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Activities of 26Al and 10Be in five chert clasts sampled from two beach ridges of late Pleistocene Lake Lisan, precursor of the Dead Sea in southern Israel, indicate low rates of chert bedrock erosion and complex exposure, burial, and by inference, transport histories. The chert clasts were derived from the Senonian Mishash Formation, a chert-bearing chalk, which is widely exposed in the Nahal Zin drainage basin, the drainage system that supplied most of the material to the beach ridges. Simple exposure ages, assuming only exposure at the beach ridge sampling sites, range from 35 to 354 ky; using the ratio 26Al/10Be, total clast histories range from 0·46 to 4·3 My, unrelated to the clasts'' current position and exposure period on the late Pleistocene beach ridges, 160–177 m below sea level. Optically stimulated luminescence dating of fine sediments from the same and nearby beach ridges yielded ages of 20·0 ± 1·4 ka and 36·1 ± 3·3 ka. These ages are supported by the degree of soil development on the beach ridges and correspond well with previously determined ages of Lake Lisan, which suggest that the lake reached its highest stand around 27 000 cal. years BP. If the clasts were exposed only once and than buried beyond the range of significant cosmogenic nuclide production, then the minimum initial exposure and the total burial times before delivery to the beach ridge are in the ranges 50–1300 ky and 390–3130 ky respectively. Alternatively, the initial cosmogenic dosing could have occurred during steady erosion of the source bedrock. Back calculating such rates of rock erosion suggests values between 0·4 and 12 m My−1. The relatively long burial periods indicate extended sediment storage as colluvium on slopes and/or as alluvial deposits in river terraces. Some clasts may have been stored for long periods in abandoned Pliocene and early Pleistocene routes of Nahal Zin to the Mediterranean before being transported again back into the Nahal Zin drainage system and washed on to the shores of Lake Lisan during the late Pleistocene. Copyright © 2003 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A morphometric study of the Bet ha’Emeq drainage system, Upper Galilee, combined with available geological and structural data, enables the detection of tectonic stages that took place in the region, as well as a better understanding of the influence of tectonic activity on surficial processes. The preservation of Senonian and young errock units in the down faulted blocks of the Bet ha’Emeq Valley implies that normal faulting at rates compatible to denudation initiated during the Miocene and lasted ~10million years. During that time, ongoing truncation continued on the uplifted block, eliminating completely the Senonian units. The relation between the Bet ha’Emeqdrainage system and adjacent structures implies that the relief of the Bet ha’EmeqValley and the development of the drainage system in it preceded the development of the secondary uplifted blocks within the Bet ha’Emeq low structure, the neighboring Zurim Escarpment, and the formation of the regional tilt of the Upper Galilee. The present relation between the Zurim Escarpment and the Bet ha’Emeq drainage system suggests no observable retreat of the escarpment since its formation more than 4 Ma.Morphologic considerations and the existence of quartz geodes derived from the Cenomanian Deir Hana Formation on abandoned saddles along the present water divide of Nahal Bet ha’Emeq suggest that the headwaters of the Bet ha’Emeq drainage system used to be in the Beit Jann tectonic block. This block is currently disconnected from the Bet ha’Emeq drainage system due to normal displacement along the Sumiand Peqi’in faults. The present morphology of the Bet ha’Emeq Valley developed since the Pliocene. A fresh fault scarp in dolomite and knick points in Pleistocenetravertine units in the western part of the Bet ha’Emeq Valley indicate late Pleistocene activity on the Bet ha’Emeq fault system. Incision of the Bet ha’Emeq drainage system as well as adjacent streams into alluvial terraces signals the response of the drainage system to the regional-scale uplift and is not associated with normal faulting of the Bet ha’Emeq system. The regional uplift is also expressed in the steep gradient of the Upper Galilee streams. [ABSTRACT FROM AUTHOR]

