The Oyambre coastal terrace: a detailed sedimentary record of the Last Interglacial Stage in northern Iberia (Cantabrian coast,Spain)

A detailed study is presented of a 15.3-m-thick Pleistocene coastal terrace located on the Cantabrian coast (northern Spain). Stratigraphic, sedimentological, topographic and micropalaeontological information is combined with a chronology based on luminescence dating to characterize the deposits. The sedimentary succession records: (i) a basal transgressive system, consisting of a wave-cut surface covered by a lower layer of beach gravels and upper beach pebbly sands; and (ii) a thicker upper highstand system (aggrading), comprising medium to very fine aeolian sands interbedded with thin palustrine muds. Luminescence dating involved a detailed sampling strategy (36 samples and two modern analogues) and the use of both quartz optically stimulated luminescence (OSL) and feldspar post-infrared infrared stimulated luminescence single aliquot regeneration protocols; feldspar results were used to confirm the completeness of bleaching of the quartz OSL signal. The quartz OSL luminescence age–depth relationship shows significant dispersion, but nevertheless two rapid phases of deposition can be clearly identified: one at ~130 ka [Marine Oxygen Isotope Stage (MIS) 5] and one at ~100 ka (MIS 5c). The top of the succession is dated to ~70 ka. The MIS 5e marine maximum flooding surface is identified at an elevation of 6.85 m above mean seal level. This elevation provides evidence of a regional sea-level highstand for this sector of the Cantabrian coast.     

Reconstruction of the late Quaternary environment of the lower Luni Plains,Thar Desert,India

Geomorphological processes in the Thar Desert of India are largely climate driven. In the lower reaches of the River Luni (the only major drainage system in the Thar Desert) a fluvio‐aeolian sequence was located at a site called Khudala. Sediments of this sequence represented a variety of depositional environments, namely aeolian, fluvially reworked aeolian, overbank deposits, gravels, and occasional evidence of pedogenesis. This provided a good opportunity to study aeolian–fluvial interaction in the region and for deducing climatic records. From the luminescence dating standpoint these sequences offered a good opportunity for a comparative study of thermoluminescence (TL), blue‐green light stimulated luminescence (BGSL) and infrared light stimulated luminescence (IRSL) on different mineral separates of identical provenance but deposited under different environments. Broadly, within experimental errors, the TL ages agreed with BGSL and IRSL ages on aeolian sands, but differed substantially in the case of fluvially reworked and proximally deposited sands and silts. The sequence provided a record spanning more than 100 ka, with an aeolian phase at > 100 ka, a channel activation phase between 70 and 30 ka and a phase of climate instability between 13 and 8 ka. This appears consistent with the records of monsoon performance during this period, which includes the Younger Dryas. It is also inferred that during the Last Glacial epoch, geomorphological processes in the Thar (both aeolian and fluvial) were dormant largely on account of their relationship with the southwest monsoon. Copyright © 2001 John Wiley & Sons, Ltd.     

Late Pleistocene fluvial dynamics in the Hochrhein Valley and in the Upper Rhine Graben: chronological frame

During the Pleistocene, the Rhine glacier system acted as a major south–north erosion and transport medium from the Swiss Alps into the Upper Rhine Graben, which has been the main sediment sink forming low angle debris fans. Only some aggradation resulted in the formation of terraces. Optically stimulated luminescence (OSL) and radiocarbon dating have been applied to set up a more reliable chronological frame of Late Pleistocene and Holocene fluvial activity in the western Hochrhein Valley and in the southern part of the Upper Rhine Graben. The stratigraphically oldest deposits exposed, a braided-river facies, yielded OSL age estimates ranging from 59.6 ± 6.2 to 33.1 ± 3.0 ka. The data set does not enable to distinguish between a linear age increase triggered by a continuous autocyclical aggradation or two (or more) age clusters, for example around 35 ka and around 55 ka, triggered by climate change, including stadial and interstadial periods (sensu Dansgaard–Oeschger cycles). The braided river facies is discontinuously (hiatus) covered by coarse-grained gravel-rich sediments deposited most likely during a single event or short-time period of major melt water discharge postdating the Last Glacial Maximum. OSL age estimates of fluvial and aeolian sediments from the above coarse-grained sediment layer are between 16.4 ± 0.8 and 10.6 ± 0.5 ka, and make a correlation with the Late Glacial period very likely. The youngest fluvial aggradation period correlates to the beginning of the Little Ice Age, as confirmed by OSL and radiocarbon ages.     

