In:
Journal of Geophysical Research: Solid Earth, American Geophysical Union (AGU), Vol. 105, No. B11 ( 2000-11-10), p. 25729-25741
Abstract:
The magnetic fabrics of the melange in the Shimanto accretionary complex of Okinawa Island were obtained from the anisotropy of magnetic susceptibility (AMS) data. The magnetic fabrics show a marked contrast between the structurally lower and upper parts of the melange; the lower part records deformation in the footwall of the decollement (D 1 ), whereas the upper part documents that in the hanging wall of the decollement (D 2 ). In the lower part of the melange the magnetic fabrics show good correlations with S 1 layer‐parallel foliation, reflecting strain geometries under layer‐perpendicular flattening. As S‐C fabrics were locally developed by heterogeneous shear during D 1 , some of the previous magnetic fabrics were rotated with S 1 . In this case, the resultant magnetic fabrics reflect “S” surfaces, and maximum AMS axes are reoriented parallel to shear directions without clear change in shape and anisotropy degree of the AMS ellipsoids. Thus “S” surfaces did not act as flattening planes but may represent the deformation through independent particulate flow and mechanical rotation. The lower part of the melange was pervasively sheared during D 2 , reflecting that it laid immediately above the decollement. However, D 1 magnetic fabrics were not modified because shear strain was accomplished by brittle microfaults without development of penetrative strain. In contrast, penetrative strain was significant in the upper part of the melange, resulting in the magnetic fabrics recording incremental strain associated with D 2 . Therefore deformation mechanism and proximity to a decollement play an important role on development of magnetic fabrics in a melange.
Type of Medium:
Online Resource
ISSN:
0148-0227
DOI:
10.1029/2000JB900251
Language:
English
Publisher:
American Geophysical Union (AGU)
Publication Date:
2000
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