Warstwa chalcedonowa w dolomitach z kopalni Bobrowniki–Blachówka

Abstract

CHALCEDONY LAYER IN DOLOMITES FROM BOBROWNIKI-BLACHÓWKA QUARRY

Summary

A chalcedony layer has been found to occur in the Triassic diplopore dolomites in a quarry at Bobrowniki-Blachówka. The layer reveals sponge spicules and silicified algae of Dasycladaceae.

The presence of this layer in dolomites points to an interruption in sedimentation and to favourable conditions for development of sponges. Silica formed as a result of sponge dissolution penetrated the surrounding carbonate rocks and silicified the algae deposited in them.
It results from the mineralogic-chemical analysis of dolomite that this rock is of calcium-ferruginous nature. The Ca-Mg ratio proves that the dolomite has been formed epigenetically, like ore-bearing dolomites.