Orbital control of the anoxic events in the Hauterivian andBarremian stages

National audienceEpisodes of Environmental Changes (EECs) correspond to reinforced greenhouseconditions associated to modifications of the carbon cycle that punctuated the EarlyCretaceous. From the latest Hauterivian to the Barremian, three EECs occurred (theFaraoni, Mid-Barremian and Taxy events). Despite the δ13Ccarb shows various trendsduring these events, they are all associated to short-lived geographic expansion oforganic-rich deposits in the western Tethys. We propose here an astronomicalcalibration of the latest Hauterivian-earliest Aptian from the Subbetic Domain (SESpain) to better constrain the pacing of these events and understand their forcingmechanisms. The sedimentary series studied are composed of orbitally-forcedhemipelagic marl-limestone alternations. Magnetic susceptibility was measured every 7cm using a Kappabridge KLY-3. Spectral analyses revealed the pervasive presence ofthe eccentricity cycles. Interpretations are notably validated by lithostratigraphic andbiostratigraphic correlations between the sections. The duration of the BarremianStage is calculated at 4.25 ± 0.17 Ma. Anchoring this duration to recently publishedradio- astrochronological time scales, the base of the Barremian Stage is dated at 125.91± 0.06 Ma and the top of the Barremian Stage at 121.67 ± 0.16 Ma. The EECs of thelatest Hauterivian and Barremian stages show a pacing of 2.34 Myr, suggesting acontrol of the long eccentricity cycle on the expansion of oceanic anoxic conditions inthe Tethys through changes in humid/arid cycle, weathering, sea level and fertilizationof the sea surface