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Comprehensive mapping and the Briticechrono geochronology provides a reconstruction of the last advance and retreat of the only land-terminating ice lobe of the western British Irish Ice Sheet. The Irish Sea Glacier was fed by ice from Lake District, Irish Sea and Wales, and extended to maximum limits in the English Midlands. During ice retreat after 27 kyrs, a series of reverse bedrock slopes rendered proglacial lakes endemic in the land-system. Not resembling the more extensive definitions of the classical ‘Glacial Lake Lapworth’, these ice contact lakes were smaller time transgressive moraine- and bedrock-dammed basins that evolved with ice marginal retreat. Combining, for the first time on glacial sediments, OSL bleaching profiles for cobbles with single grain and small aliquot OSL measurements on sands, has produced a coherent chronology from these heterogeneously bleached samples, and constrained for the Irish Sea Glacier a post 30ka ice maximum advance, 26.5±1.8ka maximum extent, and 25.3±1.6 to 20.6±2.2ka retreat vacating the region. With retreat of the Irish Sea Glacier an opportunistic Welsh re-advance 19.7±2.5ka took advantage of the vacated space and rode over Irish Sea Glacier moraines. Our geomorphological chronosequence shows a glacial system forced by climate, but mediated by piracy of ice sources shared with the larger and marine terminating Irish Sea Ice Stream to the west. The Irish Sea Glacier underwent changes flow regime and fronting environments driven by stagnation and decline as the primary impetus to advance was diverted. Ultimately, the glacier of the English Midlands display complex uncoupling and realignment during deglaciation and ice margin retreat towards upland hinterlands ~17.8 kyrs (Lake District and Pennines) and asynchronous behaviour as individual adjacent ice lobes became increasingly important in driving the landform record.

Reconstructions of climatic and environmental conditions can contribute to current debates about the factors that influenced early human dispersal within and beyond Africa. Here we analyse a 200,000-year multi-proxy paleoclimate record from Chew Bahir, a tectonic lake basin in the southern Ethiopian rift. Our record reveals two modes of climate change, both associated temporally and regionally with a specific type of human behavior. The first is a long-term trend towards greater aridity between 200,000 and 60,000 years ago, modulated by precession-driven wet-dry cycles. Here, more favorable wetter environmental conditions may have facilitated long-range human expansion into new territory, while less favorable dry periods may have led to spatial constriction and isolation of local human populations. The second mode of climate change observed since 60,000 years ago mimics millennial to centennial-scale Dansgaard-Oeschger cycles and Heinrich events. We hypothesize that human populations may have responded to these shorter climate fluctuations with local dispersal between montane and lowland habitats.

In this study, we synthesize terrestrial and marine proxy records, spanning the past 620 ky, to decipher pan-African climate variability and its drivers and potential linkages to hominin evolution. We find a tight correlation between moisture availability across Africa to El Niño Southern Ocean oscillation (ENSO) variability, a manifestation of the Walker Circulation, that was most likely driven by changes in Earth's eccentricity. Our results demonstrate that low-latitude insolation was a prominent driver of pan-African climate change during the Middle to Late Pleistocene. We argue that these low-latitude climate processes governed the dispersion and evolution of vegetation as well as mammals in eastern and western Africa by increasing resource-rich and stable ecotonal settings thought to have been important to early modern humans.

International audience; The BRITICE-CHRONO Project has generated a suite of recently published radiocarbon ages from deglacial sequences offshore in the Celtic and Irish seas and terrestrial cosmogenic nuclide and optically stimulated luminescence ages from adjacent onshore sites. All published data are integrated here with new geochronological data from Wales in a revised Bayesian analysis that enables reconstruction of ice retreat dynamics across the basin. Patterns and changes in the pace of deglaciation are conditioned more by topographic constraints and internal ice dynamics than by external controls. The data indicate a major but rapid and very short-lived extensive thin ice advance of the Irish Sea Ice Stream (ISIS) more than 300 km south of St George's Channel to a marine calving margin at the shelf break at 25.5 ka; this may have been preceded by extensive ice accumulation plugging the constriction of St George's Channel. The release event between 25 and 26 ka is interpreted to have stimulated fast ice streaming and diverted ice to the west in the northern Irish Sea into the main axis of the marine ISIS away from terrestrial ice terminating in the English Midlands, a process initiating ice stagnation and the formation of an extensive dead ice landscape in the Midlands.

