Zechstein 2 carbonate platform subfacies and grain-type distribution (Upper Permian, Northwest Germany)

Abstract

The Upper Permian Zechstein 2 Carbonate (Stassfurt Carbonate, or Ca2) platform facies of Northwest Germany can be subdivided into twelve subfacies types using slabbed cores from fifteen representative wells. Thin section and scanning microscopic analysis further provide subfacies-specific characteristics, based on distribution, size, shape, and spatial arrangement of the grains contained in the different subfacies types. Thirteen grain types can be distinguished within the different subfacies types on the Ca2-platform: 1) one type of oncoid, 2) one type of grapestone, 3) three types of peloids, 4) four types of ooids and 5) four types of aggregate grains. Both presence and composition of grains are indicative of the different subfacies types. There is also a relation between grain composition and porosity of the Ca2-subfacies types. The size and quantity of ooids correlate positively with increasing porosity, whereas an increasing amount of algal structures (algal-lamination) correlates negatively with porosity.