Demise of Late Triassic carbonate platforms triggered the onset of a tide-dominated depositional system in the Dolomites, Northern Italy

Abstract

Facies analysis of the mixed carbonate–siliciclastic Upper Triassic Heiligkreuz Formation in the Cortina–Tofane area (Dolomites, Northern Italy) shows a tide-dominated sedimentary succession developed in a marine strait environment connecting two small sub-basins on the western margin of the Tethys Ocean. Both ebb and flood paleocurrents are preserved and their directions are in agreement with the strait orientation, as inferred from the geographic position of high-relief carbonate platforms in the substrate. Facies and sedimentary structures including planar cross stratification, herringbone cross stratification, flaser to wavy to lenticular bedding and cyclical alternations of mainly oolitic–siliciclastic vs. mainly bioclastic–muddy laminae related to variations of the hydraulic regime have been described and compared with other tide-dominated systems developed in confined marine conditions, and in particular with the Plio-Pleistocene deposits of the central Mediterranean Sea. However, in contrast with all other known cases, this tidal system did not develop in tectonically confined submarine grabens or canyons, but rather in a narrow marine passage between two relict high-relief carbonate platforms.