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Historical documents provide a general chronological overview of the environmental evolution of the Yangtze River delta (YRD) during the last ca. 2000 years; however, absolute dating of the region’s late Holocene sediment is relatively rare. Optically stimulated luminescence (OSL) dating has been increasingly applied to the age determination of Holocene deposits in deltaic environments. In this study, three 23–27 m long drill cores running from south to north were collected from the Qihai plain of the northern YRD in order to reconstruct the history of this region’s formation since the late Holocene. A total of 24 samples from the three cores were subjected to OSL dating using coarse silt-sized (45–63 μm) quartz. The OSL ages range from approximately 190–3490 a revealing that the age of the delta front and delta plain facies in the coring sites are younger than 500 a while the sediments in the underlying prodelta facies are older than 2000 a. On the basis of the large age gap between the two set of deposits, we suspect that the coring sites remained submerged from 2000 to 500 years ago. As the central core has older and coarser sandy deposits than the neighbouring cores, we infer that the central core was located on a sandy mouth bar, while other cores sat within distributary channels within the estuary. The OSL ages are consistent with both the chronology implied by historical documents and other stratigraphic records in the area. This study enhances the chronological framework of land formation and delta evolution in the Qihai plain area of the YRD and thereby consolidates the conclusions derived from the application of a single technique alone.

The optically stimulated luminescence (OSL) sensitivity and OSL signal components of quartz grains were used to investigate provenance changes of Holocene sediments from the Yangtze River delta. The variation of luminescence sensitivity was observed in multiple grain aliquots and single grains of quartz from different sedimentary units of the Yangtze River delta. Laboratory experiments suggest that repeated dosing/bleaching cycles increase the luminescence sensitivity of quartz from the studied sediments. High variable thermal activation curves were observed even for samples from the same sedimentary unit, implying highly diverse sources for the delta deposits of the Yangtze River. Different sedimentary units show quartz with similar OSL component contributions, and repeated dosing/bleaching cycles and heating treatment are unable to affect the relative contributions of the fast and medium components to the bulk OSL signal. The samples from unit 1 (U1, tidal river, 15–11 ka), unit 2 (U2, estuary, 11–9 ka) and unit 6 (U6, delta plain, ca. 1 ka to the present) show relatively higher luminescence sensitivity in comparison to unit 3 (U3, tidal sand ridge, 9–4 ka), unit 4 (U4, prodelta, 4–2.5 ka) and unit 5 (U5, delta front, 2.5–1 ka), implying changing sediment sources over time. Such a temporal variation of sediment source can be explained by the transgressive/regressive history of the Yangtze River delta as well as by Asian monsoon variability since the last deglaciation. It demonstrates that luminescence sensitivity of quartz has great potential for tracing sediment sources in the Yangtze River delta, but more work is needed to characterize specific sources to establish a source-to-sink linkage.

The Yangtze (Changjiang) mega-delta, China, has a high risk of coastal erosion owing to the recent high rate of relative sea-level rise and reduced sediment supply. The study of the Holocene evolution of the delta can provide information about its response to rapid sea-level rise and changes in sediment supply caused by climate or human activity, although this has yet to be fully explored because of the lack of integrated studies using age-constrained sedimentary records. Here we document stratigraphic architecture and morphological changes over the last 11,700 years and estimate the amount of sediment trapped in the delta region on a millennial scale using a dataset of 344 sediment cores, 658 radiocarbon and 28 optically stimulated luminescence (OSL) ages (of which we obtained 64 cores, 345 radiocarbon and 28 OSL ages, and the others we sourced from the literature). Using this dataset we present the temporal and spatial morphodynamic evolution of the entire Yangtze River mouth from its early Holocene transgressive estuary to a mid- to late-Holocene regressive delta, making it possible to produce a quantitative and sequential analysis of sediment deposition. A destructive phase of the river mouth region was identified at 10 to 8 cal. kyr BP, including significant coastal erosion of tidal flats and troughs within the estuary and of tidal ridge-and-trough topography offshore; these resulted from the reshaping of the river mouth morphology caused by rapid sea-level rise at that time. As a result, the rate of sediment trapping at the river mouth declined from an average of 224 Mt yr−1 at 11.7–10 cal. kyr BP to 137 Mt yr−1 between 10 and 8 cal. kyr BP. Since delta initiation 8000 years ago, a retreat of the subaqueous delta occurred and the sediment trapping rate declined from 151 Mt yr−1 at 8–6 cal. kyr BP to 99–113 Mt yr−1 between 6 and 2 cal. kyr BP, caused by the reduction in sediment supply linked to summer monsoon weakening ~6000 years ago. In the last 2000 years the sediment trapping rate has increased to 162 Mt yr−1 due to intensified human activity. The present-day level of sedimentation in delta (49 Mt yr−1 in 2003–2011), after the completion of the Three Gorges Dam, is far lower than the ‘natural’ range in the Holocene. We thus infer a potential for system regime shift in terms of coastal erosion and a transition to a new equilibrium in delta morphology in the near future.

