The Late Quaternary History of Part of the Mid-North Coast, New South Wales, Australia

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FOR THREE years the writer has studied the geomorphological and sedimentological history of coastal areas in eastern Australia. This paper is a summary of the late Quaternary history of part of the mid-north coast, New South Wales, between Scott's Head and Crescent Head, with reference to some areas south of the divide separating the drainage systems of the Macleay and Hastings rivers (Figs. I and 2). The area between Crescent Head and Port Macquarie will be described in another publication. The mid-north coast is characterized by a series of arcuate bays separated by bedrock headlands. Although formerly embayed with offshore islands until late Pleistocene times, the coast has been straightened by dual barrier systems. In New South Wales, these have been termed Inner (Pleistocene) and Outer (Recent)1 barriers by T. Langford-Smith and B. G. Thom (in press). The barriers are separated by inter-barrier lagoonal swamps which represent a time interval between the formation of the two systems. One of the critical problems facing the geomorphologist in eastern Australia is to determine accurately the heights of depositional and eroded coastline landforms. This problem is complicated by the lack of accurate datum points and topographical maps, as well as the presence of dense vegetation in many areas. Because accurate topographical maps of the study area were not available, morphometric tests could not be completed to define particular surfaces prior to field investigations. All heights above mean sea-level were determined by dumpy level traverses (based on local bench marks or sea-level datum) or by a survey aneroid, checked to a datum before and after each reading. These heights were supplemented with those shown on maps especially compiled for flood mitigation schemes. More than 200 shallow and deep boreholes were sunk with a high-frequency vibration core-sampler, and by hand augering. Petrological and sedimentological studies were made of samples collected from various coastal depositional environments. These results have been evaulated in another publication (Hails, 1967). Figure 2 is the first geomorphological map of the area. This was compiled from information obtained during field investigations, supplemented by aerial photographic interpretation and information obtained from boring programmes and other sources.