--> Ocean Acidification in Modern Seas and its Recognition in the Geological Record: The Cretaceous/Paleogene boundary in Texas and Alabama
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Previous HitOceanNext Hit Previous HitAcidificationNext Hit in Modern Seas and its Recognition in the Geological Record: The Cretaceous/Paleogene boundary in Texas and Alabama

Malcolm B. Hart2, Andrew D. Leighton1, Christopher W. Smart2, Laura R. Pettit3, lba N. Medina-Sánchez4, Peter J. Harries5, Andrés L. Cárdenas6, Jason M. Hall-Spencer3 and Rosa Maria Prol-Ledesma4

1School of Geography, Earth and Environmental Sciences, Plymouth University, Plymouth UK.
2Marine Institute, Plymouth University, Plymouth UK.
3School of Marine Science and Engineering, Plymouth University, Plymouth, UK.
4Universidad Nacional Autonoma de Mexico, Ciudad University, Mexico DF.
5Department of Geology, University of South Florida, Tampa, FL.
6Centre for Tropical Paleontology and Archaeology, Smithsonian Tropical Research Institute, Panama

October 7, 2014 Tuesday 8:45 A.M. GCAGS, Lafayette, Louisiana

Abstract

With increasing atmospheric CO2 the oceans are becoming progressively more acidic, with the lowered pH beginning to impact on the calcification of foraminifera, pteropods, calcareous nannoplankton and other invertebrate groups. Our work in the Mediterranean Sea, Gulf of California, Caribbean Sea, and elsewhere has shown how modern assemblages are responding to Previous HitacidificationNext Hit. Around Ischia (Italy) natural seafloor CO2 vents are creating a low pH environment in which it is possible to observe the response of benthic foraminifera. At a pH of 7.8, the assemblage is already becoming less diverse and below pH 7.6 there are no calcite-secreting benthic foraminifera. In the Gulf of California, in a deeper-water setting, natural CO2 (and methane) vents are, again, lowering seafloor pH. The foraminifera show the impact of this change, although the relatively high carbonate saturation ensures that calcite-secreting foraminifera are able to live and reproduce in relatively low pH environments, only becoming impacted by dissolution effects once dead.

Using data from a number of global bioevents (Triassic/Jurassic boundary, Cretaceous/ Paleogene boundary and the Paleocene/Eocene boundary) it is now possible to determine the contribution of Previous HitacidificationNext Hit to global bioevents, both in the near-surface and in deeper-water environments caused by the migration of the carbonate compensation depth (CCD). In Texas and Alabama, the Cretaceous/Paleogene boundary successions record no direct evidence of Previous HitoceanNext Hit Previous HitacidificationNext Hit despite the proximity to the Chicxulub impact site and the proposed source of some of the CO2 (in addition to that from the Deccan Volcanic Center in India) required to cause the Previous HitacidificationNext Hit. Interpretation of changes in the biota during global bioevents is complicated by the changing nature of the oceans through time, which have switched from being aragonitic to calcitic a number of times during the Phanerozoic. The other significant change is that from a 'Neritan Previous HitOceanNext Hit' to a 'Cretan Previous HitOceanTop' in the mid-Jurassic.

AAPG Datapages/Search and Discovery Article #90196 © 2014 GCAGS, Lafayette, Louisiana, October 5-7, 2014