A 47,000 year archaeological and palaeoenvironmental record from Juukan 2 rockshelter on the western Hamersley Plateau of the Pilbara region, Western Australia

In this thesis I describe the results of my analysis of archaeological material and sediments excavated from four rockshelters on the northeast Hamersley Plateau, Western Australia and synthesise previously reported archaeological evidence from the inland Pilbara to answer two questions about Aboriginal occupation. The first question asks how humans in the inland Pilbara responded to the Last Glacial Maximum (LGM) and compares their response to those of people in surrounding areas. Archaeological evidence from areas surrounding the inland Pilbara, such as the northwest coast, the interior and the Kimberley, indicate that people abandoned sites or used them less frequently during the LGM. A unique and significant feature of the inland Pilbara is the Hamersley Plateau, a massive plateau and escarpment feature that concentrates plateau runoff into long and deep gorges with aquifer-fed pools. Previously reported sites in the inland Pilbara are not near the escarpment and suggest abandonment or reduced frequency of use during the LGM, but I present new evidence from Milly's Cave, located near the escarpment, that indicates increased use during the LGM. This evidence indicates that the pliancy of hunter-gatherer adaptive systems during the LGM may have been underestimated and the local as well as regional environments are significant in understanding hunter-gatherer adaptations to climate change. The second question asks what technological, economic and demographic changes occurred in the inland Pilbara during the middle and late Holocene and how these changes relate to those in surrounding areas. Located between the northwest coast and the interior, the inland Pilbara has been suggested to be a bridge for populations or ideas moving between the coast and the interior. New Holocene stone technologies appear at similar times in the Pilbara, northwest coast and interior, suggesting the three areas were part of regional systems of technological and economic change. Cultural changes associated with the new technologies are suggested by ethnographic information from the inland Pilbara that links the new technological types to ceremonial activities and gender-specific tasks. Archaeological evidence suggests that late Holocene increases in population dynamics in the inland Pilbara may be related to similar increases in the interior. This evidence suggests that there is a relationship between cultural, technological and economic change and population dynamics in hunter-gatherer populations.

The impact of deteriorating climatic conditions on variability in the archaeological record towards the Last Glacial Maximum (LGM) remains uncertain. Partly as a result of poor-quality data, previous studies on Upper Palaeolithic (UP) societies of North-Western Europe prior to the LGM have focused on techno-typological traditions and diversification to outline the diachronic processes through which assemblage composition changed. This study addresses the adaptive trade-offs brought about by the general climatic downturn towards the LGM in North-Western Europe, by investigating the impact of local climate and habitat characteristics on the behavioural variability that characterises Gravettian technological organisation compared to the previous Aurignacian, based on two assemblages from Walou Cave, Belgium. This site is one of the rare well-stratified sites in North-Western Europe with evidence for multiple occupation events accompanied by a fine-grained palaeoenvironmental record. We use a combination of analytical techniques (AMS, LA-ICP-MS and ZooMS) to evaluate questions about hunter-gatherer adaptations. Faunal remains at Walou Cave mirror the faunal diversity documented at numerous other Aurignacian and Gravettian sites in the broader European context, which is similar between both periods. The overall picture presented here, using multiple lines of evidence, is not entirely clear; nonetheless, the results suggest that Gravettian technologies are unlikely to solely be a product of heightened risk in relation to a significant reshuffling of food resources compared to the previous Aurignacian. Future research of the factors structuring assemblage variability prior to the LGM will have to assess whether Aurignacian and Gravettian technologies indeed offer no relative material advantage over one another, a phenomenon called ‘technological equivalence’.