Chronology of desert margin in western India using improved luminescence dating protocols

The present study provides improved chronology for the desert margin fluvial sediments of semi-arid region located in the Mahi river basin, western India. The sequence has preserved a near-continuous record of climate change since the Last Interglacial. An earlier attempt of dating based on feldspar IRSL chronology shows a combined effect of anomalous fading and unbleached components resulting in age inversions. The present work tries to explore the possibility of using blue light stimulated luminescence (BLSL) of quartz, infra-red stimulated luminescence (IRSL) of feldspar and the newly developed methodologies, like natural correction factor based single aliquot regeneration (NCF-SAR) protocol and decision making schemes based on distribution of doses and beta heterogeneity concept for luminescence dating of sediments. Observations suggest that quartz suffered from significant sensitivity changes during natural signal measurement and partial bleaching. A combination of NCF-SAR protocol and sample specific equivalent dose computation helped in arriving at better age estimate for present samples. The study also compares the criteria for the selection of different age models that are used at present. The age of the alluvial sequence is now bracketed between 10 ka (upper aeolian unit) and 75 ka (lowermost fluvial unit).     

A detailed post‐IR IRSL dating study of the Niuyangzigou loess site in northeastern China

In this study, we report standard quartz SAR OSL and post‐IR infrared (IR) stimulated luminescence (post‐IR IRSL; pIRIR₂₉₀) measurements made on sand‐sized quartz and K‐feldspar extracts from the loess‐palaeosol sequence at Niuyangzigou in northeastern China. The quartz OSL characteristics are satisfactory. Extensive pIRIR_50,290 dose recovery tests were performed by adding doses on top of the natural dose. We found that dose recovery ratios improve significantly when the test dose ranges between ~15 and ~80% of the total dose, and good dose recovery (within ±5% of unity) can be obtained up to ～800 Gy. Otherwise, the dose recovery ratio deviates from unity. The D_e values also depend on the test dose size and so we conclude that the effect of test dose size should be routinely considered in pIRIR dating. First IR stimulation plateau pIRIR₂₉₀ results are compared with multiple elevated temperature ‐pIRIR (MET‐pIRIR) data. It appears that the low temperature MET‐pIRIR data are strongly affected by poor dose recovery, but this is not the case for the pIRIR₂₉₀ results. Natural signal measurements at the highest (first IR) stimulation temperature on a sample expected to be in field saturation suggest that ~10% signal loss occurs in pIRIR signals. Long‐term laboratory bleaching experiments (>80 days) show that a constant (or very difficult to bleach) residual pIRIR₂₉₀ signal is reached after ~300 h, corresponding to a dose of 6.2±0.7 Gy. Quartz OSL and feldspar pIRIR_50,290 ages are in good agreement at least back to c. 70 ka. Beyond this the quartz ages begin to underestimate but the feldspar ages are in agreement with the expected Last Interglacial age palaeosol.     

天山乌鲁木齐河源末次冰期冰川沉积光释光测年

乌鲁木齐河源地区是中国冰川遗迹保存最丰富、地貌最典型的区域之一,是根据冰川遗迹重建第四纪冰川历史的理想地区。大量的研究工作以及技术测年结果也使其成为试验冰川沉积光释光（optically stimulated luminescence,OSL）测年可行性的理想地点。共采集了6个冰碛及上覆黄土样品用于光释光测年。提取38~63 μm的石英颗粒,运用SAR-SGC法测试等效剂量。各种检验表明测试程序是适用的。通过地貌地层关系、重复样品、已有年代的对比等方法,检验该地冰川沉积OSL测年的可行性。结果表明,OSL年代结果与地貌地层新老关系非常吻合,与已有的其他测年技术的年代结果也具可比性,表明这些样品的OSL信号在沉积之前晒退较好,OSL年代是可信的。冰川观测站侧碛垄的OSL年代为14.8±1.2 ka;9号冰川支谷口附近冰碛的OSL年代为13.5±1.1 ka和17.2±1.3 ka;上望峰冰碛的OSL年代为20.1±1.6 ka。综合OSL年代结果与此前其他测年结果,这几套冰碛垄形成于深海氧同位素MIS 2阶段应该是比较统一的认识。上望峰冰碛上覆黄土的OSL年代（10.5±0.8 ka）也印证了该结论。OSL年代指示上望峰冰碛对应于末次冰期最盛期,冰川观测站和9号冰川支谷谷口冰碛对应于晚冰期。下望峰冰碛的OSL年代为36.3±2.8 ka,对应于MIS 3阶段。下望峰冰碛的形成时代,仍有待更多沉积学以及测年工作进一步确定。     

