Pozycia stratygraficzna „strefy Actinocamax plenus” w Sudetach Środkowych

Abstract

STRATIGRAPHICAL POSITION OF THE „ZONE ACTINOCAMAX PLENUS” IN THE AREA OF MIDDLE SUDETES

Summary 

The author evaluates the stratigraphical position of a Cretaceous series found to occur within the area of Middle Sudetes, and so far referred to the zone Actinocamax plenus. On the basis of field observations made within the Cretaceous area of the Middle Sudetes, the present author draws a conclusion that the beds, called ,,plenus beds”, which rest between the Cenomanian with Pecten asper Lam. and Lower Turonian marls with Inoceramus labiatus (Schloth.), should be referred to the Lower Turonian zone Metoicoceras geslinianum (= Metoicoceras whitei), distinguished by L. F. Spath (1926). The species Actinocamax plenus (B l v.) does not fulfil the demands placed on a zone fossil, since it is known to occur already in the Lower Cenomanian and, within the Middle Sudetic Cretaceous, it appears barely in the upper part of the zone Metoicoceras geslinianum. In the subdivision hierarchy, the zone Metoicoceras geslinianum is characterized by a position, which is equivalent to the zone Inoceramus labiatus. Both zones make here the Lower Turonian stage. The deposits of the zone Metoicoceras geslinianum are one member in a discontinuous process of transgression during the Cenomanian and Lower Turonian, interrupted by several periods of stagnation and erosion. At the time, when the deposits of the zone Metoicoceras geslinianum were being laid down, the Intra-Sudetic basin was protected by sedimentary area.