The open shelf - carbonate platform succession at the Oxfordian/Kimmeridgian boundary in the SW margin of the Holy Cross Mts: stratigraphy, facies, and ecological implications

Abstract

The material from the new quarry at Sobków-Wierzbica as well as from the neighboring boreholes, supplied new data on the uppermost Oxfordian - lowermost Kimmeridgian succession in the SW margin of the Holy Cross Mts, Central Poland. These deposits represent a part of the shoaling-upward sequence, starting from basinal micritic limestones with intercalations of grainstones (derived from the prograding carbonate platform) and with episodic benthic assemblages developed in the more distant areas (due to occasional winnowing of the soft carbonate mud), up to the shallow-water grainstones marking the progressing onlap of the carbonate platform. The succession of the faunistic assemblages reveals the successive stages in the progradation of the platform. The moderately rich ammonite fauna is composed mostly of the genera Idoceras and Orthosphinctes, indicative of the Planula Zone of the uppermost Oxfordian. These new findings throw a new light on the ammonite biogeography and on the ecological aspects of ammonite distribution during the Late Oxfordian of Central Poland.