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Moore J C Mascle A et al 1990 Proceedings of the Ocean Drilling Program Scientific Results Vol 110 17 G R A I N F A B R I C M E A S U R E D U S I N G M A G N E T I C S U S C E P T I B I L I T Y A N I S O T R O P Y I N DEFORMED SEDIMENTS OF T H E BARBADOS ACCRETIONARY PRISM LEG HO1 M W Hounslow 2 3 ABSTRACT The anisotropy of magnetic susceptibility documents the generation of tectonically produced fabrics in sediments that macroscopically show no evidence of this disruption The fabric observed in initial accretion is largely produced by overprinting of the original sedimentary susceptibility anisotropy by an E W horizontal tectonic shortening and vertical extension The response of the sediments to stress during initial accretion is variable particularly near the sediment sur face and appears to reflect the inhomogeneous distribution of strain rate in the overthrust sequence The susceptibility anisotropy of sediments possessing scaly fabric is consistent with the strong orientation of Phyllosilicates seen in thin section producing a Kmin normal to the scalyness The slope sediments deposited on the accreted sequence are also af fected by tectonic shortening The accreted sequences at Sites 673 and 674 show a complex history of fabric modifica tion with previous tectonic fabrics overprinted by later fabric modifications pointing to continued tectonic shortening during the accretion process The form of the susceptibility anisotropy axes at Sites 673 and 674 is consistent with NESW shortening probably reflected in the NW SE surface expression of the out of sequence thrusts The susceptibility anisotropy appears to document a downhole change in the trend of shortening from E to W at the surface to more NESW at depth probably as a result of the obliquely trending basement ridge the Tiburon Rise INTRODUCTION To a large extent the grain fabric of a rock is indicative of the stresses that were imposed upon it during its formation and therefore the fabric can be used as a

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