Publication Date:
2010-11-30
Description:
An internally consistent 3D structural model for the central and southern Western Foothills Fold and Thrust Belt (WFFTB) was constructed from serial balanced cross sections. The level of exposure, thrust sheet thickness and degree of internal complexity observed within the WFFTB are influenced by the presence of pre-existing normal faults. Most of the faults of the Western Foothills started their activity before the deposition of the Cholan Formation (c. 3.5 Ma). Out-of-sequence faulting is common and may be due to localized erosion and fault inversion. Basement appears to be more significantly involved towards the south where a new structure, the sub-Yuching uplift, has been identified. The estimated aggregate displacement on WFFTB thrusts is uniformly about 40 km on the central segment cross sections, even in the region of greatest basement involvement. Total thrust displacement starts to decrease on the southernmost cross sections, which may be coincident with the transition from collision in the north to accretion. The restored position of the pre-existing normal faults places them as far east as the present-day Coastal Range. The WFFTB rocks must have been stripped off the Eurasian margin before significant burial could take place.
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