We examine the climatic responses to the shortwave (SW) and longwave (LW) direct radiative effects (RE) of sea salt aerosol in present day and the last glacial maximum (LGM) using a general circulation model with online simulation of sea salt cycle. The 30-year control simulation predicts a present-day annual emission of sea salt of 4,253 Tg and a global burden of 8.1 Tg for the particles with dry radii smaller than 10 μm. Predicted annual and global mean SW and LW REs of sea salt are, respectively, −1.06 and +0.14 W m−2 at the top of atmosphere (TOA), and −1.10 and +0.54 W m−2 at the surface. The LW warming of sea salt is found to decrease with altitude, which leads to a stronger net sea salt cooling in the upper troposphere. The changes in global mean air temperature by the present-day sea salt are simulated to be −0.55, −0.63, −0.86, and −0.91°K at the surface, 850, 500a, and 200 hPa, respectively. The emission of sea salt at the LGM is estimated to be 4,075 Tg year−1. Relative to present day, the LGM sea salt emission is higher by about 18% over the tropical and subtropical oceans, and is lower by about 35% in the mid- and high-latitudes in both hemispheres because of the expansion of sea ice. As a result of the weakened LGM water cycle, the LGM annual and global mean burden of sea salt is predicted to be higher by 4% as compared to the present-day value. Compared with the climatic effect of sea salt in present day, the sea-salt-induced reductions in surface air temperature at the LGM have similar magnitude in the tropics but are weakened by about 0.18 and 0.14°K in the high latitudes of the Southern and Northern Hemispheres, respectively. We also perform a sensitivity study to explore the upper limit of the climatic effect of the LGM sea salt. We assume an across-the-board 30% increase in the glacial wind speed and consider sea salt emissions over sea ice, so that the model can reproduce the ratio of sea salt deposition between the LGM and present day in the high latitudes of the Southern Hemisphere as suggested by the ice core records. This sensitivity run predicts a global emission of sea salt of 11,941 Tg year−1 with a global burden of 20.9 Tg. With such a high loading, sea salt aerosol at the LGM can have a net RE of −2.28 W m−2 at the TOA and lead to an annual and global mean cooling of 1.27°K at the surface.

The archaeology of Bald Rock 1, Bald Rock 2 and Bald Rock 3 at the sandstone outcrop of Maliwawa has established ∼25,000 years of Indigenous occupation in the Wellington Range, northwestern Arnhem Land. Flaked stone artefacts were found from the beginning of the sequence, with ground-edge axes, pounding and grinding technology and ochre recovered from deposits dating from the Last Glacial Maximum (LGM) to the recent contact period. Maliwawa was occupied during the LGM and other major regional environmental changes arising from post-glacial sea level rise and stabilisation along with the climatic variability of the Indonesian Australian Summer Monsoon (IASM) and El Niño Southern Oscillation (ENSO), supporting models that define Arnhem Land as a refugium. Lithic assemblages are represented by a quartz and quartzite flake abundance technological strategy, with an unusual lack of stone points observed, although other typical Arnhem Land Holocene retouched lithics are present. Raw material diversity in the late Holocene, alongside a variety of emergent pan-Arnhem Land rock art styles in the Wellington Range, supports the proposition of increasing exchange between Indigenous groups. These changes in the archaeological record signal the expansion of cultural systems throughout western Arnhem Land, documented historically and archaeologically, at the time of culture contact.

Lake Victoria lies in the heart of the Murray Darling Basin. During the height of the Last Glacial Maximum (LGM) up to 3 metres of wind-blown sand and dust was deposited along the top of the lunette on the eastern shore of Lake Victoria, creating an unparalleled environment for preserving archaeological remains. Aboriginal shell middens and faunal remains in stratigraphic context provide a record of human adaptation to the extreme climate variability which prevailed between 17,000 and 14,500 BP. Fieldwork at Lake Victoria centred on Gills Gully, a 1 sq km area in the central, highest area of the Lake Victoria lunette. Six LGM dates were obtained from Velesunio shell recovered from middens within this area and a stratigraphic sequence was developed for the upper ten metres of the lunette. Several shell middens were excavated in order to investigate environmental conditions and Aboriginal adaptations during the height of the LGM. LGM middens had been so gently buried by settling dust that ash, tiny bone fragments and delicate dots of scarlet ochre were preserved, and tiny air bubbles can be seen in the dusty grey overburden. Middens were composed of closely packed freshwater mussel shell interspersed with fine ash, charcoal and finely divided ochre. Remains of small macropods (hare wallaby), yabby, lizard, frog and more rarely fish and bird were present - average length of faunal fragments was less than 6 mm. A polished bone point was recovered from a shell lens dated to 16,170+/- 190 (ANU 2876). With the exception of a tiny fragment of sandstone no stone artefacts were recovered from Pleistocene middens. Between 16,000 and 15,000 BP there was a marked change in the pattern of human occupation around Lake Victoria. Chemical and physical analysis of the midden shell and the overburden shows that that the increase in midden density cannot be explained by site preservation factors. By 15,000 years earlier patterns of large, scattered charcoal-rich occupation deposits had been replaced by smaller, more numerous shell middens around 1 metre in diameter, in places so thickly clustered as to form overlapping lenses of well preserved compacted freshwater shells up to 60 cm thick, a much more intense pattern of exploitation. During the last phases of the Last Glacial Maximum Lake Victoria was an oasis an increasingly desiccated late Pleistocene landscape. It is likely that local population increased at this time and that people turned increasingly to freshwater mussels for sustenance.

