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Deformation process and kinematics of mélange in the Early Cretaceous accretionary complex of the Mino‐Tamba Belt, eastern southwest Japan
Author(s) -
Fukui Akiko,
Kano Kenichi
Publication year - 2007
Publication title -
tectonics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.465
H-Index - 134
eISSN - 1944-9194
pISSN - 0278-7407
DOI - 10.1029/2006tc001945
Subject(s) - geology , cretaceous , subduction , paleontology , clastic rock , accretionary wedge , sinistral and dextral , mesozoic , shear (geology) , seismology , structural basin , tectonics
The Kanayama unit of the Mesozoic Mino‐Tamba accretionary complex in eastern southwest Japan is a thick mélange unit composed mainly of abundant muddy matrix and variously sized clasts of chert, hemipelagic siliceous mudstone, and sandstone. Two episodes of deformation formed the mélange fabrics: the first involved fragmentation of sandstone layers in response to mud injections; the second involved layer‐parallel, noncoaxial shear that resulted in the mixing of pelagic to terrigenous clasts and the formation of S‐C‐like asymmetric fabrics with scaly foliation. The S‐C fabrics exhibit a predominantly sinistral shear sense in plan view. After fold and tilt corrections, the restored slip motion inferred from the S‐C fabrics indicates a bulk top‐to‐the‐south shear. Combining the unit's terminal fossil age and radiometric age with a regional plate reconstruction model, these data suggest that the Kanayama mélange formed along a décollement during oblique subduction of the Izanagi plate in the Early Cretaceous.