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The tempo and mode of Homo sapiens dispersal in Eurasia and the demise of Neanderthals has sparked debate about the dynamics of Neanderthal extinction and its relationship to the arrival of H. sapiens. In Italy, the so-called ‘Transition’ from Neanderthals to H. sapiens is related to the Uluzzian technocomplex, i.e. the first archaeological evidence for modern human dispersal on the European continent. This paper illustrates the new chronology and stratigraphy of Uluzzo C, a rock shelter and Uluzzian key site located in the Uluzzo Bay in southern Italy, where excavations are ongoing, refining the cultural sequence known from previous excavations. Microstratigraphic investigation suggests that most of the deposit formed after dismantling of the vault of the rock shelter and due to wind input of loess deflated by the continental shelf. The occasional reactivation of the hydrology of the local karst system under more humid conditions further contributed to the formation of specific layers accumulating former Terra Rossa-type soil fragments. Superposed on sedimentary processes, strong bioturbation and the mobilization and recrystallization of calcite have been detected. Optically stimulated luminescence (OSL) ages from Uluzzo C Rock Shelter are congruent with previously published radiocarbon ages obtained on shell beads and tephrachronology from adjacent sites preserving the Uluzzian technocomplex such as Grotta del Cavallo, confirming the onset for the Uluzzian in the area to ca. 39.2–42.0 ka. The OSL chronology from Uluzzo C also provides a terminus post quem for the end of the Mousterian in the region, constraining the disappearance of the Neanderthals in that part of Italy to ≥46 ± 4 ka.

The archaeological record of Africa provides the earliest evidence for the emergence of the complex symbolic and technological behaviours that characterize Homo sapiens1–7. The coastal setting of many archaeological sites of the Late Pleistocene epoch, and the abundant shellfish remains recovered from them, has led to a dominant narrative in which modern human origins in southern Africa are intrinsically tied to the coast and marine resources8–12, and behavioural innovations in the interior lag behind. However, stratified Late Pleistocene sites with good preservation and robust chronologies are rare in the interior of southern Africa, and the coastal hypothesis therefore remains untested. Here we show that early human innovations that are similar to those dated to around 105 thousand years ago (ka) in coastal southern Africa existed at around the same time among humans who lived over 600 km inland. We report evidence for the intentional collection of non-utilitarian objects (calcite crystals) and ostrich eggshell from excavations of a stratified rockshelter deposit in the southern Kalahari Basin, which we date by optically stimulated luminescence to around 105 ka. Uranium–thorium dating of relict tufa deposits indicates sporadic periods of substantial volumes of fresh, flowing water; the oldest of these episodes is dated to between 110 and 100 ka and is coeval with the archaeological deposit. Our results suggest that behavioural innovations among humans in the interior of southern Africa did not lag behind those of populations near the coast, and that these innovations may have developed within a wet savannah environment. Models that tie the emergence of behavioural innovations to the exploitation of coastal resources by our species may therefore require revision. Human populations in the southern Africa interior were collecting non-utilitarian objects at around 105,000 years ago, suggesting that the development of this innovative behaviour did not depend on exploiting coastal resources.

Over the last few decades, investigations of the southern African Late Pleistocene archeological record have transformed our understanding of Homo sapiens origins and evolution. However, the intensity of research on coastal and near-coastal records has surpassed that in the deep interior. One reason for the geographic bias is the rarity of well-preserved, datable rockshelter sites outside the more mountainous and karstic regions of South Africa. Here, we report stratified Middle Stone Age and Later Stone Age deposits at Ga-Mohana Hill North Rockshelter (GHN), near Kuruman, in the Northern Cape, South Africa. Contrary to a previous report, we show that the archeological deposits are in good context with minimal disturbance based on a detailed fabric analysis of plotted finds. Three dating methods, single-grain optically stimulated luminescence, radiocarbon, and uranium-thorium, indicate that the artifact-bearing deposits date to ~ 105 ka, ~ 31 ka, and ~ 15 ka. Thus, Ga-Mohana Hill North Rockshelter provides an important opportunity to investigate early human adaptation in this semiarid region of southern Africa.

