Facies evolution of the Jurassic-Cretaceous transition in the Eastern Getic Carbonate Platform, Romania: Integration of sequence stratigraphy, biostratigraphy and isotope stratigraphy

Abstract

Piatra Craiului Massif is situated in the easternmost part of the Southern Carpathians, Romania. The Kimmeridgian–lowermost Valanginian carbonate succession from this area is part of the large Getic Carbonate Platform system, and forms a 25 km long, NE-SW oriented calcareous ridge with a maximum thickness of 1200 m. Previous studies of Upper Jurassic-Lower Cretaceous carbonate platforms from Romania focused on microfacies and biostratigraphic features but few studies addressed their sequence stratigraphy. This study aims to decipher the geological evolution of the Eastern Getic Carbonate Platform by integrating sequence stratigraphic, biostratigraphic and chemostratigraphic analysis methods. The studied sections are located in the northern and central part of the Piatra Craiului Massif. Centimeter to meter thick carbonate beds or banks are common and carbonate lithologies reveal five facies associations (F1F5) of outer platform deposits and inner platform peritidal settings. The outer platform deposits contain fragments of subaerially exposed intraclasts. Such processes are indicated by the facies characteristics and isotope chemostratigraphy data. The peritidal succession is characterized by the repetition of distinct sets of small-scale sequences, each of which commonly shows a deepening to shallowing upward trend. This trend is defined by a vertical scale transition from high-energy intertidal deposits to intertidal restricted ponds, swamps or supratidal marshes. The general trend shows a shallowing upward tendency. Commonly, intertidal deposits cap the shallowest facies of the corresponding small-scale sequences. The entire peritidal succession from the Piatra Craiului Massif forms a superimposed prograding wedge on platform margin deposits. Autocyclic processes and allocyclic processes appear to be responsible for the development of this carbonate succession.