COMMUNITY COMPOSITION AND TAPHONOMY OF FOSSIL WOOD IN VALLEY-FILL FLUVIAL CHANNELS OF THE PENNSYLVANIAN BREATHITT GROUP IN EASTERN KENTUCKY

Previous studies have mentioned the occurrence of fossil wood in valley fills of the Breathitt Group, but little quantitative study has been done on its taxonomic composition or taphonomy. Here, we report the community composition and taphonomy of wood from a series of valley fills, primarily in the Hyden, Pikeville, and Grundy formations of the Breathitt Group. Fossil wood occurs in single-story and multi-story channel deposits within valley fills. Lycopsids represent 96% of the wood in these channels, with 0.7% being coniferopsid, with 1% being Calamites, and 2.4% unidentifiable to higher taxon. Nearly all lycopsid wood is macroscopically unidentifiable to genus (99%) and identifiable Sigillaria and Lepidodendron are each present but rare (<1% each). Taxonomic composition varies little between tidally influenced fluvial channels (42% of specimens) and inland fluvial channels (58% of specimens). Of those in tidally influenced fluvial channels, 98% of the wood is from lycopsids, 0.9% from coniferopsids, 0.3% from Calamites, and 1% is unknown. Of the wood in inland fluvial channels, 94% is from lycopsids, 0.5% from coniferopsids, 2% from Calamites, and 3% is unknown. Lycopsids are commonly preserved as thin coal seams that may be flat or ellipsoidal around a wood pith cast, making most of them unidentifiable. Others, like Calamites or Sigillaria are preserved as casts or coalified impressions of bark, and Lepidodendron is preserved as coalified impressions of leaf cushions. Coniferopsids are typically preserved as mineralized pith casts. The abundance of lycopsids and coniferopsids varies little between inland channels and tidally influenced channels, implying relatively uniform composition of these riparian tree communities. This uniformity may imply that climate was relatively uniform over the region and similar from one valley fill to the next. It may also suggest that there was little variation in riparian plant communities with distance from the shore.