The Moyjil site, south-west Victoria, Australia: shells as evidence of the deposit’s origin

Abstract

Characteristics of marine shellfish and other species found in a Last Interglacial (LIG) shell deposit at Point Ritchie (Moyjil) at Warrnambool in south-western Victoria have been compared to those from modern and LIG natural beach deposits, Holocene Aboriginal middens and modern Pacific Gull (Larus pacificus) middens. The research was aimed at determining whether properties such as shell speciation, size or taphonomy could identify the mechanism responsible for formation of the Moyjil deposit. Marine species found in the Moyjil deposit resemble those found in both Aboriginal and Pacific Gull middens and are non-discriminatory for the two types. Taphonomic properties such as wear and breakage pattern of opercula of the dominant species, Lunella undulata (syn. Turbo undulatus), are non-diagnostic because of post-depositional erosion and transport effects in the available specimens. The size of L. undulata opercula show clear bias toward larger individuals, in common with Aboriginal and seabird middens, when compared to natural shell deposits. Statistical analysis (ANOVA) of the size distributions shows a greater similarity of the Moyjil deposit to the two seabird middens than the two Aboriginal middens. Small individuals (operculum <10 mm diameter) of L. undulata as well as smaller shellfish species are absent from the seabird middens studied, but they are present in Aboriginal middens and in the Moyjil deposit. Overall, we conclude that shell properties alone are not sufficient to distinguish which predator collected the shellfish occurring in the deposit.