Quaternary Geochronology最新文献

Over the past two decades, stepped-terrace systems within the Loire River basin's tributaries have undergone comprehensive multidisciplinary studies, encompassing Quaternary geology, prehistory and geochronology. Surprisingly, the geochronological exploration of the Loire River itself, the longest river in France, and its fossil stepped terraces system has been relatively limited, especially in the middle section near Orléans. However, for about fifty years, this region has been pivotal in providing evidence of the historical confluence of two ancient rivers, shaping the current Loire Valley. Researchers have suggested the existence of a Plio-Pleistocene Loire paleo-river, flowing northward from the Massif Central to the Seine valley and eventually reaching the English Channel. Subsequently, this Loire River would have underwent a reorientation of its flow westward, from the Blois area to the Atlantic Ocean, after being disconnected from its previous course.

The absence of alluvial deposits in the area between the current Loire valley and the Seine valley, attributed to substantial erosion, prevents direct exploration of evidence related to the south-north paleo-river. To address this challenge, the hypothesis suggests that the preserved alluvial terraces in the intermediate sector were established post-capture, offering an opportunity to determine when this significant geological event occurred. Through the application of Electron Spin Resonance (ESR) quartz dating, a chronological model for the Middle Loire has been then constructed. This model identifies five distinct phases in the evolution of the Middle Loire system, spanning from 800 ka to the present day. These phases indicate a gradual capture process, initiating between 900 and 800 ka, resulting in alterations to fluvial dynamics and ultimately leading to the establishment of the current course approximately 250 ka.

Northern Germany is famous for its numerous Neanderthal (Middle Palaeolithic) archaeological sites and well-preserved palaeoclimate records. Nevertheless, our understanding of how hominins responded to climate fluctuations and adapted to changing environments in this region remains limited because there are only a few reliable, highly-resolved chronological frameworks of long stratigraphic successions. Most of the Middle Palaeolithic sites in this region lack a reliable chronostratigraphy beyond the radiocarbon dating range. In this study, we present a high-resolution optically stimulated luminescence (OSL) chronology derived from a ∼21 m long sediment core (Li-BPa) that was drilled in close proximity to the known Neanderthal site of Lichtenberg. Quartz OSL dating was applied to the upper 6.5 m of the core. Subsequently, the obtained quartz OSL ages were compared with feldspar post-infrared (IR) IRSL (pIRIR) measured at 290 °C (pIRIR₂₉₀), pulsed IR₅₀ (pre-pIRIR₂₂₅), and pulsed pIRIR₂₂₅ ages to select a suitable feldspar signal to date older samples. A comparison of the quartz and feldspar ages indicates that only fading-corrected pulsed IR₅₀ (pre-pIRIR₂₂₅) and pIRIR₂₂₅ ages agree well with quartz OSL ages. Finally, the age framework of the sediment sequence was established based on the 11 quartz OSL ages and 23 fading-corrected pulsed IR₅₀ (pre-pIRIR₂₂₅) and pulsed pIRIR₂₂₅ ages. The resulting Bacon age-depth model agrees with litho- and biostratigraphic designations, indicating that the whole sequence was deposited between ca. 275 ka and ca. 24 ka, corresponding to the Saalian to Weichselian periods.

Central Yakutia is a large region in northeastern Siberia characterized by extensive permafrost, large river valleys, mountain glaciers, and large massifs of aeolian sands; the geological history of the region is complex and, at present, poorly constrained. In recent years, it has been shown that aeolian sands cover up to 60% of large parts of Central Yakutia. This paper presents the results of luminescence dating of aeolian sedimentation at the Diring Yuriakh Palaeolithic site located in the middle reaches of the Lena River. Field studies identified several thick units of aeolian sand, which cover an old deflation surface with Late (Duktai culture) and Early Palaeolithic (Diring culture) artefacts. The reliability of the OSL chronology was assessed by comparison of ages based on the optically stimulated luminescence from quartz and the infra-red stimulated luminescence from potassium-rich feldspars; these age pairs are in good agreement, implying that at least the quartz grains were sufficiently bleached before sedimentation. We obtained OSL ages that reflect three periods of accumulation between the LGM and the Holocene: ∼21 ka, 15-14 ka, and 12.5–10 ka. These periods of accumulation broadly coincide with global cooling episodes during the Last Glacial Maximum, the Older Dryas, and the Younger Dryas, with some extension into subsequent warmer intervals, whereas the intervening intervals without preserved sediments are taken to reflect dune stability during warmer periods. The sand on the terraces, sourced from alluvial bars in the river channel, was blown up the valley slope during cold and dry periods when the vegetation cover was sparse. When the climate warmed, the vegetation took some time to spread, and so the accumulation of aeolian sand on the high terraces continued into the warm periods. We also infer periods of deflation (wind erosion) that occurred before 21 ka and between 20 and 15 ka, presumably due to increased aeolian activity and localized remobilization of sediment. The new OSL chronology shows that the younger artefacts located at the cape of Diring Yuriakh, belonging to the Late Palaeolithic Duktai culture, are older than 15 ka. The new ages also show that the post-LGM aeolian sand sequences at Diring Yuriakh are correlated with the regionally developed subaerial Dolkuma Formation.

