STEMMERIK, LARS
Geological Survey of Denmark and Greenland, Copenhagen, Denmark

Abstract: Upper Permian Karst-Controlled Carbonate Buildups, East Greenland: Facies, Diagenesis and Reservoir potential

Upper Permian carbonate platforms in central East Greenland consists of three depositional sequences that formed in response to Kazanian sea-level cycles. The platforms developed on the karstified surface of older Permian platforms with a topographic relief that locally exceeded 70 m. The platform successions include two types of carbonate buildups dominated respectively by bryozoans and calcareous algae.

Bryozoan-dominated buildups are most common. They are up to 80 m thick and are composed of a core of bryozoan cementstone surrounded by steeply-dipping flank deposits of brachiopods bryozoan- and crinoid-rich packstones and wackestones. These buildups developed over isolated karstic pinnacles in relatively deep water, and thus formed isolated mounds separated by areas of deeper-water shale deposition

Algal-dominated buildups are particularly common in the Karstryggen Platform where they started to form as isolated buildups over karst pinnacles. With time, these shallower water buildups merged to form a north-south trending barrier dissected by deep fluvially-modified karst channels. These buildups are composed entirely of algal cementstone with no surrounding flank deposits.

Both types of buildups were repeatedly karstified during sea-level lowstands. In the deeper-water bryozoan buildups, karstification resulted in widespread dissolution of aragonitic material and an increase of porosity to 10-15%. In contrast, karst-related dissolution in the algal buildups was associated with pervasive calcite cementation resulting in early occlusion of porosity.

AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas