Publisher © Czech Geological Survey, ISSN: 2336-5757 (online), 0514-8057 (print)
A new occurrence of bivalve borings near Dřevčice near Brandýs nad Labem (Cenomanian, Bohemian Cretaceous Basin)
Abstract
In temporary excavations west of Brandýs nad Labem, intersting Late Cenomanian deposits (Korycany Member) have been exposed. A horizon enormously enriched in Fe 3+ occurred in the quartzose sandstones in one part of the exposure. In another part, identical rock was exposed thanks to the Quaternary cryoturbation. At this site, angular fragments of sandstone yielded abundant ferrified sandstone fillings of bivalve borings. The overall features of samples indicate that the bivalves bored in partly consolidated sandy deposit (firmground) under the conditions of low sedimentation rate and episodic erosion (truncation) of borings. During restored sedimentation, the bored horizon was buried by new sand cover. The Fe3+ enrichment of a horizon with locally occurring filled borings is probably of post-Cretaceous age. The occurrence of borings restricted to only one part of the studied horizon points to patchy distribution of borers on the sea bottom. A detailed description of borings will be published separately.
