Deformation partitioning during updoming of the Sonnblick area in the Tauern Window (Eastern Alps, Austria)

Type:
Journal- or magazine-article
Author:
Kurz, Walter and Neubauer, Franz
Journal:
Journal of Structural Geology
Year:
1996
Issn:
0191-8141
Pages:
1327,1339--1337,1343
Volume:
18
Publisher:
Elsevier Ltd
Abstract:
The Sonnblick Dome forms a NE-vergent dome structure cored by basement gneisses within the southeastern Tauern Window of the Eastern Alps (Austria). A succession of ductile and brittle deformation stages documents doming and exhumation subsequent to the thermal peak of metamorphism. Contrasting deformation geometries within internal parts and along the margins of the dome are explained in terms of deformation partitioning. Subhorizontal shortening is documented by subvertical en-echelon extensional gashes within central parts of the dome. Subhorizontal as well as subvertical flattening is also documented by fold structures. During dextral transpression strike-slip is accommodated along the NE margin (Sonnblick Lamella, Möll Valley Fault) and the southern margin (Moser Fault) of the Sonnblick Dome, while vertical thickening occurred within the interior of the dome. Crustal thickening triggered unroofing and extension parallel to the dome axis which is documented by ductile low-angle normal faults in the uppermost structural sections of the dome. This normal fault system contributed to footwall uplift and exhumation of the dome structure. The Sonnblick Lamella, associated with the dextral Möll Valley Fault, forms a stretching fault where deformation is concentrated along a potential zone of weakness. This fault is interpreted to represent the transition from vertical thickening within the dome to vertical thinning at the dome margins. During upbending, the dome structure passed the isotropic stress surface that is characterized by equality of σ 1 and σ 2 . This is documented in a perturbation of the orientations of principal stress axes σ 1 and σ 2 , while σ 3 remains constant in orientation. Transpression contributed substantially to updoming and to rapid, nearly isothermal, exhumation subsequent to the thermal peak of metamorphism.
Number:
11
Language:
eng