Chronological Evidence Research Articles

Optical chronology and climatic implication of glacial advances from the southern Ladakh Range, NW Himalaya, India

Morphological, sedimentological, and chronological evidence suggests the preservation of three glacial advances of decreasing magnitude in the Puche valley (near Leh), southern Ladakh Ranges. The oldest moraine of Puche Glacier Advance-1 (PGA-1) is optically dated to the early Marine Isotopic Stage (MIS)-2 (31.5 ± 3.3 ka) that persisted until around the global Last Glacial Maxima (LGM) (22.7 ± 1.6 ka). The PGA-2 is optically dated to the post LGM (14.4 ± 1.0 ka) and perhaps was triggered by meltwater pulse (1a?) cooling. The youngest PGA-3 remains undated and could be of Holocene age. The Optically Stimulated Luminescence (OSL) ages suggest a greater role of westerlies in driving the glacier advances during the MIS-2 in the southern Ladakh Ranges and are at variance with the previous suggestions that recommended monsoon driven glacier advances. The OSL ages compared to the previously obtained 10Be surface exposure ages are younger by a magnitude. The study explores probable causes for the variance in two chronologies and suggests employing multiple dating methods to minimize the uncertainty both in terms of age and climatic interpretation.

Asian Crop Dispersal in Africa and Late Holocene Human Adaptation to Tropical Environments

Occupation of the humid tropics by Late Holocene food producers depended on the use of vegetative agricultural systems. A small number of vegetative crops from the Americas and Asia have come to dominate tropical agriculture globally in these warm and humid environments, due to their ability to provide reliable food output with low labour inputs, as well as their suitability to these environments. The prehistoric arrival in Africa of Southeast Asian crops, in particular banana, taro and greater yam but also sugar cane and others, is commonly regarded as one of the most important examples of transcontinental exchanges in the tropics. Although chronologies of food-producer expansions in Central Africa are increasingly gaining resolution, we have very little evidence for the agricultural systems used in this region. Researchers have recovered just a handful of examples of archaeobotanical banana, taro and sugar cane remains, and so far none from greater yam. Many of the suggested dispersal routes have not been tested with chronological, ecological and linguistic evidence of food producers. While the impact of Bantu-speaking people has been emphasised, the role of non-Bantu farmers speaking Ubangi and Central Sudanic languages who have expanded from the (north)east has hardly been considered. This article will review the current hypotheses on dispersal routes and suggest that transmissions via Northeast Africa should become a new focus of research on the origins of Asian vegeculture crops in Africa.

Recent progress on combining geomorphological and geochronological data with ice sheet modelling, demonstrated using the last British–Irish Ice Sheet

ABSTRACTPalaeo‐ice sheets are important analogues for understanding contemporary ice sheets, offering a record of ice sheet behaviour that spans millennia. There are two main approaches to reconstructing palaeo‐ice sheets. Empirical reconstructions use the available glacial geological and chronological evidence to estimate ice sheet extent and dynamics but lack direct consideration of ice physics. In contrast, numerically modelled simulations implement ice physics, but often lack direct quantitative comparison with empirical evidence. Despite being long identified as a fruitful scientific endeavour, few ice sheet reconstructions attempt to reconcile the empirical and model‐based approaches. To achieve this goal, model‐data comparison procedures are required. Here, we compare three numerically modelled simulations of the former British–Irish Ice Sheet with the following lines of evidence: (a) position and shape of former margin positions, recorded by moraines; (b) former ice‐flow direction and flow‐switching, recorded by flowsets of subglacial bedforms; and (c) the timing of ice‐free conditions, recorded by geochronological data. These model–data comparisons provide a useful framework for quantifying the degree of fit between numerical model simulations and empirical constraints. Such tools are vital for reconciling numerical modelling and empirical evidence, the combination of which will lead to more robust palaeo‐ice sheet reconstructions with greater explicative and ultimately predictive power.

Chronological evidence for a pre-Minoan age of pyroclastic deposits on Anafi Island, Cyclades, Greece

Pyroclastic deposits on Anafi Island, Cyclades, Greece, were initially related to the Minoan eruption (1613 BC), but later geochemical studies favored an older chronology that points at the Lower Pumice eruption of Santorini (172 ka). Here we attempt through OSL dating to provide a minimum age by dating sand-sized quartz from colluvium overlying the deposits. The chronological results excluded the possibility of being Minoan.