Homo sapiens exhibit extreme behavioural plasticity, mediated by culture and technology, that permits us to adapt rapidly to new environments and situations. Understanding the role that past climate change played in selecting for Homo sapiens’ adaptability is a key question in human evolution research. The arid and semi-arid Kalahari Basin in southern Africa is an ideal region for addressing this question because fossil, genetic, and archaeological evidence supports an early origin for Homo sapiens in southern Africa. The growing archaeological record of the Kalahari Basin reveals that significant behavioural innovations accumulated in the region over the course of the Middle and Late Pleistocene, including ochre use, hafted hunting weapons, fishing, and figurative paintings. Here, we report the results of interdisciplinary investigations at two locales in the southern Kalahari; Ga-Mohana Hill and Witberg 1. The archaeological and palaeoenvironmental record (based on U-Th dating of tufas) at Ga-Mohana Hill reveals that site occupation correlated with a previous period of increased effective precipitation ~110-100 ka, and preliminary results suggest a more complicated relationship between occupation and precipitation after that time. At Witberg 1, Middle Stone Age archaeology is associated with the shoreline of a previously unidentified palaeolake. Current investigations are focused on dating the Witberg deposits, analysing the lithic technology, and generating palaeoenvironmental archives using phytoliths and diatoms. Collectively, this research provides a rare opportunity to evaluate Middle Stone Age occupation across a changing landscape from both stratified rockshelters and sealed open-air sites, to explore the complex interactions between past climate change and early human behaviors, and to better understand the origins of Homo sapiens extreme adaptability.

Lithic surface artefacts are anthropogenically formed stone materials (stone tools and spall generated during knapping) resting atop or being semi-embedded into the uppermost sediment layer of a stratigraphic sequence on a given landform. Such surface artefacts lack a secure stratigraphic context are encountered worldwide and often comprise a significant proportion of the archaeological record. Yet, direct absolute dating techniques for constraining the age of lithic surface scatters are currently not available. Promising recent work has shown the potential of using the optically stimulated luminescence (OSL) signal from rocks to date the emplacement of gravel pavements and blocks in both, archaeological and geological contexts (e.g. Sohbati et al., 2015; Jenkins et al., 2018). We build on this work and introduce a novel way of directly dating lithic surface artefacts using OSL-rock surface burial dating. We use this approach to date a surface lithic artefact scatter site, in southern Tibet. By calculating spatially resolved OSL burial ages for slices at 1 mm increments into each artefact’s buried surface we (i) infer the timing of artefact discard by humans at the site, (ii) demonstrate that most artefacts are not in-situ but were transported downslope and/or flipped and (iii) for some samples constrain the timing and number of cycles of artefact burial and re-exhumation. This is the first time that the OSL signal is used to date sunlight exposure of artefacts. The method is not limited to archaeological contexts but can be applied to other surface clasts that yield a reasonable OSL signal too. OSL rock surface burial dating of surface clasts and artefacts thus holds great potential to (i) constrain manufacture and artefact discard by humans and (ii) detect and reconstruct post-depositional disturbances and transport pathways. We discuss the application potential of this approach in archaeology and geomorphology. References:Jenkins, G.T.H., Duller, G.A.T., Roberts, H.M., Chiverrell, R.C., Glasser, N.F., 2018. A new approach for luminescence dating glaciofluvial deposits – High precision optical dating of cobbles. Quaternary Science Reviews 192, 263-273.Sohbati, R., Murray, A.S., Porat, N., Jain, M., Avner, U., 2015. Age of a prehistoric Rodedian cult site constrained by sediment and rock surface luminescence dating techniques. Quaternary Geochronology 30, 90–99.

