Synsedimentary tensional features in Upper Triassic shallow‐water platform carbonates of the Carnian Prealps (northern Italy) and their importance as palaeostress indicators

Abstract

The extensive shallow‐water carbonate platform deposits of the Dolomia Principale Formation (Southern Alps, northern Italy) accumulated during the Late Triassic, a time of plate‐scale reorganization and rifting. Synsedimentary tensional features such as fractures, neptunian dykes, normal faults, shatter breccias and laterally discordant intraformational breccias have been studied within a well‐preserved platform‐to‐basin transition in the Monte Pramaggiore area (Carnian Prealps). These tensional features follow three preferential orientations: N–S, E–W and NE–SW. To fully explain these different arrays it is proposed that the study area experienced during the Late Triassic the waning rifting phase connected to the westward propagation of the NeoTethys (N–S extension) and the onset of the rifting phase that led in the Middle Jurassic to the opening of the Central Atlantic (E–W extension), with a contemporaneous reactivation of Early–Middle Triassic NE–SW‐orientated faults. This palaeostress analysis reveals the good potential of tensional features as reliable palaeostress indicators.