The ‘Vena del Gesso’ (Gessoso-Solfifera Fm, Messinian) is a 227 m-thick ridge along the western Romagna Apennines (Italy) consisting of up to 16 selenite cycles separated by shales and minor carbonate. The total organic carbon values of these deposits range between 0.087–0.016% (gypsum) and 3% (shales). Organic matter is dominated by black debris associated with continental debris. Algae and dynocysts are rare (<1%). The amount of amorphous organic matter is low but it may reach up to c. 40%. The 87Sr/86Sr of gypsum and carbonate vary from 0.708890 to 0.709024, yielding non-oceanic values with several exceptions that plot within error of coeval oceanic values only in the upper part of the section (from the 6° bed). The sulphur isotope composition of gypsum range between δ34S =+21.8 and +23.7‰ and may represent precipitation of δ34S-enriched gypsum due to the fractionation effect or recycling of coeval gypsum with contributions of brine-sediment redox variations. The isotope values of carbonates show a large variability (−6.4<δ18O<+6.05‰; −14.68<δ13C<+2.5‰), suggesting a complex origin by mixing of marine and non-marine waters with a significant contribution of reduced organic matter. These data point to an evaporite basin dominated by continental waters which received significant phases of marine recharge in the upper part together with a marked facies change. Because seawater recharges and a similar facies change are present in other Messinian sections, it follows that we have new possible geochemical and facies markers to correlate the Lower Evaporites across the Mediterranean.
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Evaporites Through Space and Time
This book is an exploration of varying approaches to the study of the deposition, diagenesis and stratigraphy of evaporites. The volume includes papers from chemical modellers, who work on the basis of geochemical representations of the formative water bodies, and from basin-wide depositional-stratigraphical modellers, who propose depositional scenarios that are fitted to individual basinal pictures.
Until now there have been only a few studies of evaporite formation that explain the characteristic features we observe in the real rock record. This volume is a collection of relevant papers in which these features are integrated in a realistic manner, based on our new understanding of saline water bodies, to the diverse tectonic, chemical and depositional constraints of their individual basins. In additional there are several review articles that offer oversight and extensive referencing of basins worthy of further study.
This book is a valuable resource for sedimentologists and stratigraphers looking for an up-to-date reference on evaporite deposits.