The uppermost clastic succession of Lower-Middle Buntsandstein as a record of continous sedimentation during Early Triassic trangression in the area of Grodziec syncline

Abstract

The uppermost clastic succession of Lower–Middle Buntsandstein sediments of the Grodziec syncline (North Sudetic Synclinorium) shows a high macroscopic similarity to overlaying Cenomanian deposits. That might have resulted in erroneous determination of the boundary between Triassic and Cretaceous sediments in historic drill holes. Detailed macroscopic observations were performed on cores and samples were taken for microscopic analyses. A number of features characterizing sediments of the uppermost clastic succession have been identified. These are primarily: increased kaolinite content, decrease of textural maturity, decline of bedding, lack of pebbles and argillaceous intraclasts. These features might indicate transgressive character of sediments and a deposition in a transitional: terrestrial to marine environment.