Timing of Holocene sand accumulation along the coast of central and SE Vietnam

In Vietnam, the coastal sand barriers and dunes located in front of the steep slopes of the high rising Truong Son Mountains are sensitive to climate and environment change and give evidence for Holocene sea-level rise. The outer barrier sands were deposited shortly before or contemporaneous with the local sea-level high stand along the Van Phong Bay postdating the last glacial maximum (LGM). Optically stimulated luminescence (OSL) dating yielded deposition ages ranging from 8.3 ± 0.6 to 6.2 ± 0.3 ka for the stratigraphically oldest exposed barrier sands. Further periods of sand accumulation took place between 2.7 and 2.5 ka and between 0.7 and 0.5 ka. The youngest period of sand mobilisation was dated to 0.2 ± 0.01 ka and is most likely related to reworked sand from mining activities. At the Suoi Tien section in southern central Vietnam, the deposition of the inner barrier sands very likely correlate with an earlier sea-level high stand prior to the last glaciation. OSL age estimates range from 276 ± 17 to 139 ± 15 ka. OSL dating significantly improves our knowledge about the sedimentary dynamics along the coast of Vietnam during the Holocene.     

New age constraints for the limit of the British–Irish Ice Sheet on the Isles of Scilly

The southernmost terrestrial extent of the Irish Sea Ice Stream (ISIS), which drained a large proportion of the last British–Irish Ice Sheet, impinged on to the Isles of Scilly during Marine Isotope Stage 2. However, the age of this ice limit has been contested and the interpretation that this occurred during the Last Glacial Maximum (LGM) remains controversial. This study reports new ages using optically stimulated luminescence (OSL) dating of outwash sediments at Battery, Tresco (25.5 ± 1.5 ka), and terrestrial cosmogenic nuclide exposure dating of boulders overlying till on Scilly Rock (25.9 ± 1.6 ka), which confirm that the ISIS reached the Isles of Scilly during the LGM. The ages demonstrate this ice advance on to the northern Isles of Scilly occurred at ∼26 ka around the time of increased ice‐rafted debris in the adjacent marine record from the continental margin, which coincided with Heinrich Event 2 at ∼24 ka. OSL dating (19.6 ± 1.5 ka) of the post‐glacial Hell Bay Gravel at Battery suggests there was then an ∼5‐ka delay between primary deposition and aeolian reworking of the glacigenic sediment, during a time when the ISIS ice front was oscillating on and around the Llŷn Peninsula, ∼390 km to the north. Copyright © 2017 The Authors. Journal of Quaternary Science Published by John Wiley & Sons, Ltd.

     

Infrared stimulated luminescence dating of an Eemian (MIS 5e) site in Denmark using K‐feldspar

