Australia: The Land Where Time Began

A biography of the Australian continent 

Yellabidde Cave, Northern Swan Coastal Plain, Southwestern Australia

Coastal midden sites dating to the Holocene are the main source of evidence of human occupation on the northern Swan Coastal Plain in Western Australia. In this paper Monks et al. present preliminary results of archaeological investigations at Yellabidde Cave, which is 9 km inland from the coast of the present. Cultural and palaeontological material was recovered from the sandy floor deposit of the limestone cave that was dated to 25,500 c. BP to the 19^th century. The first evidence of occupation of the region dating to the Pleistocene and Holocene indicated that Yellabidde Cave had been occupied intermittently through the Late Pleistocene and Holocene, which reflected dynamic human-environment relationships in near-coastal littoral environments of the present.

There is a long record of human occupation in southwestern Australia, sites having been discovered in the Leeuwin-Naturaliste and Perth regions, which demonstrate that there has been occupation from about 45 ka (Balme, 2014; Dortch, 2004; Pearce & Barbetti, 1981). There is limited comparable evidence of human activity prior to the Holocene in the northern Swan Coastal Plain (NSCP). Coastal midden sites have been the focus of archaeologists working on the NSCP (Dortch et al., 1984; Monks et al., 2015; Morse, 1982), though investigations of NSCP caves suggest these sites are able to provide detailed evidence for past human activities in inland ecosystems. In this paper Monks et al. report preliminary results from investigations that were carried out at a cave site that has been newly identified in the NSCP, which has contributed to ongoing research into human interaction in the past with diverse coastal plain environments.

Located 230 km north-northwest of Perth, Yellabidde Cave (Australian karst index number 6E-30), is in the country of the Amangu people, who named it following the discovery of emu (Yellabidde) eggshell throughout the deposit. The cave is situated about halfway between 2 chains of lakes in the NSCP, 9 km from the present coastline. Low limestone ridges are characteristic of the landscape, containing caves, sandplains, and biodiverse heathland of a type of known as kwongan (Beard, 1976). The entrance to Yellabidde Cave faces to the west, at the eastern end of a shallow doline, is easily accessible to both humans and large mammals.

In the front chamber 2 1x1 m squares that were 9 m apart were excavated, uncovering well-preserved archaeological and palaeontological deposits. Visible stratigraphy guided excavation, though to deep stratigraphic units, we executed an arbitrary excavation units (XUs) 2-2.5 cm thick. Excavation ceased at 155 cm below the surface (XU65) in Square 1, where at the base of the northern and eastern walls decomposing limestone was identified, and at 150 cm below the surface (XU72) in Square 2. In both squares cultural materials were found, such as stone artefacts, charcoal, and bone, and recorded in situ where possible. During section drawing charcoal was also plotted and collected. Nested 5 mm and 1.5 mm wire mesh sieves were used to dry-screen all excavated materials on site.

Stratigraphy and radiocarbon age determinations

In square 1, 9 stratigraphic units (SUs) were observed, each of which was comprised of loosely compacted sandy deposits with angular limestone clasts, which were mainly distinguished on texture and colour. There were 9 SUs revealed that were relatively damp and which contained a large organic component with minimal limestone clast inclusions. No apparent correlation was found between the sediments in the 2 squares, which suggested the cultural components formed under different conditions.

Charcoal samples were selected for radiocarbon dating from charcoal that had been recovered in situ, except in the lower SUs, where it was made necessary to date charcoal from sieve residues. All charcoal samples were AMS dated.

The lowest date from Square 1 (OZT017) was excluded, as it appeared to be intrusive. The dates obtained from the charcoal indicated that human occupation of the site was periodic from before the Last Glacial Maximum (LGM) up to the present. A charcoal sample recovered from sieve residues in SU9, 133 cm below the surface from Square 1 gave the earliest date of 25,500 cal. BP (OZT016). In Square 2 the deposit evidently accumulated more rapidly, with 1.5 m of deposit accumulating in less than 8,000 years. Monks et al. suggest Square 1 probably represents natural sedimentation that was relatively slow, and topped by occupation surfaces, while sediments in Square 2 were accumulated more rapidly, and were probably washed downslope from the front of cave.

Results and discussion

Cultural material was found in Yellabidde Cave deposit, which included burnt and unburnt bone, emu eggshell, stone artefacts, and charcoal, throughout the deposit. There were also other cultural material, which included small quantities of ochre and the remains of plants in the units dating to the Holocene in Square 1, which was associated with hearth features. The primary raw material for the manufacture of stone artefacts were quartz and limestone, a few of which appeared to be complete flakes, though most are fragmented flakes or flaked pieces that are believed to have resulted from the making or modification of tools.

Bones of terrestrial vertebrates are abundant throughout the deposit, and analysis of the faunal material is ongoing. The majority of the faunal material has been found to be comprised of mammals, and it is indicated by preliminary assessments that there are accumulations by humans, as well as such as owls, and other carnivores including chuditch (western quoll), Tasmanian devil, thylacine, and dingo. There is a small quantity of fish bone and marine mollusc shell that mostly date to the Middle to Late Holocene, which coincides with the start of midden formation along the NSCP coastline, and possibly after the midden site had stopped being used (Dortch et al., 1984; Monks et al., 2015).

A sequence of intermittent occupation of Yellabidde Cave from before the LGM through the terminal Pleistocene and the Holocene is represented by the archaeological evidence from Yellabidde Cave. It appears the use of the site was heaviest during the Holocene, though the presence of stone artefacts as well as other cultural material that are associated with a date prior to the LGM extends substantially the antiquity of occupation of the NSCP. Better understanding of the significance and extent of the deposit from the Late Pleistocene in Yellabidde Cave, as well as the nature and intensity of the use of land and resources on the NSCP during the Holocene will be the focus of future analysis.

Sources & Further reading

1. Monks, C., et al. (2016). "Pleistocene occupation of Yellabidde Cave in the northern Swan Coastal Plain, southwestern Australia." Australian Archaeology 82(3): 275-279.