The Cretaceous/Tertiary boundary in Central Poland

Abstract

Paleomagnetic stratigraphy coupled with dinocyst biostratigraphy demonstrates in the Nasil6w Quarry (topmost part of the well-known mid- and Upper Cretaceous sequence exposed along the Middle Vistula Valley) in Central Poland the presence of chalk sediments belonging to paleomagnetic periods 30 N and 29 R. The latter contains the biostratigraphic Cretaceous/Tertiary boundary. The overlying sediments can be placed in period 29 N.

Trace element studies show that iridium is present in the lower part of the greensand overlying the chalk, and exposed also in the neighboring locality Bochotnica. Iridium is also recorded in- an opoka-like filling in the shell o(the Upper Maastrichtian brachiopod Carneithyris sp. contained in the greensand.

On the basis of trace elements and ultrastructures it is suggested that dissolution has removed both a glauconitic chalk, the Cretaceous/Tertiary boundary beds, as well as an equivalent of the Danish Cerithium Limestone. The iridium-bearing elemental carbon was trapped in the greensand-timed burrows.