Optically Stimulated Luminescence Ages Research Articles

Combined different luminescence dating approaches on fluvial gravel deposits from the southern upper Rhine graben

In recent years, luminescence dating has witnessed significant advancements to overcome its traditional boundaries. However, methodological challenges persist when dating high-energy fluvial gravel deposits in proglacial settings, because partial bleaching and the scarcity of sand lenses complicate luminescence age estimation through conventional approaches. To address these issues, using rock surfaces of large clasts may overcome the limited availability of sand layers in some deposits and allow clast specific assessment of luminescence signal resetting at the time of deposition through the analyses of bleaching profiles. The Hartheim gravel pit in the southern Upper Rhine Graben of southwest Germany features a sedimentary succession deposited by distal braided river meltwater streams reworked during the late Pleistocene. Different luminescence approaches have been applied to sand lenses, the sandy matrix of gravel deposits and crystalline cobbles. Quartz optically stimulated luminescence (OSL) ages range between ∼19 and 22 ka, which represents the time just after the last glaciation maximum in the region. The OSL ages of the sandy matrix of ∼24–27 ka are in an agreement with the previous estimates, as these are from a stratigraphic lower position. However, post-IR infrared stimulated luminescence (pIRIR) ages of sand layer and sandy matrix both are some 3–6 ka older than the OSL ages, despite being internally very consistent. Luminescence depth profiles show that the signal was deeply reset in some cobbles, whereas in others only the IRSL signal in the surface layer appears to have been reset. The cobble IRSL ages show a relatively large spread, and it remains uncertain, if this is caused by incomplete bleaching or it reflects dosimetric issues. Nevertheless, overall, our results underscore the potential of rock surface luminescence dating to date fluvial deposits from the Upper Rhine Graben and similar settings.

High-resolution luminescence-dated sediment record for the last two glacial-interglacial cycles from Rodderberg, Germany

The Rodderberg Volcanic Complex (RVC) is well-known for the long climate record archived in its crater basin, which lasts for several glacial-interglacial cycles. However, a detailed chronological framework is still lacking. Here, we perform high-resolution luminescence dating on a 72.8 m-long sediment core with the optically stimulated luminescence (OSL) signal from fine-grained (4–11 μm) quartz and three kinds of post-infrared infrared (pIRIR) stimulated luminescence signals from fine-grained polymineral fractions. Together with magnetic susceptibility, grain size and quartz OSL sensitivity measurements, a numerical age framework is built for the upper half of the sediment core. Quartz OSL ages align well with pIRIR ages for the last 45 ka, but they underestimate in relation to pIRIR ages for ages beyond 45 ka. The three pIRIR signals, including the pIRIR signal at 225 °C (pIRIR225), the pulsed pIRIR signal at 150 °C (pulsed pIRIR150) and the multi-elevated-temperature pIRIR at 250 °C (MET-pIRIR250), yield consistent ages up to ca. 250 ka at a sediment depth of 37.5 m. Below that depth, dating limits of the protocols are reached. Nevertheless, our results indicate that sediments below 37.5 m predate Marine Isotope Stage (MIS) 7. Altogether, obtained ages reveal continuous dust accumulation during MIS 7 and MIS 6. One erosional event happened at the end of the Eemian (MIS 5e), which eroded the Eemian soil. The sedimentation rate during the Weichselian glacial period is tenfold lower compared to the sedimentation rate observed during MIS 7–6. This low sedimentation rate likely arises from the cessation of slope wash effects and the occurrence of various wind erosional events alternating with dust deposition as the basin is filled by dust. A notably high sedimentation rate is observed at the transition from MIS 6 to the Eemian, marked by the deposition of a 7 m-thick loess layer between 135–129 (±5) ka. This high sedimentation rate could be attributed to intensified slope wash and solifluction processes resulting from the thawing of permafrost at the time of deglaciation. Alternatively, it might be a signature of Heinrich event 11, during which strong winds brought large amounts of dust into the basin within a short time.

