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.

New data on the progradation of the Dachstein carbonate platform (Kamnik-Savinja Alps, Slovenia)

“…This kind of geometry points to the aggradation of the system in the Middle Norian. Similar aggradation of the same age was reported also from the Carnian Prealps (Italy) connected with the Middle-Late Norian extensional tectonic activity, related to the aborted westward opening of the Neotethys Ocean and the incipient rifting phase of the Ligurian-Piedmont Ocean (Carulli et al, 1998;COZZi, 2000;COZZi, 2002;COZZi & Hardie, 2003). The Alaunian aggradation is also reported from the Northern Calcareous Alps (berra, 1995;KryStyn et al, 2009).…”

Displaced South Alpine and Dinaridic elements in the mid-Hungarian zone

“…2), south of the Bükk Mts in North Hungary (Cserepes et al 2008 (Grad and Ogorelec 1980;Ramovš 1989;Gianolla et al 1998;Cozzi 2000;Dozet 2000), very similar to what was encountered in the wells south of the BAL.…”

Sedimentary record of mid-Miocene seismotectonic activity in the Sinop Peninsula, north-central Turkey

“…The sedimentary infill of open fractures and cavities in seabed, referred to as neptunian dykes, consists of sediment derived from the sidewalls and from above (Winterer and Sarti, 1994;Cozzi, 2000;Črne et al, 2007). The origin of neptunian dykes is widely attributed to seismic activity (Playford, 1980;Winterer and Bosellini, 1981;Lehner, 1991;Montenat et al, 1991;Cozzi, 2000), although similar features have also been reported from the surfaces of submarine slides (Winterer et al, 1991;Winterer and Sarti, 1994).…”

“…The dyke parabreccia component was formed by a brittle disintegration of the fissure sidewalls. The sandstone fragments show no evidence of weathering or dissolution, and their sharp edges suggest that the sand was wellcompacted and perhaps slightly cemented prior to its rupture (see Cozzi, 2000).…”