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- Cohen, Timothy, et al.
(författare)
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Continental aridification and the vanishing of Australia's mega-lakes
- 2011
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Ingår i: Geology. - 0091-7613 .- 1943-2682. ; 39, s. 167-170
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Tidskriftsartikel (refereegranskat)abstract
- 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 fi nal disconnection and a progressive drop in the level of Lake Mega-Frome represents a major climate shift to aridifi cation 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 peri-ods of enhanced tropical and enhanced Southern Ocean sources of water fi lling these lakes at different times during the last full glacial cycle.
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| 2. |
- Cohen, Timothy, et al.
(författare)
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Late Quaternary mega-lakes fed by the northern and southern river systems of central Australia : varying moisture sources and increased continental aridity
- 2012
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Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier BV. - 0031-0182 .- 1872-616X. ; 356:Special Issue, s. 89-108
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Tidskriftsartikel (refereegranskat)abstract
- Optically stimulated and thermoluminescence ages from relict shorelines, along with accelerator mass spectrometer 14C ages from freshwater molluscs reveal a record of variable moisture sources supplied by northern and southern river systems to Lake Mega-Frome in southern central Australia during the late Quaternary. Additional lacustrine, palynological and terrestrial proxies are used to reconstruct a record that extends back to 105 ka, confirming that Lakes Mega-Frome and Mega-Eyre were joined to create the largest system of palaeolakes on the Australian continent as recently as 50–47 ka. The palaeohydrological record indicates a progressive shift to more arid conditions, with marked drying after 45 ka. Subsequently, Lake Mega-Frome has filled independently at 33–31 ka and at the termination of the Last Glacial Maximum to volumes some 40 times those of today. Further sequentially declining filling episodes (to volumes 25–10 those of today) occurred immediately prior to the Younger Dryas stadial, in the mid Holocene and during the medieval climatic anomaly. Southern hemisphere summer insolation maxima are a poor predictor of palaeolake-filling episodes. An examination of multiple active moisture sources suggests that palaeolake phases were driven independently of insolation and at times by some combination of enhanced Southern Ocean circulation and strengthened tropical moisture sources.
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| 3. |
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| 4. |
- Cohen, Timothy, et al.
(författare)
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Late Quaternary mega-lakes of central Australia: varying moisture sources and increased continental aridity.
- 2010
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Ingår i: <em>EOS Transactions, </em><em>American Geophysical Union</em>, PP31B-1624. San Francisco, USA, Dec. 2010.. - Washington DC : American Geophysical Union.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Optically stimulated (OSL) and thermoluminescence (TL) ages from relict shorelines, along with accelerator mass spectrometer (AMS) 14C ages from freshwater molluscs reveal a record of mega-lake phases over the late Quaternary for Lake Mega-Frome, situated in the arid zone of South Australia. Additional lacustrine, palynological and terrestrial proxies are used to reconstruct a record that extends as far back as 105 ka and demonstrates that Mega-Frome was last joined to the adjacent mega-Eyre at 50 - 47 ka forming the largest palaeolake on the Australian continent. This time interval for hydrological decline coincides with the arrival of humans on the Australian continent and the demise of the mega-fauna. Since then, Mega-Frome has filled independently at 33 - 31 ka (Heinrich event 3) and at the termination of the Last Glacial Maximum (LGM) to depths far in excess of those seen today (up to 15 - 20 times modern lake volumes). Further evidence of subsequent lake-filling episodes is recorded immediately prior to the Younger Dryas, the mid Holocene and during the medieval climatic anomaly. We present evidence for multiple moisture sources over this time period with lake phases being driven by either an enhanced Southern Ocean circulation or an enhanced tropical moisture source or a combination of both. We show however, that southern hemisphere summer insolation maxima (monsoon proxy) is a poor predictor for past palaeo-lake filling episodes. This is the first palaeohydrological record for a large area of southern semi-arid Australia indicating a progressive shift to more arid conditions throughout the last glacial cycle
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