Cave sediments pose dating challenges due to complex depositional and post-depositional processes that operate during their transport and accumulation. Here, we confront these challenges and investigate the stratified sedimentary sequence from Wonderwerk Cave, which is a key site for the Earlier Stone Age (ESA) in Southern Africa. The precise ages of the Wonderwerk sediments are crucial for our understanding of the timing of critical events in hominin biological and cultural evolution in the region, and its correlation with the global paleontological and archaeological records. We report new constraints for the Wonderwerk ESA chronology based on magnetostratigraphy, with 178 samples passing our rigorous selection criteria, and fourteen cosmogenic burial ages. We identify a previously unrecognized reversal within the Acheulean sequence attributed to the base of the Jaramillo (1.07 Ma) or Cobb Mtn. subchrons (1.22 Ma). This reversal sets an early age constraint for the onset of the Acheulean, and supports the assignment of the basal stratum to the Olduvai subchron (1.77–1.93 Ma). This temporal framework offers strong evidence for the early establishment of the Oldowan and associated hominins in Southern Africa. Notably, we found that cosmogenic burial ages of sediments older than 1 Ma are underestimated due to changes in the inherited 26Al/10Be ratio of the quartz particles entering the cave. Back calculation of the inherited 26Al/10Be ratios using magnetostratigraphic constraints reveals a decrease in the 26Al/10Be ratio of the Kalahari sands with time. These results imply rapid aeolian transport in the Kalahari during the early Pleistocene which slowed during the Middle Pleistocene and enabled prolonged and deeper burial of sand while transported across the Kalahari Basin. • New chronology of Wonderwerk cave based on magnetostratigraphy and cosmogenic ages. • Oldowan industry in Wonderwerk is robustly correlated with the Olduvai subchron. • Onset of the Acheulean in St. 11 is older than ca. 1.07 Ma. • Cosmogenic burial ages are affected by temporal changes in the inherited 26Al/10Be. • A stabilization of the Kalahari sands during the Middle Pleistocene. [ABSTRACT FROM AUTHOR]

The long-term bedrock incision of streams in the northeastern Negev has been dictated, since the Early Pliocene, by the subsidence of the Dead Sea basin. However, this incision is accompanied by very long intervals of sediment aggradation. Here, we document the Quaternary-scale fluvial response to changing base-level, lithology, structure, and climate along the hyperarid Nahal Zafit, NE Negev. The oldest (~1–2 Ma) alluvial remnants point to a widespread beveled bedrock pediment at the base of the Hazera anticline. This pediment, like other stream-pediment-anticline relationships in the region, provides the baseline framework into which Nahal Zafit incises. During the Early to Middle Pleistocene, this pediment was the base-level for all streams emerging out of the anticlines. The tectonic subsidence of the regional base-level at the rift margin farther downstream, has caused incision and upstream migration of bedrock knickpoints, triggering the development of a wide incised valley in the Mazar syncline, adjacent to the Hazera anticline. Since ~330 ka, fluvial terraces, landslides and taluses record intervals of basin-wide fluvial deposition under prevailing hyperarid to arid climate. Despite the general arid climate, prolonged fluvial deposition intervals occurred at ca. 330–265, 230–125, and 110–20 ka. Rapid and quite short-duration bedrock incision occurred in-between these, much longer, intervals of aggradation. In addition to the proposed climatic imprint on fluvial aggradation-incision cycles and the first-order base-level control of the rift margin fault, the formation of strath terraces and distribution of stored sediments within the drainage basin point to the fundamental role that lithology and structure play in the Quaternary evolution of the NE Negev watersheds. • Base-level lowering have induced the long-term incision of a hyperarid watershed. • Lithology and structure exert inherent control over the drainage basin morphology. • Prolonged aggradation periods punctuate incision at 330–265, 230–125, and 110–20 ka. • Climate controls aggradation by increasing sediment supply and transport capacity. • Basin-specific response obscures the direct link between fluvial trends and climate. [ABSTRACT FROM AUTHOR]

