PP31F-06
Recovery of Carbonate Ecosystems Following the End-Triassic Mass Extinction: Insights from Mercury Anomalies and Their Relationship to the Central Atlantic Magmatic Province
Wednesday, 16 December 2015: 09:15
2012 (Moscone West)
Frank A Corsetti1, Alyson M Thibodeau2, Kathleen A Ritterbush3, A. Joshua West4, Joyce Ann Yager4, Yadira Ibarra1,5, David J Bottjer4, William Berelson1 and Bridget A Bergquist6, (1)University of Southern California, Department of Earth Sciences, Los Angeles, CA, United States, (2)Dickinson College, Carlisle, PA, United States, (3)University of Utah, Department of Geology and Geophysics, Salt Lake City, UT, United States, (4)University of Southern California, Los Angeles, CA, United States, (5)Stanford University, Earth Sciences, Stanford, CA, United States, (6)University of Toronto, Toronto, ON, Canada
Abstract:
Recent high-resolution age dating demonstrates that the end-Triassic mass extinction overlapped with the eruption of the Central Atlantic Magmatic Province (CAMP), and the release of CO2 and other volatiles to the atmosphere has been implicated in the extinction. Given the potentially massive release of CO2, ocean acidification is commonly considered a factor in the extinction and the collapse of shallow marine carbonate ecosystems. However, the timing of global marine biotic recovery versus the CAMP eruptions is more uncertain. Here, we use Hg concentrations and Hg/TOC ratios as indicators of CAMP volcanism in continental shelf sediments, the primary archive of faunal data. In Triassic-Jurassic strata, Muller Canyon, Nevada, Hg and Hg/TOC levels are low prior to the extinction, rise sharply in the extinction interval, peak just prior to the appearance of the first Jurassic ammonite, and remain above background in association with a depauperate (low diversity) earliest Jurassic fauna. The return of Hg to pre-extinction levels is associated with a significant pelagic and benthic faunal recovery. We conclude that significant biotic recovery did not begin until CAMP eruptions ceased. Furthermore, the initial benthic recovery in the Muller Canyon section involves the expansion of a siliceous sponge-dominated ecosystem across shallow marine environments, a feature now known from other sections around the world (e.g., Peru, Morocco, Austria, etc.). Carbonate dominated benthic ecosystems (heralded by the return of abundant corals and other skeletal carbonates) did not recover for ~1 million years following the last eruption of CAMP, longer than the typical duration considered for ocean acidification events, implying other factors may have played a role in carbonate ecosystem dynamics after the extinction.
