Conodont stratigraphy of the Upper Devonian in the Janczyce I borehole section, eastern Holy Cross Mts.

Abstract

Biostratigraphic analyses of the Janczyce I borehole section. a unique key section for regional correlations in the southern (Kielce) region of the Holy Cross Mts. area, allow placement of important lithostratigraphic boundaries within a framework of the Upper Devonian standard conodont zonation. The lowermost dated deposits (the Detrital Limestone Unit) belong to the jamieae Zone while the uppermost ones (the Black Shale and Limestone Unit) were ascribed to the Lower-Upper expansa Zones. The studies revealed a stratigraphic gap or condensation within an entirely shelf-basinal depositional system, spanning at least the Fammenian Upper through Uppermost marginifera Zones. Two characteristic cephalopod-bearing levels are present within a monotonous basinal sequence. i.e., the tentaculitoid microcoquina (linguiformis Zone) and the cephalopod limestones from Janczyce (Middle crepida Zone). The above named levels revealed a potential for precise time-correlation on at least a sub-regional scale, the first one being most probably the local equivalent of the widespread Upper Kellwasserkalk horizon.