The selective amplification of DNA in the polymerase chain reaction is used to exponentially increase the signal in molecular diagnostics for nucleic acids, but there are no analogous techniques for signal enhancement in clinical tests for proteins or cells. Instead, the signal from affinity-based measurements of these biomolecules depends linearly on the probe concentration. Substituting antibody-based probes tagged for fluorescent quantification with lasing detection probes would create a new platform for biomarker quantification based on optical rather than enzymatic amplification. Here, we construct a virus laser which bridges synthetic biology and laser physics, and demonstrate virus-lasing probes for biosensing. Our virus-lasing probes display an unprecedented > 10,000 times increase in signal from only a 50% increase in probe concentration, using fluorimeter-compatible optics, and can detect biomolecules at sub-100 fmol mL−1 concentrations. Many ligand-binding assays still rely on signals that scale linearly with probe concentration. The authors present lasing detection probes with a dye-labelled virus as the gain medium to optically amplify the signal, which could enable much higher signals than for fluorescent quantification. [ABSTRACT FROM AUTHOR]

Rivers are the most effective agent of erosion on earth, transporting massive amounts of detrital and dissolved matter into depositional basins. Therefore, the relationship between denudation of continents and the pathways of sediment transport by large rivers has been extensively examined (e.g., sediment flux gauging, basin-wide erosion rates, recognizing sediment source and mixing). However, due to the complex nature of sediment storage and transport dynamics in large-scale fluvial systems, our understanding of the seemingly simple relationship between erosion and deposition in large rivers is limited.In large-scale fluvial systems, where sediment is stored for extended periods, stable cosmogenic nuclides are a useful tool for quantifying the time sediment spends exposed during fluvial transport. We examined changes in cosmogenic Ne concentrations along an ~450 km section in the lower basin of the modern Colorado River. Sediments along the river show no clear trend between Ne concentration and distance down the river. Nevertheless, the variability in Ne concentrations can be translated to the maximal time the sediment was exposed during its transport down the lower Colorado River (~120 kyr).Applying these understandings to an ancient river, we collected Lower Cretaceous fluvial sediments from 5 locations along an ~400 km transect in the general downstream direction of the Lower Cretaceous Kurnub River. This river flowed across the passive margin of northern Gondwana into the Tethys Sea. Both variability and maximum duration of exposure (up to ~130 kyr) of sediments in the Kurnub River are similar to the Colorado River.These results, combined with the residence time of sediments in large modern rivers deduced from U-series isotopes, demonstrate that throughout the geologic record large rivers show a similarity in sediment dynamics expressed by large variability in sediment residence time ranging up to several hundreds of thousands of years. [ABSTRACT FROM AUTHOR]

In situ-produced cosmogenic 10Be and 26Al measurements are widely applied in geomorphological studies and in archaeology and paleoanthropology as a chronologic tool applicable to the past 5 Ma. While most of these measurements are made from concentrates of quartz, a ubiquitous and resistant mineral, it is of great interest to extend this method to other silicates and particularly to the amorphous silicates whose purification may not be as straightforward. This paper presents a cleaning procedure that has been applied on ten samples of various siliceous rocks (chert, granite and quartzolite). The aim is to monitor the 10Be, 27Al and 26Al concentration evolution as a function of cleaning steps. While this protocol appears suitable for 10Be, when measuring 26Al careful attention should be paid to 27Al, whose concentration should be measured regularly to ensure that a constant value is achieved and most important, allowing measuring 26Al/27Al by AMS. [ABSTRACT FROM AUTHOR]

