CHARACTERIZATION OF SOFT-SEDIMENT DEFORMATION: DETECTION OF CRYPTOSLUMPS USING MAGNETIC METHODS

Abstract

Many workers have explored anisotropy of magnetic susceptibility (AMS) of sediments as an indicator of deformation. Several studies have used deflection of the eigenvector associated with the minimum in susceptibility, V3, as a criterion for deformation. We examine the AMS record of a well-exposed slump and find that although demonstrable deformation can occur without deflecting the V3 directions, an oblate AMS fabric is transformed into a triaxial fabric during initial deformation. Transformation of the fabric from oblate to triaxial appears to be highly correlated with an increase in natural remanent magnetization scatter, whereas deflection of the V3 axes is not. We suggest that subtle soft-sediment deformation can be detected by using AMS fabric.