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 periods of enhanced tropical and enhanced Southern Ocean sources of water fi lling these lakes at different times during the last full glacial cycle.

The Central Andes play a pivotal role for glacier and climate reconstruction along the American Pole-Equator-Pole transect. Nevertheless, knowledge about late Quaternary palaeoenvironmental changes in this region is extremely limited. With the advent and application of surface exposure dating during the last few years, the establishment of more detailed glacial chronologies could provide important insights into forcings and mechanisms of glaciation and climate change. This paper reviews previously published exposure ages and compares them with independent age control on glacial chronologies and with information about the palaeohydrological conditions. Although available data are still very limited and there are remaining systematic uncertainties related to surface exposure dating, the following simplified palaeoglacial/palaeoclimate model is presented to serve as a testable hypothesis for future studies. (i) Glaciers in the humid tropical Andes were mainly temperature sensitive and therefore advanced during temperature minima. Advances are dated to 20-25 ka, $15 ka and 11-13 ka, i.e. synchronous to the global Last Glacial Maximum (LGM), the Heinrich event 1 and the Younger Dryas/Antarctic Cold Reversal. (ii) Further south and west, precipitation decreases and glaciers therefore become more precipitation sensitive. Maximum or at least prominent glacial advances as far south as 308 S are dated into the Lateglacial, i.e. synchronous with lake transgression phases (Tauca: 14-18 ka, and Coipasa: 11-13 ka). (iii) Between $30 and 408 S, glaciers reached their maximum extent much earlier during the pre-LGM ($35-40 ka). This is attributed to a northward shift and/or intensification of the westerlies, whereas conditions during the global LGM were too dry to allow for significant glacial advances. (iv) South of 408, glaciers become temperature sensitive again and reached their maximum accordingly synchronous to the global LGM.

The scale, spatial variability and implications of pre-Columbian human-induced changes in the Amazon basin are controversial. While some scholars believe that large settlements and complex societies were limited to areas with favourable environmental conditions and human disturbance was localized, others propose that social complexity developed regardless of environmental constraints and opportunities and that human disturbance was widespread. In order to understand the extent to which environmental preconditions influenced the development of pre-Columbian societies, research is needed that integrates both environmental reconstructions and archaeological data. The present study explores past human–environment interactions in the Llanos de Moxos (LM) in the Bolivian Amazon. Combining extensive fieldwork and remote sensing image analysis, we reconstruct mid- to late-Holocene fluvial activity in the southeastern LM and the formation of a sedimentary lobe left by the Grande River. The lobe deposition created the conditions for the development of fertile, drained soils. We also show how pre-Columbian inhabitants adapted to the sedimentary lobe and managed to maximize the area of land suitable for agriculture by building a drainage/irrigation infrastructure. Our results provide an interpretative framework for the diversity of archaeological remains in the LM and suggest that people reached high levels of social complexity as a result of two necessary factors: favourable environmental conditions and human ingenuity.

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Three terrestrial climate proxies are used to investigate the evolution of Holocene palaeoenvironments in southern central Australia, all of which present a coherent record of palaeohydrology. Single-grain optically stimulated luminescence from sediments supplemented by 14C from charcoal and lacustrine shells was obtained to date shoreline deposits (Lake Callabonna) and the adjacent Mt Chambers Creek alluvial fan. Our findings are complemented by a U/Th-based record of speleothem growth in the Mt Chambers Creek catchment, which we interpret to reflect increased precipitation. Together, these archives shed light on the timing of, and possible sources of water for, Holocene pluvial intervals. We identified several phases of elevated lake levels dated at ~5.8–5.2, 4.5, 3.5–2.7 and 1 kyr, most of which correspond to fluvial activity resulting from increased precipitation in the adjacent ranges. The enhanced hydrology during phases of the late Holocene likely increased the reliability of resources for regional human populations during a time of reduced winter rainfall. When considered within the framework of the current understanding of Holocene palaeoclimate in central Australia, our data suggest that the pattern of landscape response was broadly synchronous with larger scale climatic variability and punctuated by pluvial periods greater than today.