Sedimentation and diagenesis of an Oligocene manganese deposit in a shallow subbasin of the Paratethys: Thrace Basin, Turkey

Abstract

The northern part of the Thrace Basin, intermittently connected to the Paratethys seaway, was the site of micritic carbonate sedimentation during the Eocene, pisolite and coarse shell debris in the earliest Oligocene, and elastic sediments through into the Neogene. Near the transition from carbonate to elastic facies, thin and discontinuous manganese ores at Binkilic consist of interlayers of dominantly oxide and lesser carbonate minerals; these occur as disseminated, pisolitic/oolitic, concretionary and massive forms. Chief ore minerals are pyrolusite, manganite, cryptomelane, rhodochrosite and kutnahorite. In thin and polished sections, Mn carbonates in (originally calcite) monaxon sponge spicules are seen to have been replaced by Mn oxides, thus documenting the introduction of dissolved Mn, and major diagenetic alteration of primary calcite to Mn carbonate and finally to Mn oxide.