Chronology by luminescence and radiocarbon on core sediments from the northeastern pearl river plain and implications for delta process

Accurate dating is the basis for deciphering eustatic and climatic changes on deltaic sedimentary processes. In the Pearl River Delta (PRD) plain of south China, scarce robust chronology hinders the detailed interpretation of sedimentary history. In this study, quartz optically stimulated luminescence (OSL) (21 samples), feldspar post-IR IRSL (pIRIR) (4 samples) and radiocarbon (14C) (2 samples) dating were applied to obtain detailed chronological framework of core SXG06 (23-m long to bedrock) from the northeastern PRD. SXG06 consists an upper marine unit (M1) and a lower marine unit (M2), separated by a terrestrial unit (mottled clay, T1). For M1, quartz OSL and 14C samples yielded ages from 5.2 ± 0.3 to 0.32 ± 0.02 ka. The sample on top of T1 produced a quartz OSL age of 35 ± 2 ka. For other 12 samples in T1 and M2, quartz OSL signals reached saturation and generated minimum ages (>51 ka). For these the saturated quartz OSL samples, feldspar pIR50IR250 provides an age range of 123 ± 7–105 ± 7 ka. The compilation of all the above ages and previous sedimentology data reveals that: (1) M2 was formed during marine transgression of Marine Isotope Stage (MIS) 5; (2) A hiatus with an age gap of between ∼35 ka and ∼5 ka was observed, which might be due to the low sea level and resultant weathering scouring; (3) Initial M1 deposits from the northeastern PRD postdated the central and southern PRD by ∼3 ka, indicating delayed delta development in the northeastern PRD during the Holocene. (4) SXG06 experienced slow deposition 0.3 m/ka in ∼5–3 ka because of the coevally decreased sediment supply, followed by accelerated deposition rate of 3 m/ka after ∼3 ka associated with strengthen human activity.

Chronology of core sediments from the south coastal Bohai Sea of eastern Asia and its implications for sedimentary history

The Shandong Peninsula along the coastal Bohai Sea in China is a vast alluvial plain formed by the Yellow River. It is an ideal place for investigating the evolution of landform in a river–sea interaction area where chronology is key. However, detailed optically stimulated luminescence (OSL) chronology studies of cores are still limited and have mainly concentrated on the Yellow River Delta, while they are scarce on the south coast of the Bohai Sea. In this study 16 OSL samples were collected from the upper 32 m of core DZK01 (192 m in depth) to establish a chronological framework using quartz OSL. Results indicated that the quartz OSL ages ranged from 217 ± 19 ka to 1.63 ± 0.14 ka, and we believe they were the minimum ages when De > ca. 200 Gy owing to OSL signal saturation. Our dating results reveal two sedimentary hiatuses with age gaps of 71–37 ka and 37–9.5 ka. Holocene sediments are located above a depth of 11.8 m with an onset age of approximately 9.5 ± 0.6 ka. Based on the sedimentary facies and dating results, no transgression sediment has been observed during marine isotopic stage (MIS) 3. This sedimentary sequence pattern is consistent with global sea-level change. We also summarized the extents of three transgressions around the Bohai Sea, and found very different patterns for different part of the coasts, e.g., in the north, the west, and the south. This requires further investigation.

Correlations between quartz OSL dose-response curve and TL glow curve characteristics, and their implications for equivalent dose estimation

Optically stimulated luminescence (OSL) dating of quartz using the single-aliquot regenerative-dose (SAR) procedure requires construction of dose-response curves (DRCs). The shapes of DRCs and their characteristic saturation doses (D0 values) are well-known to be highly variable between samples and among individual grains from the same sample, but the factors that control DRC characteristics are imperfectly understood. Here we report correlations between OSL DRC shapes and thermoluminescence (TL) glow curve characteristics for a sample of quartz from northern Australia. Individual grains were measured using the SAR procedure and one of two preheat temperatures (160 °C and 260 °C), and grouped according to similarities in their DRC shapes. Grains from each DRC group were then physically transferred onto a separate disc for TL measurement as a multi-grain aliquot. A strong correlation was observed between DRC group and laboratory-irradiated TL glow curve shapes, along with some differences between the two preheats. Irrespective of the selected preheat, earlier saturating DRC groups are associated with the most intense 110 °C TL signal, and the least intense 325 °C TL signal, which corresponds to the main OSL trap. Later saturating DRC groups generally show the opposite trend. There are also trends within other regions of the glow curve and DRC group, such as prominent TL responses at 140–160 °C, 220–240 °C and 390–410 °C. We assessed the effect on the accuracy of equivalent dose (De) estimation using an associated radiocarbon age as an independent cross-check of the OSL ages for the DRC groups. De over- and under-estimates were obtained for some DRC groups. Most notably, grains preheated to 160 °C displayed a pattern of De values which decreased with an increase in D0. We relate this to variable concentrations of charge at the ∼230 °C TL trap prior to regenerative dose OSL measurements. OSL ages for most DRC groups preheated to 260 °C are close to the radiocarbon age, as are those of later saturating DRC groups preheated to 160 °C; the latter DRC groups have the smallest TL signals at ∼230 °C relative to the TL peak at 325 °C. The results of this study suggest that correlations between single-grain De and D0 values can occur due to underlying differences in the TL characteristics of grains with different DRC shapes. In the absence of independent age control and prior to measuring multi-grain aliquots of quartz, we recommend that OSL dating practitioners screen their samples for any single-grain patterns of De as a function of DRC shape, to determine the optimal SAR measurement conditions and data-analysis procedures for De estimation.

