Modern and Pleistocene rocky shore sequences along carbonate coastlines, southwestern Australia

Abstract

Modern rocky shores on the coast of southwestern Australia commonly are cut into Pleistocene carbonate rocks. These rocky shores provide a wealth of data on morphology and stratigraphic products that are useful for studies in ancient sequences as well as studies in Quaternary sea-level history. Four types of rocky shore are recognised: Type 1 with platform and notch and a full range of morphologic features; Type 2 with sandy beach; Type 3 with breccia; and Type 4 with truncated profile. These shore types are intergradational in space and laterally equivalent along the coast. Macro- and micromorphology, biology and sediments of rocky shores are closely related to various geomorphologic settings and tidal levels, because of the distribution and dominance of a variety of physical, chemical and biological processes acting on these shores. As a result, many of the features on modern rocky shores are diagnostic of subenvironments and indicate types of processes which have been operating. Diagnostic morphologic, sedimentologic and biologic features of modern rocky shores were used to interpret palaeoenvironments of Pleistocene rocky sequences of the Perth Basin, suggesting that the results of this study may be used to interpret similar deposits elsewhere in Pleistocene and perhaps older formations. The information can be used to identify rocky shores in a gross context, as well as to identify components, environments and processes within ancient rocky shore systems.