Synchronizing the astronomical time scales in the Valanginian-Hauterivian from the Neuquén Basin (Argentina) and the Tethyan area

• Autores: Martinez, Mathieu; Aguirre Urreta, María Beatriz; Lescano, Marina Aurora; Omarini, Julieta; Tunik, Maisa Andrea; Frederichs, Thomas; Nickl, Anna Leah; Pälike, Heiko
• Año de publicación: 2017
• Idioma: inglés
• Tipo de recurso: documento de conferencia
• Materia: Agrio Formation; ammonits; calcareous nannofossils; Cretaceous
• Institución: Consejo Nacional de Investigaciones Científicas y Técnicas

Important discrepancies between the numerical ages stated by the Geological Time Scale 2016 and radio-astrochronological works have been reported in the last years (AGUIRREURRETA et al., 2015; MARTINEZ et al., 2015; OGG et al., 2016). Large uncertainties notably exist for the Valanginian-Hauterivian stages for which the recently provided timescales are still debated. Here, we present an astronomical calibration for the Agrio Formation (Neuquén Basin, Argentina) to better constraint the durations of the Valanginian and the Hauterivian stages. The formation is divided into a lower and an upper member (called Pilmatué and Agua de la Mula members, respectively) composed of marl-limestone alternations deposited in a semi-pelagic to outer ramp environment and related to an orbital forcing. A rapidly (<0.5 myr) deposited member of continental sandstone, separates these two members. A total of 2130 bulk-rock samples have been collected each 25 cm and their mass-corrected magnetic susceptibility has been measured to detect lithological cycles. In the lower part of the Pilmatué Member (Lower Agrio), the record of the 405-kyr eccentricity cycle is obvious but its amplitude promptly decreases at younger intervals. However, the orbital cycles of precession, obliquity and 100-kyr eccentricity are recorded, allowing the duration of the Pilmatué Member to be assessed at 4.70 myr. Anchoring this duration to the CA-ID-TIMS age of 130.39 ± 0.16 Ma provided in the Pilmatué Member, the age of this member ranges from 133.76 to 129.07 ± 0.16 Ma. The age of the top of the Lower Agrio slightly overlaps the age of the base of the Upper Agrio (129.09 ± 0.16 Ma). Such an overlap falls in the range of the uncertainties in the CA-ID-TIMS ages. First correlations to the Tethyan area suggest that the early Hauterivian has a duration of 2.1 myr, falling in the range of uncertainty mentioned by MARTINEZ et al. (2015) (2.5 ± 0.4 myr), but being much longer than the duration of 1.21 myr proposed in the geological time scale 2016 (OGG et al., 2016), suggesting the duration of the Hauterivian stage has to be increased by, at least, 0.9 myr for the next compilation.
Fil: Martinez, Mathieu. Universitat Bremen; Alemania
Fil: Aguirre Urreta, María Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; Argentina
Fil: Lescano, Marina Aurora. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; Argentina
Fil: Omarini, Julieta. Universidad Nacional de Río Negro; Argentina
Fil: Tunik, Maisa Andrea. Universidad Nacional de Río Negro; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina
Fil: Frederichs, Thomas. Universitat Bremen; Alemania
Fil: Nickl, Anna Leah. Universitat Bremen; Alemania
Fil: Pälike, Heiko. Universitat Bremen; Alemania
10th International Symposium on the Cretaceous
Austria
Universität Wien
Geological Survey of Austria