<p>Present day Mediterranean Sea (MedSea) is an oligotrophic semi-enclosed basin.  Nutrient supply by rivers, net nutrient export through the Strait of the Gibraltar and the basin-wide circulation create a biological desert. Sediment core records, however, indicate periods of higher production during paleo times.</p><p>To gain insight into biogeochemical conditions during the Last Glacial Maximum (LGM), we apply a regional ocean-biogeochemistry model of the Mediterranean Sea.  A consistent forcing is available from a transient simulation with an Earth System Model (ESM) over 22,000 years based, among others, on an ice sheet reconstruction.  The ESM run provides atmospheric forcing fields, being downscaled to the regional setup, temperature and salinity conditions at the open western boundary in the Atlantic, and river runoff.  Nutrient concentrations of river discharge and at the Atlantic boundary are set to present-day estimates.  The automatic bathymetry adjustment to account for sea level variations due to meltwater fluxes is adopted from the ESM simulation. The LGM simulation starts at 22 ka to allow for a 1000 yr spinup run with transient forcing. The LGM period results are compared to a present-day simulation based on the same consistent ESM forcing.  </p><p>Colder temperatures and thus lower basin-wide evaporation, as well as a shallower sill depth at the Strait of Gibraltar, lead to lower baroclinic watermass exchange between the MedSea and the Atlantic. The zonal overturning circulation is more sluggish during the LGM than present day.  River discharge to the MedSea increases by 35% during the LGM, causing an increased net primary production near the river mouths.  Despite a higher nutrient inventory of the MedSea at the LGM, net primary production of the entire MedSea is lower than present day. Colder LGM temperatures reduce phytoplankton growth rates and increase the remineralisation length scale.</p><p>More characteristics of LGM biogeochemistry are presented and their drivers will be disentangled, also including additional sensitivity studies on changes in bathymetry.        </p>

Following its initial occupation ca 40,000 years ago, Aboriginal people using Allen’s Cave in South Australia’s arid zone experienced two major climatic changes. From the onset of the Last Glacial Maximum (LGM) at ca 30,000 cal. BP, until its peak at ca 22,000–18,000 cal. BP, aridity in Australia reached its most intense phase during the human occupation of the site. Conversely, conditions around the Allen’s Cave region during the early Holocene, 11,000–8,000 cal. BP, were the most favourable for human occupation. In this paper, we present the results of a technological and statistical re-analysis of previously excavated Allen’s Cave stone artefact assemblages, focusing on the period ca 40,000–5,000 cal. BP, to examine whether people made adjustments to stone tool manufacture in response to these climatic fluctuations. Our results and interpretations are consistent with some of the conclusions of previous scholars, primarily that the site was used for infrequent visitation rather than long-term occupation, and that little change occurred in the production of stone artefacts (despite changing environmental conditions). We also concur that lithic evidence exists for trade/exchange and/or a change in foraging range or stone curation practices at the start of the early Holocene. However, we do not support all prior claims for significant cultural and demographic changes at this time and we argue that Allen’s Cave was probably abandoned from ca 30,000 to 26,000 cal. BP. The ca 4,000 year hiatus, combined with probable increased visitation after the LGM, suggests that whilst stone tool technology remained largely consistent during the period of focus, Aboriginal people did alter their occupation patterns in response to environmental changes. On the basis of these new interpretations about the site’s occupation history, we provide updated observations in order to contribute to desert occupation modelling.

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 significantly, 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.

We estimate the sea-ice extent and basal melt of Antarctic ice shelves at the Last Glacial Maximum (LGM) using a coupled ice-shelf-sea-ice-ocean model. The shape of Antarctic ice shelves, ocean conditions and atmospheric surface conditions at the LGM are different from those in the present day; these are derived from an ice-shelf-ice-sheet model, a sea-ice-ocean model and a climate model for glacial simulations, respectively. The winter sea ice in the LGM is shown to extend up to ∼7° of latitude further equatorward than in the present day. For the LGM summer, the model shows extensive sea-ice cover in the Atlantic sector and little sea ice in the other sectors. These modelled sea-ice features are consistent with those reconstructed from sea-floor sedimentary records. Total basal melt of Antarctic ice shelves in the LGM was ∼2147 Gt a–1, which is much larger than the present-day value. More warm waters originating from Circumpolar Deep Water could be easily transported into ice-shelf cavities during the LGM because the full glacial grounding line extended to shelf break regions and ice shelves overhung continental slopes. This increased transport of warm water masses underneath an ice shelf and into their basal cavities led to the high basal melt of ice shelves in the LGM.