Buylaert, J.‐P., Huot, S., Murray, A.S. & Van den haute, P.: Infrared stimulated luminescence dating of an Eemian (MIS 5e) site in Denmark using K‐feldspar. Boreas, 10.1111/j.1502‐3885.2010.00156.x. ISSN 0300‐9483. Infrared stimulated luminescence (IRSL) dating of K‐feldspars may be an alternative to quartz optically stimulated luminescence (OSL) dating when the quartz OSL signal is too close to saturation or when the quartz luminescence characteristics are unsuitable. In this paper, Eemian (MIS 5e) coastal marine sands exposed in a cliff section on the coast of southern Jutland (Denmark) are used to test the accuracy and precision of IRSL dating using K‐feldspars. This material has been used previously to test quartz OSL dating ( Murray & Funder 2003 ): a small systematic underestimation of <10% compared to the expected age of ～130 ka was reported. In our study, a single‐aliquot regenerative‐dose (SAR) IRSL protocol is used to determine values of equivalent dose (D_e) and the corresponding fading rates (g values). A significant age underestimation (of up to ～35%) is observed; this is attributed to anomalous fading. Using a single site‐average fading rate of 3.66 ± 0.09%/decade to correct the IRSL ages for all samples provides good agreement between the average fading‐corrected K‐feldspar age (119 ± 6 ka) and the independent age control (132–125 ka). This is despite the reservations of Huntley & Lamothe (2001) that their fading correction method is not expected to work on samples older than ～20–50 ka. This fading‐corrected feldspar result is not significantly different from the overall revised quartz age (114 ± 7 ka) also presented here. We conclude that fading‐corrected IRSL ages measured using K‐feldspar may be both precise and accurate over a greater age range than might be otherwise expected.     

大理苍山世界地质公园第四纪冰碛物特征及年代测定

云南大理苍山世界地质公园具有较高的美学价值与地学科研价值,在地学研究领域中苍山又被称为点苍山。本次研究的主要区域是点苍山玉局峰北坡和点苍山西北部的罗坪山大小海子地区,本文对点苍山玉局峰北坡冰碛物和罗坪山第四纪沉积物进行了光释光年代测定,讨论了光释光测年方法在点苍山地区第四纪冰碛物测年中的适用性,测得玉局峰北坡搬运距离较远的三条冰碛垄的年龄为(31.68±3.22)~(28.01±1.95)ka BP,属于末次冰期。对罗坪山地区第四纪沉积物进行石英砂扫描电镜分析,观察到大小海子附近第四纪沉积物石英砂表面具有一定的冰川成因特征,推断罗坪山大小海子地区曾发育过第四纪冰川作用,通过光释光测年得到大小海子附近冰川沉积物年代为(136.36±10.16)ka BP,相当于倒数第二次冰期。结合前人研究,推断点苍山地区也具有发育倒数第二次冰期的可能性。     

OSL Age Determination of Archaeological Stone Structures Using Trapped Aeolian Sediments: A Case Study from the Negev Highlands,Israel

Optically stimulated luminescence (OSL) dating is widely applied to sediments in paleoenvironmental sciences. However, there are only limited examples determining the age of archaeological stone structures by OSL using dust deposits. The age of dust deposits associated with ancient buildings may be used to date the onset of settlement (sediment below structures), settlement activity (occupation layer), or the time after a settlement had been abandoned or destroyed (sediment between collapsed roofs and walls). In this study, OSL dating is applied to establish numerical dates for settlement structures situated in the Negev Highlands, Israel. Two archaeological sites are investigated to identify their occupation history, by dating nine samples of aeolian dust trapped within the remains of ancient buildings. The OSL dating technique is applied using coarse grain quartz and a standard single‐aliquot regenerative‐dose (SAR) protocol. It was possible to date the onset of sedimentation in a later phase of the human occupation or shortly after the sites were abandoned, to 3.7 ± 0.3 ka (Intermediate Bronze Age) at the central site and to 2.7 ± 0.2 ka (Iron Age) at the ephemeral site. These results are supported by archaeological evidence gained from pottery finds and the architecture of the ancient buildings.     

Luminescence dating of Middle Pleistocene proglacial deposits from northern Switzerland: methodological aspects and stratigraphical conclusions

Optically stimulated luminescence (OSL) dating was applied to proglacial deposits from the Klettgau Valley in northern Switzerland, which is understood to record several phases of glaciation prior to the Last Interglacial. The aim was to provide an independent chronology for the different sedimentary units to understand better the complex depositional history of the region. This time range requires care when assessing the reliability of the luminescence protocols applied. Equivalent doses for fine‐ and coarse‐grain quartz remained below 300 Gy, while dose response curves for both fractions continued to display growth above 500 Gy. Dose recovery tests confirmed the ability of the single aliquot regenerative (SAR) protocol to recover laboratory doses of a similar size to burial doses, and isothermal decay measurements confirmed the stability of the quartz signal. Having passed rigorous testing criteria, quartz OSL ages of up to ～200 ka were considered reliable but significantly underestimated expected ages and prompt a reconsideration of earlier interpretations of the stratigraphy for this site. Rather than representing three separate glaciations, quartz luminescence ages instead suggest that these deposits record up to four independent ice advances during Marine Isotope Stage 6. For both single grain and single aliquot feldspar dating, it was not possible to separate the conflicting influences of anomalous fading and partial bleaching. However, uncorrected feldspar central age model ages were found to be in reasonable agreement with quartz age estimates, and suggest that feldspar ages may still offer useful additional information in this region.     

