The numerical age of the Jurassic/Cretaceous system boundary

LESCANO, M.; LENA, L.; AGUIRRE-URRETA, M.B.; LOPEZ-MARTINEZ, R.; CONCHEYRO, A.

Genève

Congreso; International Meeting around the Jurassic-Cretaceous Boundary; 2018

The age of the Jurassic/Cretaceous boundary has remained elusive for the past decades.Here we examine the numerical age of the boundary by cross calibrating the numerical age of two distinct stratigraphic sections that contain well-established early Berriasian boundary markers. We present high-precision U-Pb zircon age determinations on single grains of volcanic zircon of two sections that span the Jurassic/Cretaceous: the Las Loicas section, Argentina, and the Mazatepec section in Mexico. We evaluate how well the determined boundary age agrees between these two distinct sections agree and whether we can constrain a globally valid Jurassic/Cretaceous boundary age. In Argentina the age of the boundary was determined at 140.22 ± 0.13 Ma and in Mexico at 140.9 Ma. Additionally, we also present the first age determinations in the early Tithonian in the Virgatosphinctes andesensis Zone at 147.112 ± 0.078 Ma and tentatively propose a minimum duration of -7 Ma for the Tithonian stage. These results allows us to challenge the currently accepted age for the boundary by the International Commission on Stratigraphy which calibrates the age of the boundary at -145 Ma.