KORELACJA I GENEZA PIASKOWCÓW KARBOŃSKICH W ŚWIETLE STRATYGRAFII SEKWENCYJNEJ I ICH POTENCJAŁ WĘGLOWODOROWY W PÓŁNOCNO-ZACHODNIEJ I CENTRALNEJ CZĘŚCI BASENU LUBELSKIEGO

Abstract

CORRELATION AND ORIGIN OF THE CARBONIFEROUS SANDSTONES IN THE LIGHT OF SEQUENCE STRATIGRAPHY AND THEIR HYDROCARBON POTENTIAL IN THE NW AND CENTRAL PARTS OF THE LUBLIN BASINAbstract. Sedimentological investigations of Carboniferous deposits from the Lublin Basin enabled characterisation of the depositional environment of sandstones, mudstones, claystones, carbonates and coals. A regional correlation allowed identification of 22 depositional sequences (third-order) are separated by unconformities, preserved as erosional bottoms of fluvial channels or incised valleys. Each sequences are represented by lowstand, transgressive and highstand systems tracts. Subsequently, a correlation of the sequence stratigraphy division with the Carboniferous chronostratigraphic scheme was carried out. The rise of relative sea level, being an erosional base to rivers during the low sea-level stand, was the fundamental factor affecting the facies development and thicknesses of the potentially productive fluvial sandstones. These deposits most frequently occur in incised valley systems. Medium and large sized systems of simple incised valleys are observed in the sequences 2, 4-10 and 16. Large compound systems are known from the sequences 11-15. The sandstones observed in the sequences 17-22 are associated with non-incised systems of river channels. The rise of relative sea level during the lowstand period, its fluctuations during the transgression and highstand periods, and an increased supply of sediments or its lack were the basic factors that influenced the facies development, thickness and lateral extent of alluvial plain, estuarine, deltaic and shallow shelf claystones and mudstones acting as good sealing horizons. The sandstones of the sequences 6,9,12 and 16 (filling medium and large incised valleys) and the sequence 17 (developed in systems of non-incised river channels) are predisposed to be reservoir rocks for hydrocarbon accumulations. It is due to their position as isolated bodies within the sealing claystones and mudstones relatively rich in dispersed organic matter. A comparison of the sequence scheme both with the previously used boundaries of the Carboniferous lithostratigraphic units in the Lublin Basin and with geophysical complexes questions their isochroneity and reduces their usefulness for correlations.