Biomarker Reconstruction of a High-Latitude Late Paleocene to Early Eocene Coal Swamp Environment Across the PETM and ETM-2 (Ellesmere Island, Arctic Canada)

The Paleocene-Eocene Thermal Maximum (PETM) and early Eocene hyperthermal events were characterized by a Hothouse climate state. Our understanding of the climatic impact of these hyperthermals is currently biased toward marine settings and the mid-latitudes. Here we present organic geochemical data from Stenkul Fiord, Ellesmere Island, Arctic Canada. This organic rich formation was deposited in a high northern latitude wetland setting during the late Paleocene to early Eocene, spanning the PETM and subsequent ETM-2 hyperthermals. Biomarker data (e.g., diterpenoids), combined with published palynological data from the site, indicate Cupressaceae-dominated vegetation. Biomarkers suggest that land plant composition remained fairly unchanged across the two hyperthermal events. Increases in abundance and 13C-depletion of hopanoid biomarkers (minima <-50 parts per thousand (VPDB)) highlight periods of enhanced bacterial methane consumption, particularly during the PETM. However, periods of low hopanoid delta 13C values were also found outside the hyperthermal intervals. Relatively low delta 2H values of higher plant n-alkanes (average delta 2H values of n-C25, n-C27, n-C29 similar to -230 to -270 parts per thousand (SMOW)) indicate that deposition formed during times with enhanced precipitation. The wettest intervals, as identified by the lowest delta 2H n-alkane values, contain high abundances of hopenes, indicating enhanced bacterial turnover. At Stenkul Fiord, high temperatures and CO2 concentrations likely fostered the growth of widespread wetland forests that became a CO2 sink and may have played an important role in carbon drawdown during the Early Paleogene.