Aspartic acid racemisation dating of mid-Holocene to recent estuarine sedimentation in New South Wales, Australia: a pilot study C.R. Sloss * , C.V. Murray-Wallace, B.G. Jones, T. Wallin School of Earth and Environmental Sciences, University of Wollongong, Northfield Avenue, Building 41.G33, Wollongong NSW 2522, Australia Received 9 April 2003; received in revised form 29 June 2004; accepted 20 July 2004 Abstract The degree of aspartic acid racemisation measured in radiocarbon-dated specimens of fossil estuarine molluscs, collected from Lake Illawarra, a Holocene barrier estuary in New South Wales, Australia, is evaluated in the context of results of laboratory-induced racemisation established in heating (simulated ageing) experiments. The general kinetic trend of aspartic acid racemisation in both heating experiments and fossil molluscs Anadara trapezia and Notospisula trigonella conforms to a model of apparent parabolic kinetics. Using the apparent parabolic kinetic model, numeric ages based on the degree of aspartic acid racemisation in the fossil molluscs have been calculated. An aminostratigraphy of the Lake Illawarra Holocene basin fill has been established based on the extent of aspartic acid racemisation measured in 29 specimens of fossil molluscs. Aspartic acid d/l ratios in A. trapezia and N. trigonella range from 0.079F0.005 to 0.436F0.004, representing an age range from b50 to ca. 5750 years. The aspartic acid chronology has been used to quantify rates of sedimentation within Lake Illawarra over the course of the Holocene and since European settlement. The data indicate that, for much of Lake Illawarra, the rate of sedimentation during Holocene time was b1 mm/ year. Following European settlement within the surrounding drainage basin, rates of sedimentation increased significantly to 2.6–7 mm/year. D 2004 Elsevier B.V. All rights reserved. Keywords: aminostratigraphy; estuarine bivalves; radiocarbon dating; sedimentation rates 1. Introduction Aspartic acid is one of the fastest racemising amino acids and, in temperate climate regions with suffi- ciently high effective diagenetic temperature (ca. 10– 18 8C), aspartic acid racemisation may be used to derive numeric ages over time scales of decades to centuries. Over the past decade, the degree of aspartic acid racemisation has been used to establish chronologies for Holocene successions in the Negev Desert (Goodfriend, 1991, 1992), the reworking of 0025-3227/$ - see front matter D 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.margeo.2004.07.009 * Corresponding author. E-mail address: crs03@uow.edu.au (C.R. Sloss). Marine Geology 212 (2004) 45 – 59 www.elsevier.com/locate/margeo