Imbricate and fitted fabrics in coastal boulder deposits on the Australian east coast

Abstract

Boulder deposits that exhibit a tightly interlocked or fabric are common along the coast of New South Wales and other coasts. The fitted fabric, in which adjacent clasts are packed in a three-dimensional interlocking mass, gives considerable stability to boulder deposits and enables them to resist movement even in extreme storms on exposed, high-energy coastlines. A radiocarbon age of 4780 ka on the cement of a calcite-cemented shell and rock breccia within the fabric of a fitted boulder deposit on the New South Wales central coast indicates that the boulders were deposited soon after the end of the postglacial marine transgression and that they have remained stable since that time. Other boulder deposits along the same coast show that boulder fitting can develop in less than a century, thereby imparting considerable stability and persistence to coarse marine elastic deposits.