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The kinematic history of the Pennine Nappes east of the Lepontine Dome: Implications for the tectonic evolution of the Central Alps
Author(s) -
Ring Uwe
Publication year - 1992
Publication title -
tectonics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.465
H-Index - 134
eISSN - 1944-9194
pISSN - 0278-7407
DOI - 10.1029/92tc00616
Subject(s) - nappe , geology , transpression , clockwise , paleontology , cretaceous , sinistral and dextral , fold (higher order function) , seismology , foreland basin , tectonics , structural geology , mechanical engineering , engineering
The Pennine zone of the eastern Central Alps (South, Middle, and North Pennine from top to bottom of sequence) underwent a complex structural and strain history. A first phase (D 1 ) is characterized by E‐W oriented stretching and is of Cretaceous/lower Tertiary age. D 1 structures affected most, but not all, of the South and Middle Pennine units, were probably obliterated in the North Pennine Adula nappe, and are absent in the basement nappes underneath the Adula nappe. Further deformation led to N/NW directed nappe movement (D 2 ), followed by incipient strike‐slip motion along the Periadriatic line (late D 2 ). Subsequently, large‐scale folding (D 3 ) affected mainly the nappe fronts. In the Adula nappe F3 folds verge towards the foreland, whereas the overlying units were backfolded towards the hinterland. The D 2 /D 3 events were accompanied by a complex strain pattern that is best seen in the Adula nappe and includes plane to prolate strains in the upper frontal part and oblate strains in both the lower frontal part and the interior of the nappe. D 3 backfolding was associated with the beginning of backthrusting at the Periadriatic line and was accompanied and/or followed by rapid uplift in the Lepontine dome and subsequent unroofing of the latter which led to E/NE directed extensional movements (D 4 ) in the eastern Central Alps. The D 1 event is related to the anticlockwise rotation of the Adriatic plate relative to Europe. This caused dextral transpression between the Adriatic and the European plates and partitioning of the deformation into convergence and strike‐slip. It is suggested that the North Pennine nappes below the Adula nappe were situated along a major strike‐slip fault and escaped this event. D 2 resulted from continental collision between Adria and Europe. D 2 displacement directions are subperpendicular to the Alpine arc and are best approximated by WNW/NW oriented motion of Adria. The structures and the strain pattern of D 3 are interpreted as the result of gravitational force. Late D 2 strike‐slip deformation at the Periadriatic line, D 3 backthrusting at the southern steep belt, and the unroofing stage (D 4 ) are generally attributed to dextral transpression between Adria and Europe. This approach implies that the Alpine evolution of the Central Alps was largely governed by tangential convergence between the Adriatic and the European plates.