Charakterystyka osadów kredy na obszarze Lubelskiego Zagłębia Węglowego

Aleksandra Krassowska

Abstract


Omówiono litologię i stratygrafię profilu kredy LZW. Wydzielono m.in. 5 kompleksów geofizycznych. Kredę dolną reprezentują piaszczyste osady albu środkowego i górnego. Kreda górna jest węglanowa i charakteryzuje się przechodzeniem od facji węglanowo-krzemionkowej i·wapienno-marglistej w SW części obszaru przez fację: wapieni i wapieni kredopodobnych aż do kredy piszącej w NE jego części. Stwierdzono dwie strefy zwiększonej miąższości albu. W kredzie górnej zwiększona subsydencja miała miejsce w SW części obszaru, oś maksymalnej subsydencji przebiegała jednak poza jego granicami. W północno-wschodniej części obszaru zaznaczyła się silna redukcja miąższości osadów, szczególnie w górnym santonie. górnym kampanie i dolnym mastrychcie.

THE CHARACTERISTICS OF CRETACEOUS DEPOSITS IN AREA OF THE LUBLIN COAL BASIN

The paper presents lithological and stratigraphic characteristics of the Middle and Upper Albian and the Upper Cretaceous, represented in the studied area by all the stages (from Cenomanian to Upper Maestrichtian). The stratigraphic scheme is given along with geophysical complexes differentiated in this area (Figs. 2 and 3). The importance of geophysical complexes I, II and IV, used as reference horizons for correlation, is shown. The lithofacies changes in individual stages of the Cretaceous are presented (Figs. 4, 5, 6). Moreover, original thickness of Middle and Upper Albian deposits, i.e. the first sedimentary layer formed in this area ,after a long break in sedimentation, is reconstructed in the map (Fig. 4) which, at the same time, is the map of paleorelief.

The contact of the Cretaceous and its bedrock is characterized. The studies on core material showed that top surface of Upper Jurassic limestone is usually evened, somewhat phosphatized and often corroded by boring organisms - polychaetes of the genus Polydora. The contact of the Jurassic and Cretaceous does not display weathering cover of the former deposits nor basal conglomerate but some traces of paleokarst. It should be noted that the Cretaceous begins with basal conglomerate when it rests directly on the Carboniferous.

To sum up, the studied area was a part of Late Cretaceous basin neighbouring with rapidly subsiding part of that basin in south-west and with a part characterized by impeded subsidence in the north-east. After the movements of the Subhercynian phase, i.e. at the beginning of the Santonian, the rate of subsidence of basin floor became markedly impeded in north-eastern part of the studied area, in the vicinities of Kaponosy and Wisznice. This is reflected by strong reduction in thickness of deposits, especially Upper Santonian, Upper Campanian and Lower Maestrichtian.

Chalk deposits predominate in north-eastern part of the studied area and transition from chalk to limestones is found in a belt stretching from Parczew through Łęczna to Grabowiec. The sedimentary facies changes to· more marly in character in the most south-western part of the studied area. At the end of the Late Maestrichtian, there took place regression of sea and the facies changed to that of marls and opokas.


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