Odpowiedniki warstw połomskich liasu częstochowskiego w zachodnim obrzeżeniu Gór Świętokrzyskich

Abstract

EQUIVALENTS OF THE POŁOMIA BEDS OF THE CZĘSTOCHOWA LIAS IN THE WESTERN MARGIN AREA OF THE ŚWIĘTY KRZYŻ MOUNTAINS

This paper contains the characteristics of the sandy-gravel Snochowice beds occurring in the western margin of the Święty Krzyż Mountains (Central Poland), and the comparison with the synchronic Połomia beds from the Cracow-Wieluń Jurassic Range. The author discusses lithological features of these beds, their type of stratification, directions and angles of their cross-bedding inclination, granulometric and petrographical composition of gravels, as well as rounding degree of pebbles.

The quarzites predominating among the gravel pebbles, most closely resemble those of Lower Devonian age known from ,the Święty·Krzyż Mountains. Even·so, this material derives rather from washing-out of older, Pre-Jurassic conglomerates consisting, inter alia, of quartzite pebbles. This seems to be indicated by the poor composition of gravels, limited to most resistant rocks only, simultaneously with a relatively thorough rounding, a scanty sorting of the material and a rapid decrease in the maximum size of pebbles with the increase of distance from their source area. These facts also prove the short distance of transportation of material.

The analysis of cross-bedding directions in both the Snochowice and the Połomia beds indicates the material to be derived from the substratum of the depressed Nida basin, filled by the Cretaceous deposits; here, on the top of the Palaeozoic sediments folded during the Caledonian and the Hercynian orogeny, conglomeratic series of different ages might have been developed in the Younger Palaeozoic and the Older Mesozoic time.