Interhemispheric time scale for the Hauterivian and its implications for the carbon cycle in the Berriasian-Barremian times

MARTINEZ, M.; AGUIRRE-URRETA, M.B.; SCHMITZ, M.; LESCANO, M.; OMARINI, J.; TUNIK, M.; KUHNERT, H.; CONCHEYRO, A.; RAWSON, P.; RAMOS, V.; REBOULET, S.; NOCLIN, N.; FREDERICHS, T.; NICKL, A.; PALIKE, H.

Ginebra

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

JK2018 Organizing Committee

Discrepancies in the ages and durations ofthe Berriasian to Barremian stages still exist between geological data and theproposed geological time scale 2016 (Ogg et al., 2016; Lena et al., 2018). TheHauterivian Stage suffers from these discrepancies as its duration is proposedat 3.92 myr (Ogg et al., 2016), while astrochronology in the Tethyan area (SEFrance and SE Spain) led to a duration of 5.9 ± 0.4 myr (Martinez et al.,2015). In order to reconcile these durations, we investigated the AgrioFormation in the Neuquén Basin (Western Argentina). A total of 2,200 samples werecollected every 0.25 cm and measured in magnetic susceptibility with aKappabridge KLY-2. From spectral analyses realised on these MS signals, itappears that the 100-kyr eccentricity is continuously recorded throughout theAgrio Formation, allowing duration calculations. In addition, a new U-Pb agemeasured on zircons was provided in the upper part of the Agrio Formation usingthe CA-ID-TIMS method. Thus, four U-Pb ages are now available in the AgrioFormation measured with the U-Pb CA-ID-TIMS (Aguirre-Urreta et al., 2015,2017). Notably, the astrochronological durations fit with three of the U-Pbages. A fourth age appears 300 kyr elder than suggested by astrochronology,which may be due to protracted crystallization of zircons in the magmaticchamber. This new data in the Agrio Formation, together with correlations tothe Tethyan area, highlights a revision to the duration of the HauterivianStage of 5.22 ± 0.11 myr starting at 131.29 ± 0.25 Ma and ending at 126.07 ±0.25 Ma. The previous overestimate of the duration of the Hauterivian Stage waslikely due to distortion of the 405-kyr eccentricity in the sedimentary record,as recent studies document (Laurin et al., 2017; Martinez, 2018). Thanks tothese revised ages and previous astsochronological frameworks, we were able torevise the ages and durations of stages from the Late Berriasian to theBarremian-Aptian boundary. A synthesis of δ13C measured onbelemnites (Martinez and Dera, 2015) indicate a clear 2.4-myr cycle in thecarbon cycle record which fit with the main paleoceanographic events. Higheramplitudes of this cycle are notably observed during major volcanic episodes,suggesting that acceleration of the hydraulic cycle lead to a reinforcement ofthe long-Milankovitch cycles.