What role did climate dynamics play in the evolution and dispersal of Homo sapiens within and beyond Africa, and in key cultural innovations? Were gradual climatic changes, rapid shifts from wet to dry, or short-term climate flickers the main driver of human evolution and migration? As a contribution towards an enhanced understanding of those possible human-climate interactions the Chew Bahir Drilling Project, part of the Hominin Sites and Paleolakes Drilling Project (HSPDP) and the Collaborative Research Center (CRC) 806 “Our way to Europe”, recovered two ~280 m-long sediment cores from a deep, tectonically-bound basin in the southern Ethiopian rift in late 2014. The Chew Bahir record covers the past ~600 ka of environmental history, a critical time period that includes the transition from the Acheulean to the Middle Stone Age, and the origin and dispersal of Homo sapiens. Here we present the results from our multi-proxy study of the Chew Bahir 280 m-long composite core, providing a detailed and high-resolution record of eastern Africa’s climate oscillations during the last ~600 ka. To determine sediment age we used a Bayesian model to combine ages derived from radiocarbon dating of ostracodes, optically-stimulated luminescence (OSL) dating of quartz, Argon-Argon (40Ar/39Ar) dating of feldspar grains from some key (micro)tephra layers, and correlation on the basis of geochemistry of a tephra unit in the core to a known and dated tephra in the outcrop. We used high-resolution geophysical and geochemical indicators, such as the established aridity proxy K, sediment colour and authigenic minerals to differentiate between climate fluctuations on different time scales and magnitudes. Our results show that the full proxy record from Chew Bahir can be divided into three phases with similar trends in central tendency and dispersion. Phase I from ~600 to ~430 kyr BP shows a long-term shift from humid to arid conditions while slightly increasing the variability and ending with the most extreme oscillations between full humidity and extreme aridity. The transition into Phase II (~430 to ~200 kyr BP) is marked by a pronounced millennial-scale humidity increase. Phase II reflects generally more humid conditions and there is evidence of double humidity increase tendency. Firstly, between ~430 and ~315 kyr BP (Phase IIa), and again from ~280 to ~195 kyr BP (Phase IIb), with only slight changes in long-term variability. Since ~200 kyr BP (Phase III), a long-term aridification trend sets in, similar to Phase I, but with a distinct increase in variability and amplitudes. All of these changes would have had significant implications for shaping our ancestors’ living environments, both broadening and limiting their options in response to the different degrees and rates of climatic stress. The Chew Bahir record, one of the very few long terrestrial environmental records from continental eastern Africa, can contribute to testing the influence of low versus high latitude climate change in driving the expansion, contraction and fragmentation of early human habitats.

The sediment cores of the Chew Bahir drilling project, part of the Hominin Sites and Paleolakes Drilling Project (HSPDP), from southern Ethiopia, were used to reconstruct climatic changes by analyzing the sediment geochemistry with high-resolution XRF scanning. To interpret the multidimensional XRF dataset we computed a principal component analysis. We used the first principal component (PC1) to detect changes in variability by running a windowed standard deviation analysis and additionally a change point analysis to detect the exact timing of variability changes. Additionally we used the established Chew Bahir log(K/Zr) aridity proxy, representing clay mineral chemistry- detrital input ratio and compared it to a new Chew Bahir climate indicator, the log(Ca/Ti) proxy, an evaporation signal that is probably inversely related to lake level stands. We find that the log(Ca/Ti) record is also an exceptionally good climate indicator because, compared to the established log(K/Zr) proxy, it reacts with greater amplitude to insolation-controlled signals such as orbital precession. This is confirmed by the log (Ca/Ti) record showing a very clear signal during the African Humid Period, which is however less pronounced in the log(K/Zr) record. To gain a deeper understanding of the climate cycles and their temporal evolution, we computed a continuous wavelet transformation (CWT) for each of the climate proxies, and studied temporal changes in their cyclicity. Our results indicate that in addition to the precession cycle (~ 20 kyr), the Chew Bahir climate record contains earth eccentricity cycles (~ 100 kyr), as well as half-precession cycles during high eccentricity. During low eccentricity (450-350 kyr ago), we find reduced variability, three of five changes in standard deviation, damped precession and half precession cycles, and an abrupt transition from dry to wet climate, possibly due to climatic change in high latitudes which may be related to the Mid-Bruhnes event (MBE). The results confirm that during high eccentricity the tropics are insolation controlled, largely independent of the high latitudes, whereas during low eccentricity the climate of tropical eastern Africa is sensitive to climatic drivers other than precession, possibly originating from high latitudes. Such a period occurring 450 to 350 kyr ago could have led to large regional differences in moisture availability and may have affected early humans by habitat separation, which by isolating populations, resulted in technological diversification. This possible scenario may help to explain the technological transition from Middle Stone Age (MSA) to Acheulean technology that was documented in the Olorgesailie basin during the same time period.