Post-glacial small delta process uncovered by luminescence and radiocarbon chronology of core sediments from coastal South China Sea

Reliable chronology is crucial for reconstructing delta processes. The past decades witnessed a boost of dating works on the most economically influential large deltas (i.e., subaerial area >1000 km2), but chronology remains lacking on many small deltas (i.e., subaerial area <1000 km2) that are also densely populated and economically active. Luohe River Delta (LRD) in the coastal South China Sea is such a small delta, whose evolution concerns hundreds of thousands of people, and literally no reliable dating results have been reported to support research of its processes. Herein, dating work combining radiocarbon (14C) on mollusk shells and quartz Optically Stimulated Luminescence (OSL) methods were performed on core LFZK06 from LRD, to test applicability of both methods by age comparison and to establish a chronological framework, using Bayesian age-depth models, of LRD for the first time. 14C ages are systematically c. 0.5–1 ka younger than OSL ages from the same depths. Such young bias of 14C ages in LRD contrasts with previously observed overestimated 14C results in the nearby Pearl River Delta (PRD), likely due to the distinction in bedrock types between Luohe River (granites and sandstones only) and Pearl River (limestone prevalence causing hardwater effect) drainages. Ages of core LFZK06 span from 57 ± 7 ka to 3.42 ± 0.05 cal ka BP and contain a hiatus between 57±7–11.9 ± 1.7 ka. Holocene deltaic sequence of the core shows three-stage sedimentary processes: (1) rapid deposition of prodelta/delta front sediments at 10.2‐0.4+0.5 ka–7.7‐0.3+0.4 ka related to rapid sea level rise, (2) hiatus during 7.7‐0.3+0.4 ka–5.7‐0.8+0.5 ka likely due to reduced sediments input or river channel migration, (3) rapid accumulation of delta plain sediments during 5.7‐0.8+0.5 ka–3.42‐0.85+0.42 ka reflecting depocenter shift toward core location. Moreover, changes of quartz OSL sensitivity were detected, indicative of sediment provenance transition. A change in sediment source from nearby granite weathering towards fluvial long-transported materials occurred at a depth of 24.7 m, with low quartz OSL sensitivity in the gravelly layer below (11.9 ± 1.7 ka) and one magnitude higher quartz OSL sensitivity in prodelta deposits above (10.2‐0.4+0.5 ka).

Underestimated single-aliquot quartz OSL ages of Late-Pleistocene sediments due to the dominance of medium component

Optically stimulated luminescence (OSL) dating technique has increasingly been employed to establish chronologies for coastal deposits since the Late Pleistocene. However, the commonly used single-aliquot quartz OSL dating method may yield inaccurate ages due to factors such as partial bleaching, luminescence characteristics, and the age limit of quartz. In this study, taking the Yangtze River Delta (YRD) as an example, single-aliquot and single-grain OSL dating using varying grain-sized quartz and K-feldspar were cross-checked to establish appropriate dating method for Late-Pleistocene sediments in coastal areas. The quartz OSL signals of the upper 24 m Holocene sediments were dominated by the fast component, and the ages obtained through OSL and AMS 14C ages agree. Conversely, the lower 24–91 m section, representing the last glacial-interglacial cycle, reveals a notable underestimation of quartz OSL ages, with a maximum underestimation of 250%, attributed to the influence of signal components. For samples within the dating limit of quartz (less than 70 ka), the single-grain method effectively mitigates the issue associated with the signal component. Single-grain K-feldspar technique proves valuable for accurately determining the age of those older sediments exceeding 70 ka. Through cross-checking between different OSL dating methods, sediments initially attributed to marine isotope stage (MIS) 3 (36–60 ka) are re-identified as deposited during MIS 5 (80–130 ka). This study highlights the necessity of assessing the variability in luminescence characteristics before applying a single OSL dating protocol to all samples from different sedimentary facies within a single core.

