Cycle Stacking and Long-Term Sea-Level History in the Lower Cretaceous (Gavrovo Platform, NW Greece)

Abstract

ABSTRACT The stacking pattern of peritidal shallowing-upward cycles of a continuously exposed Barremian to upper Albian section from an isolated carbonate platform in the Gavrovo-Tripolitza Zone (NW Greece) has been analyzed. The 541 m thick succession is located in an intraplatform setting with an overall mud-dominated facies development. It comprises 252 peritidal cycles, which show a systematic increase in cycle thickness from the Barremian to Albian. Comparison of the cycle stacking pattern of the section, which spans 35 m.y., and several published curves of long-term eustatic sea-level history show striking similarities. Comparison of cycle stacking pattern in Greece with a time-equivalent section measured near Potrero Garcia in Mexico suggests preservation of similar trends in Fischer pl ts in the two areas even though a difference in mean cycle thickness indicates different rates of subsidence in Greece and Mexico. This implies that the shallow-water carbonates of the Gavrovo platform are recording second-order eustatic sea-level variations. Closely spaced samples throughout the section allow evaluation of the degree of early diagenetic alteration of depositional facies within the shallowing-upward cycles. The degree of vadose diagenetic overprinting of intertidal and subtidal facies and multiple overprinting of individual cycles support a predominantly allocydic control of deposition by low-amplitude, high-frequency sea-level fluctuations during Early Cretaceous greenhouse climate. However, expected time gaps of different lengths in the succession during sea-level lows ands may bias the direct translation of cycle stacking pattern into third-order sea-level curves.