Sets of sandy beach ridges and intervening swales define shoreline sections of the shallow St Lucia wetland system within the iSimangaliso Wetland Park, World Heritage Site in northern KwaZulu-Natal province, South Africa. The sets comprise 3–10 beach ridges, the most prominent being 80–150 m wide and rising 0.5–2 m above the adjacent swales. The highest beach ridge crests elevated 3.2–4.6 m above mean sea level are furthest from the present shoreline and the lowest ridges, rising about 0.5 m above the swales, occur closest to the present mean lake level shoreline. This investigation assesses the genesis of the sandy beach ridges on five strand plain remnants within the estuarine lake. The ridges were topographically surveyed and their ages estimated using optically stimulated luminescence (OSL) dating. OSL dating reveals that the oldest beach ridge formed around 6240 years ago, with a sequence of beach ridges having accumulated during the period ~4000 to 1500 years ago reflecting coeval accretion around the lake. The present mean lake level shoreline was only reached within the past ~600 years. Sedimentation changed from marine-dominated to lacustrine deposition in the estuary during the period of beach ridge accretion. The dated beach ridges, supported by new radiocarbon dates of fixed biological indicators from Holocene intertidal zone settings on the coast, are used with published sea-level curves to set the context of periodic beach ridge accretion in the marine-linked estuarine lake. The dated ridges suggest that episodic regression of the estuarine lake shoreline occurred after a mid-Holocene sea-level highstand. The record of sea-level change is also reflected by the long-term natural shrinking and shallowing of the proto-St Lucia lagoon/estuarine lake in the context of reduced marine influences due to closure of former marine channels by progressive barrier dune accretion. The sequence of coeval beach ridges reflects a pulsed lowering of relative sea-level in the shallowing estuarine lake. Height differences between the coeval ridges at sites around the lake reflect local environmental controls including the range of wind fetch distances across shallow lake compartments, wave height and wind-induced seiche effects.

Changes in East Asian summer and winter monsoon intensity have played a pivotal role in the prosperity and decline of society in the past, and will be important for future climate scenarios. However, the phasing of changes in the intensity of East Asian summer and winter monsoons on millennial and centennial timescales during the Holocene is unclear, limiting our ability to understand the factors driving past and future changes in the monsoon system. Here, we present a high resolution (up to multidecadal) loess record for the last 3.3 ka from the southern Chinese Loess Plateau that clearly demonstrates the relationship between changes in the intensity of the East Asian summer and winter monsoons, particularly at multicentennial scales. At multimillennial scales, the East Asian summer monsoon shows a steady weakening, while the East Asian winter monsoon intensifies continuously. At multicentennial scales, a prominent ∼700–800 yr cycle in the East Asian summer and winter monsoon intensity is observed, and here too the two monsoons are anti-phase. We conclude that multimillennial changes are driven by Northern Hemisphere summer insolation, while multicentennial changes can be correlated with solar activity and changing strength of the Atlantic meridional overturning circulation.

Climatic change is widely acknowledged to have played a role in the dispersal of modern humans out of Africa, but the timing is contentious. Genetic evidence links dispersal to climatic change ~60,000 years ago, despite increasing evidence for earlier modern human presence in Asia. We report a deep seismic and near-continuous core record of the last 150,000 years from Lake Tana, Ethiopia, close to early modern human fossil sites and to postulated dispersal routes. The record shows varied climate towards the end of the penultimate glacial, followed by an abrupt change to relatively stable moist climate during the last interglacial. These conditions could have favoured selection for behavioural versatility, population growth and range expansion, supporting models of early, multiple dispersals of modern humans from Africa.

The Qinghai-Tibetan Plateau is an important area for the study of Quaternary glaciation. Optically stimulated luminescence (OSL) dating has the potential to contribute to the chronology of glaciation in this region, but it is important to assess the accuracy of OSL dating of these glacial sediments. In this study, single grain quartz OSL signals are examined for five glacial samples collected from the moraines outside the Baiyu Valley, southeastern Tibet. The quartz grains exhibit poor luminescence characteristics, with a small proportion of grains passing the screening criteria. Grains which pass the screening criteria have relatively low signal intensity, leading to De values with large uncertainties. MAM and CAM were used to determine De values for these samples. The OSL ages are consistent with the sequence of events derived from the geomorphological relationship of the samples, and also with previous published radiocarbon ages. However, it is more difficult to reconcile the OSL ages and the terrestrial cosmogenic nuclide (TCN) 10Be ages. Analysis of both single grain quartz OSL data and TCN 10Be data is complex in this area. Further work is required to increase confidence in the OSL ages generated for the glacial sediments from this region.

