The associations occur in a zonal arrangement and correspond to the characteristics of the silicic, advanced argillic and argillic alteration terminology. more ABSTRACT The Tertiary latitic rock from Gossendorf, in the Gleichenberg Volcanic Area, Styria, Austria, has in places been completely altered to various associations of the secondary minerals opal-C/-CT, alunite, kaolinite, and montmorillonite. Some of the mineral associations, however, may not be explained by a single alteration process, but must be regarded as the result of multi-stage alteration in which alteration products from weak leaching are super-imposed on alteration products from intense leaching.ĪBSTRACT The Tertiary latitic rock from Gossendorf, in the Gleichenberg Volcanic Area, Styria, Au. The results of experimental alteration tests on the latitic rock in open hydrological systems suggest that these secondary minerals and some of the associations observed in the field as well as their zonal distribution, may have been formed by an originally strongly acid solution rich in SO42- which, undergoing progressive chemical variation by reaction with the rock, exhibits a chemical gradient. These associations occur in a zonal arrangement, in which the innermost part has been totally altered to opal and moreover has retained its original latitic structure. more Summary The latitic rock mined at the Gossendorf open pit in the Gleichenberg Volcanic Area of Styria, Austria, has in places been completely altered to various associations of the secondary minerals opal-C/-CT, alunite, kaolinite and montmorillonite. doi: 10.1180/claymin.2012.047.4.09.Summary The latitic rock mined at the Gossendorf open pit in the Gleichenberg Volcanic Area of St.
Micromilieu-controlled glauconitization in fecal pellets at Oker (Central Germany) Clay Minerals. Chapter 6 A review of the Chemical Index of Alteration (CIA) and its application to the study of Neoproterozoic glacial deposits and climate transitions. A., (Eds.) International Geological Correlation Programme, Project 326 Oligocene-Miocene Transitions in the Northern Hemisphere, Excursion Guide-Book Mongolia: Oligocene-Miocene Boundary in Mongolia 36–39.īahlburg H, Dobrzinski N. A brief lithologo-genetic characteristics of Eocene-Oligocene and Miocene deposits of the Valley of Lakes and Begger depression. Geochemistry of Sandstones from the Upper Miocene Kudankulam Formation, Southern India: implications for provenance, weathering, and tectonic setting. Palaeogeography, Palaeoclimatology, Palaeoecology, 299, 399–412.Īrmstrong-Altrin JS, Lee YI, Verma SP, Ramasamy S. Stepwise change of Asian interior climate preceding the Eocene-Oligocene Transition (EOT). A second, regional-scale aridification occurs at ~25 Ma and corresponds to a late Oligocene marked mammalian turnover in the Valley of Lakes sediments.Ĭlimate change Illitization Miocene Mongolia Oligocene Paleosol.Ībels, H. Our novel δ 13C and δ 18O record suggests an early Oligocene aridification in Central Asia at ∼31 Ma, whereas the Oligocene glacial maximum shows no increase in aridification. An exception is the δ 13C (and δ 18O) isotope values of authigenic carbonate found in calcrete horizons that still record the ambient climatic conditions prevailing during paleosol formation. Moreover, the diagenetic growth of illite resulted in a strong overprinting of the sediments and, subsequently, largely disturbed the pristine mineralogical and geochemical composition of the sediments that could have carried any palaeo-climatic information. This finding contradicts the current conceptual view that the fine fraction of the sediments is of aeolian origin. The obtained results show that temperate hydrothermal fluids induced a strong illitization of the fluvial and lacustrine sediments. In order to precisely elucidate the climatic evolution of the region, we studied the mostly siliciclastic sediments with several levels of paleosols for their sedimentology, mineralogy, major and trace element composition and δ 13C and δ 18O composition. The palaeontological record of this region is an exceptional witness for the evolution of mammalian communities during the Cenozoic global cooling and regional aridification.
The Valley of Lakes is approximately a 500-km elongate depression in Central Mongolia, where Eocene to Miocene continental sediments are long known for their outstanding fossil richness.
0 kommentar(er)
