Paper No. 3
Presentation Time: 2:00 PM


GREENE, Sarah E.1, MARTINDALE, Rowan C.2, RITTERBUSH, Kathleen A.3, BOTTJER, David4, CORSETTI, Frank A.4 and BERELSON, William M.4, (1)School of Geographical Sciences, University of Bristol, Bristol, BS8 1SS, United Kingdom, (2)Jackson School of Geosciences, University of Texas at Austin, 1 University Station C1100, Austin, TX 78712, (3)Department of Geophysical Sciences, University of Chicago, 5734 S Ellis Ave, Chicago, IL 60637, (4)Department of Earth Sciences, University of Southern California, Los Angeles, CA 90089,

While demonstrating ocean acidification in the modern is relatively straightforward, identifying paleo-ocean acidification requires multiple lines of evidence. Aside from geochemical carbonate chemistry proxies (many of which are as yet ill-suited for deep time application), three main lines of evidence have been applied to fingerprint paleo-ocean acidification: 1) identification of a suitable acidification trigger; 2) a global sedimentary record of temporary carbonate depletion; 3) an extinction signature of selectivity against acidification-susceptible organisms. Each of these criteria is fraught with its own pitfalls when applied to deep time. In the first case, the timescales of acidification-relevant carbon cycle processes can challenge dating precision. In the second, the rock record is a constructive archive while ocean acidification is essentially a destructive (and/or inhibitory) phenomenon. In the third, the experimental biological data on susceptibility to acidification as yet lack robust consensus for many geologically-relevant clades.

Nonetheless, in combination these criteria can be applied to identify geological events consistent with ocean acidification. As a test case, the record of the end-Triassic mass extinction passes all three criteria. 1) The eruption of the Central Atlantic Magmatic Province and the associated massive and rapid release of CO2 coincident with the end-Triassic mass extinction provide a suitable trigger for an acidification event (full carbonate undersaturation in the surface ocean is possible but improbable). 2) Tentative evidence for a global paucity of carbonate across the end-Triassic mass extinction versus the adjacent stratigraphy is consistent with a predicted sedimentary response to acidification. 3) The end-Triassic mass extinction was particularly selective against acidification-sensitive organisms (more so than perhaps any other extinction event).