Because of its role as a model system with tunable quantum fluctuations and quenched disorder, and the desire for optical control and readout of its states, we have used high-resolution optical absorption spectroscopy to measure the crystal-field excitations for Ho3+ ions in LiHoxY1-xF4 from the terahertz to visible regimes. We show that many of the excitations yield very narrow lines visibly split even by the nuclear hyperfine interaction, making Ho3+ in LiHoxY1-xF4 a candidate host for optically addressable electronuclear qubits with quality factors as high as Q=4.7×105, where the higher-lying levels are electronic singlets. Optical transitions in the easily accessible near- and mid-infrared are narrow enough to allow readout of the ground-state electronuclear qubits responsible for the interesting magnetism of LiHoxY1-xF4. While many of the higher-lying states have been observed previously, we also report here detailed spectra of terahertz excitations. The strengths of the electric and magnetic dipole crystal-field transition lines of five of the lowest excited spin-orbit manifolds of dilute LiYF4:Ho3+ were calculated and compared with measurement. The magnitude of the nuclear hyperfine coupling was used to assign the correct upper and lower states to transition lines. [ABSTRACT FROM AUTHOR]

The vast Kalahari Basin is characterized by uplifted margins, terrestrial sedimentation within semi endorheic sub-basins, subdued morphology and tectonic quiescence. This intracratonic basin has been subjected to a prolonged period of subsidence affecting its sedimentary fill by plate motion and climatic cycles. Provenance studies of Kalahari Group sediments mainly focused on the surficial deposits that represent only the last phase of sedimentation, leaving unresolved questions related to the rest of the strata. The southern Kalahari Group succession exposed along the walls of the Mamatwan Mine, Northern Cape, South Africa, reveals three main depositional environments: a bottom low-energy water-body, a middle fluvial, high-energy environment and an upper aeolian sandy unit. The entire section, which was deposited during the early to middle Quaternary, records significant environmental and depositional changes suggesting a highly dynamic landscape. The fully exposed section (55 m) of the Kalahari Group at Mamatwan Mine was analysed for its mineralogy, elemental composition, Sr, Nd and Pb isotopic ratios and iron species. Isotopic fingerprints were used to determine the source rocks of the sediments. The basal part of the section was derived from the distant Angolan highlands supporting previous suggestions for the existence of a paleo, trans-Kalahari drainage system. Weathering sensitive indices show that these sediments underwent considerable chemical weathering typical to humid areas. Mineralogical assemblage and iron phases imply that a brackish and alkaline shallow water-body existed during the early-middle Pleistocene contemporaneous with relative dense hominin occupation of the area. During the Early-Middle Pleistocene transition, the lacustrine environment was rapidly filled with volcano-sedimentary Archean clasts that were derived mainly from the surrounding hills and experienced limited degree of source rock chemical weathering, but underwent subsequent groundwater alteration by iron, silica, and calcium-rich solutions and precipitation of calcrete and silcrete duricrusts. These changes in provenance and depositional environments may be related to tectonic adjustments along the southern margins of the Kalahari basin. Ultimately, a shift into an aeolian-transport dominated landscape occurred in the region. This was accompanied by reduced surface water availability and a supply of sediments from Paleoproterozoic western and north-western source areas following the establishment of the modern wind regime. [ABSTRACT FROM AUTHOR]

Deciphering aspect-related hillslope asymmetry can enhance our understanding of the influence of climate on Earth's surface morphology and the linkage between topographic morphology and erosion processes. Although hillslope asymmetry is documented worldwide, the role of microclimatic factors in the evolution of dryland cliffs has received little attention. Here, we address this gap by quantifying aspect-dependent bedrock weathering, slope-rill morphology, and subcliff clast transport rates in the hyperarid Negev desert, Israel, based on light detection and ranging (LiDAR)-derived topography, clast-size measurements, and cosmogenic 10Be concentrations. Cliff retreat rates were evaluated using extrapolated profiles from dated talus flatirons and 10Be measurements from the cliff face and sub-cliff sediments. We document systematic, aspect-dependent patterns of south-facing slopes being less steep and finer-grained relative to east- and north-facing aspects. In addition, cliff retreat and clast transport rates on slopes of the south-facing aspect are faster compared to the other aspects. Our data demonstrate that bedrock weathering of the cliff face and the corresponding grain size of cliff-derived clasts delivered to the slopes constitute a first-order control on cliff retreat and sediment transport rates. We demonstrate that the morphology of the cliff and the pattern of bedrock weathering co-vary with the solar radiation flux and hence that cliff evolution in hyperarid regions is modulated by aspect-dependent solar radiation. These results help to better understand interactions between climate and dryland surface processes. [ABSTRACT FROM AUTHOR]