Climate control on the evolution of Late Pleistocene alluvial‐fan and aeolian sand‐sheet systems in NW Germany

The Late Pleistocene was characterized by rapid climate oscillations with alternation of warm and cold periods that lasted up to several thousand years. Although much work has been carried out on the palaeoclimate reconstruction, a direct correlation of ice‐core, marine and terrestrial records is still difficult. Here we present new data from late Middle Pleniglacial to Lateglacial alluvial‐fan and aeolian sand‐sheet deposits in northwestern Germany. Records of Late Pleniglacial alluvial fans in central Europe are very rare, and OSL dating is used to determine the timing of fan aggradation. In contrast to fluvial systems that commonly show a delay between climate change and incision/aggradation, the small alluvial‐fan systems of the Senne area responded rapidly to climatic changes and therefore act as important terrestrial climate archives for this time span. The onset of alluvial‐fan deposition correlates with the climate change from warm to cold at the end of MIS 3 (29.3±3.2 ka). Strong fan progradation started at 24.4±2.8 ka and may be related to a period of higher humidity. The vertical stacking pattern of sedimentary facies and channel styles indicate a subsequrent overall decrease in water and sediment supply, with less sustained discharges and more sporadic runoffs from the catchment area, corresponding to an increasing aridity in central Europe during the Late Pleniglacial. Major phases of channel incision and fan aggradation may have been controlled by millennial‐scale Dansgaard–Oeschger cycles. The incision of channel systems is attributed to unstable climate phases at cold–warm (dry–wet) or warm–cold (wet–dry) transitions. The alluvial‐fan deposits are bounded by an erosion surface and are overlain by aeolian sand‐sheets that were periodically affected by flash‐floods. This unconformity might be correlated with the Beuningen Gravel Bed, which is an important marker horizon in deposits of the Late Pleniglacial resulting from deflation under polar desert conditions. The deposition of aeolian sand‐sheet systems (19.6±2.1 to 13.1±1.5 ka) indicates a rapid increase in aridity at the end of the Late Pleniglacial. Intercalated flash‐floods deposits and palaeosols (Finow type) point to temporarily wet conditions during the Lateglacial. The formation of an ephemeral channel network probably marks the warm‐cold transition from the Allerød to the Younger Dryas.     

Optically stimulated luminescence chronology of terrace sediments of Siang River,Higher NE Himalaya: Comparison of Quartz and Feldspar chronometers

Four levels of terraces located along Siang River, north of Main Central Thrust at Tuting, NE Himalaya are dated using Optically Stimulated Luminescence (OSL). The dating technique is applied using (1) Blue LED stimulation on Quartz (2) Infrared Stimulated Luminescence (IRSL) stimulation on Feldspar at 50 °C and (3) Infrared Stimulated Luminescence stimulation on Feldspar at an elevated temperature of 225 °C. The results indicated that the later two protocols on feldspars yielded overestimated ages that suggested incomplete bleaching of luminescence signals in feldspar. The ages derived using quartz suggested a nearly continued valley aggradation from >21–8 ka with three phases of bedrock incision. The phase of aggradation coincides with a climatic transition from cold and dry Last Glacial phase to warm and wet Holocene Optimum. The bedrock incision phases centered at <21 ka, ∼11 ka and ∼8 ka indicate towards major episodes of tectonic uplift in the region around Tuting.     