In the area of the European-Asian border, in the Ural Mountains, the southern boundary of permafrost has moved in meridional direction by more than 1000 km in response to Quaternary climate variations. During cold climate states, permafrost extended as far south as the Southern Ural (53°N). We studied three independent archives in three caves in the Southern Ural (Shulgan-Tash, Victoria and Grandioznaya) in order to gain insights into the long-term dynamics of permafrost in the region.Common speleothems (e.g., stalagmites and flowstone) require liquid water to form, and are therefore restricted to permafrost-free periods. Cryogenic cave carbonates (CCC) form when the temperature in the cave is close to or slightly below 0°C (permafrost conditions). These two types of speleothems were dated using the 230Th-U method in order to determine the timing of permafrost and permafrost-free conditions. As a novel indicator of freezing conditions in caves we identified frost wedges in silty cave sediments filled by sand. These sands were dated using OSL to constrain the timing of sub-zero rock temperatures (required to form frost wedges) in caves.Stalagmites, abundant in in South Uralian caves, exhibit two prominent growth phases, associated with interglacials – MIS 5e and Holocene. In addition, mm-thin layers of flowstone formed in one chamber of Shulgan-Tash cave in association with smaller-scale warming episodes during MIS 3 (Greenland interstadials GI-9 and GI-8) and MIS 2 (GI-1; Bølling-Allerød). All CCC in Shulgan-Tash and Victora caves yielded MIS 3 ages, typically lagging cooling events (Greenland stadials) GS-16.1, GS-15.1, GS-13, GS-12, GS-10, and GS-7 by several hundred years up to one 1 ka. CCC from Grandioznaya cave formed during a single episode following GS-1 (Younger Dryas). Sand filling frost wedges in Victoria cave was washed into the cave during MIS 2, ca. 24-25 ka BP. Apparently, during this time the karst massif hosting the cave was engulfed by permafrost (to a depth of at least 90 m) and flow of water through the cave was severely restricted, which led to back-flooding of the cave passage and the accumulation of several m-thick silt deposits, interspersed with thin sand layers.

Grassridge rock shelter is located in the high elevation grassland foothills of the Stormberg Mountains in the Eastern Cape of South Africa. This places Grassridge at an important biogeoclimatic intersection between the Drakensberg Mountains, the South African coastal zone, and the interior arid lands of southern Africa. First excavated in 1979, the approximately 1.5 m stratigraphic sequence was divided into two major occupational components: a 50–70 cm thick Later Stone Age component dating between 7–6 ka and an underlying 50–80 cm thick Middle Stone Age component dated to 36 ka at the base. Here we present a reanalysis of the Grassridge stratigraphic sequence that combines new optically stimulated luminescence and radiocarbon age estimates with sedimentological and microbotanical analyses to evaluate site formation processes and the palaeoenvironmental context of human occupations. Results indicate a complex history of geogenic, anthropogenic, and biogenic inputs to the depositional sequence that are interspersed with pulsed human occupation from 43–28 ka, 13.5–11.6 ka, and 7.3–6.8 ka. Microbotanical remains indicate a cooler, drier grassland environment in MIS 3 that transitions to a warmer, moister grassland environment dominated by summer rainfall in the middle of MIS 1. The pulsed occupational sequence identified at Grassridge is characteristic of the Pleistocene and Holocene record across the greater high elevation grassland region of South Africa, which, based on comparison with other currently available evidence, seems linked to a complex system of forager mobility entwined with rapidly fluctuating palaeoenvironments across the last glacial to interglacial transition.

Between 2013 and 2016, Scarp Archaeology developed and implemented an extensive excavation research program across the eastern Hamersley Plateau, an arid and mountainous physiographic region in the Pilbara biogeographical region of Western Australia. More than 100 rock shelters were excavated during the program, resulting in the documentation of 22 rock‐shelter sites with Pleistocene‐age Aboriginal archaeological deposits. This paper presents the radiometric determinations for these Pleistocene rock‐shelter sites, which collectively suggest that the eastern Plateau was occupied by 45000 years ago. The paper further develops a hypothesis that there was a substantial shift in the incidence and intensity of rock‐shelter occupation during the Last Glacial Maximum, c.30000–20000 years ago, where there was a substantial downturn in the use of most rock‐shelter sites, and in some instances rock shelters were abandoned. However, after the Last Glacial Maximum, we posit that a widespread reoccupation of the region soon occurred. Our research also offers an examination of artefact discard through time, illustrating changes in raw material discard and technology and the likely correlations with procurement and subsistence strategies.

An excavation and survey program at West Angelas, in the Pilbara region of Western Australia, shows that the poorly watered interior area of the Hamersley Plateau was first occupied soon after the conclusion of the Last Glacial Maximum, and that significant use of this area probably only occurred during the mid to late Holocene. Although current archaeological research shows that Aboriginal groups have occupied areas of the Hamersley Plateau for more than 40,000 years, the permanent and prolonged use of the more marginal or ecologically suboptimal foraging environments of the interior plateau is a comparatively recent development in the region’s long archaeological record.

