17:15 〜 19:15
[BPT04-P03] N2-fixation as a response to Large Igneous Province activity during the end-Triassic mass extinction
キーワード：Mass Extinction, Triassic, Compound-specific isotopes, Biomarker
The end-Triassic mass extinction (ETE), that occurred 201 Ma, saw fundamental ecological and environmental shifts resulting from the laterally extensive Large Igneous Province (LIP) termed the Central Atlantic Magmatic Province (CAMP). This event serves as an ancient analogue to potential future climate-forced ecological and environmental changes given similar rates of CO2 increases observed between the CAMP and anthropogenic activity. A critically overlooked aspect of the ETE is resolving changes in the aquatic nitrogen cycle. Currently, no compound-specific nitrogen isotopes exist for the ETE, despite their importance in accurately recording nitrogen cycle shifts in the geological record. We investigated the nitrogen and carbon isotopic composition of deoxophylloerythroetioporphyrin (DPEP; d15NDPEP, d13CDPEP) that derives from chlorophyll-a at a pivotal ETE locality; St. Audrie’s Bay, UK. During a correlative carbon isotope excursion, elevated d15NDPEP values further support the emergence of microbial mats driving this excursion. In the extinction horizon, 15NDPEP, d13CDPEP, and the d15N differences between DPEP and total nitrogen (TN) reveals the expansion of cyanobacteria and increases in N2-fixation, estimated to account for 50-75% of production. Although further d15NDPEP investigations are needed, d15NTN records from diverse depositional settings suggest N2-fixation was wide-spread during the ETE and likely a common response to LIP activity.