Glacial and deglacial climatic patterns in Australia and surrounding regions from 35 000 to 10 000 years ago reconstructed from terrestrial and near-shore proxy data

The region of western Georgia (Imereti) has been a major geographic corridor for human migrations during the Middle and Upper Palaeolithic (MP/UP). Knowledge of the MP and UP in this region, however, stems mostly from a small number of recent excavations at the sites of Ortvale Klde, Dzudzuana, Bondi, and Kotias Klde. These provide an absolute chronology for the Late MP and MP–UP transition, but only a partial perspective on the nature and timing of UP occupations, and limited data on how human groups in this region responded to the harsh climatic oscillations between 37,000–11,500 years before present. Here we report new UP archaeological sequences from fieldwork in Satsurblia cavein the same region. A series of living surfaces with combustion features, faunal remains, stone and bone tools, and ornaments provide new information about human occupations in this region (a) prior to the Last Glacial Maximum (LGM) at 25.5–24.4 ka cal. BP and (b) after the LGM at 17.9–16.2 ka cal. BP. The latter provides new evidence in the southern Caucasus for human occupation immediately after the LGM. The results of the campaigns in Satsurblia and Dzudzuana suggest that at present the most plausible scenario is one of a hiatus in the occupation of this region during the LGM (between 24.4–17.9 ka cal. BP). Analysis of the living surfaces at Satsurblia offers information about human activities such as the production and utilisation of lithics and bone tools, butchering, cooking and consumption of meat and wild cereals, the utilisation of fibers, and the use of certain woods. Microfaunal and palynological analyses point to fluctuations in the climate with consequent shifts in vegetation and the faunal spectrum not only before and after the LGM, but also during the two millennia following the end of the LGM.

During the Last Glacial Maximum (LGM) and subsequent deglaciation, the Great Basin in the southwestern United States was covered by numerous extensive closed-basin lakes, in stark contrast with the predominately arid climate observed today. This transition from lakes in the Late Pleistocene to modern aridity implies large changes in the regional water balance. Whether these changes were driven by increased precipitation rates due to changes in atmospheric dynamics, decreased evaporation rates resulting from temperature depression and summer insolation changes, or some combination of the two remains uncertain. The factors contributing to these large-scale changes in hydroclimate are critical to resolve, given that this region is poised to undergo future anthropogenic-forced climate changes with large uncertainties in model simulations for the 21st century. Furthermore, there are ambiguous constraints on the magnitude and even the sign of changes in key hydroclimate variables between the Last Glacial Maximum and the present day in both proxy reconstructions and climate model analyses of the region. Here we report thermodynamically derived estimates of changes in temperature, precipitation, and evaporation rates, as well as the isotopic composition of lake water, using clumped isotope data from an ancient lake in the northwestern Great Basin, Lake Surprise (California). Compared to modern climate, mean annual air temperature at Lake Surprise was 4.7 °C lower during the Last Glacial Maximum, with decreased evaporation rates and similar precipitation rates to modern. During the mid-deglacial period, the growth of Lake Surprise implied that the lake hydrologic budget briefly departed from steady state. Our reconstructions indicate that this growth took place rapidly, while the subsequent lake regression took place over several thousand years. Using models for precipitation and evaporation constrained from clumped isotope results, we determine that the disappearance of Lake Surprise coincided with a moderate increase in lake temperature, along with increasing evaporation rates outpacing increasing precipitation rates. Concomitant analysis of proxy data and climate model simulations for the Last Glacial Maximum are used to provide a robust means to understand past climate change, and by extension, predict how current hydroclimates may respond to expected future climate forcings. We suggest that an expansion of this analysis to more basins across a larger spatial scale could provide valuable insight into proposed climate forcings, and aid in climate model process depiction. Ultimately, our analysis highlights the importance of temperature-driven evaporation as a mechanism for lake growth and retreat in this region.