Studies of modern sediments, their sedimentology and depositional processes are important for understanding the behaviour of the luminescence characteristics of quartz and feldspar in fluvial settings. Previous studies have shown large variations in OSL characteristics of quartz from different fluvial systems, while the IRSL and pIRIR signals from K-feldspar have been understudied. We test the effects of fluvial setting on luminescence characteristics by collecting modern (

Travertines are carbonates precipitated from hydrothermal springs and are relatively common on the Tibetan plateau and occur along tectonically active faults. The Karakoram fault system is an active strike-slip fault that extends from the Pamir into southwestern Tibet, where it controls the course of the upper Sutlej River and the occurrence of several hydrothermal springs, including the Tirthapuri hot springs. Multiple fluvial terraces that are partly capped by travertine are preserved in the Tirthapuri area. Four main fluvial terrace levels (labelled as T1 to T4 with increasing height above river) were identified and several meter-thick travertine platforms occur on the current river level as well as the T2 and T3 terraces. Sedimentological and petrographic observations suggest that the travertine platforms were deposited on active floodplains of the paleo- and modern Sutlej River, and preserved from fluvial erosion because travertine precipitation was immediately followed by vertical river-bed incision and thus terrace abandonment. Results of 230Th/U in combination with luminescence dating show that the deposition of travertine platform and river incision that led to the formation of T3 terrace (∼93 m above the Sutlej) took place at ca. 127.5 ka. The development of terrace T2 and overlying travertine platform (∼28 m above the Sutlej) occurred between ca. 10.0 and 8.8 ka. Fluvial incision has arrived at the modern level at least ca. 0.2 ka ago. Both the travertine deposition and major river incision are likely triggered by the intensified Indian summer monsoon and are linked to phases of maximum monsoon strength. During strong monsoon phases, a large quantity of moisture is transported into southwestern Tibet, activating hot springs and thus travertine precipitation, facilitating fluvial incision and stripping off sediments from the regional hill-slopes. At least over the last glacial cycle we suggest that the Tirthapuri travertine and associated fluvial incision are sensitive indicators of (peak) monsoonal activity and can thus provide valuable insights into past climate change and climate-driven landscape evolution on the southwestern Tibetan Plateau. Comparison of our findings with published data further suggests that monsoon-controlled fluvial aggradation and incision during the early Holocene is synchronous in southwestern Tibet and the adjacent sector of the Himalayan orogen (north-western Sub-to High Himalaya).

Archaeological surface assemblages composed of lithic scatters comprise a large proportion of the archaeological record. Dating such surface artifacts has remained inherently difficult owing to the dynamic nature of Earth-surface processes affecting these assemblages and because no satisfactory chronometric dating technique exists that can be directly applied to constrain the timing of artifact manufacture, discard, and thus human use of the landscape. Here, we present a dating approach based on optically stimulated luminescence (OSL)-OSL rock-surface burial dating-and apply it to a lithic surface scatter in Tibet. We generate OSL burial ages (age-depth profiles) for each artifact, outline the methodological complexities, and consider the artifact burial ages in the context of local-scale Earth-surface dynamics. The oldest age cluster between 5.2 and 5.5 thousand years is likely related to quarrying activities at the site and thus represents the oldest chronometric age constraints for human presence on the south-central Tibetan plateau.

Post-depositional mixing processes are extremely common and often obscure a record of deposition in dune and sand sheet deposits. We show that the upper half metre of a dune in southeastern Australia is currently being turned over through bioturbation, but that single-grain OSL dating and contextual knowledge can be used to identify and model these modern mixing processes. In the sandy deposits investigated, mixing processes were observed to be acting to a predicable depth of ∼50–60 cm. This observation was used to develop a conceptual framework that can be applied to buried deposits and used to temporally constrain the evolution of the landform and quantify rates of mixing. When our mixing zone conceptual framework was combined with the MAM we show that phases of significant dune aggradation occurred at ∼29.9, ∼18.3, ∼10.3 ka, and continued through the Holocene. We also present an approach using single-grain OSL data to estimate downward mixing rates, which show a strong depth dependency and are coherent with previously reported mixing rates. Modern downward mixing rates indicate that the upper ∼50 cm (Zone 1) will be completely turned over on millennial time scales. While caution needs to be used when interpreting archaeological and OSL data from bioturbated sandy environments, our results demonstrate that contextual knowledge and single-grain OSL data can resolve mixing processes and contribute to an understanding of landscape evolution.