Expansion and contraction of Hulun Buir Dunefield in north-eastern China in the last late glacial and Holocene as revealed by OSL dating

Optical stimulated luminescence (OSL) study on sand and fossil soils from Hulun Buir Dunefield in Eastern China is reported in this paper. Aeolian dune sequences responded to the climate change by alternations of aeolian sand and dark sandy soils, which corresponded to arid and humid conditions, respectively. Optical dating using the single aliquot regeneration technique with quartz was applied to the deposits. The results indicate that the soils and underlying aeolian sand correspond to the Holocene optimum (HO) and the last late glacial, respectively. Combined with studies of OSL dating of 13 profiles and grain-size, magnetic susceptibility, total organic carbon, sediment color and scanning electron microscopy measurements for two representative sections, indicate the expansion in the last late glacial sand was 10 times that of today. The dune field was not totally stabilized by vegetation cover until HO (10–5 ka BP).     

Pleistocene and Holocene aeolian facies along the Huelva coast (southern Spain): climatic and neotectonic implications

The stratigraphic relationships, genesis and chronology, including radiocarbon dating, of the Quaternary sandy deposits forming the El Asperillo cliffs (Huelva) were studied with special emphasis on the influence of neotectonic activity, sea-level changes and climate upon the evolution of the coastal zone. The E-W trending normal fault of Torre del Loro separates two tectonic blocks. The oldest deposits occur in the upthrown block. They are Early to Middle Pleistocene fluviatile deposits, probably Late Pleistocene shallow-marine deposits along an E-W trending shoreline, and Late Pleistocene and Holocene aeolian sands deposited under prevailing southerly winds. Three Pleistocene and Holocene aeolian units accumulated in the downthrown block. Of these, Unit 1, is separated from the overlying Unit 2 by a supersurface that represents the end of the Last Interglacial. Accumulation of Unit 2 took place during the Last Glacial under more arid conditions than Unit 1. The supersurface separating Units 2 and 3 was formed between the Last Glacial maximum at 18 000 ¹⁴C yr BP and ca. 14 000 ¹⁴C yr BP, the latter age corresponding to an acceleration of the rise of sea level. Unit 3 records wet conditions. The supersurface separating Units 3 and 4 fossilised the fault and the two fault blocks. Units 4 (deposited before the 4th millennium BC), 5 (> 2700 ¹⁴C yr BP to 16th century) and 6 (16th century to present) record relatively arid conditions. Prevailing wind directions changed with time from W (Units 2–4) to WSW (Unit 5) and SW (Unit 6).     

Direct luminescence chronology of the Epipaleolithic Kebaran site of Nahal Hadera V,Israel

We report direct luminescence ages for the culture‐bearing sediments of the Kebaran site of Nahal Hadera V (NHV) in the coastal plain of Israel. Although the site contains, in addition to rich lithic deposits, plentiful mammalian bone, it has proved to be undatable using radiocarbon dating, in spite of the fact that the cultural context places the time of occupation well within the range of radiocarbon dating. In contrast, luminescence dating of the site sediments proved successful. Luminescence ages were determined using the single aliquot additive‐dose (SAA) method, applied to sand‐sized quartz extracts to determine past equivalent doses (D_e). Dose rates (R) were calculated using thick source alpha counting for the uranium (U) and thorium (Th) concentrations and x‐ray fluorescence analysis for the potassium (K₂0) concentration. Of the five samples collected at the site, four represent cultural and subcultural deposits and the fifth represents the geological substrate for the archaeological deposit, a quartz‐rich, carbonate‐cemented dune sand known as aeolianite or kurkar. The luminescence age of the kurkar is 42.7 ± 6.3 ka. Human occupation of the site occurred between 21.3 ka and 14.0 ka ago, during the Last Glacial Maximum. © 2003 Wiley Periodicals, Inc.     

The onset of dune formation in the Strzelecki Desert,South Australia

This study is concerned with the Late Quaternary climatic chronology of the Strzelecki Desert dunefields in central Australia. The sand ridges comprise layers of quartz sand, some of which include palaeosol horizons with carbonated rootlets providing excellent opportunity for dating of alternations of dune building and stability by using optically stimulated luminescence (OSL). Deduced from the OSL age of the oldest aeolian layer dated, we conclude that the onset of aridity dates back to at least ∼65 ka. Older phases of aeolian activity though, following a fluvial depositional phase 160 ka ago, cannot be excluded, although no aeolian layers giving evidence for this have been found in the two dunes dated here. Unconsolidated dune sands in the upper part of one section with Late Holocene (4 ka to modern) depositional ages indicate a reactivation of the dunefield in recent times.From the crosscheck of ¹⁴C ages of the carbonated rootlets with OSL results it is concluded that under the given environmental conditions radiocarbon dating of the calcareous rootlets is not able to provide reliable ages for the phase of soil development.     