Here we report luminescence dating results on exhumed fault rocks from the North Tehran Fault (NTF, Iran), including the fault gouges. The NTF is an oblique-dip thrust fault expanding from west to east at the northern fringe of the megacity of Tehran. Although the fault is known to be active and a major threat to the city, only little is known about its earthquake history. We present first data on the timing of past fault motion using dating of fault rocks. Three sites have been selected for this study in which the fault damage zone is associated with Eocene volcaniclastic rocks (Karaj Formation). The fault gouge, transitional and damage zone were sampled for which we observed slip planes in the field. The fault rocks are composed of quartz and alkali feldspar favourable for luminescence dating. However, our study reveals that the quartz optically stimulated luminescence (OSL) signal of the Karaj Formation does not seem to have a measurable fast decaying signal component. Instead, the post-infrared stimulated luminescence at 225 °C (pIRIRSL₂₂₅) of polymineral fine-grain fraction appears to be the most feasible signal for these samples. The first luminescence-based results presented here comprise an age range from 45 ± 5 ka to 72 ± 13 ka for fault gouges and transitional zone. Since dating the transitional zone close to the fault gouge led to a younger age than the fault gouge at one site, we conclude that the sampling location plays a crucial role in dating exhumed fault rock using luminescence dating. The obtained ages are far older than those of the previous palaeoseismological studies that dated earthquake-related sedimentary features in the region. Therefore, more research is required to shed light on the resetting mechanism and condition of these fault rocks due to the recent activity of the NTF.

Quartz optically stimulated luminescence (OSL) sensitivity is varied and related to Earth surface processes and, thus, it has been shown to be a useful tool for appraising sediment recycling and provenance investigations. These investigations are mainly based on OSL data purposely measured for sensitivity calculations. However, it has been recently shown that the relative sensitivity of the quartz OSL fast component (%BOSL_F) from the first test dose (T_n) signal from an OSL dating measurement using the Single Aliquot Regenerative-dose (SAR) protocol can be used to discriminate sediment sources. Here, we investigate the possibility of characterizing %BOSL_F for provenance purposes using not only T_n signals but all other OSL signals obtained over SAR protocol cycles from OSL dating measurements. We address the %BOSL_F behaviour over SAR cycles (if conservative or not), the %BOSL_F dependency on dose-size, differences between %BOSL_F values given by natural/regenerative and test dose signals, and %BOSL_F application for provenance studies. Quartz sand grains data from twenty Late Quaternary sediment samples, representing orogenic and cratonic sources and diverse depositional contexts from South America, Africa, and Asia, are included in the analysis. All calculations were performed using data that have been previously obtained for equivalent dose estimation. The key finding is that the averaged %BOSL_F of all SAR signals was representative of the samples' characteristic sensitivity and could satisfactorily discriminate samples from known sources, mainly in the case of high-sensitivity samples. We could distinguish sediment source areas by averaging the %BOSL_F of OSL signals from SAR natural/regenerative and test doses together. Likewise, laboratories worldwide could produce regional/global sediment provenance fingerprinting reference data using their dating measurements accumulated throughout the last decade.

Parts of Central Asia have been dominated by high dust flux since the start of the Quaternary. The resulting loess-palaeosol deposits are important archives for landscape and climate changes, but there is a lack of chronological data for the subaerial deposits of Southern Tajikistan. Our study presents a high-resolution luminescence chronology for the Khonako II section in the Khovaling region. Thirty-seven samples were collected from the first ∼8 m of the section, corresponding to the Holocene soil and the upper part of the Loess 1 (L1) unit. We applied quartz OSL dating to the coarse-silt fraction (40–63 μm) and polymineral pIRIR_200,290 dating to the very fine sand fraction (63–90 μm). The polymineral pIRIR_200,290 signal has satisfactory characteristics. The quartz dose response curve displays a non-single exponential growth above ∼100 Gy, thus, the D_e values were estimated by fitting a single exponential function plus linear component to the dose response data. To assess the pIRIR_200,290 residual dose at deposition, we used the offset between our quartz and polymineral chronologies from Khonako II and equivalent doses measured on modern dust samples from Tajikistan and Uzbekistan. The resulting 9.2 ± 0.4 Gy dose was then subtracted from the pIRIR_200,290 doses for final age calculation. The quartz OSL and pIRIR ages are then generally consistent. The obtained high-resolution luminescence chronology shows that the upper part of the L1 unit accumulated during the end of marine isotope stage (MIS) 3 and through MIS 2 (39–20 ka). The average dust accumulation rates (DAR) increased from ∼31 cm ka⁻¹ to 41 cm ka⁻¹ between MIS 3 and MIS 2. The DAR reached a peak of ∼71 cm ka⁻¹ at 21 ka. A hiatus of ∼7–9 ka was then identified between the end of the last glacial maximum (LGM) and the beginning of the Holocene, and the average DAR decreased during the Holocene. Our results indicate a continuous high dust flux in the Khovaling plateau over the last 39 ka, but reworking processes and potential deflation events mark the LGM-Holocene transition. High-resolution luminescence dating studies in Tajikistan are therefore important to detect potential discontinuities in the sequences and provide an independent timescale for interpreting the climate proxies and calculating dust accumulation rates.