Tectonic geomorphology and Quaternary slip history of the Fuyun fault, southwestern Altai Mountains, central Asia

The northwest-trending Altai Mountains of central Asia expose a complex network of thrust and strike-slip faults that are key features accommodating intracontinental crustal shortening related to the Cenozoic India-Asia collision. In this study, we investigated the Quaternary slip history of the Fuyun fault, a right-lateral strike-slip fault bounding the southwestern margin of the Altai Mountains, through geologic mapping, geomorphic surveying, and optically stimulated luminescence (OSL) geochronology. At the Kuoyibagaer site, the Fuyun fault displaces three generations of Pleistocene–Holocene fill-cut river terraces (i.e., T3, T2, and T1) containing landslide and debris-flow deposits. The right-lateral offsets are magnified by erosion of terrace risers, suggesting that river course migration has been faster than slip along the Fuyun fault. The highest Tp2 terrace was abandoned in the middle Pleistocene (150.4 ± 8.1 ka uppermost OSL age) and was displaced 145.5 +45.6/–12.1 m along the Fuyun fault, yielding a slip rate of 1.0 +0.4/–0.1 mm/yr since the middle Pleistocene. The lower Tp1 terrace was abandoned in the late Pleistocene and aggraded by landslides and debris flows in the latest Pleistocene–Holocene (36.7 ± 1.6 ka uppermost OSL age). Tp1 was displaced 67.5 +14.2/–6.1 m along the Fuyun fault, yielding a slip rate of 1.8 +0.5/–0.2 mm/yr since the late Pleistocene. Our preferred minimum slip rate of ~1 mm/yr suggests the Fuyun fault accommodates ~16% of the average geodetic velocity of ~6 mm/yr across the Altai Mountains. Integration of our new Fuyun slip rate with other published fault slip rates accounts for ~4.2 mm/yr of convergence across the Chinese Altai, or ~70% of the geodetic velocity field.

Millennial-scale fluctuations of palaeo-ice margin at the southern fringe of the last Fennoscandian Ice Sheet

Abstract. The paper presents the first terrestrial record of millennial-scale palaeo-ice margin oscillations at the southern fringe of the last Fennoscandian Ice Sheet (FIS) during the last glacial cycle. The study area is located in northern Poland close to the last FIS maximum limit. The chronology and dynamics of palaeo-ice margin oscillations at the southern fringe of the FIS are based on combined luminescence and 10Be surface exposure dating. Optically stimulated luminescence (OSL) was used to date sandy deposits (fluvioglacial sediments and aeolian deposits filling fossil periglacial wedges) intercalating basal till layers. The most likely age of the tills was constrained by Bayesian modelling of the sequence of OSL ages and lithostratigraphy. 10Be surface exposure dating was used on erratic boulders left during the final retreat of the last FIS and resting on the surface of glacial landforms. Our results, which are mainly based on OSL chronology and Bayesian modelling, indicate millennial-scale oscillations of the last FIS in northern Poland between ∼19 and ∼17 ka. The last FIS retreated and re-advanced over a relatively short period of time (2–3 ka), leaving lithostratigraphic records (basal tills) of three ice re-advances over a millennial-scale cycle: 19.2±1.1, 17.8±0.5 and 16.9±0.5 ka. Despite 10Be surface exposure ages obtained for 14 erratic boulders being poorly clustered, the main mode of age distribution occurs at ∼18 ka and indicates a possible signal of the ice sheet retreat after one of the re-advances. We explore the dynamics of these oscillations and compare the proposed cycles of the southern FIS advances and retreats with existing patterns of the last deglaciation and millennial-scale fluctuations of the last FIS inferred from marine records.

