T200 Mass Extinctions: Volcanism, Impacts, and Catastrophic Environmental Change II

Tuesday, 21 October 2014
8:00 AM - 12:00 PM
223/224

MASS WASTING DURING THE CRETACEOUS-TERTIARY TRANSITION IN THE NORTH ATLANTIC: RELATIONSHIP TO THE CHICXULUB IMPACT?

Paper number: T200-5
Program: Technical Sessions
Time: 8:55 AM – 9:10 AM

Authors

Abstract

Deep-sea sections in the North Atlantic are claimed to contain the most complete sedimentary records and ultimate proof that the Chicxulub impact is Cretaceous-Tertiary boundary (KTB) in age and caused the KTB mass extinction. We performed a multi-disciplinary evaluation of North Atlantic deep-sea Sites 384, 386 and 398 based on high-resolution planktonic foraminiferal biostratigraphy, stable isotopes, clay and bulk-rock mineralogy and granulometry, in order to assess the age, stratigraphic completeness and nature of sedimentary disturbance. Results show a major KTB hiatus at Site 384 with zones CF1, P0 and P1a missing, spanning at least ~540 ky as also observed at Site 1049 and throughout the Caribbean. This KTB hiatus is likely the result of erosion due to intensified Gulf Stream current circulation at times of major climate and sea level changes.

At Sites 386 and 398, previous studies interpreted discrete intervals of disturbed sediments associated with a thin impact spherule layer as due to impact-generated earthquakes destabilizing continental margins prior to settling of impact spherules. Our improved age control indicates deposition in the early Danian zone P1a(2) (upper Parvularugoglobigerina eugubina zone) more than 100 ky after the KTB. At Site 386, reworked Cretaceous species (35%) are common and sediments contain high calcite, mica and kaolinite, in contrast with the in situ red-brown clay devoid of carbonate, suggesting reworked shallow water sediments. Mass wasting is indicated by normal size grading through the disturbed interval with horizontal lamination at the base followed by mottled, mixed sediments. At Site 398, reworked Cretaceous species are less common (<10%) but high abundance of shallow benthic species and higher mica, in detriment of smectite, also indicate mass wasting with reworking of shallower sediments. We propose that mass wasting deposits are the result of earthquakes associated with increased tectonic activity in the Caribbean during the early Danian well after the Chicxulub impact.