Condensed Cretaceous sequence with stromatolites in the Polish Jura Chain

Abstract

The Cretaceous stromatolites from the Polish Jura Chain (western margin of the Miechów synclinorium) are described. The high-energy, shallow marine water below the intertidal zone is postulated as an environment of their formation. A considerable content of cellophane gives them a composite, partly biosedimentary and partly inorganic character. In the northern area (Pniaki), the stromatolites overile condensed Cenomanian-Turonian deposits, the microfacial analysis of which reveals a cyclic detrital inflow. The appearance of the stromatolitic layer is preceded by an increase in the detrital inflow, connected with the decrease in rate of sedimentation and probably, shallowing. The submarine nondepositional surface occurs in both the northern (Pniaki) and southern (Bocieniec) area in the top of the stromatolitic layer. Since at Bocieniec, this layer is connected with conglomerate, the age of which has, on the basis of Lewesiceras peramplum (Mantell), been determined as Turonian, the stromatolitic layer is also assigned to the Turonian.