The presence of boulders, a result of rockfall events, at the foot of cliffs testifies for a mass wasting process which is widely observed and is often considered to be triggered by earthquakes. Here we investigate boulders under an overhanging cliff with an emphasis on the principal factors that control boulder size. We used a conceptual cantilever beam model to predict the expected maximum length of the overhanging cliff. We then compared these calculated lengths to those of the field observed boulders and the length of the overhanging cliff ledge. Our observations show that the actual lengths of the boulders and overhanging cliff are much shorter than expected from the model. As the study area is located in a tectonically active region, we first suggested solving this discrepancy by adding the possible effect of ground motion on the size of a boulder. Detailed pseudo-static and dynamic analysis of the effect of earthquakes on the failure of rock beams shows that boulder length may not significantly be shortened by induced ground motions. We therefore conclude that strong earthquakes, although triggering rockfalls, are not expected to control the resultant size of the boulders found at the base of overhanging cliffs. We alternatively suggest that the maximum length of a boulder is strongly controlled by the rock strength. We conclude that the maximum boulder size that may fall during an earthquake event can be predicted by calculating the cantilever critical length including the effect of the rock size on its tensile strength. This, together with the measured rock discontinuities in an overhanging cliff suggests an upper-bound for the volume of the falling boulders, a crucial factor in assessing rockfall hazards. [ABSTRACT FROM AUTHOR]

Abstract: Talus flatiron sequences are ubiquitous landforms in arid and semiarid regions characterized by horizontal erodible rocks capped by more resistant rocks. Alternating phases of deposition and erosion lead to the formation of generations of talus flatirons in which ancient ones are located farther from the source cliff. The existing conceptual model of this systematic spatial distribution of talus flatirons is related to glacial–interglacial climatic cycles and to relatively high rates of cliff retreat. Three groups of talus flatirons were analyzed in the northeastern hyperarid Negev desert. The analyses include mapping, age determination using optically stimulated luminescence and cosmogenic nuclide exposure dating, electrical resistivity tomography and sedimentological and soil analyses. All talus flatirons contain gypsic-salic soil catena typical to hyperarid climate (<80mmyr−1). No pedogenic indicators of past wetter environments such as buried calcic soil horizons, evidence of intense biogenic activity, or buried organic material were observed. 10Be exposure ages of the talus flatirons suggest that they were deposited during the middle Pleistocene; ~610ka and ~170ka for the oldest and intermediate-aged talus flatiron groups, respectively. These ages, combined with the present location of the talus flatirons relative to the source cliff yield retreat rates of 6–12 and ~200mMa−1 for the bedrock cliff and talus flatiron apex, respectively, and in opposite directions. Our results show that (a) climatic changes at glacial–interglacial time scales are not the main controls over the formation of talus flatiron generation, and (b) that significant cliff retreat is not the main cause for the systematic spatial distribution of talus flatiron generations relative to the cliff. Our results indicate that the process of talus flatiron formation in the Negev desert must be associated with the balance between production, deposition, and removal of clasts under hyperarid conditions with only a minor cliff retreat. [Copyright &y& Elsevier]

