Successive foraminiferal faunas and inferred palaeoenvironments associated with the postglacial (Holocene) marine transgression, Gulf St Vincent, South Australia John H. Cann, 1 * Colin V. Murray-Wallace, 2 Naomi J. Riggs 2 and Antonio P. Belperio 3 ( 1 School of Natural and Built Environments, University of South Australia, Mawson Lakes SA 5095, Australia; 2 School of Earth and Environmental Sciences, University of Wollongong, NSW 2522, Australia; 3 Minotaur Resources Ltd, 247 Greenhill Road, Dulwich SA 5065, Australia) Received 10 January 2005; revised manuscript accepted 16 August 2005 Abstract: Gulf St Vincent is one of a pair of elongate, triangular, shallow water embayments into the southern coast of continental Australia. From the southern floor of this embayment, within a shallow basin-like depression where present-day water depth is about 40 m, vibracore SV23 recovered c. 4 m of late Quaternary sediments. The uppermost 1.5 m of this core comprises postglacial (Holocene) marine deposits; six radiocarbon ages for the interval 64 /130 cm downcore are all around 10000 cal. yr BP, while two for 18  /24 cm are several thousandyears younger. Radiocarbon analysis of an oyster shell at 154 cm yielded a minimum age of c. 37000 cal. yr BP. Well-preserved benthic foraminifera are abundant in all the recovered sediments. The early phase of Holocene marine sedimentation in Gulf St Vincent was marked by the development of a marginal marine, perhaps lacustrine to estuarine environment, as signified by the presence of oogonia, gypsum crystals and the foraminifera Miliolinella labiosa and Elphidium cf. articulatum. Development of seagrass meadows followed; these were inhabited by Nubecularia lucifuga and Discorbis dimidiatus . As the marine transgression proceeded, the environment remained somewhat restricted, as indicated by Ammonia beccarii, but numbers of this species declined giving way to Massilina milletti as conditions began to resemble those of the modern Gulf St Vincent. Culmination of the transgression provided the conditions necessary for the dominance of Ammobaculites reophaciformis and Flintina triquetra. A. reophaciformis and F. triquetra therefore record the final episode of the transgression and transition to the modern, deeper water environment. At several lower horizons they also occur as conspicuous spikes, equivalent to their modern abundance. These spikes, which coincide with equivalent decreased numbers of A. beccarii, are interpreted to represent downward bioturbation of the overlying deeper water sediment. Key words: Foraminifera, bioturbation, oogonia, Holocene, marine transgression, postglacial, Gulf St Vincent, South Australia. Introduction Gulf St Vincent and the adjoining Spencer Gulf are elongate, triangular marine embayments into the southern margin of the Australian continent (Figure 1). Gulf waters are relatively shallow, mostly less than 40 m deep in Gulf St Vincent. Regional annual rainfall is low so there is minimal input of siliciclastic sediment from fluvial sources. In shallow, subtidal coastal areas, luxuriant seagrass meadows and algae support marine invertebrate faunas that have generated widely dis- tributed carbonate bioclasts. Entire and comminuted mollusc shells and foraminifera are abundant in the surficial sediments *Author for correspondence (email: john.cann@unisa.edu.au) The Holocene 16,2 (2006) pp. 224  /234 # 2006 Edward Arnold (Publishers) Ltd 10.1191/0959683606hl907rp