Geological Quarterly最新文献

The Zn-Pb mineralization in the Bou-Izourane district, located in the High Atlas Mountains of Morocco, contains estimated reserves of 40 200 tons of ore with an average grade of 20% Zn and 3.5% Pb. It is developed on N–S to NNW–SSE-trending faults that cut Liassic carbonate marl deposits. The paragenetic mineral sequence consists of galena, sphalerite and late-stage calcite. Oxidation phases of galena into cerussite and sphalerite into smithsonite are common in the Bou-Izourane ore, linked to the infiltration of meteoric waters and the oxidation of these sulphides. The Zn-Pb mineralization runs parallel to the fluorite veins associated with the igneous rocks of Tamazeght, but no petrographic or field relationship has been demonstrated between these two mineralizations (i.e., Zn-Pb and fluorite). The distribution of rare earth elements and yttrium (REY) in the Zn-Pb mineralization of Bou-Izourane shows a notable similarity with the Mississippi Valley Type (MVT) mineralization of the Central High Atlas of Morocco, although the concentrations more closely resemble those of REY in fluorite linked to the magmatic-hydrothermal activity of Tamazeght. However, the analysis of their distribution in post-fluorite calcite and post-Zn-Pb calcite reveals a strong concordance, suggesting that these two calcites are associated with the same phase and have a common origin. The classification of the Zn-Pb prospect in Bou-Izourane remains controversial, fluctuating between an MVT-type mineralization, similar to most Zn-Pb mineralizations in the Central High Atlas of Morocco, and a mineralization linked to the magmatic-hydrothermal activity of Tamazeght, which could provide heat and metallogenic material. Characterizing the Zn-Pb ore of Bou-Izourane is crucial for the future exploration of zinc and lead deposits in the High Atlas of Morocco and could advance the development of Zn-Pb mining in the region, from artisanal exploitation to professional mining

Oxygen isotope palaeotemperature studies of Paleozoic limestones are based mainly on brachiopod shell material which is resistant to diagenesis and generally precipitated in oxygen isotopic equilibrium with ambient sea water. Here we present brachiopod C and O stable isotopic data from the Baltoscandian Ordovician-Silurian succession, and evaluate palaeotemperature and palaeoenvironmental variability during deposition of the Estonian Shelf facies. As the region has not been influenced significantly by tectonic events or deep burial diagenesis, the carbonate rocks and fossils are well-preserved in most of the locations studied. δ¹⁸O values for the Ordovician and Silurian carbonates and brachiopods range between ~–7 and 0‰. High δ¹⁸O values, locally accompanied by higher δ¹³O values, correspond to cooling if the isotope signal reflects the original oxygen isotopic composition in sea water and vice versa. Several Ordovician-Silurian δ¹³O_brac excursions identified on the Estonian Shelf reflect global palaeoenvironmental history and events, being synchronous with previously documented excursions in the bulk carbonate stable isotopic curves. Combining the published and new d13Cbrac and δ^13O_brac data allows us to address chemostratigraphic correlation of the interval from Lower Ordovician (Floian) up to the topmost Silurian (Přídolí). The δ^18O_brac data corroborate warmer temperatures during Early Ordovician (Floian-Dapingian) and a cooling trend into the Mid-Ordovician documented by previous studies in different palaeobasins. The Hirnatian isotopic carbon excursion (HICE) episode reveals the minimum temperature in this interval and the post-HICE data suggest a rising temperature trend. Another temperature minimum is evident in the strata reflecting the Ireviken Event (Sheinwoodian). Our study shows that brachiopod d18O values from the Ordovician-Silurian carbonates may tentatively be interpreted as reflecting major temperature trends

In addition to specimens attributable to Pliopetaurista dehneli (Pteromyini), already described by Sulimski (1964), the fossil tooth material collected at the Upper Pliocene (MN 16b) site of Węże 2 in southern Poland comprises specimens assignable to other representatives of the Sciuridae. These include Tamias orlovi (Marmotini), Blackia miocaenica (Pteromyini) and Sciurus warthae (Sciurini). All these species are otherwise relatively rare in the fossil record. Along with another MN 16b site, Frechen, as well as the MN 16 sites of Rębielice Królewskie 1A and Rębielice Królewskie 2, Węże 2 thus represents one of the youngest occurrences of B. miocaenica in the fossil record. P. dehneli, B. miocaenica and S. warthae are considered to have inhabited dense forests while T. orlovi probably also lived in more open wooded environments.

This study examines the impact of prehistoric human activities on the landscape of the Subcarpathian Loess Plateau, focusing on areas such as the Kańczuga Plateau in southeastern Poland. Through a multidisciplinary approach that integrates archaeological excavation, soil profile analysis, and geomorphological survey techniques, environmental changes are traced from the Neolithic through the early Middle Ages. A key aspect comprises various soil types, particularly chernozems and brown soils, which have been influenced by early agricultural practices like deforestation and land cultivation. The use of radiocarbon and Optically Stimulated Luminescence (OSL) dating of soil profiles and archaeological sites provides insights into the timeline of human-induced erosional and depositional processes and deposits ranging in age from the Palaeolithic period to the early Middle Ages. The results highlight significant soil erosion and colluvial deposit formation, especially during periods of intensified agriculture. These changes in specific soil types underscore the substantial impact of human activities and climatic variations on land relief and soil cover in the Late Holocene. This study contributes to a deeper understanding of human-driven landscape alterations in loess areas, offering valuable insights for environmental management and conservation on the Kańczuga Plateau, in the Sandomierz Basin, and in other similar geomorphological settings.