WILDFIRE PALEOECOLOGY ALONG THE CRETACEOUS COAST OF APPACLACHIA, THE INFLUENCE OF PALEOGEOGRAPHY AND PALEOCLIMATE AT THE ARLINGTON ARCHOSAUR SITE, TEXAS

The Arlington Archosaur Site (AAS) is a fossil locality from the Cretaceous (Cenomanian) Woodbine Formation that occurs in North Texas. The AAS fossil exposures occur within a 2 m section of peat and paleosol. The peat is fossil rich and contains vertebrate fossils of fish, amphibian, turtle, crocodyliform and dinosaur, as well as the remains of numerous trees. Overlying the peat is a paleosol sequence containing dinosaur, crocodyliform, and lungfish. The paleosol contains two distinct horizons. The upper is mottled and well-rooted with numerous calcareous concretions, within which are preserved charcoal, from individual fragments to large stumps and root systems. The lower horizon is a gray mudstone lacking root traces and preserving the majority of the fossils. Concretions likely formed during the dry season, where the water table dropped to the level of the lower horizon, which remained waterlogged year round. The climate in this part of Appalachia during the Cenomanian was generally moist, with a distinct dry season. The beginning of the wet season may have begun with tropical storms that struck the peninsula and sparked wildfires via lightning strikes. The paleogeographic setting was a coastal plain that stretched along a peninsula in the southern interior seaway of southwest Appalachia. We propose the name Rudradia for this paleogeographic peninsula, named for Rudra the storm god.

Evidence of wildfires was found via abundant charcoal, evidence of storms is supported by hummocky beds and a mapped trend seen in the distribution of fossil logs. Charcoal conglomerate beds and numerous fragments are visible throughout the exposed outcrop, occurring below, within, and above the fossil horizons. The presence of charcoal conglomerates is typical of coastal systems where burned materials were transported by river channels. Within the fossil bearing peat bed, > 20 fallen carbonized logs were mapped demonstrating a common NE-SW trend. Above the peat bed, charcoal roots and stumps in the paleosol followed by a charcoal debris flow deposit all lend support to multiple wildfire events that disturbed the coastal ecosystem. We suggest that periodic wildfires were influential in driving diversity at the AAS and provides an opportunity to study the Intermediate Disturbance Hypothesis in a coastal Cretaceous ecosystem.