Carbonate hillslopes are often soil mantled and display a classic convex morphology. In this study we examine controls on carbonate hillslope denudation and morphology using a modified regolith mass balance equation to account for chemical weathering and dust input--two fluxes that are commonly neglected in settings with silicate-dominated bedrock. We utilize seven study sites in the Eastern Mediterranean across a significant gradient in the mean annual rainfall and dust deposition flux. Combining cosmogenic 36Cl-derived hilltop denudation rates with an estimate of the regolith chemical depletion and the quantified fraction of dust in the regolith we predict hilltop curvature and compare our predictions with observations based on high-resolution airborne LiDAR (light detection and ranging).Denudation rates vary from 5 to 210 mm/k.y. and increase with mean annual rainfall. Less resistant carbonates (chalk) experience faster denudation rates relative to more resistant dolo-limestone and are less prone to chemical weathering. Soil production exhibits a humped dependency on soil thickness.The observed hilltop curvature varies as a function of rainfall and dust flux with a minimum at sub-humid sites. While trends in hilltop convexity are often solely attributed to variations in erosion rate, our results illustrate the additional effects of dust production and chemical depletion. Our mass balance model implies that drier sites in the south probably experienced a more intricate history of regolith production due to dust flux fluctuations. Thus, by incorporating dust flux and chemical weathering to the classic hillslope evolution model we are able to identify a complex relation between hilltop curvature, soil production, and climate. [ABSTRACT FROM AUTHOR]

The Gulf of Elat-Aqaba (GEA), located in the southern part of the Dead Sea Transform (DST), is one of the most active segments of the Dead Sea fault system. Yet, some fundamental details concerning its evolution in space and time are still not fully understood. To better constrain the tectonic history of this region, we study a succession of alluvial, lacustrine, and fluvial deposits in the north-western edge of the GEA, which belong to the Quaternary Eilot and Garof Fms. The Eilot Fm. represents low-energy shallow freshwater bodies and sabkhas, which predate the development of the deep part of the basin. Later, in response to the subsidence of the basin, the Garof Fm. was deposited in alluvial fans that built up following the increase in the depositional energy. Cosmogenic burial ages combined with magnetostratigraphy show that these Fms. were deposited as early as 3.03 Ma and as late as 1.65 Ma, depending on the applied age model. Considering the present depth of the northern GEA, this age indicates a maximum subsidence rate of the head of the GEA of ∼1.98mm/yr. We suggest that faults along the onshore margin of the deep basin were active during the deposition of the Garof Fm. and subsequently became inactive, while the faulting activity migrated toward the center of the basin. Closed Holocene basins north of the present seashore, such as the Elat and Evrona playas, which may represent a modern analogue to the Plio-Pleistocene morphology, raise the possibility that the GEA head is still propagating northward. • Quaternary sedimentary units in the head of the Gulf of Elat-Aqaba are analyzed. • Paleomagnetic records and cosmogonic burial ages constrain the sediments' age. • The Gulf is spreading northward with an evaluated subsidence rate of ∼2 mm/yr. [ABSTRACT FROM AUTHOR]

Despite the worldwide ubiquity of carbonate terrains, quantification and understanding of rates and patterns of carbonate erosion are still lacking. Carbonate landscapes are prone to chemical weathering (dissolution) and should therefore be strongly influenced by climatic variables such as precipitation. However, isolating the impact of these variables is difficult, as denudation rates are also influenced by tectonic processes and lithology. This study focused on deciphering 10³-105 yr denudation patterns across Mount Hermon, Israel, exploiting its climatic gradient (1500-600 mm/yr) and homogeneous lithology (Jurassic limestone). The concentrations of in situ cosmogenic 36Cl in bedrock and sediment samples were utilized to characterize the spatial distribution of denudation and examine its potential drivers. Our results indicate differential denudation rates of Mount Hermon hilltops. The subalpine region (1700-2200 m, ~1300-1500 mm yr-1, mean annual temperature of 7 °C) yielded an average hilltop denudation rate of 19 ± 5 mm k.y.-1 (n = 5), while hilltops at intermediate altitudes (1000-1600 m, ~900-1200 mm yr-1) seem to erode faster at 42 ± 8 mm k.y.-1 (n = 7). In addition, soil cover seems to enhance denudation rates relative to bare bedrock conditions. This highlights a major difference between carbonates and silicates, where numerous silicates data sets suggest an exponential decrease in bedrock weathering and soil production as the soil thickness increases. Our new 36Cl results, in conjunction with previously measured average hilltop lowering rates within the subhumid Mediterranean climate across the Judean mountain range (500-600 mm yr-1, 19 ± 7 mm k.y.-1), suggest that optimum conditions for carbonate denudation and chemical weathering occur below the tree line, where soil is abundant, pCO2 is higher, and snow cover is scarce. This observation has intriguing implications in terms of long-term landscape evolution-an increase in the elevation of a mountain range above the tree line may provide negative feedback, which will decrease its hilltop erosion rate. [ABSTRACT FROM AUTHOR]

