Gypsum in Diatomaceous Strata of the Trans-Urals Region: Morphology, Lithogeochemistry, and Genetic Link To Global Warming at the Paleocene-Eocene Boundary

Abstract

This paper reports the geochemical, structural, and textural properties of evaporite minerals (gypsum) interbed-ded with from the Early Paleogene diatomite and clastics exposed in the diatomite quarry in the Kamyshlov town quarry, Trans-Urals region (Sverdlovsk Oblast, Russia). This article is the first to reveal the occurrence of these atypical minerals in local sediments for the Trans-Urals region, dating from the Paleocene to the Early Eocene. The investigated aggregates included gypsum, anhydrite, and diatomite. Gypsum crystallization occurred rapidly in the low-density non-lithified stratum of the seafloor sediment under warm conditions. Gypsum elemental composition reflects its genesis in a low bio-productivity environment strongly influenced by the influx of highly mineralized groundwater. Terrigenous influx (coarse-grained quartz and fine clay fractions) is high. As a result, radial-fibrous stellate gypsum crystals formed in the fissures that penetrated the diatomite stratum. Geochemical indicators, such as Sr/Ba ratios, show that the salinity of the watershed was variable at the onset of evaporitic con-ditions. Chronologically, gypsum formation is dated to the beginning of the transgressive cycle (early Eocene, the end of the Paleocene-Eocene Thermal Maximum (PETM)) or to the end of post-PETM sedimentation. (c) 2022 Elsevier B.V. All rights reserved.