Apparent Association of Bryozoan Chert Artefacts and Quartz Geometric Microliths at an Open-Air Site, Arumvale, South-Western Australia

Abstract

Bryozoan chert is well known as a stone much used by Aborigines in western coastal districts of southwestern Australia from late Pleistocene times until approximately the attainment of mid-Holocene high sea levels, when the sources of this stone are thought to have been submerged (Glover 1984). Artefacts of this material thus provide a useful chronological marker, just as geometric microliths and other microlithic tools are generally thought to be indicative of late Holocene assemblages or sites. Excavations at Arumvale have revealed a succession of stone artefact assemblages similar in most respects to those at the Dunsborough and Walyunga open-air sites, which together provide what could be termed a provisional Holocene stone industrial sequence for this region (Ferguson 1981; Pearce 1977, 1978; cf. Anderson 1984:35-36). At all three sites, mid- to early Holocene or older assemblages consisting largely of quartz, but including varying quantities of bryozoan chert artefacts, are overlain by essentially quartz assemblages lacking significant numbers of bryozoan chert pieces. Featured in these later assemblages are geometric microliths and, in the case of Walyunga (Pearce 1978:Table l), several other distinctive 'late phase' tools. In 1973, one of us (CED) noticed the Arumvale site through the presence of stone artefacts eroding from the dune faces cut by Caves Road. The numerous bryozoan chert artefacts in these cuttings suggested that the site could be at least partly contemporaneous with the limestone cave site of Devil's Lair, 3 km NNW of Arumvale, and this has been confirmed by radiocarbon dates (Dortch 1979, 1984; cf. Dortch 1974:205, 1975a:l5). Although the stone artefact assemblages from the two neighbouring sites have much in common, their relationship within a hypothetical exploitative network has not been developed.