Rock salt mass in the Paleoproterozoic sequence of the Onega trough in Karelia (from the Onega parametric well data)

7.5 Abundant Marine Calcium Sulphates: Radical Change of Seawater Sulphate Reservoir and Sulphur Cycle

“…Finally, thick-bedded anhydrites (Morozov et al 2010;Krupenik et al 2011a) were recently discovered when a c. 3,500-m-deep drillhole in the Onega Basin in the eastern Fennoscandian Shield intersected 13 C-rich dolostones of Lomagundi-Jatuli age at a depth of 2,115 m (335 m thick) followed by massive anhydrite and anhydrite-magnesite rocks (c. 100 m thick), nodular shale interbedded with massive anhydrite (190 m thick) and a c. 194-m-thick halite formation (70-75% halite, 12-20% anhydrite, 10-15% magnesite) containing large blocks (up to 1 m) of bedded, coarse-grained anhydrite and magnesite (Fig. 7.56a-c).…”

8.1 The Great Oxidation Event

“…The FAR-DEEP core materials exhibit many of these features, including pseudomorphs after gypsum and anhydrite. In addition, other available core materials demonstrate that massive sulphate deposition occurred during the Palaeoproterozoic (Morozov et al 2010;Krupenik et al 2011;Fig. 8.5).…”

1.1 Tectonic Evolution and Major Global Earth-Surface Palaeoenvironmental Events in the Palaeoproterozoic

“…The anhydrite strata are associated with the 13 C-rich dolostones of the Tulomozero Formation and represent the Lomagundi-Jatuli isotopic excursion, thus falling within the 2.22-2.06 Ga time-interval. This new discovery (Morozov et al 2010) may cause us to rethink our interpretations of Palaeoproterozoic oceanic sulphate chemistry.…”