Numerical Simulation of the Syn‐ to Post‐Depositional History of a Prograding Carbonate Platform: The Rosengarten, Middle Triassic, Dolomites, Italy

Abstract

A combination of thermal history, numerical basin-reverse and sequence-stratigraphic forward modelling is applied to the Mesozoic outcrop analogue of the Rosengarten carbonate platform area in the Dolomites of northern Italy. This integrated multidisciplinary approach of numerical simulation quantifies the thermal, subsidence, geometrical and subsequent facies evolution of the area. Calibration data during modelling were vitrinite reflectance (VR) and apatite fission-track (FT) analyses as well as detailed outcrop studies. Vitrinite reflectance values in strata underlying the carbonate platform vary between 0.5 and 0.8% VR r ; apatites from these formations reveal cooling ages of around 165.6 Ma and track lengths of approximately 9.8 µm. This low thermal maturity combined with the FT data in apatites indicates a relatively cool (<110 • C), protracted (between 250 and 30 Ma) and shallow burial (thickness of eroded strata overlying present-day topography is <1100 m), as well as a fast exhumation from the Middle Miocene onward. Maximum temperatures are reached during the Middle/Late Triassic, when the basal heat flow was elevated owing to regional volcanic and hydrothermal activity. Local anomalies in vitrinite reflectance of up to 1.1% VR r in the immediate surroundings of the Predazzo/Monzoni volcanic centre show that its thermal influence decreased rapidly with increasing distance. The geometrical evolution of the Middle Triassic (Anisian/Ladinian) Rosengarten platform is twofold: the first stage reveals aggradation, the second progradation of the platform margin. Basin-reverse modelling results indicate that these two intervals originate from a temporal change in tectonic subsidence. Spatial variations in flexural and tectonic subsidence along the 6 km transect are insignificant due to the rigidity of the basement (up to 2500 m of Late Permian ignimbrites). During the first stage of platform evolution, high pulse-like total subsidence rates of up to 820 m Myr −1 led to aggradation, whereas the subsequent drop to 100 m Myr −1 initiated platform progradation. The short-spanned subsidence peak was linked to block movements in a strike-slip tectonic setting (Cima Bocche Anticline-Stava Line approximately 10 km southeast of the study area). Stratigraphic forward modelling quantifies the sediment volumes involved in the geometrical evolution of the platform. In order to replicate platform architecture, constant carbonate accumulation rates between 900 and 1000 m Myr −1 -increasing from periplatform environments to the slope -have to be assumed throughout the existence (approximately 5.8 Myr) of the Rosengarten. As the carbonate factory successfully keeps up with the modelled accommodation rates, it must have completely recovered from the Permian-Triassic biotic crisis during the onset of platform growth in latest Anisian times despite the low biotic diversity of the platform succession seen elsewhere in the Dolomites. Our forward modelling confirms that the main carbonate factory was situated on the slope at water dep...

Burial history and thermal maturity of Mesozoic rocks of the Dolomites, Northern Italy

“…Sample coverage of maturity measurements by selected previous publications (Tscherny 2006;Emmerich et al 2008;Blendinger et al 2013) is shown in Fig. 1.…”

“…In four samples neither vitrinites nor solid bitumen has been detected (13/643, 13/688, 13/710 and 13/711). New obtained data (this study) were compared to literature data from other parts of the Dolomites (Buggisch 1978;Schulz and Fuchs 1991;Bielefeld 1998;Tscherny 2006;Emmerich et al 2008;Blendinger et al 2013). Thus, a total number of 75 samples with vitrinite reflectance values is available (''Appendix Table 4'').…”

“…This was suggested by Tscherny (2006) as well, based on his and additional literature data. Furthermore, Emmerich et al (2008) analyzed sandstones of the Gröden Fm. at the Rosengarten, around 20 km south of the Frötschbach area, and classified VRs higher than 0.9 % VR r as ''not used: proximity to a volcanic dyke''.…”

“…Suchy et al 1997;Mählmann and Giger 2012) and Slovenia (Rainer et al 2009). In the Dolomites only a few studies, partly published in German, focused on reconstruction of thermal maturity (Emmerich et al 2005(Emmerich et al , 2008Tscherny 2006;Tscherny et al 2011;Blendinger et al 2013). Tscherny et al (2011) performed numerical modeling for the area east of the city of Corvara (Fig.…”

Multi-scale three-dimensional distribution of fracture- and igneous intrusion- controlled hydrothermal dolomite from digital outcrop model, Latemar platform, Dolomites, northern Italy

“…Several Triassic carbonate platforms in the Dolomites, northern Italy, (Figure 1) are considered outcrop analogues for subsurface (dolomite) hydrocarbon reservoirs, for instance the Sella Group (Antonellini and Mollema, 2000), Pale di San Lucano (Blendinger and Meissner, 2006) and the Rosengarten or Catinaccio (Emmerich et al, 2009). Also in the Latemar, several aspects, such as platform geometry and fracturing, are covered in the literature as outcrop analogues.…”