the Middle Devonian of the North American midcontinent.

Silurian carbonate high-energy deposits of potential tsunami origin: distinguishing lateral redeposition and time averaging using carbon isotope chemostratigraphy

“…Both lithologies of the Muksha Formation are abruptly truncated by the overlying Ustya Formation. The contact between Muksha and Ustya formations can be correlated with a widespread upper Homerian sequence boundary recorded in the Baltic Basin (Calner and Jeppsson, 2003), in the Anglo-Welsh Basin (Ray et al, 2010;, and in eastern US (McLaughlin et al, 2008;Brett et al, 2012a;Brett et al, 2012b). In Podolia, the Homerian outcrops are distributed approximately along the depositional strike, and their basinward equivalents located westward of the study area are covered with upper Silurian and younger strata.…”

Shallow-water onlap model for the deposition of Devonian black shales in New York, USA: REPLY

“…Black shale of the Portwood Formation in Kentucky (Tully Limestone equivalent) immediately overlies major karst features with up to 3m of relief (Brett et al, 2004). Brett et al (2018) also report karst and paleosol development under the organic-rich, wood-bearing Blocher Shale (age-equivalent to the Geneseo) elsewhere on the Cincinnati Arch. These examples clearly demonstrate that subaerial exposure does occur on at least some Devonian unconformities and that Devonian black shales can and do immediately overlie subaerial exposure surfaces.…”

Time-richness and phosphatic microsteinkern accumulation in the Cincinnatian (Katian) Ordovician, USA: An example of polycyclic phosphogenic condensation

“…Thus, if shell bed textural maturity and phosphate content are both a product of condensation, then shell bed SSF content should increase with increasing textural maturity. Cycles are after Holland (1993) and Holland, Patzkowsky (1996, and Brett et al (2018;this volume)…”

“…Phosphatic microsteinkerns are composed of CFA that fills cavities, and generally range in size from 0.25 to 1.5 mm in diameter or minimum width. Preliminary work in recognizing these particles (Dattilo et al, 2015(Dattilo et al, , 2016(Dattilo et al, , 2018 utilized EDS scans of thin sections and dissolution with acetic acid to liberate non-soluble phosphatic residue. We determined that we could visually identify phosphatic steinkerns with confidence from thin sections in these rocks; no other materials have precisely the same optical properties and shapes/habits (Fig.…”

“…Arrows mark the approximate stratigraphic levels for phosphorite examples 1, 2 and 3, which are illustrated in Fig. 4A, B, and C respectively.Cycles are afterHolland (1993) andHolland, Patzkowsky (1996, andBrett et al (2018;this volume)…”