Coastal flooding catastrophes have affected human societies on coastal plains around the world on several occasions in the past, and are threatening 21st century societies under global warming and sea-level rise. However, the role of coastal flooding in the interruption of the Neolithic Liangzhu culture in the lower Yangtze valley, East China coast has been long contested. In this study, we used a well-dated Neolithic site (the Yushan site) close to the present coastline to demonstrate a marine drowning event at the terminal stage of the Liangzhu culture and discuss its linkage to relative sea-level rise. We analysed sedimentology, chronology, organic elemental composition, diatoms and dinoflagellate cysts for several typical profiles at the Yushan site. The field and sedimentary data provided clear evidence of a palaeo-typhoon event that overwhelmed the Yushan site at ∼2560 BCE, which heralded a period of marine inundation and ecological deterioration at the site. We also infer an acceleration in sea-level rise at 2560–2440 BCE from the sedimentary records at Yushan, which explains the widespread signatures of coastal flooding across the south Yangtze coastal plain at that time. The timing of this mid-Holocene coastal flooding coincided with the sudden disappearance of the advanced and widespread Liangzhu culture along the lower Yangtze valley. We infer that extreme events and flooding accompanying accelerated sea-level rise were major causes of vulnerability for prehistoric coastal societies.

Establishing a reliable chronology is essential for understanding delta evolution, which is normally performed using radiocarbon (14C) dating and the recently emerging technique of optically stimulated luminescence (OSL). The application of the latter one to the Holocene Yangtze River (Changjiang) Delta deposit is still quite limited. In this study, two 60.9-m-long cores were collected from Taizhou (TZ) and Nantong (NT) within the paleo-incised valley of the Yangtze River, and a total of seven and nine OSL samples were collected from the TZ and NT cores, respectively. In addition, ten accelerator mass spectrometry (AMS) 14C ages of the TZ core were presented with eight AMS 14C ages that were previously obtained from the NT core. The single-aliquot regenerative-dose (SAR) protocol was applied to coarse silt-sized (45–63 μm) and fine sand-sized (90–125 μm) quartz. The results showed that the grains in the 45–63 μm size fractions appeared to be better bleached than those in the 90–125 μm size fractions, and the detection of insufficiently bleached sediments is required in order to obtain accurate age estimates. The ages adopted for the samples range from 3 ka to 9 ka for the TZ core, and from 1 ka to 14 ka for the NT core, which were in general internally coherent within the limits of experimental errors and with respect to their stratigraphic order. The AMS 14C age of the TZ core were significantly older than their OSL ages, while those from the NT core generally showed good agreement with their OSL ages. One should be cautious when using AMS 14C to date deltatic deposits. Based on the OSL ages, two periods of rapid accumulation rates can be found in both cores, which are linked to the rapid sea level rise in early Holocene and migration of delta front facies in late Holocene. These investigations indicate that OSL technique is an effective method with which to date Holocene deltaic deposits, especially in coarse sedimentary layers where organic carbon material is sparse.

