Aboriginal artefacts on the continental shelf reveal ancient drowned cultural landscapes in northwest Australia

This article reports Australia’s first confirmed ancient underwater archaeological sites from the continental shelf, located off the Murujuga coastline in north-western Australia. Details on two underwater sites are reported: Cape Bruguieres, comprising > 260 recorded lithic artefacts at depths down to −2.4 m below sea level, and Flying Foam Passage where the find spot is associated with a submerged freshwater spring at −14 m. The sites were discovered through a purposeful research strategy designed to identify underwater targets, using an iterative process incorporating a variety of aerial and underwater remote sensing techniques and diver investigation within a predictive framework to map the submerged landscape within a depth range of 0–20 m. The condition and context of the lithic artefacts are analysed in order to unravel their depositional and taphonomic history and to corroborate their in situ position on a pre-inundation land surface, taking account of known geomorphological and climatic processes including cyclone activity that could have caused displacement and transportation from adjacent coasts. Geomorphological data and radiometric dates establish the chronological limits of the sites and demonstrate that they cannot be later than 7000 cal BP and 8500 cal BP respectively, based on the dates when they were finally submerged by sea-level rise. Comparison of underwater and onshore lithic assemblages shows differences that are consistent with this chronological interpretation. This article sets a foundation for the research strategies and technologies needed to identify archaeological targets at greater depth on the Australian continental shelf and elsewhere, building on the results presented. Emphasis is also placed on the need for legislation to better protect and manage underwater cultural heritage on the 2 million square kilometres of drowned landscapes that were once available for occupation in Australia, and where a major part of its human history must lie waiting to be discovered

Stone artefacts on the seabed at a submerged freshwater spring confirm a drowned cultural landscape in Murujuga, Western Australia

We report the discovery and identification of five ancient stone artefacts associated with a submerged freshwater spring at the underwater archaeological site WH1 in Murujuga (Dampier Archipelago), Western Australia. A limiting date applied to the site based on timing of inundation suggests it was occupied in the Late Pleistocene or Early Holocene. The site is situated well below the intertidal zone having been recorded at 14 m depth in Flying Foam Passage. This discovery highlights the high potential of these submerged springs as archaeological survey targets. We discuss results of a recent survey that expands the number of confirmed artefacts located at WH1 and the geomorphological context in a large calcareous depression associated with a freshwater source. This study demonstrates how submerged landscape research using a suite of technologies can reveal archaeological assemblages in this tropical geomorphological environment, and that adapted techniques could be applied to other tropical conditions such as mangrove coasts, large deltaic plains, or reef-building environments. There are likely thousands of drowned archaeological sites on the continental shelf of the tropics, extending from the intertidal zone to the lowest point of the culturally occupied landmass, at approximately 130 m below modern sea level

The integrated cultural landscape of North Gidley Island : Coastal, intertidal and nearshore archaeology in Murujuga (Dampier Archipelago), Western Australia

Recent studies conducted in Murujuga Sea Country have confirmed that Indigenous Australian archaeology does not end at the modern shore. Since the earliest peopling of the Australian continent, sea levels have fluctuated, dropping as much as 130 m below modern mean sea-level during the Last Glacial Maximum (LGM). During this period, the continent (including Australia and New Guinea) represented a landmass one-third larger than present day Australia. As sea levels rose following the LGM, this extensive cultural landscape was inundated. The recent reporting of archaeological remains in a submerged context at Murujuga has enabled an integrated analysis of the archaeological landscape, based on direct evidence from archaeological sites that were originally formed on dry land, but are now located in intertidal and submerged environments. This study applies a landscape analysis centred on the submerged Cape Bruguieres channel site, and the Gidley Islands, where submerged, intertidal and coastal archaeology has been recorded. Aerial, pedestrian, and intertidal archaeological surveys were conducted to investigate the onshore and offshore landscape, providing new evidence with which to place the stone artefacts in the Cape Bruguieres channel into a wider context. Rock art engravings, grinding patches, quarries and upstanding stones – some of which are in the intertidal zone – point to the use of a landscape that is now submerged and to the possibility of discovering new underwater sites. By integrating evidence from subtidal and intertidal contexts with the onshore record, we explore the cultural landscape above and below the ‘waterline’ as a continuum

A multi-scalar approach to marine survey and underwater archaeological site prospection in Murujuga, Western Australia

During the past 20,000 years approximately one-quarter of the continental landmass of Australia was inundated by postglacial sea-level rise, submerging archaeological evidence for use of these landscapes. Underwater archaeological sites can offer substantial insights into past lifeways and adaptations to rapidly changing environments, however the vast scale of inundation presents a range of challenges in discovering such sites. Here we present a suite of methods as a model methodology for locating sites in submerged landscapes. Priority areas for survey were based on palaeoenvironmental contexts determined from the onshore archaeological record. Remote sensing was used to identify seabed composition and indicators of palaeolandscapes where high potential for human occupation and site preservation could be identified in Murujuga (or the Dampier Archipelago), northwestern Australia. Target locations were surveyed by scientific divers to test for the presence of archaeological material. Application of this methodology resulted in the discovery of the first two confirmed sub-tidal ancient Aboriginal archaeological sites on Australia's continental shelf. Survey methods are discussed for their combined value to identify different classes of landscapes and archaeological features to support future underwater site prospection

Correction: Aboriginal artefacts on the continental shelf reveal ancient drowned cultural landscapes in northwest Australia.

[This corrects the article DOI: 10.1371/journal.pone.0233912.]