For over 30 years, the radiometric chronologies of Newman Rockshelter and Newman Orebody XXIX have been central to archaeological discussions on the Pleistocene Aboriginal occupation of the Hamersley Plateau and greater Pilbara region. Until 2009, these two sites were heralded as having the oldest evidence of human occupation on the plateau, dating to the last glacial maximum (LGM) ∼ 26–20 ka. More recently however, the excavations at several other rockshelters have shown that ancient Aboriginal peoples occupied the Hamersley Plateau many thousands of years before the onset of the last glacial cycle, when regional climatic conditions were wetter and more amenable. This paper presents the results of our re-excavation of both Newman Rockshelter and Newman Orebody XXIX. Our research has resulted in the compilation and analysis of large lithic datasets for each of these sites and the construction of geo-chronologies using modern radiometric techniques, including AMS-radiocarbon dating and optically stimulated luminescence dating. These new radiometric chronologies and artefact data indicate that both sites were occupied between 45 and 40 ka. Despite having significant early occupational evidence, neither of the rockshelters present strong evidence for sustained or persistent site use during the LGM proper ca. 23–19 ka; however, there is substantial evidence for more routine occupation of these localities during the terminal Pleistocene and Holocene.

Recent work has shown that the optically stimulated luminescence (OSL) signal can be used to determine the duration of daylight exposure for rock surfaces, complementing the surface exposure dating technique using cosmogenic nuclides. In this study we investigate the feasibility of using the newly developed OSL Surface exposure dating technique (OSL-Surf) to date flake scars at lithic quarry sites. We performed the first quantitative validation of the model describing the OSL-Surf dating technique using a controlled laboratory experiment. Our results show that longer laboratory bleaching durations yield deeper OSL-depth profiles, validating the use of OSL-Surf approach for relative dating of rock surfaces with different exposure ages. The OSL-surf model fitted to the OSL-depth profiles (excluding one outlier) yields accurate estimates of known exposure duration, thus confirming the method's usefulness as an absolute dating tool. Consequently, we used the OSL-Surf technique to determine an exposure duration of 117 ± 37 a for a previously unknown-age flake scar that is related to human exploitation of a lithic quarry site in Tibet. The problem of finding a known-age rock surface for parameter calibration was solved by revisiting the sampling site and collecting the scar remaining after earlier sample collection, which has a precisely known exposure age (1.667 a in this study) and identical lithology and irradiation aspect as the flake scar. The calibration sample yielded a measurable OSL-depth profile that could be used to calibrate the model to estimate the exposure duration of a flake scar associated with human exploitation of the area. Finally, we observe that the μ parameter of the OSL-Surf model varies considerably between the laboratory-bleached and two naturally daylight-bleached datasets, despite having identical lithologies. We thus infer that, in addition to lithological controls, the μ parameter is primarily sensitive to the daylight irradiation geometry and only weakly dependent on spectrum of the incident light; this interpretation implies a narrow effective bleaching wavelength band in quartzite. From the practical viewpoint, our results suggest that geometrical factors deserve a careful consideration both while designing the laboratory bleaching experiments as a surrogate of natural bleaching, as well as while choosing the field calibration samples.

Playa margins are often characterised by a wide spectrum of landforms, which provide links between major lake stands, as recorded by beach ridges, and the detailed stratigraphic and paleoenvironmental information stored in lacustrine sediments. We mapped playa marginal geomorphology at Lake Frome, South Australia, documented the sedimentary characteristics, and analysed microfossil assemblages in selected sediments. Using a luminescence based approach, the sediments were summarised in four main stratigraphic units. During the later stages of Marine Isotope Stage (MIS)5 fluvio-deltaic sediments were deposited (Unit 1), indicating significant runoff from the adjacent Flinders Ranges into partly freshwater-dominated lakes. No sediments were dated between ∼70 and 25 ka, but renewed sediment delivery from the Flinders Ranges and re-deposition characterised the playa margin LGM and the early Holocene (Unit 2). The most recent phase of depositional activity is reflected by source-bordering dunes and lake marginal spit formation (Unit 3). Short-lived flooding events in the late Holocene are recorded by lake floor sediments and terminal splays (Unit 4). Our findings outline a dynamic late Quaternary playa margin, and highlight the complementary role which playa marginal landforms and sediments may play for the interpretation of runoff, sedimentary dynamics and paleoenvironments related to high regional lake levels.