A multidisciplinary study was conducted in a newly discovered Paleolithic locality, named 'Evron Landfill. This locality is a part of the Lower Paleolithic complex of 'Evron located at the western Galilee, Israel. Examination of artifacts has enabled the cultural attribution of 'Evron Landfill to the Early Acheulian, while detailed paleomagnetic stratigraphy places the hominin occupations near the Brunhes–Matuyama transition ~0.77 Ma. This age is constrained by cosmogenic isotope burial dating of the sediments overlying the Paleolithic finds, providing a minimum age of ~0.66±0.11 Ma for hominin activity at the site. These results are further supported by the biochronological information derived from the faunal assemblage. Comparative analyses of faunal remains and lithic artifacts from 'Evron Landfill demonstrate similarities to the assemblages from the Early Acheulian site of Evron Quarry, located ~300 m to the south. Pedo-sedimentological analyses indicate that hominin activity took place in a marsh environment in proximity to the Mediterranean coast, which probably fluctuated in both space and time with a fluvial environment. In addition, this study provides important data about ancient coastal activity during the early to middle Pleistocene. [ABSTRACT FROM AUTHOR]

Abstract Thermally-Transferred Optically Stimulated Luminescence (TT-OSL) from quartz is an extended-range luminescence dating technique, with an assumed potential to date sediments as old as early Pleistocene (0.8–2.6 Ma). However, one of the main drawbacks of the TT-OSL signal is its relatively low thermal stability. The few and scattered estimates in the literature of the relatively low thermal stability highlight the possibility that some reported TT-OSL ages are thermal artefacts (i.e. minimum ages only). In this study, we rigorously investigate the thermal stability of the main TT-OSL source trap, using a combination of laboratory and analytical techniques (varying heating rates, isothermal decay, alongside several models) on multiple aliquots of a modern sand sample from the eastern Mediterranean coastal plain. The varying heating rates method constrains the Arrhenius parameters of the TT-OSL main trap to E = 1.50 ± 0.06 eV and s = 1012.8±0.6 s−1; these values translate into a trap lifetime of 3. 2 − 1.9 + 4.8 Ma at 10 °C. Isothermal decay data further exhibits significant departures from first-order kinetic behavior, which can be well captured by either the general order kinetics model, or a Gaussian distribution of first-order systems. However, extrapolations of these models to geological timescales are at odds with a large volume of observations, thus suggesting that the deviation from first-order kinetics may be a laboratory artefact. Overall, our study reinforces the concern, that thermal loss progressively affects the TT-OSL signal in the Ma-scale age range, and that some previously reported results may be "minimum ages" only. Highlights • The kinetic parameters and lifetime of the main TT-OSL source trap were investigated. • A combination of analytical techniques and different models were used. • The kinetic parameters were constrained to E = 1.50 ± 0.06 eV and s = 1012.8±0.6 s−1. • The lifetime of the main TT-OSL source trap was calculated to. 3. 2 − 1.9 + 4.8 Ma at 10 °C. • Over geological timescale the trap's behavior is best described by first order kinetics. [ABSTRACT FROM AUTHOR]

