Cyclostratigraphy of a Tithonian-Valanginian Carbonate Ramp Succession, Southern Mendoza, Argentina: Implications for the Jurassic?Cretaceous Boundary in the Neuquén Basin

KIETZMANN, D.A.; PALMA, R.M.

Lisboa

Congreso; First International Congress on Stratigraphy; 2013

We conducted detailed sedimentological, sequence-stratigraphic, and cyclostratigraphic analyses on four sections of the Vaca Muerta Formation. This unit is characterized by a decimetre-scale rhythmic alternation of marls and limestones. It consists of five facies associations, which represent basin to middle carbonate ramp deposits. The rhythmic vertical organization shows a well-ordered hierarchy of cycles, where elementary cycles, bundles of cycles, and superbundles within the Milankovitch frequency band are recognized. Cyclostratigraphic data allowed us to build a floating orbital scale for the lower Tithonian?lower Valanginian interval in the Neuquén Basin. Orbital calibration of these sections is consistent with Riccardi?s biostratigraphic scheme, which places the Jurassic?Cretaceous boundary within the Substeueroceras koeneni ammonite Zone (equivalent to Durangites spp., Jacobi/Grandis, and initial Occitanica standard zones).