Quaternary Geochronology最新文献

A technique for parameterizing rock surfaces for luminescence surface exposure dating involves the use of known age rock surfaces which may host no surficial alterations or weathering rinds. However, exposure dated rock surfaces often host subsurface weathering rinds or foreign surficial components, which may impact the development of luminescence depth profiles in the rock material. To observe any effects of depth profile development and parameterizations of naturally altered rock surfaces, controlled exposure experiments were conducted on surface altered and surface non-altered luminescence saturated quartzite samples from the top and bottom portions of rock surface cores, collected from two erratic members of the Foothills Erratics Train, Alberta. Spatially resolved OSL laser scanning techniques were used to acquire two-dimensional OSL maps of the surface core samples for depth profile generation. Results produced varied intensities of depth profile data scatter and depth profile parameterizations between surface altered and non-altered samples. Several cores which exhibited surface alterations produced lower attenuation coefficients than comparable cores with no surface alterations, possibly from the effects of surface features and weathering rinds attenuating light intensity for OSL stimulation. These trends indicate samples hosting surface alterations such as weathering rinds, lichen cover, and staining may offer parameterizations which are inequivalent to rock surfaces with no surface altered components, and that depth dependent, multi-order parameterizations may be needed to adequately parameterize rock surfaces hosting surface altered features for exposure dating.

Fluvial deposits in piedmont environments are usually enriched by cobbles, which can be used for luminescence dating, as an alternative to the conventionally employed sand-sized minerals. In this study, a modified multi-elevated-temperature post-infrared infrared stimulated luminescence (MET-pIRIR) procedure was employed to establish luminescence-depth profiles of upper and lower sides of fluvial cobbles and obtain the burial ages of cobbles from high terrace of the Manas River in northern Chinese Tian Shan. The age-stimulation temperature (A-T) plateau was combined with the conventional age-depth (A-D) plateau in luminescence-depth profile to evaluate the reliability of burial ages of cobble luminescence dating from the aspects of fading and bleaching of signals. When the signal was only bleached to a limited depth given rise to no A-D plateau, the A-T plateau could serve as an internal-check to evaluate the degree of bleaching of the luminescence signal just through a single rock slice. Our results showed that self-evidenced and reliable buried ages of fluvial cobbles could be determined by only using first sub-surface rock slice in the presence of A-T plateau. Thereafter, the deposition age of cobble from top of T6 terrace and bottom of T5 terrace were ∼23.6–24.0 ka and ∼22.7 ka, respectively, inferring a very fast incision rate of ∼20 mm/a. The observed variability in bleaching depth between upper and lower sides across different cobble samples suggested complex transport dynamics.

Tabun Cave, located on the slopes of Mount Carmel (Israel), constitutes one of the key Levantine Palaeolithic sites because of its exceptionally long sequence (ca. 25 m) that has yielded a suite of lithic industries spanning the Lower and Middle Palaeolithic periods. This site is also known to have produced human remains found in the Middle Palaeolithic layers: a Neanderthal female skeleton (C1), and a mandible (C2) commonly classified as Homo sapiens but whose attribution is still debated.

Determining the chronology of Levantine Palaeolithic caves has often been limited by severe diagenetic processes, affecting the accuracy of age results obtained using trapped-charge dating methods. Characterising the mineralogical composition of the sediments in such conditions is an important step that was done in this study using Fourier transform infrared (FTIR) spectroscopy. We show that most of our sediment samples underwent diagenesis from the decomposition of guano, ash or bones, based on the presence of authigenic phosphates, which may impact the dose rate. Considering this information, we report here age results obtained using post-infrared infrared stimulated luminescence (pIRIR₂₉₀) of polymineral fine grains for Tabun Cave.

Our pIRIR₂₉₀ ages are in overall agreement with thermoluminescence (TL) dating results obtained previously on burnt flints, reinforcing the antiquity of key transitions in the Middle Pleistocene record from Tabun Cave. The ages suggest that the Lower to Middle Palaeolithic transition at Tabun, possibly coinciding with the arrival of Homo sapiens in the Levant, may be constrained between 265 ± 26 ka (late Lower Palaeolithic, Bed 72, Unit X) and 288 ± 29 ka (early Middle Palaeolithic, Beds 63–64, Unit IX), while the age of the base of the overlying mid-Middle Palaeolithic Layer C (Unit I; Beds 22-19) ranges between 204 ± 18 ka and 192 ± 14 ka. Consequently, the Tabun C2 mandible discovered at the base of Layer C may prove to be among the oldest Homo sapiens fossils found outside Africa.

