Structural geometry and timing of deformation in the Chainat duplex, Thailand
Published:January 01, 2007
M. Smith, S. Chantraprasert, C. K. Morley, I. Cartwright, 2007. "Structural geometry and timing of deformation in the Chainat duplex, Thailand", Tectonics of Strike-Slip Restraining and Releasing Bends, W. D. Cunningham, P. Mann
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The Chainat duplex is about 100 km in a north–south direction, and was developed along the predominantly sinistral Mae Ping fault zone, which was active during the Cenozoic. The duplex is manifested as eroded, north–south- and NW–SE-striking outliers of Palaeozoic and Mesozoic rocks rising from the surrounding flat plains of the Central Basin (a Pliocene–Recent post-rift basin). Satellite images, geological maps and magnetic maps have been used to reconstruct the structural geometry of the duplex, which is composed of a series of north–south-striking ridges, bounded to the north and south by NW–SE-striking faults. Overall, the duplex has the geometry of analogue restraining-bend models with relatively low displacement. No well-developed duplex-traversing short-cut faults linking the principal displacement zones are apparent. The duplex shows evidence for widespread sinistral motion, as well as some dextral reactivation the latter of which is particularly marked in the eastern part of the duplex. The main sinistral activity ended at about 30 Ma: subsequently, minor, episodic reactivation of the duplex may have occurred. Detailed timing of events cannot be determined from structures within the duplex, but the evolution of adjacent rift basins suggests that stresses developed during episodes of inversion may have also caused reactivation of strike-slip faults (sinistral for NW–SE to north–south striking faults) during the Miocene. Minor episodic dextral motion may also have been of Late Oligocene–Miocene and/or Pliocene–Recent age.
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Tectonics of Strike-Slip Restraining and Releasing Bends
Restraining and releasing bends are common, but enigmatic features of strike-slip fault systems occurring in all crustal environments and at regional to microscopic scales of observation. Regional-scale restraining bends are sites of mountain building, transpressional deformation and basement exhumation, whereas releasing bends are sites of topographic subsidence, transtensional deformation, basin sedimentation and possible volcanism and economic mineralization. Because restraining and releasing bends often occur as singular self-contained domains of complex deformation, they are appealing natural laboratories for Earth scientists to study fault processes, earthquake seismology, active faulting and sedimentation, fault and fluid-flow relationships, links between tectonics and topography, tectonic and erosional controls on exhumation, and tectonic geomorphology.
This volume addresses the tectonic complexity and diversity of strike-slip restraining and releasing bends with 18 contributions divided into four thematic sections: (1) a topical review of fault bends and their global distribution; (2) bends, sedimentary basins and earthquake hazards; (3) restraining bends, transpressional deformation and basement controls on development; (4) releasing bends, transtensional deformation and fluid flow.