New stratigraphic and genetic model for the dolomitic Cretaceous Pinda reservoirs in Angola: Part II - Compelling arguments against early dolomitization and early leaching

Abstract

This is the second contribution to the stratigraphic and genetic model of the Pinda Group. The mid-Cretaceous Pinda Group of the Congo basin in the northern Angolan offshore is a transgressi-ve supersequence. Its lower part is made of Bufalo and Pacassa facies that correspond respectively to mixed and calcareous-dolomitic grain-dominated fabrics. Both facies were strongly diagenetically alte-red, mostly by dolomitic replacement and leaching. Contrary to opinions expressed by other authors that both styles of alteration are early diagenetic phenomena, there is substantial evidence for a burial origin with dolomitic replacement and leaching of calcite having started at depths not less than 150 m and 400 m, respectively.