SOIL-PORE AND PARTICLE ORIENTATIONS CAUSED BY ACTIVE FAULTING: A MICROMORPHOLOGICAL PERSPECTIVE

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Abstract
The orientations of soil pores and particles were studied in order to determine the effect of active faulting on soil pores and particles. The results from thin sections prepared from soil samples collected adjacent to an active fault indicate that the pores and particles show a significant preferred orientation, perpendicular to the maximum principal stress direction in the area, and there seem to be different stages of secondary calcite filling the voids and channels in the Bk horizon of the profile studied. This study indicates that soil pore and particle orientation analyses may help to determine maximum and minimum principal stress directions, amounts of horizontal and oblique displacements on an oblique-slip fault. Secondary calcite filling of voids and channels (K-horizon or caliche formation) may alter soil structure; therefore, orientation analyses may not be very conclusive. In this context, the development of the different stages of secondary calcite most likely indicates the magnitude of leaching before and after faulting in the Holocene epoch.