Breccias of the Adnet Formation: indicators of a Mid-Liassic tectonic event in the Northern Calcareous Alps (Salzburg/Austria) |
| |
Authors: | F Böhm J -L Dommergues C Meister |
| |
Institution: | (1) Institut für Paläontologie, Universität Erlangen, Loewenichstrasse 28, D-91054 Erlangen, Germany;(2) Centre de Géodynamique sédimentaire et Evolution géobiologique, URA CNRS 157, Centre des Sciences de la Terre de l'Université de Bourgogne, 6 Bd. Gabriel, F-21100 Dijon, France;(3) Département de géologie et de paléontologie, Muséum d'histoire naturelle, 1, route de Malagnou, c.p. 434, CH-1211, 6 Genève, Switzerland |
| |
Abstract: | Stratigraphy, lithology and depositional structures of Liassic red limestone-breccias of the Adnet Formation, including the Adnet Scheck , were studied at several outcrops of the Northern Calcareous Alps (NCA) south-east of Salzburg. A four-fold lithostratigraphic division is proposed for the Adnet Formation of the Osterhorn Mountains: the hemipelagic Schmiedwirt (Sinemurian) and Kehlbach (Carixian) members are separated from the pelagic Saubach Member (Toarcian) by a layer of amalgamated breccias (Scheck Member, probably Domerian to early Toarcian). Several other breccia beds occur locally from the base of the Kehlbach Member up to the lower Saubach Member. Although the sediments overlying the Scheck Member breccias are of coeval age, the ages of the underlying strata are very different. This can be explained by submarine Liassic erosion during a period of resedimentation from the middle Carixian until the early Toarcian. At least 10–15 m of partly lithified sediments were eroded by gravity flows. The entire Kehlbach Member and up to two-thirds of the Schmiedwirt Member were removed at Adnet. The breccias originated from submarine debris flows. Repeated flows over a long period and the depositional setting exclude a triggering by sea-level fluctuations. Most probably they arose from tectonically triggered slumps and slides of superficial sediments. The Scheck was initiated on the steep upper slope of the drowned Triassic Adnet reef and flowed to the north-east. The Pliensbachian to early Toarcian period of tectonic activity indicated by the breccias was the most important during the Liassic in the Osterhorn Mountains and other parts of the NCA. From the large-scale regional distribution of the breccias and in accord with published data, a roughly northeast trending strike-slip fault zone is proposed, crossing the NCA south of the Osterhorn block, with a peaking activity during the Pliensbachian to early Toarcian as the cause of the tectonic movements. |
| |
Keywords: | Synsedimentary tectonics Stratigraphy Depositional model Debris flows Submarine erosion Scheck breccia |
本文献已被 SpringerLink 等数据库收录! |
|