Coastal Evolution of Satingpra Peninsula, Songkhla Province: Implications for Understanding Songkla Lagoon Formation

Songkhla Lagoon has been studied for decades, but there is no clear evidence of its origin. As a barrier to the lagoon, the Satingpra Peninsula plays a crucial role in understanding its formation. Eleven sediment samples from sand ridges and tidal flats on the Satingpra Peninsular were collected and analysed for granulometry and geochronology. Both coarse-grained and fine-grained quartz-rich fractions were utilised to prepare samples of aliquots. The optically stimulated luminescence (OSL) dating was performed using the single-aliquot regenerative dose method for a determined (deposited) age. In addition, previous research, geological surveys and geochronological data were combined to explain their formation in this region. The OSL ages in the present study indicated that the late Holocene regression occurred between 0.36 and 3.27 ka (ka stands for 1,000 years). Integrated with previous studies, recorded ages dating back to the mid-Holocene sea level rise (ca. 6.5 ka) and the subsequent late-Holocene decline, indicate that both the old lagoon and middle beach ridge exhibit a sand ridge formation that runs parallel to the shoreline, extending from the south to the north. The middle sand, in this study, formed from about 3.02 to 1.5 ka ago resulting in the lagoon being isolated from the sea during that time. The lagoonal tide led the deposition as the present tidal flat from 3.3 to 1.7 ka. About 2.19 ka ago, the inner and middle ridges formed due to wind-driven processes influenced by a dry climate. This was followed by a continued sea level regression, leading to the formation of the outer ridge around 1.5 ka ago when the sea level was 1.4 m below the present sea level. However, it’s essential to consider this sea level data in relation to the tectonic and human-induced land motions in the surrounding area. HIGHLIGHTS OSL ages, based on average dose model at the Northern Satingpra Peninsula were 1.04 - 3.27 ka. The old sand ridges of the Satingpra Peninsula prograde northward after mid Holocene sea level highstand. Paleo sea level based on wind-wave sediments contact was 1.4 m lower than present day at 1.46 ka. GRAPHICAL ABSTRACT

Flood events in the lower reaches of the Yellow River: OSL and radiocarbon dating on the Anshang site

The lower reaches of the Yellow River have witnessed numerous episodes of flooding and considerable shifts in its course. Examining flood records within the Yellow River basin offers invaluable insights into ancient human settlements, agricultural practices, trade routes, and technological advancements of ancient Chinese civilizations. However, dating these fluvial sediments poses a considerable challenge due to either the scarcity of organic material for radiocarbon (14C) dating or the potential incomplete bleaching of sediments for optically stimulated luminescence (OSL) techniques. This study focused on the Anshang site located in Henan Province, we obtained OSL ages from distinct grain size fractions of quartz and cross-verified them with independent acceleration mass spectrometry (AMS) 14C ages. The findings revealed that both coarse quartz grains (CG) and medium quartz grains (MG) underwent complete bleaching in silt-dominated flood deposits and shallow lacustrine deposits. Conversely, the OSL ages of CG and MG quartz were notably overestimated by approximately 3–6 ka in silty clay-dominated flood deposits. Upon comparing the OSL ages with AMS 14C ages, it was evident that bulk organic matter AMS 14C ages aligned with CG OSL ages in shallow lacustrine deposits, but they appeared older than CG OSL ages in flood deposits. However, the AMS 14C ages from plant demonstrated good consistency. Consequently, we successfully identified flood-lacustrine sediments dating back to approximately ∼13 ka, ∼8–3 ka, ∼2.6 ka, ∼1 ka, and the last few hundred years, aligning well with historical documentation and earlier research. The regional evidence presented herein enhances our understanding of the applicability of OSL dating and AMS 14C dating in fluvial-lacustrine sediments. Armed with these new ages, we constructed a reference chronology for archaeological localities situated in the fluvial sediments of the lower reaches of the Yellow River.

Combined optically stimulated luminescence and radiocarbon dating of aeolian dunes in Arctic Sweden

AbstractMultiple parabolic sand dune fields formed in Arctic Sweden after the last deglaciation, facilitated by an abundance of loose glaciofluvial sediment, limited vegetation cover and strong winds. Following initial stabilisation, these dunes underwent repeated reworking after fire events, as evidenced by the presence of buried soils, charcoal layers and redeposited sands in the dune stratigraphy. These reworking events may be driven by wider climate forcing; however, to date, no chronological framework exists for this activity in Sweden. As such, here, we apply quartz optically stimulated luminescence (OSL) dating of Arctic Swedish sand dunes using two dunes at the sites of Vastakielinen and Jorggástat. Resultant double‐SAR (single aliquot regenerative dose) quartz OSL ages are in good agreement with independent ages provided by 14C dating of charcoal fragments recovered from charcoal layers within the dunes, and we conclude that the chosen protocol is generally well suited for dating aeolian reworking of dune sediments in Arctic Sweden. While feldspar contamination limits precise age assignment for initial dune movement, our results nonetheless suggest repeated and long‐lasting aeolian activity in Arctic Sweden throughout the Holocene and, although there are differences in detail, further suggest some general trends in terms of dune stability and reworking over Arctic Fennoscandia.

