STRATIGRAPHY AND STRUCTURAL GEOLOGY OF THE PUNTA ROLLE-CASTALLAZZO AREA, DOLOMITE ALPS, ITALY

The stratigraphic section of the Punta Rolle-Castallazzo area of the Dolomite Alps of Northeastern Italy is typical of the region, with a basement of lower Paleozoic Alpine Basement Complex quartz-white mica schists overlain nonconformably by the Permian Ignimbriti Formation, followed by a Permian to Triassic sedimentary section of continental to shallow marine origin. The sedimentary section begins with the Permian Val Gardena Sandstone, a fluvial to evaporitic unit with sediment largely derived from the underlying Ignimbriti volcanic rocks; includes the evaporite (gypsum-anhydrite) rich Bellerophon Formation; and is capped by the Triassic Werfen Formation and overlying massive dolomites that are namesake of the region. We divide the Werfen Formation into nine members characterized by distinctive mappable lithofacies. Structurally, the area is complexly folded and faulted. Marked thickness variations between eastern and western sections of the Ignimbriti Formation reveal the presence of pre- to early Permian, northwest trending normal fault. Alpine deformation reactivited this fault and created a host of associated northwest and northeast striking, cross-cutting thrust, high-angle reverse, normal, and strike-slip faults. Flower structures occur at the upper levels of some faults. Diabase dikes follow northwest trending joints and faults. Thrust faults verge to the south, as do mesoscopic, northeast trending folds. The mesoscopic folds occur in the weaker Werfen section between and beneath dolomite massifs; and disharmonic, non-tectonic folding of the underlying evaporitic Bellerophon Formation rendered that unit into a dismembered formation with limited stratigraphic continuity. Gentle macroscopic, N30-40° W trending folds are superimposed on N70°E trending mesoscopic scale folds. The overall structural development fits within a regional pattern of thrusting and transpressional faulting in the southern Dolomiti associated with the Valsugana Thrust (Line).