The accumulation rate of recent deposits in a delta environment is critical to the study of delta dynamics and their sustainable management. The most commonly used dating approach for recent (210Pb, 137Cs and 239 + 240Pu), while alternative techniques, such as microplastics dating, are emerging. In this study, a 180-cm sediment core from the Yangtze River (Changjiang) subaqueous delta was dated using multiple techniques, including 210Pb, 137Cs, 239 + 240Pu geochronology, microplastics content, and optically stimulated luminescence (OSL) dating. The radionuclide profiles show an irregular profile of 210Pb, while 239 + 240Pu exhibit a clear peak of activity at 74 ± 2 cm, which is linked to the maximum global fallout in 1963. Microplastics were not detected below a depth of 90 cm with maximum counts occurring in the top 16 cm. OSL analysis was conducted on the dominant grain size of the quartz (around 4–11 µm) and the ages were ~60 years older than those derived from 210Pb, 137Cs, 239 + 240Pu, and microplastics analyses. We infer that the relatively old quartz OSL ages are most likely caused by residual OSL signals arising from poorly bleached grains at the time of deposition. The profiles of 210Pb, 137Cs and 239 + 240Pu activities, microplastics content, and OSL ages indicate a variable sedimentation rate over the last ~200 years reflecting the dynamic nature of delta deposits. This study shows that both OSL and microplastics particles are promising dating tools for recent young deltaic sediments, and their combined use, alongside radionuclide methods, increases the reliability of age determination.

Optically stimulated luminescence (OSL) dating has gained increased use in dating deltatic deposits, however, its application can be hindered by the problem of incomplete bleaching. To address this limitation, we test the single-grain OSL method for the first time in the Yangtze River delta. A total of eight OSL and 14 AMS 14C samples were obtained from a 50.8 m long sediment core from the incised valley of the delta. Quartz extracted from eight OSL samples from the core was first measured with small multi-grain aliquots using medium- (45–63 μm) and coarse-grained (90–125 μm or 150–180 μm) fractions to test the internal consistency of their respective ages. The results showed that four of five medium-grained quartz samples appeared to be well bleached. In contrast, the coarse-grained quartz samples revealed poor bleaching, except for two samples from the delta front facies. Five coarse-grained quartz OSL samples were further analyzed using a single-grain OSL technique. Only 0.5–0.7% of the grains passed the rejection criteria. Single-grain OSL dating is appropriate for age determination of coarse-grained sediments which have been affected by incomplete bleaching. However, it consumes a lot of instrument time. Central and minimum age models (CAM and MAM) were used to calculate the burial age of the samples; MAM ages fit best in the stratigraphic sequence. Small aliquots are recommended as effective in identifying incomplete bleaching for medium- or coarse-grained quartz. A comparison of AMS 14C dates and OSL ages shows that 14C values are 1–3 ka older than OSL ages. According to the OSL ages, core SD experienced rapid accumulation 10–8 ka and in the last 2 ka. The former is linked to rapid sea-level rise in early Holocene, while the latter is primarily due to the migration of depo-center towards the core site, rather than entirely increased sediment delivery caused by human activities.

Morphological mosaics in early Asian humans Excavations in eastern Asia are yielding information on human evolution and migration. Li et al. analyzed two fossil human skulls from central China, dated to 100,000 to 130,000 years ago. The crania elucidate the pattern of human morphological evolution in eastern Eurasia. Some features are ancestral and similar to those of earlier eastern Eurasian humans, some are derived and shared with contemporaneous or later humans elsewhere, and some are closer to those of Neandertals. The analysis illuminates shared long-term trends in human adaptive biology and suggests the existence of interconnections between populations across Eurasia during the later Pleistocene. Science , this issue p. 969

Sediment source identification is critical for understanding delta evolution processes and for managing delta sustainability, particularly for deltas experiencing significant recent fluvial sediment discharge. Sediment sources for the Yangtze River Delta (YRD) are commonly assumed to be derived from the Yangtze River, despite the fact that the YRD is a tide-dominated delta that can receive marine-sourced sediments in addition to fluvial inputs. In particular, potential contributions from the neighbouring sediment-laden Yellow River, when it discharged into the Yellow Sea during 1128–1855 CE, remains unclear. Here we present provenance analysis of three cores from the northern YRD using size-specific magnetic characterizations. We find that magnetic properties of sediments younger than ~400 years have large differences among the studied cores. Comparison of magnetic properties to potential sources, including the major Yangtze River tributaries (i.e., Jinsha River, Jialing River, and Han River) and Old Yellow River (OYR), indicates that the northern core received enhanced Yellow River sediment loads over the last 400 years, while the southern core had a dominant Yangtze influence, which is most pronounced in size fractions less than 16 μm. This interpretation is supported by geochemical results. The documented spatial sediment source heterogeneity is caused by differences in tidal-fluvial interaction among delta distributary channels. Our results imply that the neighbouring OYR delta to the north exerts a remote influence on the YRD through longshore transport. This coastal connectivity between deltas should be assessed when forecasting future tide-dominated delta changes in the context of global change.

