EDTA-insoluble residues from the Zechstein Ca-2 unit (Late Permian), the Logumkloster-1 Well, Denmark

EDTA-insoluble residues of carbonate rock samples from the Upper Permian Ca-2 unit of the Løgumkloster-1 well have been investigated by X-ray diffraction, scanning electron microscopy, instrumental neutron activation analysis, and magnetic measurements. The sediments have undergone severe diagenesis including dolomitization and anhydrite mineralization. Two original facies types have been recognized, an oolitic shoal facies, and a lagoonal carbonate facies. The mineralogy of the inorganic insoluble residue reflects the facies type division: the lagoonal facies contains muscovite, feldspar and quartz; the shoal facies contains a non-crystalline silicate phase, quartz, and mica. It is thought that the muscovite in the lagoonal facies is derived from weathering of exposed basement highs. The non -crystalline silicate phase in the shoal facies is thought to be a diagenetic phase precipitated at a rather late stage in the diagenetic history.