Stratygrafia i mikrofauna dolnego malmu w rejonie Olkusza - Kluczów

Alina Siewiak



In view of the ranges established for the occurrence of individual species of foraminifers and microfaunal assemblages, the author distinguished in the Lower Malm of the Olkusz-Klucze (Cracow-Częstochowa Jura Chain) the substages: Divesian, Neuvizyan, Argovian. The Neuvizyan-Argovian boundary he established mainly by its lithology on the basis of sporadic samples taken for microfaunal examinations from the Argovian.

Among index forms characterizing the various substages there should be mentioned: for the Upper CalIovian - Frondicularia supracalloviensis W i ś n., .Frondicularia glandulinoides W i ś n., Saracenaria cornucopiae (S c h w a g.), Planularia tricarinella (R e u s s); for the Devisian - Marginulinopsis radiata (T e r q.), Spiroculina difficillis W i ś n.; for the Neuvizyan - Epistomina mosquensis U h l i g, Trocholina conica (S c h l u m b.), Planularia polypora (G u m b.), Ophthalmidium carinatum marginata (W i ś n.); for the Argovian - Spirillina polygyrata G li m b., Spirillina tenuissima G li m b., Paalzowella turbinella (G u m b.).

An interrelation between the foraminifer fauna and the lithological composition of the sediments has been clearly observed. Thus a exuberant development of foraminifer species may be seen in the marly sediments of the Divesian and the Neuvizyan, and a scantiness of microfauna in the calcareous sediments of the Argovian. This seems to be proof that the sedimentary environment in which marly sediments are formed, was favorable to the development of foraminifers; the small number of conglomeratic forms shows that these marls have not been .deposits of very deep waters.

Ultimately is has been determined by the author's research that, in this region, the oldest Jurassic sediments are Upper Callovian, laid down directly on top of Triassic sediments.

In the discussed area there may be observed, within relatively short distances, a considerable variableness in thickness of the Jurassic sediments. On the one hand, this may be proof of a marked differentiation of the Pre-Jurassic substratum on to which the Jurassic transgression proceeded; on the other hand it suggests the possibility of Cimmerian movements during the period of the upper part of the Bathonian and the Lower Callovian.

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