220-1 Using Ecological Gradients in Offshore Facies to Infer Stacking Patterns: Pennsylvanian Breathitt Group of Eastern Kentucky, U.S.A.

Session: Life and Environments Through Time and Space: Multi-Record Approaches to Stratigraphic Paleobiology (Posters)

Poster Booth No.: 127

Presenting Author:

Spencer Shroyer

Authors:

Shroyer, Spencer W.¹, Bennington, J Bret², Holland, Steven M.³

(1) Department of Geology, University of Georgia, Athens, Georgia, USA, (2) Department of Geology, Environment, and Sustainability, Hofstra University, Hempstead, New York, USA, (3) Department of Geology, University of Georgia, Athens, Georgia, USA,

Abstract:

Sequence-stratigraphic stacking patterns are commonly based on the shallowest facies, but in the Pennsylvanian Breathitt Group of eastern Kentucky, these have commonly been truncated by incised valleys. Because offshore to prodeltaic environments are commonly lithologically uniform, here we explore using their fossil associations to infer stacking patterns. We analyze three datasets: Chesnut (1991), who reports the presence of species from the 41 marine tongues of the Breathitt, Bennington (1995), who collected species abundance data from four major marine tongues, and new species abundance data collected for this study from 14 marine tongues of the Pikeville, Hyden, and Four Corner formations of the Breathitt. These data were ordinated using Detrended Correspondence Analysis (DCA) and Non-Metric Multidimensional Scaling (NMS), with NMS generally yielding more interpretable results. The ordinations reveal four overlapping fossil associations. The first is dominated by pedunculate brachiopods (spiriferids, orthids, athyrids, and terebratulids), solitary rugosans, crinoids, bryozoans, and trilobites, many of which are suspension feeders associated with shelly substrates. The second comprises lingulid, chonetid, and orthotetid brachiopods, suspension feeders adapted to soft substrates. The third contains bivalves and productid brachiopods, as a mix of suspension and deposit feeders that are generally adapted to soft substrates. The fourth association is dominated by gastropods but also contains bivalves. In stratigraphic columns of individual marine units, the pedunculate brachiopod association passes upwards to the bivalve-productid association and in turn to the gastropod-dominated association, suggesting upward shallowing. Thus, these associations appear to be separated along gradients correlated with water depth and substrate consistency that are expressed along ordination axes one and two. However, neither water depth nor substrate consistency aligns perfectly with axes one and two: these gradients are inclined relative to the ordination axes. Such a pattern is produced when the two gradients — water depth and substrate consistency — are near equal in their strength. Because a water depth gradient is expressed, it may be possible to use the deepest-water samples in each marine tongue to establish stacking patterns among the marine tongues in the Breathitt Group. This approach may have broader application to inferring sequence-stratigraphic stacking patterns in other study areas that are dominated by lithologically uniform offshore to prodelta facies.

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

doi: 10.1130/abs/2025AM-8719

© Copyright 2025 The Geological Society of America (GSA), all rights reserved.