Osady górnej kredy północno-wschodniej Polski w świetle badań mikropaleontologicznych

Abstract

THE UPPER CRETACEOUS DEPOSITS IN NORTH EAST POLAND IN THE LIGHT OF MICROPALAEONTOLOGICAL RESEARCHES

Summary

The present paper deals with the Upper Cretaceous and Lower Palaeocene deposits occurring in the northwestern area of Poland, stretching along the boundary line between the Polish People's Republic and the Lithuanian Soviet Socialist Republic. In the area here considered Bartoszyce IG-1 is the westernmost bore hole and Krasnopol IG-1 the easternmost one. Some years ago a great stratigraphical break embracing Coniacian, Santonian and Campanian deposits has been discovered when analysing foraminifers from the Upper Cretaceous formations pierced by the bore hole Ełk IG-1 situated south of the area under discussion. At Ełk the α-Turonian beds, i.e. zone with Inoceramus labiatus and the lower part of the zone with Inoceramus lamarcki have not been encountered, as well (E. Gawor-Biedowa, 1964). Investigations made in the area situated north of Ełk have shown that here stratigraphical breaks also occur. The Cenomanian has been discovered only in the bore holes Bartoszyce and Gołdap, where it is developed in a facies of mudstone-glauconite sands or glauconite sands. Maybe that the coarse-grained sandstone with glauconite resting under the Turonian beds at Krasnopol is also of Cenomanian age. However, the presence of the Cenomanian deposits has not been proved by faunistic evidences. A complete series of Turonian beds occurs no doubt at Bartoszyce and Gołdap and, although incomplete, at Krasnopol. It is also possible that no samples have been taken for microfaunistic analyses from the lowermost Turonian beds at Krasnopol and therefore deposits of the α-zone of this stage have not been documented. The Turonian at Bartoszyce is represented mainly by limestones with cherts. At Gołdap it consists, at the lower part, probably of chalk, at the higher part, of marl. At Krasnopol the Turonian is built up mainly of chalk, locally with flints. As regards quantity of species and of individuals the most numerous foraminifers occur in the Turonian deposits at Krasnopol. A great stratigraphical break has been ascertained to occur above the Turonian beds. At Bartoszyce it embraces Coniacian and Santonian at Gołdap - Coniacian, Santonian and the lowermost beds, of the lower part of Campanian. At Krasnopol, the Turonian is overlain by the Dano-Palaeocene deposits. No bore hole has demonstrated that the Campanian deposits are completely developed. At Gołdap the lowermost beds of this stage are lacking, at Bartoszyce - the uppermost ones. Maestrichtian has been proved only at Gołdap, where the lowermost beds of this stage have been encountered. The Maestrichtian foraminifers are noted to occur as redeposited fragments in the Dano-Palaeocene formations at Krasnopol, a fact proving that at the Palaeocene time a denudation of the Maestrichtian deposits took place in the area considered. It appears that the lowermost beds determined at Krasnopol as Dano-Palaeocene, belong to the Danian (245,50÷234,50 m), and the overlying ones - no doubt to the Palaeocene (234,50÷158,50 m).