Late Weichselian fluvio‐aeolian sands and coversands of the type locality Grubbenvorst (southern Netherlands): sedimentary environments,climate record and age

The Weichselian Late Pleniglacial and Lateglacial aeolian stratigraphy (Older Coversand I, Beuningen Gravel Bed, Older Coversand II, Younger Coversand I, Usselo Soil, Younger Coversand II) in the southern Netherlands has been reinvestigated in its type locality (Grubbenvorst). Sedimentary environments have been reconstructed and related to their climatic evolution based on periglacial structures. In addition, 22 optically stimulated luminescence (OSL) ages have been determined that provide an absolute chronology for the climatic evolution and environmental changes of the coversand area. From this work it appears that, prior to 25 ka fluvial deposition by the Maas dominated. After 25 ka fluvial activity reduced and deposition occurred in a fluvio‐aeolian environment with continuous permafrost (Older Coversand I). This depositional phase was dated between 25.2 ± 2.0 and 17.2 ± 1.2 ka. The upward increase of aeolian activity and cryogenic structures in this unit is related to an increase of climatic aridity and a decrease in sedimentation rate during the Last Glacial Maximum (LGM). The Beuningen Gravel Bed, that results from deflation with polar desert conditions and that represents a stratigraphic marker in northwestern Europe, was bracketed between 17.2 ± 1.2 and 15.3 ± 1.0 ka. Based on this age result a correlation with Heinrich event H1 is suggested. Permafrost degradation occurred at the end of this period. Optical ages for the Older Coversand II unit directly overlying the Beuningen Gravel Bed range from 15.3 ± 1.0 ka at the base to 12.7 ± 0.9 ka at the top. Thus this regionally important Older Coversand II unit started at the end of the Late Pleniglacial and continued throughout the early Lateglacial. Its formation after the Late Pleniglacial (LP) maximum cold and its preservation are related to rapid climatic warming around 14.7 ka cal. BP. The Allerød age of the Usselo Soil was confirmed by the optical ages. Copyright © 2007 John Wiley & Sons, Ltd.     

Hebei loess section in the Anyemaqen Mountains,northeast Tibetan Plateau: a high‐resolution luminescence chronology

The extensive aeolian deposits of the Tibetan Plateau (TP) represent important environmental archives, recording information about the past interplay between the Asian monsoon and Westerlies and the link between dust accumulation and Quaternary glaciations. In the northeast TP, mantles of sandy loess form a distinct belt lying between 3500 and 4500 m a.s.l. on the east‐facing slopes of the Anyemaqen Mountains. However, there is little chronological information about the loess deposits in this region. This study provides a detailed chronology for loess formation in the region using luminescence dating. A total of 29 samples were collected from an 8‐m‐thick homogeneous loess section at Hebei (HB) in order to date sand‐sized (63–90 μm) quartz and K‐feldspar fractions using optically stimulated luminescence (OSL) and infrared stimulated luminescence (IRSL and pIRIR) signals, respectively. The resulting quartz and feldspar ages are in good agreement over the last 40 ka; beyond this (i.e. D_e >120 Gy), the quartz age is underestimated, and the pIRIR₁₇₀ feldspar ages are considered more reliable. The HB loess section records continuous environmental information from c. 50 to c. 30 ka, i.e. throughout Marine Isotope Stage (MIS) 3. Mass accumulation rates (MARs) varied considerably over this period with increased dust accumulation around c. 38 ka and after c. 32 ka; in between, and at the beginning of MIS 3 (50–40 ka), the dust accumulation rate was ~50% lower. Finally, the HB section also records a MIS 2 hiatus of c. 17 ka duration, probably resulting from deflation. This study implies that loess deposition on the TP is predominantly an interglacial/interstadial phenomenon and the TP may be deflating at the same time as the Chinese Loess Plateau is accumulating, at least during MIS 2.