Origin and depositional background of the Holocene black soil in Northeast China: Evidence from grain-size analysis and optically stimulated luminescence dating

The fertile Holocene black soil of Northeast China make it a major grain producing region, however, this soil is increasingly vulnerable to erosion. Knowledge of the origin and depositional background of the black soil in Northeast China can provide a reference for the conservation of the soil resources of this region. To this end, we examined the grain-size characteristics of the Holocene black soil across the plains in Northeast China, and we conducted optically stimulated luminescence (OSL) dating of the underlying stratum. The western Holocene black soils have a bimodal grain-size distribution similar to that of the sandy loess deposits on the Chinese Loess Plateau. In contrast, the eastern Holocene black soils mostly have a trimodal grain-size distribution similar to that of reworked loess in flood plains. From west to east, the median grain size and the sand content gradually decrease from >120 μm to <20 μm and from >80 % to <20 %, respectively. This eastward fining trend is consistent with the prevailing westerly winds during the dust storm season, indicating a wind-blown origin for the black soil material which was transported primarily from the adjacent sandy lands. Furthermore, our OSL ages reveal that the underlying stratum of the Holocene black soil was primarily deposited during the last glacial period, with the relatively wide depositional age range of 2–65 ka. This suggests unstable geomorphological conditions in Northeast China prior to the formation of the black soil, which may have resulted from the enhanced erosion and decreased vegetation cover.

A new OSL dose model to account for post-depositional mixing of sediments

In applications of optically stimulated luminescence (OSL) dating to unconsolidated sediments, the burial age of a sample of grains is estimated using statistical models of the distribution of the experimentally determined equivalent doses of the grains, together with estimates of the environmental dose rate. For grains that have been vertically mixed after deposition (e.g., due to bioturbation), existing dose models may fail to appropriately account for the complexity of the mixing process, thus producing inaccurate age estimates of the original time of deposition of the ‘native’ grains in any particular sample (usually the quantity of most interest). Here we introduce a new dose model, the asymmetric Laplacian mixture model (ALMM), developed for vertically mixed samples with single-grain dose distributions. The approach is based on a continuous statistical mixture that models the displacement of grains in both upward and downward directions. The central dose of the native grains in each sediment sample is estimated by the ALMM, as well as the parameters associated with overdispersion of single-grain dose distributions and the (modelled) mixing process. Using Bayesian methodology, we apply the model to two series of vertically contiguous samples collected at the site of Nawarla Gabarnmang in northern Australia. Independent age estimates obtained from radiocarbon dating of charcoal fragments support the OSL ages for the native grains estimated by the ALMM. Moreover, our study includes sensitivity analyses that show the model is robust to variation in the experimental error of the OSL data, as well as a simulation study that demonstrates the model’s good ability to recover the simulated central dose and its excellent coverage properties. The ALMM is introduced in the context of compound Gaussian distributions, a broadly encompassing statistical framework that includes many of the most commonly used dose models. This unifying and accessible perspective on the statistical modelling of dose distributions will support practitioners in selecting an appropriate model for samples affected by post-depositional mixing, and hopefully stimulate further theoretical developments. A new R package rstanosl is provided that fits the ALMM and other commonly used dose models using Hamiltonian Monte Carlo methods via the Stan programming language.

Disentangling late quaternary fluvial and climatic drivers of palaeohydrological change in the Najaf Sea basin, Western Iraq

