FACIES TYPES AND DEPOSITIONAL ENVIRONMENTS OF A MORPHOLOGICALLY DIVERSE CARBONATE PLATFORM: A CASE STUDY FROM THE MUSCHELKALK (MIDDLE TRIASSIC) OF UPPER SILESIA, SOUTHERN POLAND

摘要

The detailed sedimentological study of the 150-m-thick Muschelkalk succession, deposited on a small (~200 by 80 km), morphologically diverse Upper Silesian carbonate platform during four major marine-transgressive pulses of the Tethys Ocean, enhanced the understanding of the depositional history, palaeogeography, and facies distribution. A total of thirty-five lithofacies types were identified, described and interpreted in terms of depositional settings. These different lithofacies represent various shallow-marine environments along the platform transect, from peritidal to offshore areas. The vertical and lateral organization of the lithofacies delineated was caused by the interplay of platform morphology, third-order eustasy and the long-term tectonic evolution of the area. Accordingly, the carbonate system studied is a good example of the influence of large-scale processes on the facies architecture of carbonate platforms. In general, all of the four Transgressive Systems Tracts are characterized by similarity in lithofacies composition and vertical succession and by minor lateral change, indicating only limited influence of the three large-scale factors mentioned on lithofacies development and distribution during transgressions. In contrast, each of the four associated Highstand Systems Tracts comprises an individual (unique) lithofacies assemblage displaying substantial regional and local variation, which indicates that the filling of accommodation space during highstands strongly depended on the extrinsic processes.