New field data combined with existing isotopic ages for the Western Province granites in peninsular Thailand allow a tentative kinematic history for the KMF and RF to be constructed:
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The KMF and RF are zones of major strike-slip faulting divided into four phases:
D1 low grade ductile dextral strike-slip shear complete before 87 Ma.
D2 medium to high grade ductile dextral strike-slip shear after 72 Ma and before 56 Ma.
D3 brittle sinistral and sinistral reverse oblique strike-slip shear after 52 Ma.
D4 brittle dextral strike-slip shear at about 23 Ma.
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Ductile dextral shear pre-dates both the India–Eurasia collision and ductile sinistral shear on the MPF and TPF, to which the KMF and RF had been assumed to be conjugate.
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They may instead have accommodated the southern margin of a band of orogenesis in western Sundaland, which may be linked to cessation of subduction southeast of the northern tip of Sumatra in the Late Cretaceous.
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Eocene–Oligocene D3 reactivation of the fault zones during regional extension under a broadly N–S maximum principal stress was coeval with basin development offshore, and the resumption of subduction around the south of Sundaland.
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Onshore transpression during D3 resulted in deep rooted positive flower structures which exhumed slivers of the metamorphic shear zone.
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Early Miocene inversion, particularly in the Cenozoic basins nearest the faults, may be linked to D4 strike-slip faulting across the fault zones.