Plunge pool deposits from Australia's 'Top End' are considered as important archives of past monsoonal activity in the region. The available chronology of these deposits was so far based on thermoluminescence (TL) dating and indicated maximum flood magnitudes during the Last Glacial Maximum in contrast with more arid conditions as deduced from other archives of the region. This study revisits plunge pool deposits at Wangi Falls by applying multiple and single-grain Optically Stimulated Luminescence (OSL) dating of quartz and high-resolution gamma spectrometry, supported by radiocarbon dating of organic material. The aim is to reappraise the existing chronology and investigate if the deposits are affected by partial bleaching, post-depositional mixing and/or problems related to annual dose determination. The latter seems to have a minor impact on the ages at most. Equivalent Dose (D e ) distributions are broad, in particular for single grains, but apparently not result from partial bleaching or post-depositional mixing. Rather, microdosimetry caused by radiation hotspots in the sediment and zircon inclusions in the quartz grains is considered problematic for these sediments. The results presented here imply that the previous TL chronology overestimated the real deposition age of the sediments.

Central to the debate over the extinction of many of Australia's last surviving megafauna is the question: Was climate changing significantly when humans arrived and megafauna went extinct? Here we present a new perspective on variations in climate and water resources over the last glacial cycle in arid Australia based on the study of the continent's largest lake basin and its tributaries. By dating paleoshorelines and river deposits in the Lake Eyre basin, we show that major hydrological change caused previously overflowing megalakes to enter a final and catastrophic drying phase at 48 ± 2 ka just as the giant bird, Genyornis newtoni, went extinct (50-45 ka). The disappearance of Genyornis and other megafauna has been previously attributed to "ecosystem collapse" coincident with the spread of fire-wielding humans. Our findings suggest a climate-driven hydrological transformation in the critical window of human arrival and megafaunal extinction, and the results call for a re-evaluation of a humanmediated cause for such extinctions in arid Australia.

The optically stimulated luminescence (OSL) signal from quartz grains is most often used to estimate the depositional age of sediments that were fully bleached during transport and have not been mixed after deposition. However, sediment that is transported fluvially may not have been exposed to sufficient sunlight to bleach the latent OSL signal, while stable land surfaces on which soils are developing will likely be subject to mixing processes such as pedoturbation. In these cases, large equivalent dose ( D e ) datasets derived from individual sand-sized quartz grains can shed light on the depositional and post-depositional histories of sedimentary deposits. Here, we report the results of geochronological investigations of Mt Chambers Creek alluvial fan, on the eastern footslopes of the Flinders Ranges, South Australia. We collected 13 OSL samples from bank exposures and pits excavated into relict floodouts to reconstruct late Quaternary alluvial dynamics. Single-grain D e datasets yielded overdispersion-values of between 26 and 68%. Most of these values are significantly higher than the overdispersion values obtained during dose-recovery experiments, suggesting that many deposits were poorly bleached, mixed, and/or experienced significant dose rate heterogeneity. Single-grain measurements of a sample from the modern floodout demonstrate that partial bleaching is minor and cannot explain the D e distributions for Holocene and Pleistocene samples. The results of systematic application of the finite mixture model (FMM) to all D e datasets in conjunction with contextual observations suggest that post-depositional mixing by pedoturbation has significantly affected the deposits and observed OSL data. For most samples, we infer that the most populous FMM component represents deposition and that secondary components represent intrusive younger grains or partially bleached older grains. The fan-wide presence of contemporaneous intrusive grain-populations suggests that post-depositional mixing occurred in phases, possibly associated with intervals of increased pedoturbation.