Mountain glaciers at ∼26–19 ka, during the global Last Glacial Maximum near the end of the last 10 5 yr glacial cycle, are commonly considered on the basis of dating and field mapping in several well-studied areas to have been the largest of the late Quaternary and to have advanced synchronously from region to region. However, a numerical sensitivity model (Rupper and Roe, 2008) predicts that the fraction of ablation due to melting varies across Central Asia in proportion to the annual precipitation. The equilibrium-line altitude of glaciers across this region likely varies accordingly: in high altitude, cold and arid regions sublimation can ablate most of the ice, whereas glaciers fed by high precipitation cannot ablate completely due to sublimation alone, but extend downhill until higher temperatures there cause them to melt. We have conducted field studies and 10 Be dating at five glaciated sites along a precipitation gradient in Mongolia to test the Rupper/Roe model. The sites are located in nearby 1.875 × 1.875° cells of the Rupper/Roe model, each with a different melt fraction, in this little-studied region. The modern environment of the sites ranges from dry subhumid in the north (47.7° N) to arid in the south (45° N). Our findings show that the maximum local advances in the dry subhumid conditions predated the global Last Glacial Maximum and were likely from MIS 3. However, we also found that at ∼8–7 ka a cirque glacier in one mountain range of the arid Gobi desert grew to a magnitude comparable to that of the local maximum extent. This Holocene maximum occurred during a regional pluvial period thousands of years after the retreat of the Pleistocene glaciers globally. This asynchronous behavior is not predicted by the prevailing and generally correct presumption that glacier advances are dominantly driven by temperature, although precipitation also plays a role. Our findings are consistent with and support the Rupper/Roe model, which calls for glaciation in arid conditions only at high altitudes of sub-freezing temperatures, where the melt fraction in ablation is low. We expect a heterogeneous pattern of glacial responses to a changing modern climate in cold arid regions; an individual glacier advance should not be necessarily interpreted as evidence of cooling climate. [ABSTRACT FROM AUTHOR]

One of the most significant environmental processes that occurred at the transition from the last glacial phase into the present inter-glacial phase in arid regions was the shift from aggradation to incision in the drainage systems. This is evident by the sharp transition from a fluvial regime depositing fine-grained sediment within the wadis to intensive incision which formed gullies and narrow channels that dissected the late Pleistocene sediments. In order to investigate this transition, we studied three small-scale basins in the arid region of the Negev Highlands, southern Israel. Although the selected basins drain toward different base levels, their geomorphological parameters, particle size distribution of alluvial units and their OSL ages are similar. Sediments from the penultimate glacial cycle are found in patches in the bigger catchments. Fluvial loess was widely deposited since at least 67 ka until after 28 ka, covering valleys and slopes. Between ~ 28 and ~ 24 ka, loess was washed from the slopes into the channels, exposing the underlying colluvium. At ~ 24 ka erosion began with the transport of slope colluvium as gravels into the valleys that eroded the underlying loess sediments. Incision became dominant at ~ 12 ka and is still ongoing and intensifying. Dust and reworked loess continued to be deposited during the main incision stages. It is proposed that the transition from aggradation to incision was controlled by rates of loess supply and removal. Until ~ 24 ka dust choked the drainage system and only after reduction in dust supply was erosion and incision possible. It began first on the slopes and then in the channels. Our results show that an increase in precipitation is not a prerequisite for initiation of incision as is often assumed. Similar processes are described in other arid zones around the world. [ABSTRACT FROM AUTHOR]

Evaluating the impact and implications of eolian repositories that mark large-scale climatic transitions requires knowledge about the timing of their emplacement and the mechanisms responsible for their production, which remain highly uncertain. Here we apply numerical modeling of cosmogenic nuclide data, measured in the largest continuous terrestrial body of sand on Earth, to determine settings under which the sand was generated, by constraining the timing of sand introduction into the interior of southern Africa. Our findings reveal that major events of sand formation and accumulation in the Kalahari Basin occurred between ~2.2 and 1 Myr ago. The establishment of the Kalahari sand field corresponds to regional, continental, and global scale morphotectonic and climatic changes that contributed to the mass production and widespread dispersion of sand. These changes substantially altered existing habitats, thus constituting a crucial milestone for flora, fauna, and hominins in southern Africa during the Pleistocene., (© 2022. The Author(s).)