AbstractThe water resource provided by lake basins in the western desert of Iraq is important for human occupation of areas outside the Tigris‐Euphrates floodplain, both in the past and into the future. This paper presents the first geomorphological and geochronological study of the date of formation of the Najaf Sea and the only such study of any lake basin to the west of Mesopotamia. Geomorphological shoreline features and a palaeochannel linking to the Euphrates were studied and dated using optically stimulated luminescence (OSL) and radiocarbon dating. Provenance was determined using heavy mineral analysis. Past environments in the Najaf Sea were reconstructed by molluscan analysis. The earliest OSL ages date from c. 30 000 and 22 000 years ago and seem to predate lake formation. Younger OSL ages date the highest lake level at c. 19 m asl to between 1620–1760 AD (base) to 1906–1974 AD (near surface). The radiocarbon ages are affected by a freshwater reservoir effect, but the maximum ages recorded for either of the c. 15 m and c. 17 m asl shorelines are c. 800 cal. BC. This predates the first archaeological sites in the Najaf basin and is similar to maximum ages of c. 850 and c. 1100 cal. BC from the associated palaeochannel. This timing does not seem to be linked to a humid climate event. We therefore conclude that the establishment of the Najaf Sea in the Najaf basin occurred as a result of an avulsion event within the Euphrates system that diverted flow to the basin. The trigger for this avulsion event likely related to rapid sediment accumulation and may have been either autogenic or driven by human activity. This study therefore suggests that Najaf Sea formation facilitated human expansion beyond the Tigris‐ Euphrates floodplain and occurred due to avulsion of the Euphrates.

Nubian Levallois Technology During MIS 5: Refitted Lithic Sequences and OSL Ages of Dimona South, Israel, and Their Broader Implications

The site of Dimona South is a knapping locality in the Negev desert of Israel, situated at the raw material source. A test excavation followed by a salvage excavation conducted during 2020 revealed a partly buried archaeological layer that was exposed over an area of ~ 40 m2 and yielded a well-preserved lithic assemblage. Optically stimulated luminescence (OSL) ages of sediments within and above the archaeological layer fall within MIS 5. With a lithic assemblage dominated by Nubian Levallois technology, this site provides a rare opportunity for analysis of a well-dated, in situ Nubian assemblage. A refitting study in combination with an attribute analysis of the whole assemblage allowed the reconstruction of the Nubian reduction sequence. Our analyses indicate that a specifically pre-planned Nubian point production system existed at the site. It is characterized by the early preparation of an acute distal ridge and its careful maintenance throughout the reduction process until the cores were exhausted. These characteristics stand out from most Levantine Middle Paleolithic assemblages.The discovery of Dimona South allows us to revisit some of the technological issues at the heart of debates about Levallois Nubian technology that could not be addressed from analyses of partial surface assemblages. These new data from a secure and dated context are crucial to the inter-site and regional technological comparisons, informing our views of the Nubian technology and its role in the Middle Paleolithic world of eastern Africa, Arabia and the Levant.

Beach-ridge formation as a possible indicator for an open Limfjord – North Sea connection

Raised beach ridges are prograded sequences of wave-built deposits that may provide valuable information about past relative sea-level changes, climate change and coastal evolution. In the Limfjord in northern Denmark, the Early and Middle Holocene sea-level changes are well-constrained. However, our understanding of Late Holocene sea-level fluctuations is limited, and the exact period when the coastal barrier between the Limfjord and the North Sea formed remains uncertain. In this study, we use optically stimulated luminescence (OSL) dating to determine the age of raised beach ridges at Gjellerodde in the western part of the Limfjord. The OSL ages presented here indicate that the beach ridges formed during three periods at 3.3–2.7, 1.4–1.0, 0.2–0.1 ka. In addition our data suggest a c. 0.2 mm/yr relative sea-level fall during the Late Holocene. The three distinct periods of beach-ridge formation coincide with periods when the Limfjord was open towards the North Sea as documented in historical records and marine records. This suggests that OSL dating of beach ridges can be used as a potential indicator for determining when the connection between the Limfjord and the North Sea was open in the Late Holocene.

Quaternary sedimentation over the Precambrian basement of Borborema Province (NE, Brazil): Tectonic and climatic controls

This study characterizes the existence of Quaternary sediments in the Transversal Zone of the Borborema Province (Northeastern Brazil). The sediments comprise paleosoils, unconsolidated sands and gravel deposits, which overlie Precambrian basement rocks. The new data on these deposits includes sedimentological and stratigraphic aspects, and age definition through quartz optically stimulated luminescence (OSL) method. The outcrops were subdivided in two broad groups (named RL and Rca) referring to nearby towns where the samples were collected. OSL ages from the RL group provided ages between ca. 160.15 ± 38.26ka to 4.30 ± 2.18ka, whereas the sediments in the Rca group present OSL ages from 67.45 ± 18.24ka to 7.67 ± 2.74ka. The geochronological results reveal that these sediments were deposited during a time period from the Pleistocene to the Holocene. Deposits are chronocorrelated to Post-Barreiras (ca. 74-2ka in age), apart from the Barreiras Formation (ca. 25 to 17Ma in age), by an expressive hiatus in the Northeast Brazil. Our investigation suggest that the sediments, in the study area, are a reworking of crystalline basement and differs genetically from Post-Barreiras in the coastal zone, which are reworked from the Barreiras Formation. The combination of intense humid chemical weathering during the Pleistocene-Holocene influenced the quaternary deposition in the study area. In addition, the regional brittle tectonic reactivation of shear zones also during the Paleogene influenced the space of accommodation that allowed the deposition of these sediments.