The climate of the Last Glacial Maximum (LGM) over South America is simulated using a regional climate model with 60‐km resolution, providing a simulation that is superior to those available from global models that do not resolve the topography and regional‐scale features of the South American climate realistically. LGM conditions on SST, insolation, vegetation, and reduced atmospheric CO2 on the South American climate are imposed together and individually. Remote influences are not included. Annual rainfall is 25–35% lower in the LGM than in the present day simulation throughout the Amazon basin. A primary cause is a 2–3 month delay in the onset of the rainy season, so that the dry season is about twice as long as in the present day. The delayed onset occurs because the low‐level inflow from the tropical Atlantic onto the South American continent is drier than in the present day simulation due to reduced evaporation from cooler surface waters, and this slows the springtime buildup of moist static energy that is needed to initiate convection. Once the monsoon begins in the Southern Hemisphere, LGM rainfall rates are similar to those in the present day. In the Northern Hemisphere, however, rainfall is lower throughout the (shortened) rainy season. Regional‐scale structure includes slight precipitation increases in the Nordeste region of Brazil and along the eastern foothills of the Andes, and a region in the center of the Amazon basin that does not experience annual drying. In the Andes Mountains, the signal is complicated, with regions of significant rainfall increases adjacent to regions with reduced precipitation.

The Cuddie Springs site in south-eastern Australia provides the first evidence of an unequivocal association of megafauna with humans for this continent. Cuddie Springs has been known as a fossil megafauna locality for over a century, but its archaeological record has only recently been identified. Cuddie Springs is an open site, with the fossil deposits preserved in a claypan on the floor of an ancient ephemeral lake. Investigations revealed a stratified deposit of human occupation and fossil megafauna, suggesting a temporal overlap and an active association of megafauna with people in the lead up to the Last Glacial Maximum, when conditions were more arid than the present day. Two distinct occupation phases have been identified and are correlated to the hydrology of the Cuddie Springs lake. When people first arrived at Cuddie Springs, sometime before 30,000 BP, the claypan on the lake floor was similar to a waterhole, with five species of megafauna identified. Flaked stone artefacts were found scattered through this level. After the lake dried, there was human occupation of the claypan. The resource base broadened to include a range of plant foods. Megafauna appear to be just one of a range of food resources exploited during this period. A return to ephemeral conditions resulted in only periodic occupation of the site with megafauna disappearing from the record around 28,000 BP. The timing of overlap and association of megafauna with human occupation is coincident with the earliest occupation sites in this region. The archaeological evidence from Cuddie Springs suggests an opportunistic exploitation of resources and no specialised strategies for hunting megafauna. Disappearance of megafauna is likely to be a consequence of climatic change during the lead up to the Last Glacial Maximum and human activities may have compounded an extinction process well under way.

We present here a revised reconstruction of the Ross ice drainage system of Antarctica at the last glacial maximum (LGM) based on a recent convergence of terrestrial and marine data. The Ross drainage system includes all ice flowlines that enter the marine Ross Embayment. Today, it encompasses one‐fourth of the ice‐sheet surface, extending far inland into both East and West Antarctica. Grounding lines now situated in the inner Ross Embayment advanced seaward at the LGM (radiocarbon chronology in Denton and Marchant 2000 and in Hall and Denton 2000a, b), resulting in a thick grounded ice sheet across the Ross continental shelf. In response to this grounding in the Ross (and Weddell) Embayment, ice‐surface elevations of the marine‐based West Antarctic Ice Sheet were somewhat higher at the LGM than at present (Steig and White 1997; Borns et al. 1998; Ackert et al. 1999). At the same time, surface elevations of the East Antarctic Ice Sheet inland of the Transantarctic Mountains were slightly lower than now, except near outlet glaciers that were dammed by grounded ice in the Ross Embayment. The probable reason for this contrasting behavior is that lowered global sea level at the LGM, from growth of Northern Hemisphere ice sheets, caused widespread grounding of the marine portion of the Antarctic Ice Sheet, whereas decreased LGM accumulation led to slight surface lowering of the interior terrestrial ice sheet in East Antarctica. Rising sea level after the LGM tripped grounding‐line recession in the Ross Embayment, which has probably continued to the present day (Conway et al. 1999). Hence, gravitational collapse of the grounded ice sheet from the Ross Embayment, accompanied by lowering of the interior West Antarctic ice surface and of outlet glaciers in the Transantarctic Mountains, occurred largely during the Holocene. At the same time, increased Holocene accumulation caused a slight rise of the inland East Antarctic ice surface.