The Jurassic-Cretaceous transition in deep- and shallow-water carbonate depositional settings: a case study from the easternmost Getic Carbonate Platform (Southern Carpathians, Romania)

The Postavaru Massif is located in the easternmost part of the Getic Carbonate Platform from the Southern Carpathians. The described sections are unevenly distributed in all four tectonic compartments of the Postavaru Massif (Brasov, Cristian, Rasnov and Postavaru). Eighteen sections were studied to highlight the biostratigraphic and facies evolution of the Upper Jurassic-Lower Cretaceous (Kimmeridgian-upper Berriasian) transition. Ten facies associations (FA 1-10) were described and they indicate a general shallowing upward tendency, from slope to platform-margin and inner-platform depositional settings. In other cases, the vertical facies stacking patterns indicate a general deepening-upward tendency, at the Upper Jurassic-Lower Cretaceous transition. The micropaleontological assemblage consists of encrusting organisms, dasycladalean algae, foraminifera and pelagic microfossils (calpionellids). As a general rule, this assemblage characterizes four main intervals and stages: Kimmeridgian-upper Tithonian, lower Berriasian, upper Tithonian-Berriasian and upper Berriasian. The carbonate succession from the Postavaru Massif shares similar characteristics with other parts of the Getic Carbonate Platform (Cioclovina-BaniAMP;x21b;a area, Buila-VanturariAMP;x21b;a Massif, Piatra Craiului-Dambovicioara Zone, Western part of Bucegi Massif). Finally, the presence of Lower Cretaceous (Berriasian) deposits is well documented by interpreting various assemblages of microfossils. This study combines microfacies and biostratigraphic analysis techniques to decipher the interplay between environmental conditions, facies distribution and biostratigraphic evolution at the Upper Jurassic-Lower Cretaceous transition, in the easternmost GCP. The Tithonian-Berriasian transition is marked by a continuity of sedimentation, in shallow and deep water depositional environments.