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) interbedded 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 conditions. 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.