Many archaeological sites were excavated in China, but rarely in the adjacent coastal areas. An archaeological site at Huangniliang in the coastal area of Shandong Province, northern China was excavated in 2013. Abundant stone artifacts including hammers, cores, flakes, chunks, and retouched tools are found in the silty aeolian sediments. In this study, optically stimulated luminescence (OSL) technique was employed to establish the chronological framework of the site. Medium-grained (45–63 μm) quartz was extracted from six sediment samples for dating. The equivalent doses obtained with the single-aliquot regenerative-dose (SAR) protocol are shown to increase with depth. Three samples from the stone-tool containing layer yield OSL ages ranging from 54 ka to 59 ka, providing the earliest geochronological evidence for the presence of humans in the eastern coast of Shandong peninsula during the early period of Marine Isotope Stage (MIS) 3.

Danjiangkou Reservoir Region (DRR) is one of the areas where Acheulean-like stone technology (Mode 2) was reported in central and south China. It is located at the end of the upper reaches of the Hanshui River (the largest tributary of the Yangtze River). Systematic field investigations documented more than ninety Paleolithic sites along the fluvial terraces of the Hanshui and Danjiang Rivers (the latter a tributary of the upper reach of the Hanshui River). Subsequent excavations at more than 30 sites led to the discovery of a large number of Paleolithic stone artifacts in the past decade, showing that early hominins lived in the region at least by the early part of the Middle Pleistocene. However, little is known from the archaeological record about the context of the sites and their formation processes, the technological characteristics of the stone artifact assemblages, and whether they truly belong to Mode 2 technology or just to core and flake technology, and the overall hominin behavioral patterns and adaptation during the Middle to Late Pleistocene. Maling locality 2A (ML2A) is buried in the front edge of the third alluvial terrace of the Danjiang River. Archaeological excavations, undertaken at the site in 2011, recovered 1026 stone artifacts from a red clay deposit. Preliminary OSL dating and geomorphological comparisons between the terraces in the Hanshui River system suggest that the site is dated to the late Middle Pleistocene. Patterns of artifact concentration suggest that the site was buried in secondary context where the stone artifacts were transported by water from a relatively higher location nearby. The artifacts, primarily made on quartzite and quartz cobbles, include cores, whole flakes, various fragments, retouched pieces, two bifaces and a hammerstone. All flaking is by direct hard hammer without core preparation. The majority of flakes in the early stages of core reduction indicate that the cores are not extensively reduced. Choppers are the predominant core category, together with discoids, polyhedrons, and core scrapers. It should be noted that two bifacially flaked cobbles can classed as mode 2 implements. Eleven retouched pieces are recognized, and they were casually modified by direct hammer percussion. Although only two bifaces were excavated from this site, many more are recorded in the larger study area. The ML2A artifact assemblage may be considered as a Chinese variant of an Acheulean-like (Mode 2) industry. It can be deduced that Homo erectus was likely the responsible for manufacturing the stone artifacts.

National Natural Science Foundation of China [41302135]; China Postdoctoral Science Foundation [2012M520383]; Strategic Priority Research Program of Chinese Academy of Sciences [XDA05130202]

Shuidonggou (SDG) has long been recognized as the type site complex for the Chinese Late Paleolithic, as defined by the presence of blade technology and by its chronology. Recent field and laboratory research conducted in the past decade has revealed the presence of Paleolithic ornaments and two different technological components of an industry equivalent to the early Upper Paleolithic – Levallois-like blades and simple core and flakes which appear at SDG localities. Although clearly important for Paleolithic research in China and broader Old World prehistoric studies, relatively little is known about the SDG site formation processes and the specifics of site context. Here, we explore the various formation processes and sedimentary context associated with the stone artifact assemblage from one key site – Shuidonggou Locality 7 (SDG7). Contrary to earlier suggestions that the SDG7 lithic accumulations are the result of secondary deposition, our study indicates that SDG7 has been preserved in near-primary context. Features that were previously argued to reflect fluvial disturbance are in fact localized collapse features caused by saturated sediment load in loess deposits in a lakeshore context. Multiple lines of evidence support the argument that the site preserves the original foraging behavior of the SDG hunter–gatherers. This evidence consists of the sedimentary matrix and the distribution patterns of archaeological materials (particularly the artifact assemblage composition, debitage size distribution, artifact conditions, orientation analysis, inclination, and spatial patterning). The SDG7 archaeological deposits were buried rapidly in shallow lake margin deposits of fine sands, silts, and clays that were minimally disturbed and subjected only to relatively low energy hydraulic forces. This indicates that the SDG7 occurrences are suitable for early hominin behavioral studies in North China at the start of the Late Paleolithic.

