The inheritance of soil fabric from joints in the parent rock

The origin of ped faces in subsoils has been variously ascribed to the activities of organisms, stress-strain history and to alternating wetting and drying cycles. At three sites in the Sydney Basin the orientation of ped faces in the in situ B horizons of soils developed in dolerite and shale were measured and found to be similar to the orientation of planar joints in the parent rock. Joints in the rock, when inherited by the soil material, provided flaws which could be exploited by shrink and swell phenomena, gradually becoming permanent features. Horizontal ped faces appeared to be inherited joint or bedding planes, affected by the slope of the site to the extent that their dip increased in a downslope direction. This work confirmed previous soil fabric studies by Lafeber (1965) and demonstrated fabric anisotropy and inheritance from the parent rock.