T15 Understanding the Links between Life, Biogeochemical Cycles, and Environmental Feedbacks throughout the Mesozoic

Sunday, 22 September 2024
8:00 AM - 12:00 PM
207B

BIOTURBATION SHAPES MARINE NUTRIENT CYCLING FOLLOWING THE PERMIAN-TRIASSIC MASS EXTINCTION

Paper number: T15-2
Program: Technical Sessions
Time: 8:05 AM – 8:20 AM

Authors

Abstract

During the end-Permian mass extinction (EPME) ca. 252 Ma, a global loss of bioturbation provides critical evidence for the collapse of marine ecosystems, likely triggered by rapid ocean warming and deoxygenation. However, the loss of bioturbation may not only have been a consequence of environmental deterioration but also a driver, by limiting the cycling of nutrients between sediments and seawater and delaying the recovery of marine ecosystems for most of the Early Triassic. Here we test this hypothesis through combined analysis of bioturbation and sediment geochemistry using records of the Permian-Triassic transition at four different localities in Svalbard. We find that bioturbation intensities are inversely correlated with organic carbon (Corg), organic phosphorus (Porg), and sulfur (S) content, a pattern that is independent of changes in seafloor redox or sedimentation style and persistent across the entire Early Triassic. Decreases in Corg, Porg and S are primarily associated with increases in bioturbation, and specifically the presence of biodiffusion (particle mixing) rather than bioirrigation (sediment ventilation by open burrows). In contrast to Porg, we find that non-organic reactive P (i.e. the combination of authigenic and iron-bound P, which comprises the majority of total P within these sediments) does not correlate with overall bioturbation intensity but increases with the combined presence of biodiffusion and bioirrigation.

Our findings indicate that the initial return of shallow-tier bioturbators after the extinction (in the early Griesbachian) greatly enhanced organic matter and sulfur oxidation within the sediment pile, promoting efficient recycling of Corg, Porg and S. However, total P burial did not change until the later return of deep-tier bioturbators and more diverse mixing styles (late Griesbachian-Dienerian), which may have promoted P sequestration within authigenic and iron-bound phases. Our findings suggest that bioturbation may have acted as a potential feedback on seafloor habitability after the EPME through its effects on C, S, and P cycling, at least on a local scale. More broadly, our work demonstrates that bioturbation-nutrient relationships inferred from modern marine settings can be detected in ancient sedimentary records, making our approach applicable to other intervals of Earth history.

Geological Society of America Abstracts with Programs. Vol. 56, No. 5

doi: 10.1130/abs/2024AM-402158

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