MICROFOSSIL CHARCOAL AND BLACK CARBON PROXIES FOR PALEOWILDFIRE RECONSTRUCTION DURING THE PETM

The Paleocene Eocene Thermal Maximum (PETM, 56 Ma) is marked by a 5-8°C increase in global temperatures, a negative Carbon Isotope Excursion (CIE), and a 100-fold increase in charcoal a diagnostic remnant of wildfires. However, because counts of charcoal abundance rely on isolating visible charcoal grains from the sediment it has a limited capacity to examine the global extent of PETM wildfires as locations distant from fire require atmospheric char or soot deposition that is unlikely to be detected via manual identification. In addition to quantifying charcoal, this study examines the quantity and isotopic composition of black carbon (BC; the condensed aromatic fraction of pyrogenic carbon produced from fire) using the benzenepolycarboxylic acid (BPCA) method. Investigating BC extent and dynamics during the PETM will enhance our understanding of wildfires at this critical juncture in geologic history and offer insights into Earth's response to carbon perturbations. The main research objective is to evaluate black carbon distribution in Mid-Atlantic Coastal Plain sediments to determine whether BPCA molecular markers are capable of tracking wildfire activity through the PETM. Using the BPCA method, preliminary analysis of PETM sediments from Surprise Hill revealed that BC in sediments was elevated 60-fold at the onset of CIE (1.76 ±0.14 μg-C/mg-dw) compared to background BC levels (0.03 ± 0.00 μg-C/mg-dw). This peak in BC is nearly coincident with the peak in charcoal observed at the boundary. Preliminary BPCA-specific isotope data also indicate a substantial shift in BC δ¹³C through the PETM that mirrors the negative CIE observed in charcoal and foraminifera isotope records.