HR: 0830h
AN: H51D-1090    [PDF]
TI: Himalayan Sackung and Associations to Regional Structure
AU: * Shroder, J F
EM: jshroder@mail.unomaha.edu
AF: Univ. of Nebraska at Omaha, Dept. of Geography & Geology, Omaha, NE 68182 United States
AU: Bishop, M P
EM: bishop@data.unomaha.edu
AF: Univ. of Nebraska at Omaha, Dept. of Geography & Geology, Omaha, NE 68182 United States
AU: Olsenholler, J
EM: jolsenho@cosmos.unomaha.edu
AF: Univ. of Nebraska at Omaha, Dept. of Geography & Geology, Omaha, NE 68182 United States
AB: Recognition of sackung slope failure or deep-seated, rock-slope deformation in the Himalaya has been rather limited, in part because: (1) many geoscientists do not recognize its characteristics; (2) large-scale aerial photographs and topographic maps used to identify the characteristic surficial, topographic manifestations of the failure type are commonly low-level state secrets in that region; and (3) no systematic survey for sackung has ever been made in the Himalaya. In the Pakistani-controlled, western Himalaya, some unconventional access to aerial photographs in the Kaghan and Nanga Parbat areas allowed first recognition of several characteristic ridge-top grabens and anti-slope scarps. Later release of declassified, stereo imagery from the CORONA and KEYHOLE satellite series enabled discovery of other examples in the K2 region. Comparison of mapped sackung failures with geologic base maps has demonstrated some coincidence of sackung with various structural trends, including synformal structures in upper thrust plates or along the traces of high-angle faults. In all probability these structural trends have provided plentiful ancillary planes of weakness along which gravitationally driven sackung is facilitated. Sackung failure in the Himalaya appears to be a spatially scale-dependent manifestation of a gravitational-collapse continuum of the brittle, upper crust, mainly involving mountain ridges. In contrast, gravitational collapse of the whole range may involve some similar failures but also include listric faulting, as well as subsidence movement into zones of ductility at depth. Temporal scale dependence of sackung may also be threshold dominated, wherein initial long-continued, slow failure ultimately leads to the commonly catastrophic rock-slope collapses recently recognized throughout the western Himalaya and now differentiated from their original mismapping as glacial moraines. Such sackung in Himalayan terrain undergoing active deglaciation from global warming may increase catastrophic slope-failure hazard.
DE: 1625 Geomorphology and weathering (1824, 1886)
DE: 1824 Geomorphology (1625)
DE: 8010 Fractures and faults
SC: Hydrology [H]
MN: 2003 Fall Meeting