Luminescence surface exposure dating is a newly developed geochronological technique that allows the age of geological or archaeological rock surfaces to be accurately constrained. This dating method requires measuring and calibrating the depth-dependent luminescence signal below an exposed surface and relies on the assumption that neither the shape of the daylight spectrum nor the light attenuation change significantly with depth into the rock. However, lithologies with mm-scale heterogeneity in their mineral distribution or those lacking high sensitivity quartz present a challenge, partly because light attenuation with depth is not necessarily constant in such samples. Addressing these challenges is important for further development of the luminescence surface exposure dating technique. Here we investigate the shape of luminescence-depth profiles in lithologies revealing complex fabrics such as coarse-grained granitic gneisses or gneisses with distinct planar metamorphic layering. We also present luminescence-depth profiles from quartzite, a lithology that appears – at first glance – highly homogenous. We find that the spatial distribution of opaque mineral phases in the metamorphic samples and precipitation of iron hydroxides in the quartzite strongly influence the 3-dimensional transparency and, consequently, the light attenuation with depth, and are the main cause for the observed scatter in the OSL- and IRSL-depth profiles in our samples. The data suggest that for rocks of heterogeneous lithology (i) close petrographic analysis of luminescence-depth profiles are required to ensure that the cores used for calibration have similar mineralogical composition (and thus light attenuation with depth) to those used to calculate a luminescence rock surface exposure age, and that (ii) RGB depth profiles appear to provide a useful semi-quantitative tool for such analysis.

Here we present an integrated earth surface process and paleoenvironmental study from the Tingri graben and the archaeological site of Su-re, located on the southern rim of the Tibetan plateau, spanning the past ca. 30 ka. The study area is characterized by cold climate earth surface processes and aridity due to its altitude and location in the rain shadow of the Mount Everest–Cho Oyu massif and is thus sensitive to climatic and anthropogenic perturbations. In this highly dynamic geomorphic environment, paired-cosmogenic nuclide results from boulders on a massive hummocky moraine in the southern Tingri graben reveal complex exposure histories that limit our capability of directly dating the corresponding glacial advance, and shed a note of caution on previously published single-nuclide-based exposure ages along the northern Himalaya. Based on geomorphic considerations, however, the moraine clearly represents the local last glacial maximum, and likely coincided with a ∼344 ± 109 m drepression of discontinuous permafrost zone relative to today during the global last glacial maximum (gLGM). This greatly intensified permafrost and periglacial hillslope processes and led to fluvial aggradation of the valley floors of ≥12 m. We observe formation of a thick (≥50 cm) pedo-complex starting at ca. 6.7 ka before present (BP) and erosional truncation at ca. 3.9 ka BP. Widespread landscape instability and erosion characterize the region subsequent to 3.9 ka and intensifies in the 15th century AD. Several lines of (geo)archaeological evidence, including the presence of pottery sherds, sling-shot projectiles and hammer stones within the sedimentary record, indicate human presence at Su-re since ca. 3.9 ka BP. Our data suggest that in the Su-re-Tingri area climatic conditions were warm and moist enough to allow vegetation expansion and soil formation only from ca. 6.7–3.9 ka, followed by weakening of the Indian summer monsoon (ISM) strength between ca. 4.2 and 3.9 ka, which is a prominent climatic event in the wider Asian monsoon region, and reflected in the investigation area by the 3.9 ka erosional boundary. Merging our Holocene landscape reconstruction with the geoarchaeological evidence, we speculate that the combined effect of Little Ice Age (LIA) cooling and an anthropogenic overuse of the landscape led to climatically induced landscape degradation and ultimately to an anthropogenically triggered ecological collapse in the 15th century. Such a scenario is in-line with regional historical data on declining monastery construction and migration of the ethnic group of the Sherpas. From an earth surface dynamics perspective, we find that transient landscape processes on the southern rim of the Tibetan plateau are strongly linked to millennial scale changes in the ISM intensity and duration. We identify three types of unidirectional non-linear ISM-landscape interactions. Given that the Tibetan plateau is the largest high-altitude landmass on our planet and our limited understanding of several of the key earth surface processes on the plateau, we pinpoint the need for more long-term (Quaternary scale) empirical data particularly on permafrost and periglacial processes and human-environment interactions.