The Guxiang Glaciation, a key reference for classifying late Quaternary glaciations on the Tibetan Plateau, has been dated to MIS 6 using cosmogenic ¹⁰Be exposure dating of two boulders. However, additional dating methods are needed to evaluate and improve its chronology. In this study, we used the post-infrared infrared stimulated luminescence (post-IR IRSL) signal at 225 °C from single K-feldspar grains to date a lateral moraine corresponding to the Guxiang Glaciation in the Bodui Zangbo Valley, southeastern Tibetan Plateau. Six samples from glaciofluvial sand lenses interbedded within the moraine were analyzed. The L_nT_n method was utilized for D_e determination to avoid truncation in D_e distribution and age underestimation. A common standardized growth curve (SGC) was established for all samples, and the least-squares (LS)-normalized L_n/T_n values of the brightest grains were selected for L_n/T_n and D_e estimation using the central age model (CAM). Using one fading-correction model, the post-IR IRSL ages (159 ± 9 ka to 181 ± 11 ka, average value of 173 ± 4 ka) fall within the expected MIS 6 interval and align with previous ¹⁰Be exposure ages. However, the ages are close to the limit of the method, and a different model for correcting fading suggests a much older age (average 308 ± 27 ka). This study reveals both the potential and challenges of single-grain K-feldspar luminescence dating as a means to establish chronological control for glaciations beyond the last glacial period on the Tibetan Plateau.

Single-grain OSL dating of quartz is a popular approach to OSL dating, even when incomplete bleaching is not likely to be significant. However, little testing of the accuracy of single-grain dating has been published; particularly for samples older than 50 ka. In this study, we investigate the accuracy of single-grain quartz OSL dating, when a significant number of individual grains are no longer able to accurately measure the burial dose because of saturation effects. We compare standard multi-grain OSL results with those obtained from single-grain OSL measurements for five OIS substage 5e (Eemian) samples (∼128 ka). We show that for these samples, standard multi-grain quartz dose estimation results in dose estimates in good agreement with the predicted doses (four of the five samples recover age control), but that standard frequentist single-grain dating procedures significantly underestimate the age controls, i.e. the measured to predicted dose range between 0.42 ± 0.03 and 0.84 ± 0.06, where the underestimation increases with increasing relative number of grains in saturation. Attempting to remove the inevitable bias in the dose estimation resulting from a significant number of saturated grains (by using the D_c criterion) reduced the underestimation, i.e. the measured to predicted dose ratio range between 0.63 ± 0.05 and 0.94 ± 0.08, but only the sample with the smallest absorbed dose is consistent with the age control. Using Bayesian analysis (“BayLum”) the ratio of measured to predicted dose range between 0.75 ± 0.07 and 1.14 ± 0.08, but only two of the five samples agree with the independent age control. Our results have implications for the evaluation of single-grain OSL dating of quartz in the 100–200 Gy natural dose range.

The Paleolithic site of Kalinga, in the Cagayan River Basin (Luzon Island), has recorded the oldest known traces of human occupation of the Philippine archipelago dated at 709 ± 68 ka. The island of Luzon is further known for its endemic Hominin Homo luzonensis (Callao cave) recently dated at 134 ± 14 ka, which makes it the oldest human remains in the Philippines.

The present study provides new chronological data on the Kalinga site and surrounding localities on the left bank of the Cagayan Valley and tackles the question over the geochronology of the human settlement of the basin. Following the discovery of some abundant paleontological remains and lithic artefacts on surface, several excavations took place since the 1970s. In 2014, new research in the area by our team on a site named Kalinga led to the recovery of hundreds of undisturbed archaeological remains (lithic tools and butchery marks). Apart from the early Middle Pleistocene ages obtained for the Kalinga site, the geochronology of the area is still largely unknown. Through the use of ESR on bleached quartz and ⁴⁰Ar/³⁹Ar single crystal laser fusion on plagioclase dating methods, the chronology of four archaeological sequences has been here constrained for the first time. Our results highlight a human occupation presence between 796 ± 70 ka and 273 ± 20 ka reducing the chronological gap between Kalinga site and Callao Cave, placing the Cagayan basin as a cornerstone to better understand the human arrival in insular Asia.

Located in the interior of the Tibetan Plateau (TP) and at the headwaters of the Yangtze River, the Damqu Wetland ranks among the world's highest and is highly sensitive to global climate change. Due to its remoteness and harsh, uninhabitable conditions, the sedimentological and geomorphological studies are still absent by far. Establishing a reliable chronology for sediments is crucial for this unique geographic region. Here we initiated this effort and focused on two riverbank profiles, located in the southeastern of the alpine Damqu Wetland, DQ1 (4.8 m in depth) and DQ2 (3.3 m in depth). A combination of chronological methods, including quartz Optically Stimulated Luminescence (OSL), K-feldspar post-IR InfraRed Stimulated Luminescence (pIRIR), and radiocarbon dating methods, as well as magnetic susceptibility and particle size analysis, were conducted on these profiles to establish the depositional history and reveal the palaeoenvironmental conditions of the Damqu Wetland. The dating results indicate that profiles DQ1 and DQ2 were deposited during ∼59–0.20 ka and ∼265–1.12 ka, respectively. It is interesting to note that the D₀ of quartz OSL growth curve has a value as high as 129 Gy. Both profiles exhibit depositional hiatuses, with time gaps between 37 ± 2 and 2.9 ± 0.2 ka for DQ1 and between 265 ± 16 and 4.8 ± 0.4 ka for DQ2, likely due to fluvial erosion during the period of from deglaciation to middle Holocene. The resumed sediment accumulation since the mid-late Holocene is probably mainly attributed to declined fluvial erosion in response to reduced rainfall. The darker sediment layers at depths of 0.9 m–0.7 m and 0.3 m–0.1 m in DQ2, combined with magnetic susceptibility and particle size analyses results, suggest two regional climatic optimum periods at around 4.5 ka and 1 ka. Overall, our research establishes the chronological framework of the Damqu wetland since the Late Quaternary and highlights the significant impact of climate changes on fluvial processes and wetland evolution in the remote interior TP.

