Meso-/Cenozoic basin and carbonate platform development in the SW-Dolomites unraveled by basin modelling and apatite FT analysis: Rosengarten and Latemar (Northern Italy)

Abstract

The Rosengarten and Latemar Middle Triassic carbonate platforms indicate similar subsidence patterns during equivalent times of platform evolution as calculated by numerical basin reverse modelling. In the case of Rosengarten and Latemar, thermo-tectonic subsidence is the most significant among all three subsidence components (thermo-tectonic s., flexural s., compaction-induced s.). Hence, the influence of differential tectonics–as recorded in the formation of structural highs and lows in the Dolomites during the Lower to Middle Anisian–almost ceases in Late Anisian times. Basin modelling of Rosengarten and Latemar requires the correlation and integration of two sets of chronostratigraphic data from Buchenstein Fm (basin) and Schlern Dolomite Fm 1 (platform). Subsidence modelling argues for a microcycle (i.e. a single shallowing-upward cycle) duration of less than 1.97 ka in the cyclic succession at Latemar. However, previous time series analyses identify Milankovitch-cyclicities in larger-order cycle stacking patterns and thus indicate a microcycle duration of 4.2 ka. According to each model, total subsidence reaches values of 650–700 m/Ma (4.2 ka model) or 780–850 m/Ma (1.97 ka model) during the first stage of platform evolution. As both platforms successfully keep up with this subsidence peak, it is evident that the carbonate factory–despite its low diversity–must have recovered from the P/T faunal crisis. After this regionally observed peak, subsidence drops and triggers fast progradation at Rosengarten. Subsidence in the study area is controlled by active strike-slip tectonics and the subsequent formation of a magmatic chamber (Predazzo/Monzoni) above the deep-reaching Truden/Stava line. The area close to this tectonic line and to the volcanic centre of Predazzo/Monzoni undergoes a higher heat flow pulse during the Late Ladinian and is possibly buried at shallower levels than the Rosengarten area. As shown by fission tracks in apatites, the heat flow pulse almost disappears laterally underlining the localised thermal influence of the Late Ladinian volcano-thermal event of Predazzo/Monzoni.