Geomorphic evidence for mid-late Holocene higher sea level from southeastern Australia

摘要

An elevated sheltered pocket beach sequence at Batemans Bay, NSW, Australia, composed of shelly fine- to medium-grained sand provides geomorphic evidence of higher than present sea level during the mid-late Holocene. The sequence is composed of a sand facies with variable amounts of shell and contains a number of well-defined dipping reflectors identified in ground penetrating radar (GPR) profiles indicative of a small prograded beach system. This beach succession is overlain by storm or tsunami deposits. The beach deposit accumulated between 2500 and 5000 cal BP under relatively high energy conditions within a more open immature estuary during a period of higher sea level. Both deposits have been preserved by a low energy mangrove facies that accumulated after the recent fall in sea level cut off ocean wave activity from the area approximately 2000-2500 cal BP. This beach sequence provides new evidence for a period of higher sea level 1-1.5 m higher than present that lasted until at least c. 2000-2500 cal BP and adds complementary geomorphic evidence for the mid to late Holocene sea-level highstand previously identified along other parts of the southeast Australian coast using other methods.