The Youfang Paleolithic site, located in the eastern Nihewan Basin, Hebei Province, China, was discovered in 1984. However, the microblade assemblages which were excavated from the site lacked reliable chronological data. In this study, an optical dating technique was applied to nine samples from Late Pleistocene eolian sequences at the site. The ages of three samples from artifact-bearing deposits were in the range of ca. 26–29 ka with depths between 2.1 m and 2.9 m obtained with medium-grained quartz, corresponding to Marine Isotope Stage 3 (MIS3). These displayed evidence of a longer-term climate trend, in which the climate became gradually warmer and more humid. The sample from the upper culture layer was dated to 26.4 ± 2.1 ka. Five samples taken from the lower culture layer yielded ages between ca. 28 ka and 43 ka. The results suggest that human occupation at the Youfang site ranged from ca. 26 ka to 29 ka. Indeed, the Nihewan Basin yields the oldest microblade site in northern high latitudes (40° N), and offers a unique opportunity to study the emergence and characteristics of microblade technologies in northeast Asia. Nevertheless, extensive archeological field surveys and excavations are still needed to understand further the developmental process of microblade technologies in the region.

The post-IR IRSL protocol with single K-feldspar grains was applied to three samples taken from a fluvial sedimentary sequence at the archaeological site of the Dali Man, Shaanxi Province, China. K-feldspar coarse grains were extracted for measurement. Approximately 30–40% of the grains were sufficiently bright to measure, and after application of rejection criteria based on signal strength, recuperation, recycling ratio and saturation dose, ∼10–15% of the grains were used for D e calculation. The relationship of signal decay rate and form of D e ( t ) with the recovery dose were investigated. The dose recovery ratios of the samples after initial bleaching with the four different light sources were within uncertainties of unity. No anomalous fading was observed. The over-dispersion of the recovered dose and D e values were similar, suggesting neither incomplete resetting of the post-IR IRSL signals nor spatially heterogeneous dose rates significantly affected the natural dose estimates. The values of D e obtained with the single K-feldspar grain post-IR IRSL protocol were in the range ∼400–490 Gy. Combining all of the measured single-grain signals for each of the individual samples (into a ‘synthetic single aliquot’) increased the D e estimates to the range ∼700–900 Gy, suggesting that the grains screened-out by the rejection criteria may have the potential to cause palaeodose over-estimation, although this finding requires a more extensive investigation. Thermally transferred signals were found in the single K-feldspar grains post-IR IRSL protocol, and the proportion of thermally transferred signal to test-dose OSL signal (stimulation at 290 °C) from the natural dose was higher than from regenerative doses, and the proportion was grain- and dose-dependent. As such, TT-post-IR IRSL signals at 290 °C have the potential to cause dose underestimation, although this may be reduced by using larger test-dose irradiations. Our study demonstrates considerable potential in the post-IR IRSL method in providing chronological control in studies relevant to human evolution in the later-Pleistocene.

Comparisons of seven protocols for equivalent dose ( D e ) determination using the conventional optically stimulated luminescence (OSL) signal and the recuperation OSL (ReOSL) signal were made on a sample that is representative of a series of samples taken from a lacustrine sedimentary sequence at the archaeological site of Xuchang Man. Fine-grained quartz (4–11 μm) was extracted and the OSL signal was found to be dominated by the fast component. The D e values obtained using different protocols varied from 222 ± 4 Gy to 368 ± 8 Gy. The dose response curves were all fitted with a single saturating exponential function except in the case of the multiple-aliquot additive dose protocol with sensitivity correction for the recuperated OSL signal (ReMAAD). The characteristic saturation dose ( D 0 ) values obtained with the conventional OSL signal varied between 107 ± 6 Gy and 154 ± 7 Gy and showed no relationship with D e values. The ReMAAD dose response curve was linear, and yielded an equivalent dose of 269 ± 12 Gy. The ReMAAD protocol may potentially serve as a means of dating relatively older samples provided the bleaching at the time of deposition was complete.