In this study, geomorphological, sedimentological, and geochronological work was conducted on unconfined and confined reaches of three rivers in the eastern interior of South Africa in order to quantify the relative rates of floodplain reworking and alluvial preservation along river courses with variable valley confinement and lithology. Using optically stimulated luminescence (OSL) dating techniques, new chronologies for the Schoonspruit and Mooi River were created and the existing Klip River chronology was expanded. The results suggest that floodplains in both unconfined and confined reaches preserve complex spatial and temporal patterns of alluviation, although differences in boundary conditions lead to variation in the processes and rates of floodplain construction and reworking. On the Klip and Mooi Rivers where local base levels are stable, channels in unconfined reaches rework floodplain sediments through slow lateral migration punctuated by local erosion during avulsion events. On the Schoonspruit where base level has lowered, the channel in the unconfined reach is incised, the floodplain is abandoned, and a large gully has formed. In the confined reaches of all three rivers, the narrow floodplains are reworked by scour and fill activity and limited lateral migration. The OSL results suggest that unconfined reaches preserve relatively continuous alluvial records that extend into the Pleistocene, while the floodplains in the confined reaches preserve relatively discontinuous alluvial records biased toward the late Holocene. The alluvial geochronologic records in these systems preserve signals of changes in local base level controlled by variation in lithology and incision rather than climate change. By defining the processes, rates, and patterns of floodplain reworking in reaches with different degrees of valley confinement and channel incision, the findings contribute to understanding how rivers build, modify, and preserve alluvial sedimentary archives.

The geological record preserved in coastal salt marshes provides an opportunity to determine past hurricane activity during the Late Holocene in New England, USA. High precision dating is important to correlate overwash sand layers associated with hurricane strikes between different sites along the coastline. Three different optical dating methods have been tested and compared with independent age control; i) optically stimulated luminescence from quartz, ii) infrared stimulated luminescence from K-feldspar, and iii) a subtraction method. Quartz and K-feldspar dating results for three samples in a core from Round Hill Beach Marsh are in stratigraphic order and they are consistent within errors with radiocarbon ages and with each other. Subtraction dating results agreed with the quartz and K-feldspar ages for two of the three samples, but the subtraction age of the youngest sample gave an age underestimate. Replicate equivalent dose values from quartz showed a larger variation than those from feldspars, and this resulted in larger errors for the quartz and subtraction ages than those based on feldspars. K-feldspar yields the most precise optical ages, but is complicated by the need to correct for anomalous fading. Both quartz and K-feldspar are suitable for optical dating of hurricane overwash deposits in New England.

Optical dating has been applied to sediments preserved in Little Sippewissett Marsh, Massachusetts, USA, which are associated with overwashing of the beach barrier during hurricane strikes on the coast. The aims were to determine the hurricane landfall frequency, and make comparisons with independent age control and the historical record. Written sources of hurricane activity along the American east coast are only considered reliable back to the mid 19th century, but the sedimentary record is potentially much longer. Optical dating was applied to quartz grains extracted from thirteen samples within a sediment core from the salt-marsh. Variability in the luminescence characteristics between aliquots was observed and ~ 33% of the measured aliquots were discarded based upon the ratio of the fast component to the medium component. The majority of the samples gave normal dose distributions implying homogeneous resetting of the luminescence signal at the time of deposition, but three of the samples required application of the minimum age model (MAM). Ages ranging between 20 ± 2 and 594 ± 38 years were obtained and are broadly in agreement with independent chronologies, thus demonstrating the potential of optical dating in this setting. The hurricane record based upon optical dating extends approximately 300 years further back in time than the official National Oceanic Atmospheric Administration (NOAA) record. The localised nature of hurricane landfalls means that it will be necessary to collect multiple cores from a number of different sites in order to build up a complete hurricane record for this part of the coast.

Plater, A. J., Stupples, P., Roberts, H. M. (2009). Evidence of episodic coastal change during the Late Holocene: The Dungeness barrier complex, SE England. Geomorphology, 104 (1-2), 47-58.

The conterminous United States contains an extensive and generally well-studied record of Last Glacial loess. The loess occurs in diverse physiographic provinces, and under a wide range of climatic and ecological conditions. Both glacial and non-glacial loess sources are present, and many properties of the loess vary systematically with distance from loess sources. United States’ midcontinent Last Glacial loess is probably the thickest in the world, and our calculated mass accumulation rates (MARs) are as high as 17,500 g/m 2 /yr at the Bignell Hill locality in Nebraska, and many near-source localities have MARs greater than 1500 g/m 2 /yr. These MARs are high relative to rates calculated in other loess provinces around the world. Recent models of Last Glacial dust sources fail to predict the extent and magnitude of dust flux from the mid-continent of the United States. A better understanding of linkages between climate, ice sheet behaviour, routing of glacial meltwater, land surface processes beyond the ice margin, and vegetation is needed to improve the predictive capabilities of models simulating dust flux from this region. r 2003 Elsevier Ltd. All rights reserved.

