Sahul

Sahul
listfiles/Kanguole · CC BY-SA 4.0 · source
Name	Sahul
Countries	Australia, Papua New Guinea, Indonesia
Region	Oceania

Sahul is the Pleistocene continental landmass that connected present-day Australia, New Guinea, and the Tanimbar Islands when lower sea levels exposed the continental shelf known as the Sahul Shelf. It functioned as a biogeographic province and migration corridor linking the terrestrial faunas and floras of these islands and served as a setting for significant human dispersals associated with Out of Africa migrations and later regional adaptations. Research into Sahul integrates data from marine geology, archaeology, paleoclimatology, and biogeography to reconstruct its changing margins and biological communities.

Geography and geology

Sahul comprised the exposed parts of the Australian continental margin, including the Great Barrier Reef edge, the Gulf of Carpentaria, the Arafura Sea and the Torres Strait region, extending to the Sahul Shelf and adjoining the Sunda Shelf across the modern Lesser Sunda Islands. Tectonically, Sahul sits on the ancient Australian Plate whose collision with the Pacific Plate and the Indian Plate influenced uplift and basin formation such as the Timor Trough and the Banda Sea basins. Sediment cores from the Coral Sea and seismic reflection profiles across the Arafura Shelf reveal layered deposits and paleoshorelines that chronicle repeated marine transgressions linked to glacial cycles documented at sites like Lake Eyre and the Murray-Darling Basin.

Pleistocene land bridge and sea-level changes

During glacial maxima of the Pleistocene epoch, global ice volume locked water in continental ice sheets such as the Laurentide Ice Sheet and the Fennoscandian Ice Sheet, lowering sea level by as much as ~120 meters and exposing the continental shelves that formed Sahul. The resulting land bridge between New Guinea and Australia persisted during stadials and interstadials recorded in oxygen isotope records from Vostok and EPICA ice cores. Rapid meltwater pulses tied to events like Meltwater Pulse 1A caused marine transgression that fragmented Sahul into the modern islands and continental Australia. Paleoshoreline reconstructions using radiocarbon-dated coral terraces at Ningaloo Reef and optically stimulated luminescence records from the Kimberley clarify timing and extent of exposure and inundation.

Flora and fauna

Sahul hosted a distinctive assemblage combining Gondwanan lineages and Indo-Pacific immigrants: megafaunal taxa such as Diprotodon, Megalania, and Procoptodon coexisted with endemic marsupials including Thylacoleo and diverse monotremes related to Platypus ancestors. Avifauna included ancestral forms related to cassowaries and cockatoos, while paleobotanical proxies from pollen records in New Guinea Highlands and the Nullarbor Plain indicate sclerophyll forests, eucalyptus-dominated woodlands, and montane rainforests. Marine incursions brought reef-associated taxa like tridacna clams and coral genera recorded at Coral Sea sites, and biogeographic patterns elucidated by phylogeography link Sahul taxa to Gondwanan distributions evidenced in Antarctica fossils and modern relatives in South America.

Human migration and archaeology

Archaeological evidence places anatomically modern human occupation on Sahul by at least ~65,000 years ago, with sites in the Arhem Land and Lake Mungo regions providing lithic assemblages and human remains that inform on early occupation. Stone tool technologies resembling those from Southeast Asia and the Greater Sunda Islands appear alongside shell midden deposits and hearth features excavated in the Madjedbebe rock shelter and submerged contexts on the Sahul Shelf. Models of seafaring capability and navigation consider crossings of the Wallace Line and routes via the Lesser Sunda Islands and the Bird's Head Peninsula into Sahul. Genetic studies linking modern populations of Indigenous Australians, Papua New Guineans, and Austronesian-speaking groups draw on ancient DNA and mitochondrial haplogroup phylogenies to reconstruct demographic expansions, founder effects, and subsequent contact events with populations represented in Lapita archaeological horizons.

Paleoclimate and environmental change

Paleoclimate proxies from speleothems in the Kimberley caves, marine isotope stages recorded in ODP cores from the Timor Sea, and pollen sequences from peat deposits in the Papuan lowlands chart fluctuations in monsoon intensity, aridity, and forest cover across Sahul during glacial–interglacial cycles. Shifts in the Intertropical Convergence Zone and the strength of the El Niño–Southern Oscillation influenced fire regimes inferred from charcoal layers and megafaunal habitat contraction inferred from extinction chronologies. Coupled climate models linking boundary conditions used by the Paleoclimate Modelling Intercomparison Project replicate vegetation mosaics and precipitation gradients that align with archaeological signals of mobility and resource use.

Cultural significance and modern usage

In contemporary scholarship and heritage discourse, Sahul functions as a framework for discussing biogeographic history, indigenous occupation, and conservation bioregions spanning Queensland, Northern Territory, and the Papua New Guinea Highlands. Museums such as the Australian Museum and the National Museum of Natural History (Netherlands) curate megafaunal fossils and archaeological artifacts that connect Indigenous knowledge holders, including Aboriginal Australians and Highlands Papuans, with scientific narratives. The term also appears in paleontological and paleoenvironmental literature, regional planning for marine protected areas like the Great Barrier Reef Marine Park, and transnational collaborations including the International Union for Conservation of Nature and UNESCO World Heritage assessments of cultural landscapes.

Category:Pleistocene Oceania