Late Maastrichtian–Paleocene chronostratigraphy from Seymour Island, James Ross Basin, Antarctic Peninsula: Eustatic controls on sedimentation

Abstract

The Paleocene (66–56 Ma) was a critical time interval for understanding the geological history in high palaeolatitudes after the end of Cretaceous event (recovery from mass extinction, palaeoclimate, global sea level changes, among others). The sedimentary succession from Seymour Island (Antarctic Peninsula) provides key reference material from this important phase of the early Cenozoic. A detailed age model is proposed for the Lopez de Bertodano Formation (LBF), Sobral Formation (SF) and Cross Valley–Wiman Formation (CVWF) based on a new magnetostratigraphic section which integrates previous dinoflagellate cyst biostratigraphy, Iridium anomaly (K-Pg boundary), U-Pb zircon dating (airfall tuff) and strontium isotope values from macrofossils. The new composite magnetostratigraphic section, which includes the Cretaceous–Paleogene boundary, has been correlated to the GPTS from C29r up to C24r. The top of the LBF is confirmed as latest Maastrichtian to earliest Danian (~65.4 Ma) in age. The overlying SF is mostly Danian in age (~65.2– ~63 Ma) and CVWF is Selandian–Thatenian (~61.3–56.9 Ma). LBF, SF and CVWF are unconformity-bounded units (alloformations) that record the geological evolution of the James Ross Basin during a period of relative decreasing tectonism but coeval with volcanic activity. Unconformity based internal units have been recognized, dividing each formation into allomembers (LBF: Molluscan and Cenozoic; SF: A, B and C; CVWF: Diaz, Aranado, Bahia Pinguino). The new age model allows correlation of base-level changes with eustatic sea-level fluctuations. The bases of the SF and CVWF are correlated with the 65.3 and 61.5 Ma sea level lowstands. Citation:Montes M, Beamud E, Nozal F, et al. Late Maastrichtian–Paleocene chronostratigraphy from Seymour Island, James Ross Basin, Antarctic Peninsula: Eustatic controls on sedimentation. Adv Polar Sci, 2019, 30(3): 303-327, doi: 10.13679/ j.advps.2018.0045