Thrust belt architecture of the central and southern Western Foothills of Taiwan
Fernando A. Rodriguez-Roa, David V. Wiltschko, 2010. "Thrust belt architecture of the central and southern Western Foothills of Taiwan", Hydrocarbons in Contractional Belts, G. P. Goffey, J. Craig, T. Needham, R. Scott
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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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Onshore fold–thrust belts are commonly perceived as ‘difficult’ places to explore for hydrocarbons and are therefore often avoided. However, these belts host large oil and gas fields and so these barriers to effective exploration mean that substantial unexploited resources may remain. Over time, evaluation techniques have improved. It is possible in certain circumstances to achieve good 3D seismic data. Structural restoration techniques have moved into the 3D domain and increasingly sophisticated palaeo-thermal indicators allow better modelling of burial and uplift evolution of source and reservoirs. Awareness of the influence of pre-thrust structure and stratigraphy and of hybrid thick and thin-skinned deformation styles is augmenting the simplistic geometric models employed in earlier exploration. But progress is a slow, expensive and iterative process. Industry and academia need to collaborate in order to develop and continually improve the necessary understanding of subsurface geometries, reservoir and charge evolution and timing; this publication offers papers on specific techniques, outcrop and field case studies.