New Insights in Tectonics, Depositional Settings and Hydrocarbon Habitat of the Permo-Triassic in the Southern Permian Basin

Geluk, Mark C., Shell Exploration and Production International b.v, Assen, Netherlands

Recent study acquired new insights in the development of the Southern Permian Basin (SPB). Rather than one basin, the SPB actually comprises three basins, separated by subtle swells. These basins have both a different origin and subsequent history. High-resolution stratigraphic correlations of the Permo-Triassic interval were carried out to (i) align the var­ious stratigraphies, and (ii) to define a basin-wide framework for the SPB area. A series of high-resolution paleogeographic maps capture the current insights in basin evolution.

Late Carboniferous to Middle Permian rift/wrench tectonics triggered slab detachment and a prolonged period of extrusive volcanism in the North German Basin. These process­es resulted in the collapse of the Variscan Mountains. Initially molasse-type sediments were deposited, followed by eolian sediments and salts. Subsidence was essentially driven by thermal lithosphere contraction, amplified by the loading effect of evaporites. This is reflect­ed by the gradual expansion from the sedimentation area over all three basins in Middle and Late Permian times.

In Triassic times, these basins were progressively modified by rift tectonics. These rifts (Central North Sea, Horn and Glückstadt grabens) dissected mainly the North German Basin, and locally up to 9,000 m of Triassic sediments accumulated in the rifts. In the Anglo-Dutch Basin and Polish Trough differential subsidence ceased. During the Triassic, sedimentation patterns underwent a major reorganisation, owing to the Late Triassic uplift of Fennoscandia and variations in the access of marine influence in the basin and climatic variations.

Permian hydrocarbon plays extend over the entire SPB, whereas Triassic plays are restricted mainly to the western parts.