HR: 1340h
AN: T23D-1647    [Abstracts]
TI: Incipient graben formation in the NW Himalaya (Himachal Pradesh, India)
AU: * Hintersberger, E
EM: estherh@geo.uni-potsdam.de
AF: Institut fuer Geowissenschaften Universitaet Potsdam, Haus 27 Karl-Liebknecht-Str. 24, Potsdam-Golm, 14476, Germany
AU: Strecker, M R
EM: strecker@geo.uni-potsdam.de
AF: Institut fuer Geowissenschaften Universitaet Potsdam, Haus 27 Karl-Liebknecht-Str. 24, Potsdam-Golm, 14476, Germany
AB: GPS data and regional geological compilations show that the highest sectors of the Higher Himalaya are currently undergoing extension. This has been mainly explained with radial extension along the curvature of the Himalayan arc. However, close inspection of neotectonic extension phenomena using high-resolution satellite imagery from the upper Sutlej Valley of the NW Himalaya (Himachal Pradesh, India) suggests that the recent extension direction is rather oriented E-W, and that N-S graben-bounding normal faults in southern Tibet may propagate southward. This assessment is further corroborated by our new detailed structural field investigations and fault kinematic analysis. Our studies reveal that these normal faults cut all previously generated structures, documenting the recent activity of this fault generation. The average offset of these N-S striking, steeply dipping normal faults is in the cm to dm range for a single fault plane. However, since these brittle faults are part of a densely spaced network, the cumulative offset must be significant. Fault kinematic analysis of slickensides demonstrates that these structures are an integral part of a N-S oriented zone of diffuse E-W extension between the Leo Pargil gneiss dome in the north and the Garhwal Himalaya in the south. This E-W extension is also compatible with the orientation of T-axes of earthquake focal mechanisms obtained in the same region. Although different data sets document ongoing E-W extension, the reason for this phenomenon is not well understood. Despite the fact that some of the normal faults cut Quaternary and Tertiary units, and earthquakes occur within the realm of the extensional Leo Pargil gneiss dome, the ubiquitous occurrence of these structures within the Higher Himalaya suggests an orogen-wide origin, independent of extensional processes associated with dome formation. Alternatively, we therefore interpret the neotectonic extensional evolution of this region to reflect a very early state of a graben system propagating southward that is influenced by the E-W tensional stress regime that governs the southern Tibetan Plateau.
DE: 8002 Continental neotectonics (8107)
DE: 8010 Fractures and faults
DE: 8015 Local crustal structure
DE: 8168 Stresses: general
DE: 9320 Asia
SC: Tectonophysics [T]
MN: 2007 Fall Meeting