HR: 1330h
AN: T42B-0296 [PDF]
TI: Mechanisms for creating accommodation space during early Tertiary sedimentation in Tibet.
AU: * Studnicki-Gizbert, C
EM: chrissg@mit.edu
AF: Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139 United States
AU: Burchfiel, B C
EM: bcburch@mit.edu
AF: Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139 United States
AB:
The Tibetan plateau is for the most part underlain by rocks of pre-Cenozoic age, a fact that has hindered the identification
of Cenozoic shortening structures that can be unequivocally related to the effects of India-Asia collision. Notably, however,
the Qiangtang block contains a number of small, short wavelength basins filled with terrestrial sediments of early Tertiary
age. Where these basins have been well studied, sedimentation is recognized as having occurred coevally with compressional
deformation. The classic treatment of compressional basins appeals to accommodation space created by the flexure of an
elastic plate in response to loads created by adjacent thrust fault bound ranges. It is unlikely that the Tertiary basins of
the Qiangtang block formed in this manner. The wavelength of a classically modelled flexural basin is a basically a function
of the thickness of the elastic plate and the density difference between sedimentary fill and ductile material underlying the
plate. Assuming a model of elastic flexure, the very small wavelengths (5 - 30km) characteristic of Qiangtang basins would
then imply extremely thin (~ 1-5 km) effective elastic plate thicknesses. These very low values are difficult to reconcile
with any reasonable characterization of crustal rheology. Instead, these relatively small basins likely record the creation
of accommodation space created by differential uplift across the strike of folds and faults. Stratal geometries and
sedimentation rates reflect the kinematics and geometries of local compressional structures and the mechanical basis for the
creation of accommodation space remains uncertain. Finally, the origin of these basins makes it unlikely that early Tertiary
sedimentation represents a significant fraction of the upper crust of Tibetan plateau.
DE: 8102 Continental contractional orogenic belts
DE: 8105 Continental margins and sedimentary basins
DE: 9320 Asia
DE: 9604 Cenozoic
SC: Tectonophysics [T]
MN: 2003 Fall Meeting