Multi-proxy record of orbital-scale changes in climate and sedimentation during the Weissert Event in the Valanginian Bersek Marl Formation (Gerecse Mts., Hungary) |
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| Institution: | 1. Department of Geology, St. Lawrence University, 23 Romoda Dr., Canton, NY 13617, United States;2. Emeritus, Department of Geosciences, Virginia Tech, Blacksburg, VA 24061, United States;1. Université Paris Sud, Laboratoire GEOPS, UMR 8148, Orsay F91405, France;2. CNRS, Orsay F91405, France;3. Institut des Sciences de la Terre, Université de Lausanne, Bâtiment Géopolis, 1015 Lausanne, Switzerland;4. Institut des Dynamiques de la Surface Terrestre, Université de Lausanne, Bâtiment Géopolis, 1015 Lausanne, Switzerland;5. UPMC Univ Paris 06, UMR 7207, CR2P, 4 place Jussieu, 75252 Paris, France;6. UMR–CNRS 7193 ISTeP, Institut des Sciences de la Terre–Paris, Université Pierre et Marie Curie, 4 place Jussieu, 75252 Paris CEDEX 5, France |
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| Abstract: | The Valanginian positive carbon isotope excursion and associated environmental changes, known as the Weissert Event, is the first in the series of Cretaceous Earth system perturbations. Here, we develop a multiproxy cyclostratigraphy from a 31.2-m-thick Upper Valanginian to lowermost Hauterivian section of the Bersek Marl Formation in Gerecse Mountains, Hungary, comprising alternating marlstone layers of varying clay and carbonate content. The bulk carbonate δ13C signal shows sustained, elevated values (up to 2.7‰) up to 19.2 m, followed by a decreasing trend upsection. Together with biostratigraphic data, this suggests that the lower part of the section was deposited during the plateau phase of the Late Valanginian Weissert Event. Spectral analyses of the multiproxy dataset, including magnetic susceptibility measurements and gamma-ray spectroscopy on the lower part of the section, led to the identification of precession, obliquity, and long and short eccentricity signals. A mean sedimentation rate of 14 m/Myr was calculated based on astronomical tuning. The cyclicity in the proxy signals reflects dilution cycles induced by the fluctuating rate of detrital runoff into the basin. This supports the idea that orbitally-forced humid-arid cycles controlled the pelagic alternating sedimentation during the Early Cretaceous throughout the Tethyan area. |
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| Keywords: | Cyclostratigraphy Carbon isotope excursion Early Cretaceous Stable isotopes Magnetic susceptibility Gamma-ray spectroscopy |
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