129-68 Still Muddy: Palynology Across the K-Pg Boundary in the Jackson Purchase Region of Kentucky

Abstract:

The Independence School Site in the Jackson Purchase region of Kentucky contains a near-complete record of deposition in terrestrial environments from the upper McNairy Formation (Cretaceous) through the lower Clayton Formation (Paleocene). The original palynological investigation of the site in 1970 suggested that this region was coastal, with a mosaic of onshore and near-shore environments. Preliminary re-study of widely spaced samples completed in 2023 supports this, with dinoflagellates and foraminiferal test linings, indicating marine deposition only present in a 10-cm thick bed approximately halfway between a basal lignite and the iridium spike. Plant palynomorphs preserved suggest that the area received moderate to high precipitation, had warm temperate to subtropical temperatures, and uplands likely resembled the mixed mesophytic forests present in the region today. The sediments themselves record first deposition in a topogenous mire, followed by freshwater wetlands that (perhaps) transition to marginal marine environments, then terrestrial near-shore environments. A mixed assemblage of Cretaceous and Danian palynomorphs present at the level of the iridium spike may be suggestive of reworking, or of sample contamination during collection. This re-study left multiple questions, resulting fine-scale re-sampling of the site in spring of 2025. Here we present the results to date of palynological study of these samples, with improved interpretation of variations in paleoecology and paleoclimate recorded across the K-Pg Boundary in Kentucky.

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