Cretaceous-Paleogene mass extinction: Asteroid impact, volcanism or both?

SIAL, ALCIDES N.; JIUBIN CHEN; LACERDA, L.D.; V. C. TEWARI; M. K. PANDIT; GAUCHER, CLAUDIO; FREI, ROBERT; FERREIRA, VALDEREZ P; S. CIRILLI; PERALTA, SILVIO H; C. KORTE; J. A. BARBOSA; N. S. PEREIRA

Colonia

Congreso; Congreso Geológico Uruguayo; 2016

Asociación Geológica Uruguaya

We focus here on the bolide impact versus volcanism debate concerning the mass extinction in the Cretaceous-Paleogene boundary (K?Pg). While the iridium content in the K-Pg layer and He isotopes in fullerenes are regarded as proxies for the Chicxulub asteroid impact, we investigated the use of Hg as a proxy for volcanism straddling this boundary, using distal and proximal sections in relation to the Deccan volcanic center. Notable Hg/TOC spikes have been observed in the studied sections: (a) spike I: in the Meghalaya (India), Gubbio (Italy) and Højerup (Denmark) sections within the CF2 planktic foraminiferal biozone, (b) spike II: large Hg/TOCat the K?Pg boundary in these same sections and (c) spike III: within the P1a planktic foraminiferal subzone in these three and Jhilmili (India) sections. These three Hg/TOC spikes probably resulted from distinct volcanic episodes of Deccan trap main stage (phase-2) and represent true Hg loading to the environment (spike I is probably related to the Poladpur eruptive pulse and spike III, to the Ambenalli one). Besides volcanism, scavenging of Hg by anoxia on seafloor may have contributed Hg to the generation of spike II as stratigraphic record of Mo/Al redox proxy exhibits negative shift in the K-Pg boundary in most studied sections, suggesting decrease in oxygenation. The Chixulub impact may have triggered the enormous Poladpur, Ambenalli and Mahabaleshwai (Wai Subgroup) lava flows of the Deccan trap main stage.