HR: 1340h
AN: T23D-1644    [Abstracts]
TI: Rigid Basement and the Evolution of the Pakistani Convergent Margin
AU: * Haq, S S
EM: shaq@purdue.edu
AF: Department of Earth and Atmospheric Sciences, Purdue University, 550 Stadium Mall Road Civil Eng. Bldg., West Lafayette, in 47907-2051,
AU: Davis, D M
EM: ddavis@notes.cc.sunysb.edu
AF: Department of Geosciences, Stony Brook University, ESS Building, Stony Brook, ny 11790- 2100,
AB: In Pakistan, along the western edge of the Indian-Eurasian collision there are a series of fold-and-thrust belts that have highly variable strikes and shortening directions with respect to the local relative plate motion. Much of the complexity in the deformation of this margin can easily be explained by the shape, location, and long-term motion of a fragment of relatively rigid oceanic lithosphere that is believed to underlie the Katawaz Basin. In particular, the deformation that has formed the Sulaiman Range and Lobe is a direct consequence of the Katawaz Basin's over all higher strength. The presence of deformed sedimentary strata in the basin comparable to those presently found in the Indus delta are indicative of the basins long-term motion parallel to the Chaman fault zone. In Pakistan, the transition in the strike and shortening directions occurs over a short distance compared to the width of the fold-belts and the length of the margin. We present a series of analog models along with detailed quantitative analysis that we compare to the observed deformation as indicated by both geologic and geophysical data. By quantitatively distinguishing the style and magnitude of deformation in each of a variety of analog experiments we are able to evaluate the viability of various alternative models that have been proposed for fold- belt formation and evolution of the Pakistani margin, including our favored model. The model that best fits the geological and geophysical evidence suggests that the complexity of the Pakistani margin is a result of the long- term northeastward migration of the Katawaz basin along the curving trend of the Chaman fault zone. The vertically integrated mechanical strength of the Katawaz basin allows it to act as a strong ‘backstop' that has relative motion to both stable India and stable Eurasia. This northeastward motion and the resulting clockwise rotation of the Katawaz ‘block' during the margin's development can explain the location and intensity of eastward shortening and the pattern of seismicity observed in the Sulaiman Lobe and range, the formation of Kingri Fault and Sibi reentrant.
DE: 8104 Continental margins: convergent
DE: 8108 Continental tectonics: compressional
DE: 8118 Dynamics and mechanics of faulting (8004)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting