Quaternary Geochronology最新文献

Loess–palaeosol sequences serve as valuable archives of changes in climate and atmospheric mineral dust deposition. However, little work has been conducted on Holocene loess in the Arctic, despite the sensitivity of this region to climate changes. Aeolian silt/loess profiles in the ice-free region of western Greenland near Kangerlussuaq were sampled to develop a robust age framework using both luminescence and bulk organic matter radiocarbon dating. Radiocarbon ages generally show consistent age increases with depth but are likely offset to younger ages due to sediment mixing in the upper 10–20 cm of the profiles. Quartz OSL signals exhibit insensitivity, while low-temperature infrared stimulated luminescence performed at 50 °C (IR₅₀) and the post-IR IRSL at 180 °C (pIRIR₁₈₀) signals of polymineral fine grain revealed a consistent natural inherited dose of approximately 5 Gy for pIRIR₁₈₀ and an unbleachable residual of around 2 Gy for IR₅₀, with substantial fading rates in the latter. This led to a notable age overestimation when compared with bulk organic matter radiocarbon ages. To develop an appropriate dating approach, we evaluated the differential bleaching rates of feldspar IR₅₀ and pIRIR₁₈₀ signals, and corrected for modern inherited doses. Radiocarbon ages measured on the bulk organic carbon oxidised at 400 °C (LT ¹⁴C) increased very consistently with depth, allowing calculation of accumulation rates. The presence of the atmospheric radiocarbon bomb signal at depth indicated down-mixing of surface material into the profile, which caused negative (younger) age offsets. The offset-corrected radiocarbon-based age-depth model could be compared to the luminescence results.

We show that a combination of LT ¹⁴C with polymineral pIRIR₁₈₀ dating allows the development of age models for these deposits. This multi-chronological approach reveals that loess accumulation in the region was initiated around 4 ka, probably consisting of two main phases of loess accumulation at 4–3 ka and <1 ka. The initial phase matches the proposed onset of aeolian sand activity in the wider region, but post-dates local ice retreat by c. 3 kyr. The more recent phase of accumulation also matches the timing of increased sand accumulation in the region and likely coincides with Neoglacial to Little Ice Age ice advances, or even enhanced dust activity in the last decades.

It is crucial to establish a robust chronology for understanding late Quaternary sedimentation processes and environment changes in response to sea-level fluctuation on shelves. The shelf of the East China Sea (ECS) is featured by huge terrigenous sediment input and striking land -sea interaction during the late Quaternary. However, there remains controversy in chronostratigraphic rebuilding of transgression and regression deposits during eustatic-glacial cycles, mainly due to a lack of reliable dating data. In this study, an extensive comparison of 17 optically stimulated luminescence (OSL) and 15 AMS ¹⁴C ages from core TBF-1 (upper 40 m) provides a constraint in chronostratigraphic reconstruction since Marine Isotope Stage (MIS) 5. OSL ages range from 9.5 ± 0.7 to 67.3 ± 4.8 ka at depths from 2.00 to 28.00 m, while ¹⁴C ages range from 6645 to 41435 cal a BP at depths from 0.02 to 17.52 m. Regression analysis demonstrates a high level of agreement between OSL and ¹⁴C ages, with r² values of 0.91 and 0.90, respectively. For Holocene sediments (U1), both OSL and ¹⁴C methods are applicable in tidal sand ridges, however, it should be noted that ¹⁴C ages may exhibit a young bias of up to 3 ka. For pre-Holocene sediments (U6-U2), OSL ages are robust within saturation limitation of OSL signal (D_e up to ca. 166 Gy), cross-checked by feldspar post-IR IRSL (pIRIR) dating protocol. Nevertheless, the shell ¹⁴C ages (11620 and 10390 cal a BP at depths of 13.95–14.56 m) in Last Glacial Maximum (LGM) fluvial sediments of U2 are significantly underestimated, because of their susceptibility to recrystallization and overgrowth, resulting in carbon exchange with environment. While the peaty layer's¹⁴C age in deltaic deposition (17.50 m, U5) was determined to be 36420 cal a BP, coincided with OSL age of 39.6 ± 3.9 ka. The chronostratigraphy since MIS 5 for core TBF-1 exhibits a significant correlation with previously published cores SFK-1, DZQ4, and DH02, on the ECS outer shelf. Through the evaluation of those underestimated ¹⁴C ages and saturated OSL ages, we re-elucidated the primary sedimentary facies and their respective formation periods. This sedimentary stratigraphic illustration exhibits significant consistency with eustatic-glacial cycles. The renewed chronological framework for ECS shelf allows better correlation between the late Quaternary sedimentary evolution and the land-sea interaction on open shelves dominated by siliciclastic sedimentation.

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.

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.

It is very important to distinguish the strata of different periods in the Quaternary period, especially the Middle Pleistocene and Late Pleistocene strata, for stratigraphic division, depositional environmental analysis and climate evolution analysis. In this study, the Shinaimiao (SNM) borehole sequence in Hebi City, Henan Province (China) was established by both electron spin resonance (ESR) and magnetostratigraphy methods. Both Al (eighteen samples) and Ti-Li (eight out of the eighteen samples) centers were measured using the Multiple Aliquots Additive Dose (MAAD) method. In addition, hundreds of magnetostratigraphic samples were measured to determine the precise position of the Matuyama/Brunhes (M/B) boundary. The results show that: (1) The equivalent dose (D_E) values of the Al and Ti-Li centers are consistent within the error range, demonstrating that the Multiple Center (MC) approach has worked. (2) The ESR dating results are consistent with the order of sedimentation (the ages get older with depths) and with magnetostratigraphic results of the B/M boundary within the error range, indicating that the ESR ages obtained from the Al and Ti-Li centers are reliable in this study. (3) By comprehensive analysis of the dating results and lithology characteristics, the stratigraphic ages of the SNM borehole with a depth of 126.93 m spans from Neogene to Holocene, but part of the early Pleistocene strata are missing.

The emerging use of quartz luminescence properties to characterize Earth-surface processes shows promise, with optically stimulated luminescence (OSL) sensitivity proposed as a valuable tool for provenance or sediment history tracing. However, the geologic processes that lead to quartz sensitization remain unclear. Here we study the impact of source rock and surface processes on the luminescence properties of quartz sand from bedrock and modern and Late Pleistocene alluvium generated from a mountainous catchment in northern Utah, USA. Continuous wave and linear modulated OSL are used to characterize the luminescence sensitivity and intensity of the fast-decay component. We compare the OSL sensitivity with sand-grain provenance and with proxies for surface processes such as topographic metrics, cosmogenic ¹⁰Be-derived erosion rates, chemical weathering indices, and magnetic susceptibility. Late Pleistocene sediment has low OSL sensitivity and a weak fast-decay component, similar to bedrock samples from the source area. In contrast, modern alluvium is dominated by the fast-decay component and has higher and more variable OSL sensitivity, with no clear relationship to upstream bedrock source. There is, however, an inverse relationship between OSL sensitivity and catchment-averaged erosion rates and a positive relationship with chemical weathering indices and magnetic susceptibility. These metrics suggest that the modern alluvium has experienced increased residence time in the shallow critical zone compared to the Late Pleistocene sediments. We suggest that changes in hillslope processes between the effectively wetter, cooler Pleistocene and the dryer, warmer conditions of the Holocene enhanced the luminescence properties. The results suggest that climatic controls on rates and processes of chemical and mechanical weathering and sediment transport and residence within the critical zone are encoded in the luminescence properties of quartz sand.

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.