![]() The 87Sr/86Sr ratios of the dedolomite are significantly higher, between 0♷082 and 0♷087. The δ18O and δ13C values of the Winnipegosis dedolomite vary from −12♸‰ to −11♹‰ VPDB (Vienna Pee Dee Belemnite) and from −0♵‰ to +1♷‰ VPDB, respectively both values are significantly lower than those for the corresponding dolomite. This type of crystalline limestone is interpreted as dedolomite, based on petrographic observations. In particular we propose that the fracturation and the first phase of dedolomitization (fabric A) occurred during the glacial period, while extensive calcite precipitation and brecciation (fabric B) formed during the interglacial periods, dominated by a warm climate during which extensive soil cover and karst processes developed.Ībstract: Limestone consisting of finely to medium crystalline calcite mosaics is present in the upper part of the Winnipegosis Formation on the east-central margin of the Elk Point Basin where the overlying Prairie Evaporite deposits have been removed. The field mapping, analytical data and the geomorphology of the areas where the dedolomitized patches are more frequent, in correspondence of a narrow passage of the lower Camonica valley, allowed us to infer that the dedolomitization developed during glacial-interglacial phases particularly active in the region during the Pleistocene. Radiometric absolute age determination (230U/234Th) indicates that calcite cements precipitated in the last 100000 years: are during which the area was subject to several advances and retreats of glacial tongues. The negative δ18O and δ13C values of the calcite cements and the calcitic fraction of the dedolomitized fabrics suggest precipitation in presence of meteoric water derived fluids. The petrographic analyses, integrated using cathodoluminescence and electron scanning microscope allowed to find out that dedolomitization process is composed of a first phase of dolomite dissolution along permeable path ways, both at the macro and at the micro scale, followed by calcite precipitation in the pore spaces. This study was aimed to reconstruct the dedolomitization process and to propose a relevant genetic model. Two main fabrics have been recognized: the fabric A is formed by a reticulate of small fractures filled by calcite and surrounded by fine grained calcitized halos, the fabric B is associated to more intense fracturation process that locally gave rise to breccia fabric moreover a ochre-reddish internal sediment is locally present in small cavities or as a breccia matrix a huge speleothem-like cementation is associated to these dedolomitized fabric. ![]() ![]() The calcareous lenses show an irregular, elongated (up to few meters large) shape they are usually located along fault-fracture systems and extending along the strata bedding. Dark grey, bedded dolostones (basal Dolomia Principale), outcropping along the both lower slopes of Iseo Lake (lower Camonica Valley), show a complex network of dedolomitized white-grey areas. This up to 2 km thick carbonate platform succession has been massively dolomitized from early to shallow burial diagenesis. ![]() TL DR: In this paper, the authors reconstruct the dedolomitization process and propose a relevant genetic model to find out that the process is composed of a first phase of dolomite dissolution along permeable path ways, both at the macro and at micro scale, followed by calcite precipitation in the pore spaces.Ībstract: The studied area belongs to a south vergent thrust and fold belt of the Southern Alps of central Lombardy where the norian Dolomia Principale crops out.
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