Continental aridification and the vanishing of Australia\u27s megalakes

The nature of the Australian climate at about the time of rapid megafaunal extinctions and humans arriving in Australia is poorly understood and is an important element in the contentious debate as to whether humans or climate caused the extinctions. Here we present a new paleoshoreline chronology that extends over the past 100 k.y. for Lake Mega-Frome, the coalescence of Lakes Frome, Blanche, Callabonna and Gregory, in the southern latitudes of central Australia. We show that Lake Mega-Frome was connected for the last time to adjacent Lake Eyre at 50-47 ka, forming the largest remaining interconnected system of paleolakes on the Australian continent. The final disconnection and a progressive drop in the level of Lake Mega-Frome represents a major climate shift to aridification that coincided with the arrival of humans and the demise of the megafauna. The supply of moisture to the Australian continent at various times in the Quaternary has commonly been ascribed to an enhanced monsoon. This study, in combination with other paleoclimate data, provides reliable evidence for periods of enhanced tropical and enhanced Southern Ocean sources of water filling these lakes at different times during the last full glacial cycle. © 2011 Geological Society of America

Raised Coral Terraces at Malakula, Vanuatu, Southwest Pacific, Indicate High Sea Level During Marine Isotope Stage 3

International audienc

Carbon isotope variability in the bone collagen of red kangaroos (Macropus rufus) is age dependent: Implications for palaeodietary studies

Isotopic assessment of bone collagen is often used as an environmental tracer in both contemporary and palaeoenvironmental studies. However, variability in the isotopic composition of this tissue remains poorly understood for naturally occurring and wild populations of animals. In this study the stable carbon isotope composition of both diet and bone collagen was assessed for a population of red kangaroos (Macropus rufus). Animals sampled ranged in age from approximately 10 months to 15 years. The diet of this population, estimated from faeces collected in the field, varied from predominantly C-4 grasses in late summer ((sic)C-13-16,5%) to mostly C-3 herbage in late winter ((sic)C-13-22,5%), with a long-term average (sic)C-13 of between -19 and -20%. Bone collagen was enriched in(13)C by 3 to 4% in older animals relative to pouch young. Isotopic analysis of hair, used to assess more recent diet in individuals, indicated that diet selection was similar in all animals that had been weaned. We suggest that the most likely explanation for the age-dependent relationship in the (sic)C-13 of bone collagen occurs because milk (the only source of nutrition in suckling kangaroos) is not fractionated in the same manner as plant-derived carbon during its assimilation into skeletal tissue. If this is the case, then such a relationship should be most predominant in mammals that have low birth weights (relative to the adult mother) and gain significant weight from milk. Whatever the precise mechanism(s) for the observed fractionation, bone collagen of kangaroos seems to retain an isotopic memory of the carbon laid down prior to weaning, which takes several years to be diluted and replaced with carbon derived from an "adult" herbaceous diet. These results have implications for palaeoecological research where fossil skeletal tissue is used as dietary or environmental tracers particularly if the relative age of the animals sampled is unknown

Stable isotope record and its palaeoenvironmental interpretation for a late Middle Pleistocene speleothem from Victoria fossil Cave, Naracoorte, South Australia

A speleothem from Victoria Fossil Cave, South Australia, provides a continuous stable isotope record from 185 to 157 ka. Oxygen isotope analysis indicates that, at commencement of deposition, mean annual temperatures were much lower than at present and that between 178 and 162 ka regional surface temperatures were similar to today. Such high temperatures during an interstadial are surprising but may be attributable to increased continentality due to low sealevels. Carbon isotope analysis indicates the presence of an active vegetation cover dominated by C3 plants during the interstadial while a sparse vegetation dominated by C4 grasses appears to have been dominant during full-glacial conditions. Variations in moisture availability and vegetation productivity are probably closely related to stages in pressesional cycle. (C) 2000 Elsevier Science Ltd

From savannah to rainforest: changing environments and human occupation at Liang Lembudu, Aru Islands, Maluku (Indonesia)

[Extract] The Aru Islands lie near the edge of the Australian continental shelf in the Arafura Sea, approximately 150 km south of the coast of Papua (fonner1y Irian Jaya). For at least the first 40,000 years of occupation of Sahul they formed part\ud of a continuous land bridge linking Australia and New Guinea. During this time they would have been a dissected limestone plateau on the exposed Carpentarian Plain. About 14,000 years BP sea level rose and began to encircle the island group, separating it from Australia and by 11,500 years BP it was completely separated from New Guinea. The presence on Am of numerous marsupials, the cassowary and Birds of Paradise attest to this shared history, a fact first recognised by Darwin's co-discoverer of the theory of evolution by natural selection, the naturalist Alfred Russel Wallace (Wallace 1869).\ud \ud While the waters to the east of the Aru Islands are relatively shallow, reflecting the previous land bridge with Papua and NW Australia, the continental shelf to the west descends steeply. Along most of the northwest coastline of the Am Islands the 100 m isobath is located as little as 10 km away (Figure 15.1).\ud Recent research into sea level changes in the Australian region indicates that between 70,000 and 40,000 years BP sea level was between -50 and -90 m below its present position (Chappell 1994). This means that along most of the north and northwest coast of Australia the earliest evidence for colonisation will now be submerged and the earliest date for colonisation probably unknowable. Sites along the greater part of the present coastline may have been located up to 200 km inland at the time of their initial occupation. The steeply shelving offshore profile on the west coast of Aru makes it one of the few entry points into Sahul where evidence of early settlement is likely to be preserved