Chronology and paleoclimatic context of hominin occupations in the Fenhe River Basin of northern China during the middle to Late Pleistocene

The relationship between climate change and hominin evolution over the Pleistocene in East Asia is still poorly understood, in particular due to the limited number of archaeological finds and fossils with reliable chronologies. Paleolithic sites preserved in loess-paleosol sequences in eastern Chinese Loess Plateau provide prospective evidence for understanding hominin evolution and dispersion across the Middle to Late Pleistocene in northern China. The Fenhe River Basin has been known as a key area for paleolithic sites and fossil hominins. Here, quartz Optically stimulated luminescence (OSL) and K-feldspar post-infrared infrared stimulated luminescence (pIRIR) dating was employed on 61 samples from 13 paleolithic sites in the Fenhe River Basin. The reliability of the ages are checked by analysis of luminescence characteristics and comparison between quartz OSL and K-feldspar pIRIR ages. Paleoclimatic records were established using alternating loess-paleosol sequences, and multi-proxy indices of grain size, magnetic susceptibility, CaCO3 and color from the dated sites. These results provide the reliable chronology for hominin presence in the Fenhe River Basin spanning the past three glacial-interglacial cycles. Our results show that this region experienced predominantly dusty, dry and cold conditions during glacials and comparatively moist and warm interglacial conditions, that are sensitive to variations in East Asian Summer and Winter Monsoon (EASM and EAWM respectively) intensities over glacial-interglacial timescales. The Fenhe River Basin is a key geographic refuge for hominins during glacial-interglacial climatic changes in northern China. It was occupied over glacial and interglacial periods spanning at least the last 370 ky, and the evidence for hominin presence is especially clear from ∼250 to 60 ka and since ∼35 ka. The frequency of hominin activity, as indicated by the number of archaeological sites and density of stone artifacts, increased during warm and humid periods of MIS 7 and MIS 5, in contrast to the cold, windy, and dry period of MIS 6. Site numbers increased in MIS 3 and the Last Glacial Maximum, in association with microblade technology. The dating results indicate that hominins with ‘modern’ features may have occurred in the Fenhe River Basin ∼140 ka ago, however, the exact timing of modern human occupation in the region needs a more combined approach consisting of morphological, ancient DNA and geochronological studies.

10Be Exposure Age Dating of Moraine Boulders and Glacially Polished Bedrock Surfaces in Karakoram and Ladakh Ranges, NW Himalaya: Implications in Quaternary Glaciation Studies

AbstractTerrestrial cosmogenic nuclide (TCN) dating has emerged as one of the most useful techniques in the last two decades for quantifying geomorphological processes and building the chronology of late Quaternary glacial advances/retreats. The chronology based on TCN and optically stimulated luminescence (OSL) dating of glacial landforms from the northwestern (NW) Himalaya suggests that glaciers responded to a complex interaction between temperature and moisture essentially derived from either of the climate systems, the Indian Summer Monsoon (ISM) and the Mid‐latitude Westerlies (MLW). The discrepancies between the TCN ages obtained on moraine boulders/bedrock surfaces, and the OSL ages on the stratigraphically equivalent deposits, highlighted the need for a detailed investigation. The present study attempts to build the chronology of Quaternary glaciation events in the Karakoram and Ladakh Ranges using TCN dating of stratigraphically constrained moraine boulders and striated bedrock surfaces. The TCN ages from glacially eroded surfaces (GES) having prominent striations are narrowly clustered around the Marine Isotopic Stage‐2 (MIS‐2). Agreement between GES TCN ages and OSL ages on the stratigraphically equivalent moraines suggests negligible geological inheritance. The glacial advance during MIS‐2 can be attributed to the combined effect of reduction in north hemispheric insolation and enhanced westerly precipitation. However, relict non‐glacial surfaces and moraine boulders with minimal ice flow modifications yield wide age distributions, most likely suggesting denudational events (interglacials) and/or contribution from tributary valley flanks.