Accurate chronologies are fundamental for detailed analysis of palaeoenvironmental conditions, archaeological reconstructions and investigations of Holocene coastal morphological changes. Chronological data enable estimation of rates of shoreline progradation, and provide appropriate context for forecasting future coastal changes. A previously reported radiocarbon chronology for the Moruya coastal plain in south-eastern Australia indicated a decelerating overall rate of progradation with minimal net seaward shoreline movement in the past ~2500 years. Single-grain and multi-grain aliquot optically stimulated luminescence (OSL) analyses demonstrate that marine sands from this region have excellent luminescence characteristics. A series of OSL ages across this coastal barrier indicates a remarkably linear trend of Holocene shoreline progradation. The linear trend of seaward shoreline movement indicates that the barrier has grown at an average rate of 0.27 m/yr with successive ridge formation every ~110 years. The oldest ridge on the barrier appears to correspond to cessation of rapid post-glacial sea-level rise, and the large foredune at the seaward margin of the barrier is

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.

Optically stimulated luminescence (OSL) ages from a relict shoreline on Lake Callabonna record a major pluvial episode in southern central Australia between 1050 70 and 1100 60 Common Era (CE), w ...

The elevated temperature infrared stimulated luminescence (IRSL) and post-IR IRSL signals of potassium (K)-feldspars have recently garnered attention for their minimal rates of anomalous fading. The post-IR IRSL signal has been used to obtain age estimates for geological deposits, mostly in Europe. Studies on the behaviour of the IRSL and post-IR IRSL signals of K-feldspars from a wider range of geographic regions and depositional contexts are needed, particularly for regions where the OSL signal from quartz is poorly behaved. Discrepancies in the literature regarding the behaviours of the IRSL and TL signals of K-feldspars also highlight the need to characterise the behaviours of samples from a wide variety of contexts. This paper begins to address this problem by characterising and comparing the IRSL signals of a metamorphic and a volcanic K-feldspar sample from two sites in East Africa, a region in which the OSL signal from quartz has generally proven problematic for dating. We demonstrate that the metamorphic and volcanic K-feldspars have substantially different TL glow curves that respond differently to IR stimulation. The sample of metamorphic K-feldspar from Tanzania (MR9) has a peak at 430 °C that is associated with the IRSL signal and an optically less-sensitive peak at 350 °C, while the sample of volcanic K-feldspar from Ethiopia (MB3) exhibits a single broad TL region centred at ∼230 °C that responds differently to IR stimulation. Differences in the change of IRSL decay curve shape with stimulation temperature suggest that the processes of IRSL production many vary between the two samples. Using dose recovery tests, we demonstrate that the IRSL (50 °C), IRSL (225 °C) and post-IR IRSL (50 °C, 225 °C) signals of sample MR9 are suitable for dose and age estimation using the single-aliquot regenerative-dose procedure, while those of sample MB3 are less suitable. The post-IR IRSL signal of the latter sample performs poorly in tests of SAR suitability and the three signals exhibit extremely high fading rates over laboratory timescales (g 2days > 19%/decade).

Mumba rockshelter is a key archaeological site for the Middle and Later Stone Age occupation of East Africa, but its chronology has remained unresolved. We report the results of a dating study, focussing on the characterisation of the optically stimulated luminescence (OSL) and infrared stimulated luminescence (IRSL) properties of quartz- and potassium-rich feldspar grains. Quartz has previously proven troublesome for dating in East Africa. We identified five general types of quartz grain behaviour, based on the shapes of their OSL decay and dose–response curves. Dose recovery experiments and measurement of the natural samples revealed particular problems with quartz grains that had hyperbolic dose–response curves, low characteristic saturation doses and anomalously large changes in sensitivity between regenerative-dose cycles. The use of pulsed irradiation during measurement and standard and additional quality-assurance criteria during data analysis reduced the number of grains that suffered from these problems. We applied these procedures to individual grains of quartz from eight samples and, using appropriate statistical models, identified post-depositional mixing in three samples. The remaining samples had scattered equivalent-dose distributions typical of quartz grains that had received variable beta dose rates during burial. Stratigraphically consistent OSL ages were obtained for all but the deepest sample. Feldspar ages were estimated for the latter sample and three other samples, using the elevated temperature IRSL signal that exhibited low rates of anomalous fading. Fading-corrected feldspar ages for the latter three samples are consistent with their single-grain quartz ages, but single-grain dating is needed to address problems of post-depositional mixing.