New excavations at Fa’ahia (Huahine, Society Islands) and chronologies of central East Polynesian colonization

The six-hectare site of Vaito'otia-Fa'ahia on Huahine Island in the Leeward Societies is renowned for its wealth of material culture typifying early East Polynesian settlement, including items of wood and fibre preserved by waterlogging, through the research of Yosihiko Sinoto and colleagues in particular. However, the stratigraphy for much of the excavated area is sketchy and no precise chronology of settlement is available. Renewed excavations in the Fa'hia site area in 2007, although relatively limited in scope produced more stratigraphic detail, additional faunal remains and artefacts, including a patu, and 12 new radiocarbon dates on short lifespan material from the lowest cultural layer which indicate initial human occupation about AD 1050-1160. In the light of this result, recent arguments for earlier initial colonisation of Central East Polynesia are reviewed. Chronological evidence adduced in these relies primarily upon radiocarbon samples with potentially substantial inbuilt age, and it is concluded that there is no compelling case for colonization of the region prior to the early eleventh century AD.

Characterizing anatexis in the Greater Himalayan Sequence (Kumaun, NW India) in terms of pressure, temperature, time and deformation

We applied field observations combined with P-T pseudosection modelling, zircon U-Pb geochronology and bulk rock geochemistry along the Kali River Valley, Kumaun Himalaya to understand conditions of peak metamorphism and partial melting of the Greater Himalayan Sequence (GHS) along with spatiotemporal relationship between anatexis and fault activation. The southern tectonic boundary of GHS or the Main Central Thrust (MCT) is marked on the basis of structural, metamorphic and chronological evidences. Outcrop-scale observations suggest generation of partial melt at the base of the MCT. This partial melt migrated to higher structural levels and finally emplaced as tourmaline bearing leucogranite in the northern tectonic boundary of the GHS, which is marked by the South Tibetan Detachment Zone (STDZ). P-T pseudosection modelling shows that GHS have experienced muscovite dehydration melting at 9.2–9.8 kbar and 720°–725 °C, 8.4–8.7 kbar and 700°-710 °C, 7.8–8.4 kbar and 700–720 °C respectively at its lower, lower-middle and middle structural levels. Zircon U-Pb geochronology suggests that the GHS underwent suprasolidus peak metamorphism and post-peak anatexis during a time span of ~26–22 Ma at the base of the MCT and ~32–27 Ma at the middle structural level. The MCT is at least ~22 Ma old, being synkinematic to the partial melting event that took place at its base. Diachronous and brief episodes of partial melting and absence of sillimanite zone at the base of the GHS help us envisage a ‘critical taper wedge’ scenario, where partial melt weakened the overlying Himalayan wedge and triggered gravity collapse that formed the STDZ.

The Technological and Chronological Implication of 14C Concentrations in Carbon Samples Extracted from Mongolian Cast Iron Artifacts

ABSTRACTCast iron objects recovered primarily in eastern Mongolia, spanning the Xiongnu through the Early Historic periods (ca. 3rd BC–AD 17th century), were examined for their radiocarbon (14C) concentration and microstructure. Most of the samples examined were found to have originated from charcoal-based smelting with a few exceptions that were made using a mineral coal-based technique. A comparison of 14C dates with dates derived from artifact typology allowed the charcoal-smelted objects to be classified into two groups, based on whether the radiometric and typological periodization are in agreement or not. In addition, those with differing 14C and typological dates can be divided into two subgroups with and without evidence for a melt treatment applied after original casting. These conflicting dating results are confusing and would seem to provoke skepticism about the use of 14C measurements for dating iron artifacts. We demonstrate however that 14C analysis, when combined with metallographic examination and other lines of chronological evidence, can clarify the history of a given iron object and its multiple users, often separated in time by more than a millennium.

