6 research outputs found
Orbital controls and high-resolution cyclostratigraphy of Late Jurassic Early-Cretaceous in the Neuquén Basin
Detailed cyclostratigraphic analyses have been made from seven TithonianâHauterivian sections of the Vaca Muerta and Agrio Formations, exposed in southern Mendoza area of the NeuquĂ©n Basin. Both lithostratigraphic units are characterized by decimeter-scale rhythmic alternations of marlstones and limestones, showing a well-ordered hierarchy of cycles, including elementary cycles, bundles, and superbundles. According to biostratigraphic data, elementary cycles have a periodicity of ~18â21 ky, which correlates with the precessional cycle of the Earthâs axis. Spectral analysis based on time series of elementary cycle thicknesses allowed us to identify frequencies of ~400 ky, and ~90â120 ky, which we interpret as the modulation of the precessional cycle by the Earthâs orbital eccentricity. A third band frequency of ~40 ky was also identified that can be assigned to the obliquity cycle. Cyclostratigraphy enabled the construction of almost continuous floating astronomical time scale for the TithonianâHauterivian, for which a minimum duration of 5.67 myr for the Tithonian, 5.27 myr for the Berriasian, >3.45 myr for the Valanginian, and 5.96 myr for the Hauterivian have been assessed. Additionally, the likely transference mechanisms of the orbital signal to the sedimentary record are analyzed, proposing the coexistence of carbonate exportation and dilution as the dominant mechanisms.Fil: Kietzmann, Diego Alejandro. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Oficina de CoordinaciĂłn Administrativa Ciudad Universitaria. Instituto de Geociencias BĂĄsicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias BĂĄsicas, Aplicadas y Ambientales de Buenos Aires; ArgentinaFil: Iglesia Llanos, Maria Paula. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Oficina de CoordinaciĂłn Administrativa Ciudad Universitaria. Instituto de Geociencias BĂĄsicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias BĂĄsicas, Aplicadas y Ambientales de Buenos Aires; ArgentinaFil: Kohan Martinez, Melisa. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Oficina de CoordinaciĂłn Administrativa Ciudad Universitaria. Instituto de Geociencias BĂĄsicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias BĂĄsicas, Aplicadas y Ambientales de Buenos Aires; Argentin