Stratygrafia osadów środkowego oksfordu w Polsce (bez Karpat)

Abstract

STRATIGRAPHY OF THE MIDDLE OXFORDIAN DEPOSITS IN POLAND (EXCEPT FOR THE CARPATHIAN AREA)SummaryThe Middle Oxfordian deposits are known to occur within a vast extra-Carpathian area of Poland. Natural exposures are found only in the Cracow Wieluń Jura Belt and within the marginal area of the Świętokrzyskie Mts. In the remaining  part of the extra-Carpathian area of Poland, deposits of this age occur under a cover of younger formations and are frequently evidenced faunistically in numerous bore holes. Two facies have been distinguished in Poland within -the Middle Oxfordian deposits:  siltstone-marly and carbonate facies. On account of a different development of the deposits and, concequently, of different faunistic criteria, the elaboration of a uniform stratigraphical section appeared to be necessary.Stratigraphy of the Middle Oxrfordian deposits developed in a siltstone-marly facies was already earlier elaborated by the present author (L. Malinowska, 1966). This article deals, with the stratigraphy of the Middle Oxfordian deposits of carbonate facies, and the author discusses  general subdivision of the Middle Oxfordian of the extra-Carpathian area of Poland. Carbonate deposits occupy the eastern and central areas of the country. Within this facies two rock types may be distinguished: platy limestones with  flints and rocky limestones with sponges, as well as detrital limestones, sponge bioherms or near-biohermal deposits, dolomitic at places. A detailed stratigraphy of the Middle Oxlfordian deposits of carbonate facies may be determined mainly on the basis of the fauna gathered at the exposures in the area of the Cracow-Wieluń Jura Belt, and in the, marginal area of the Świętokrzyskie Mts. In the remaining regions, deposits of this age were found in the following bore holes: Rzadka Wola, Kąkowa Wola, Augustopol TH 5, Wierbka on Pilica, Piekary and Środa. However,  only in the sections at Piekary and Środa were determined cephalopods that allow to correlate the Middle Oxfordian horizons between the deposits of carbonate and siltstone-marly facies (L. Malinowska 1960, 1966). In consequence, the ammonite fauna found in both siltstone-marly and carbonate deposits permits to establish a uniform faunistic section for the Middle Oxfordian of the extra-Carpathian area of Poland. A common occurrence of the representatives of the families  Cardioceratidae and Perisphinctidae  (Tab. 1) in the deposits of both facies is here, although in different proportions, of considerable importance. In the siltstone-marly deposits Cardioceratidae prevail, and Perisphinctidae are less frequently found, whereas in the coarbonate deposits the situation changes diametrally. Nevertheless, in both types of deposits common species occur such as Perisphinctes (Dichotomosphinctes) wartae B u k., Ochetoceras canaliculatum (B u c h), O. hispidum (O p p.), Amoeboceras alternans (Q u.), Cardioceras tenuiserratum (O p p.) that are a basis for establishing the uniform subdivision of the Middle Oxfordian.The following are horizons proposed by the present author for the Middle Oxfordian deposits of the extra-Carpathian area of Poland: lower horizon – Perisphinctes chloroolihicus and Cardioceras tenuiserratum, and upper horizon – Amoeboceras alternans and Perisphinctes wartae. It should be stressed here that the species P. (Dichot.) wartae B u k. is a characteristic form of the upper horizon of the Middle Oxfordian and not of the Upper Oxfordian as it was suggested by H. Salfeld (1914)  and by other research workers.Evidently, the author refers to the horizons distinguished by S. Różycki (1953) and completes them with the fauna of Cardioceratidae.