Sequence stratigraphy with emphasis on platform-related parasequences of the Zechstein 2 carbonate (Ca2) – the northern platform margin of the Southern Permian Basin (NE Germany)

Abstract

Facies analysis combined with sequence stratigraphic interpretation of the Upper Permian carbonate (Ca2) of NE Germany (i.e. northern basin margin of the Southern Permian Basin) confirm the existence of a rimmed platform with a steep and tectonically structured slope. The karstified A1 platform is overlain by deposits of a thin transgressive systems tract (TST) and a thick highstand systems tract (HST) which shows two larger-scale regressive shallowing-upwards cycles (4th order) with typical stacking patterns of small-scale cycles (5th order). The TST consists of bitumen-rich mudstones with reworked clasts of anhydrite and early cemented wacke- to grainstones, and it shows two, probably 5th-order, deepening-upwards cycles. The first larger-scale shallowing-up cycle on the Ca2 platform (4th-order) is dominated by aggradation of the bar and shoal deposits, whereas the second one is dominated by progradation. The tops of both cycles are characterised by erosional and exposure surfaces. Various types of small-scale shallowing-upwards cycles (5th-order) are observed in the bar, in the intertidal and in the algal-dominated supratidal environment, showing pronounced transgressive boundaries. On the slope and in the basin, equally thick TST and HST are observed. These incorporate carbonate turbidites which indicate "highstand shedding" from the platform. Various orders of relative sea-level variations are discussed. Controlling factors include tectonics, climate, and eustatic processes. A combined carbonate and evaporite sequence was found on the upper Ca2 slope, which may indicate a Ca2-lowstand systems wedge.