Profil osadów karbonu w podłożu brzeżnej niecki między Toruniem a Warszawą

Halina Kmiecik, Antoni Żelichowski



In Poland, the knowledge of the Carboniferous is especially poor in area stretching between Toruń and Warsaw. The sedimentary carboniferous has been penetrated by several boreholes west of Warsaw and only a single one, Sierpc 2, north-west of Warsaw. Other boreholes made in this area recorded igneous and volcanic rocks dated at the Carboniferous (Fig. 1). On the basis of analyses of geological setting and radiometric and palynological data, the following succession of the Carboniferous has been established for that zone.
The oldest rocks occurring here are syenites and diabases intruding Lower Paleozoic rocks. Syenites have been dated at 347 and 348 m.y. by T. Depduch (2) and, therefore, at the Tournaisian, and diabases - at the Tournaisian and Visean. The Upperer Visean and Namurian, inferred in areas situated further to south-west and south-east (see Fig. 1), are missing here as this area has ,been mostly subjected to denudation at that time. The Carboniferous basin has not entered the area before the Westphalian. Palynological studies showed the presence of rocks ranging in age from the Westphalian A to D. Their thickness increases to south-west to over 1000 m. In comparison with the Lublin region, Westphalian D rocks appear to be widely distributed north-west of Warsaw, stretching towards NE. Figure l shows map of Permian subcrops of Carboniferous and older rocks, accompanied by sketch cross-section reflecting differentiation in lithology and thickness of these rocks. The difference with respect to the Lublin region is connected with the presence of conglomerates formed of rhyolitic rocks in the Dęblin Formation in the vicinities of Mszczonów and Nadarzyn. The source area for the rhyolite material should be looked for further to SW. Claystones and siltstones of the Magnuszew Formation, found in the borehole Sierpc 2, yield rich assemblages of Monoletes spores, including Thymospora, Punctatosporites, Torrispora and Latosporites. They represent the youngest Carboniferous rocks with palynological record (full list identified spores is given in the Polish text), found in this zone.
Porphyres penetrated by the boreholes Konopki l and Ciechanów l, dated at 287-304 m.y. by T. Depciuch (2), are the youngest Carboniferous rocks here.

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