A high-resolution chronology for Peoria (last glacial period) Loess from three sites in Nebraska, midcontinental North America, is determined by applying optically stimulated luminescence (OSL) dating to 35–50 μm quartz. At Bignell Hill, Nebraska, an OSL age of 25,000 yr near the contact of Peoria Loess with the underlying Gilman Canyon Formation shows that dust accumulation occurred early during the last glacial maximum (LGM), whereas at Devil’s Den and Eustis, Nebraska, basal OSL ages are significantly younger (18,000 and 21,000 yr, respectively). At all three localities, dust accumulation ended at some time after 14,000 yr ago. Mass accumulation rates (MARs) for western Nebraska, calculated using the OSL ages, are extremely high from 18,000 to 14,000 yr—much higher than those calculated for any other pre-Holocene location worldwide. These unprecedented MARs coincide with the timing of a mismatch between paleoenvironmental evidence from central North America, and the paleoclimate simulations from atmospheric global circulation models (AGCMs). We infer that the high atmospheric dust loading implied by these MARs may have played an important role, through radiative forcing, in maintaining a colder-than-present climate over central North America for several thousand years after summer insolation exceeded present-day values.

The Maputaland area of northeastern South Africa is characterized by extensive dune- fields which developed during polyphase reworking of regional aeolian cover sand from the Mid-Pleistocene to the Holocene. Extended parabolic dunes, many preserved only as wind-rift trailing limbs, as well as areas of sinuous crested dunes, hummocky dune systems and the high, composite, accretionary coastal barrier dune cordon are the dominant dune forms. There are few natural sections exposing the stratigraphic succession and unequivocal relative age relationships between dune systems are uncommon. A ground penetrating radar (GPR) survey of dunes and representative aeolian sand stratigraphic units was undertaken in order to investigate the internal structure of the different dune forms and identify stratigraphic relationships between buried sedimentary units. The GPR profiles revealed that the trailing limbs of almost all the parabolic dunes that were surveyed comprise stacked sand units, separated by low-angle reflections interpreted as bounding surfaces, which accumulated through polyphase vertical accretion. Most extended parabolic dunes are aligned north-south and the upper parts of the dunes are characterized by inclined reflections in GPR profile interpreted as large-scale sets of cross-stratification with apparent dips toward the west. A hummocky dune revealed cross-stratified aeolian sand superimposed on a truncated dune form and probably formed through deflation of pre-existing dunes. Using 100 MHz and 200 MHz antennae, it is clear that GPR is capable of imaging very fine sedimentary structures and buried erosional surfaces in the homogeneous aeolian sand of Maputaland. At some of the sites investigated, the buried sand units identified were sampled by hand-augering for infrared-stimulated luminescence dating. The age determinations on these samples suggest that vertical accretion of up to 7 m of sand occurred intermittently over variable time scales up to 25 000 years on some parabolic dune limbs during the Late Pleistocene. In some complex dunefields, adjacent dunes were mobilized at different times, suggesting that remobilization was localized. The implications of the complex internal structure and vertical accretion of extended parabolic dunes are discussed in the context of changes in vegetation cover and water table due to seasonal and short-term cyclical climate variations as well as long-term climate change patterns during the last glacial cycle and the Holocene.

A comparative study using quartz optically stimulated luminescence (OSL) and feldspar post-infrared infrared stimulated luminescence (post-IR IRSL) was undertaken on Quaternary fluvial sediments from an unnamed tributary of the Moopetsi River in South Africa. The aim is to assess whether the post-IR IRSL signal can be used to date incompletely bleached sediments. Several post-IR IRSL signals using varying stimulation and preheat temperatures were investigated; of these the post-IR IRSL225 signal was deemed most appropriate for dating because it bleached most rapidly. The feldspar post-IR IRSL225 equivalent dose (De) values from this site are consistently larger than those from quartz OSL, probably due to differences in the bleaching characteristics of the two signals. Additionally, the post-IR IRSL225 De values within a sample showed less variation in precision than the quartz De data, possibly due to greater averaging between grains in the feldspar small aliquots. The agreement between ages based on the OSL and post-IR IRSL225 signals was better for younger samples (50 ka); the cause of this variation is unclear.