Sediments of the Lena River represent an important environmental archive for understanding the Quaternary history of North-Eastern Siberia. However, at present, the structure, origin and age of the Lena River terraces are poorly known. This article presents results of lithofacies analysis and absolute dating of the Ust’-Buotama section exposing the fourth (Bestyakh) terrace of the Lena River. We report the first quartz and K-feldspar luminescence ages, the reliability of which was argued by age relations and standard tests. Three stratigraphic units have been recognized in the section (depths from the top): lacustrine-alluvial deposits (85–120 m) of the Mavrinka Formation; aeolian sand deposits of the Dolkuma Formation (23–85 m), and Holocene aeolian dune sediments (0–23 m). The resulting chronology suggests that the sediments of the Mavrinka Formation were deposited no later than 300 ka (MIS 9 or later). Deposition of the Dolkuma Formation occurred from ∼30 ka to ∼15 ka (late MIS 3 - late MIS 2). Holocene aeolian dune formed during initial Neoglacial cooling post climatic optimum (c. 5.5 cal ka BP). More extensive Late Holocene dune sediments which formed ∼400 years ago are coeval with Little Ice Age (11th-19th centuries).

The aeolian sediments in the Central Shandong Mountains (CSM) in eastern China provide a faithful carrier of climate and sea-level variations outside of the Chinese Loess Plateau. However, due to the lack of or limited application of absolute dating protocols, previous studies of Shandong loess have focused mainly on loess deposited since the last interglacial period, with fewer studies on provenances and climate changes recorded in older penultimate interglacial period characterized by a long duration and significant climate fluctuations, which is not helpful to understand the spatiotemporal pattern changes of East Asian monsoon. In this study, multi-elevated-temperature post-infrared infrared-stimulated luminescence (MET-pIRIR) dating method was utilized to obtain the absolute ages from the Dongheishan (DHS) section in CSM region. Preheat plateau and dose recovery tests indicate that the MET-pIRIR signals of 250 °C and 300 °C have negligible anomalous fading and they can give reliable ages for the loess since ∼270 ka. Luminescence dating results suggest that the DHS loess mainly accumulated from 265 ± 12 ka to 93 ± 4 ka. The loess sedimentation rates during ∼195 ± 18–108 ± 4 ka were much lower than expected in the DHS section, which occurred approximately correlates with the Qingshui erosion period (∼136 ka), as indicated by the planation surface outside the CSM. Both the grain-size characteristics and sedimentation rate variations suggest that the dust sources of the DHS loess were primarily proximal sediments, which is possibly due to frequent variations in dust provenances caused by plentiful precipitation during the interglacial periods and diversions of the Yellow River. This study implies that the CSM loess with a good chronology could be utilized to decipher regional sedimentation and climatic changes processes.

The Caspian region provides the basis of the stratigraphy and palaeogeography of the Pleistocene of Central Eurasia, and has been actively studied for more than 200 years. Many issues concerning the palaeogeographic history of the various basins of Caspian Quaternary remain unsolved, but the main problem centres on uncertainties in the chronology. Previous chronological studies have focused on a detailed description of the sedimentation history in the Lower Volga and Eastern Caucasus, ignoring a number of unique sites on the eastern Caspian coast, mainly due to inaccessibility. We obtained access to one of the most complete sections, western Cheleken, located on the Caspian coast of Turkmenistan. Within this sandy and generally lowland coast, the western part of the Cheleken peninsula forms a 10 km wide cliff opening a unique series of Middle Pleistocene - Holocene sediments which record in detail the history of Caspian transgressions and regressions. Stratigraphical, geomorphological and palaeontological studies of the section were supplemented with luminescence and radiocarbon dating. Analysis of Caspian molluscs and luminescence ages allowed the reconstruction of the sedimentary history of this region during one of the most important events of the Caspian Basin: the Early and Late Khazarian, Khvalynian and Novocaspian transgression/regression series. Luminescence dating of quartz and feldspar provided 12 OSL, IR₅₀ and pIRIR₂₉₀ ages, comparison of which showed that quartz grains were sufficiently bleached before deposition. Our chronology provides, for the first time, a deeper understanding of the sedimentation and environmental history in this region and the entire Caspian Sea. The Early Khazarian transgression occurred here at ∼220–200 ka (MIS 7). The Late Khazarian stage recorded in shallow-marine clays had relatively stable level ∼150–130 ka ago. In the second half of MIS 5 sea-level decreased and sedimentation was controlled by a large river, most probably the palaeo-Amu-Daria. The Early Khvalynian stage started at ∼27 ka and continued presumably until ∼14 ka.