High-resolution Hg chemostratigraphy: A contribution to the distinction of chemical fingerprints of the Deccan volcanism and Cretaceous?Paleogene Boundary impact event

SIAL, ALCIDES N.; JIUBIN CHEN; LACERDA, L.D.; PERALTA, SILVIO H; GAUCHER, CLAUDIO; FREI, R.; CIRILLI, S.; FERREIRA, VALDEREZ P.; MARQUILLAS, R.; BARBOSA, J.; PEREIRA, N.S.

PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2014 vol. 414 p. 98 - 115

0031-0182

There is a renewed interest in volcanism as the major trigger for the Cretaceous ‒Paleogene transition (KTB) dramatic climatic change with decrease in biodiversity and mass extinction. We have used Hg contents as proxy for volcanic activity at the classical localities of Gubbio and Stevns Klint that exhibit easily recognizable KTB layer, and at a near-complete succession at the Bajada del Jagüel locality bracketing the KTB in the Neuquén Basin, Argentina. These three localities display similar δ13Ccarb pathways with markedly negative excursion at the KTB layer. Bulk-rock oxygen isotopes yielded similar pathways at the KTB layer in these localities and, if near-primary, the negative δ18O excursion at the KTB in Gubbio and Bajada del Jagüel suggest warming temperatures at this transition, whereas the negative excursion immediately followed by positive one at Stevns Klint points to warming followed by cooling. At Stevns Klint, Hg contents reach 250 ng.g−1 within the KTB layer (Fiskeler Member) while within the Scaglia Rossa Formation at Gubbio, three Hg spikes across the KTB are observed, one of them within the KTB layer (5.3 ng.g−1). Hg shows several spikes across the KTB in Neuquén Basin (up to 400 ng.g−1 in the Jagüel Formation). The phenomenon that caused dramatic changes at the KTB expelled huge amounts of Hg to the atmosphere as recorded by these high Hg levels. The co-variation between Hg and alumina in the studied sections suggest that Hg is probably adsorbed onto clays. Four δ202Hg values for the KTB layer at Stevns Klint vary from -2.34 to -1.06 ? (relative to NIST 3133), within a range in consonance with volcanogenic Hg. Hg contents are perhaps powerful tool in the assessment of the role of volcanic activity during extreme climatic and biotic events, such as those during the KTB. Furthermore, Hg isotopes may become a key in the solution of the role of meteorite impact versus volcanism as the predominant cause of past global catastrophes and mass extinction.