The emergence of ‘standing stone’ monuments within the European Late Prehistoric landscape is considered to be associated with a pivotal human cultural transition from hunting and gathering to agriculture and permanent settlement, being the earliest monuments currently dated by radiocarbon to the 5th millennium BCE. However, many standing stones were first erected, subsequently collapsed, and then re-erected during the following three millennia. The excavation of the site of an apparently in situ statue-menhir at Cruz de Cepos in NE Portugal provided the rare opportunity in Iberian prehistory to apply radiocarbon and luminescence techniques to establish the date of construction. On the basis of the iconography, the standing stone was assigned to a sculptural tradition of north-western and western Iberia, loosely dated to the Early/Middle Bronze Age (ca. 2000/1900–1250 BCE). The optically stimulated luminescence (OSL) and dosimetry characteristics of quartz extracted from sediment samples taken from locations associated with the socket pit and surrounding backfilling deposits were examined, producing OSL single grain ages at eight locations. Comparison of the OSL and calibrated radiocarbon ages shows very good agreement, with the mid-3rd millennium BCE dates confirming original erection during the Copper Age and not a much later transformation of the monument. These encouraging results indicate that OSL has the potential to provide reliable dating of depositional processes related to the construction process and is suitable for wider application to megalithic monuments of this type.

Assessing the adequate bleaching of quartz Electron Spin Resonance (ESR) signals at the time of deposition is essential for sediment ESR dating. In this study, we focus on the Datong volcanic group is situated in Datong City, Shanxi Province, and is among the most renowned volcanic groups in China. The eruption within the Datong volcanoes during a geological period resulted in extensive high-temperature lava flow that directly overlaid Quaternary lacustrine deposits and subjected the underlying lacustrine layers to high-temperature heating. Thus, an investigation of the field profile in the Yujiazhai area, southeast of the Datong Volcanic Group, shows a novel approach for assessing the bleaching extent of ESR centers. This is accomplished by comparison of the D_E values of the Al and the Ti–Li centers in partly-heated layer sample. The result reveals that quartz Al and Ti–Li centers in the lacustrine sediments appear to undergo sufficient bleached during transportation and natural bleaching processes in the study area. Furthermore, this study provides insight into the chronology of volcanic eruption in the Yujiazhai area, estimating an eruption age of approximately 300 ka. This volcanic activity most likely corresponds to the third volcanic activity period in the Datong region.

The middle reaches of Yarlung Tsangpo, situated on the southern Tibetan Plateau, have experienced extensive river damming events due to glacier advances, resulting in the formation of several ancient dammed lakes. These palaeolakes offer invaluable insights into past hydrological and geomorphological dynamics on the Tibetan Plateau. In this study, we reported a newly identified ancient dammed lake, named the Xiaru palaeolake, located upstream of the Ganglai Gorge in the uppermost segment of the middle reaches of Yarlung Tsangpo, and conducted a pioneer chronological investigation of the lake using K-feldspar post-IR IRSL (pIRIR) dating. Quartz minerals from most lacustrine and fluvial sediments can not provide reliable ages characterized with low intensity and large inter-aliquot scatter in equivalent doses (D_e). In contrast, the K-feldspar exhibited much greater luminescence intensity and narrower D_e distribution using the pIRIR₂₂₅ dating protocol. Residual, dose recovery, and fading tests demonstrated that the pIRIR₂₂₅ signals are well bleached with a relatively low fading rate, making it a more suitable dosimeter for dating applications in the study area. The pIRIR₂₂₅ ages, derived through single aliquots, standard growth curve (SGC), and single grain measurements, reveal a major phase of the Xiaru Lake between 24.1 ± 1.0 ka and 15.8 ± 1.1 ka, that commenced aligning with the global Last Glacial Maximum. Furthermore, one lacustrine sample dated to 29.9 ± 2.2 ka suggests the possibility of multiple damming events in Ganglai Gorge during the last glacial period, although further evidence is required for a comprehensive interpretation.