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Astronomical calibration of the late Jurassic – early Cretaceous western Tethys
Johannes Monkenbusch, Nicolas Rudolph Thibault, Mathieu Martinez

Building: Muséum d'Histoire Naturelle de Genève
Room: Lobby /Hall/
Date: 2018-12-05 12:06 PM – 12:09 PM
Last modified: 2018-12-01


DSDP Site 534A (Blake Bahama Basin) archives an almost complete succession of Western Tethys, mid Tithonian to early Barremian marl-limestone alternations, across a total length of 336 metres. Despite the stratigraphic importance of the Jurassic-Cretaceous boundary, very few long-term cyclostratigraphic studies have been published so far across that interval. To strengthen the stratigraphy of this important system boundary, we integrate cyclostratigraphy with already existing magnetostratigraphic (Ogg, 1987), chemostratigraphic (Bornemann and Mutterlose, 2008; Littler et al., 2011; Tremolada et al., 2006) and biostratigraphic (Barlower et al., 1989; Baumgartner, 1983; Bergen, 1994; Bornemann and Mutterlose, 2008; Habib and Drugg, 1983; Remane, 1983; Roth, 1983; Tremolada et al., 2006) frameworks. Tuning to the La2010d solution (Laskar et al., 2011) reveals a duration of 19.8 million years for the studied part of the core, and the preservation of a wide array of Milankovitch periodicities from the 20 kyr precession cycle up to 9.1 Myr eccentricity grand cycles. Comparison of our Ca/Fe elemental ratio to trends in carbon isotopes show a pacing of the Weissert event by the 9.1 Myr eccentricity cycle, with maxima in carbon isotope values coinciding with the maximum of this grand cycle. Astronomical forcing by grand eccentricity cycles appears as an important mechanism for the development of this widespread oceanic anoxic event.