Rewizja stratygrafii osadów jury środkowej w Gorzowie Wielkopolskim

Abstract

REVISION OF STRATIGRAPHY OF THE MIDDLE JURASSIC DEPOSITS FROM GORZÓW WIELKOPOLSKI (WEST POLAND)SummaryThe paper deals with the revision of stratigraphy of the Middle Jurassic deposits encountered in the bore hole Gorzów Wielkopolski. The stratigraphy was preliminarily established in 1959 (J. Znosko, 1959a). In the stratigraphical nomenclature the term Kuiavian (Vesulian) has for the first time been used, according to the recommendation of the Polish Jurassic Colloquy that took place in 1964 in Warsaw. Originally, Lower Bathonian and Upper Kuiavian (Upper Vesulian) have been distinguished in the Middle Jurassic section of the Gorzów Wielkopolski area. The revision of the stratigraphy demonstrated that the upper member of the Lower Jurassic is transgressively overlain by the sandstones of the zone Stephanoceras humphriesi of the Upper Bajocian, 2 m in thickness. On an erosional fragment of Bajocian there are found, preceded by a fairly great stratigraphical gap, the sandstones of the zone Parkinsonia subarietis of the Middle Kuiavian, to occur also transgressively. Their thickness is also 2 m. On an erosional fragment of the Middle Kuiavian, in turn, there rests completely developed Upper Kuiavian represented by two zones: Parkinsonia ferruginea and Parkinsonia compressa. The thickness of this substage amounts to 20 metres. Towards the top it passes into the deposits of the zone Perisphinctes tenuiplicatus of the Lower Bathonian, 10,5 m in thickness. The deposits are eroded away and transgressively overlapped by the glauconite sandstones of Middle Cretaceous age. All the distinguished zones contain index ammonites.