AN ISOLATED CARBONATE BANK IN THE ZECHSTEIN MAIN DOLOMITE BASIN, WESTERN POLAND

Abstract

Isolated carbonate banks in starved basins are very attractive targets for hydrocarbon prospecting. In the Zechstein (Late Permian) Main Dolomite (Ca2) Basin of Western Poland, six such banks or isolated platforms have been penetrated by wells, and gas and/or oil has been found in all of them. The largest is the Chartów Platform. which lies a few tens of kilometres from the edge of the carbonate shelf and shows well‐defined facies zonation, Three shallowing‐upward cycles may be distinguished in the bank‐edge sands, while the central (lagoonal) region and lower slope show a single deepening‐upward sequence. Local rapid subsidence, usually balanced by the rate of deposition, is inferred for the edge of the Chartów Platform: this subsidence was not balanced in other zones. The driving force for increased local subsidence may have been related to subtle block movements, and the break‐up of the P21 (Werra) evaporite platform. The rate of increased subsidence fluctuated: pulses of relatively rapid subsidence disturb the sequence, which was controlled by sea‐level fluctuations. Differential subsidence and sea‐level changes are common during the evolution of evaporite basins, and isolated platforms similar to the Chartów structure may be common in other evaporite basins, where isolated banks are located between the central and marginal areas.