Sedimentary Evolution and Transgressions of the Western Subei Basin in Eastern China since the Late Pliocene

AbstractSedimentary sequences in the Subei Basin are complex and have been affected by interactions between the ocean and rivers since the Late Pliocene, including the Yellow River, Huaihe River, and the Yangtze River. This sedimentary evolution, in particular the timing of Pleistocene transgressions, has long been a matter of controversy owing to the lack of precise chronological evidence. The aim of this study is to explore the evolution of the sedimentary environment throughout the past 3.00 Ma in this region on the basis of a comprehensive analysis of particle size and foraminifera and ostracods collected in the TZK9 core from the Subei Basin combined with geochronological studies of magnetostratigraphy, AMS14C and optically stimulated luminescence (OSL). The results show that fluvial facies in the sedimentary environment from 3.00 to 1.01 Ma. There were fluvial facies and reflects six sea‐level high stands from 1.01 to 0.25 Ma. The study area was affected by four large‐scale transgressions since 0.25 Ma. The four marine sedimentary layers known as DU7 (buried at 48–52 m), DU5 (buried at 35–41 m), DU3 (buried at 16–23 m), and DU1 (buried at 2–4 m) are recorded in the MIS7 (210–250 ka), MIS5, MIS3, and Holocene, respectively. The magnitude of the DU5 transgression was identical to that of the DU3 transgression, both were larger than the DU7 transgression, and the DU1 transgression was the weakest. The variation of transgression strength reflects the influence of global changes in sea level, tectonic subsidence, shell ridges, and sand dams. In the TZK9 core, we found evidence of seven sea‐level high stands from the Early–Middle Pleistocene, and the first one caused by regional rapid subsidence and could be traced back to 0.83‐0.84 Ma. The sea‐level high stands and the age of the first one recorded above was different from other cores in eastern China, this was caused by the lack of absolute age control and the differences in paleotopography during this period. This study reconstructs sedimentary evolution, determines the transgression and its age, establishes the chronology since the Late Pliocene, and provides a scientific framework for further paleoenvironmental and tectonic studies. The results of this study highlight the important role that local tectonics and global sea level play in the sedimentary evolution and transgressions that have occurred in the western Subei Basin.

Lepenski Vir chronology and stratigraphy revisited

This article offers a new look at the stratigraphy and chronology of Mesolithic and Neolithic deposits at Lepenski Vir, particularly based on newly available Accelerator Mass Spectrometry (AMS) dating and aDNA genomic evidence. It focuses on a detailed analysis of several key contexts for which new radiocarbon dates are available while at the same time reviewing taphonomic and age-offset problems when dating human remains and other materials affected by the aquatic reservoir effect in the Danube Gorges area. The robust chronological evidence as well as available stratigraphic data overwhelmingly show that the start of the main and iconic phase of the occupation of this site, represented by the architecture of trapezoidal buildings and sculpted sandstone boulders, should unequivocally be dated to the period of the Mesolithic-Neolithic transition in the last two centuries of the seventh millennium cal BC. At this time, local forager populations of distinct hunter-gatherer genetic ancestry came into contact and mixed with incoming Neolithic, farming populations of north-western Anatolian genetic ancestry, based on the available genomic data but also supported by studies of material culture traditions. The article deals directly with the recent criticism of this chrono-stratigraphic model for Lepenski Vir.

New Radiocarbon Dates from Nasera Rockshelter (Tanzania): Implications for Studying Spatial Patterns in Late Pleistocene Technology

AbstractLate Pleistocene and Holocene evidence from multiple rockshelters in north-central Tanzania suggests a regional pattern of changing technological behaviors through time. We use independent chronological evidence to test if the proposed technological patterns across space were also temporally equivalent. We applied AMS radiocarbon dating methods to the carbonate fraction of five ostrich eggshell fragments from Mehlman’s 1975-1976 excavations at Nasera rockshelter and compared our results to recent re-dating efforts of Mumba rockshelter. We document radiocarbon results >46 ka at Nasera in Level 5, indicating that associated and underlying technologies (including what Mehlman termed the ‘Nasera Industry’) are older than previously documented. Backed pieces first appear >46 ka at Nasera, which is in accordance with recent evidence from nearby rockshelters like Enkapune ya Muto, Panga ya Saidi, and potentially Kisese II. We also provide an age of 11,260-11,710 calBP for the ‘Silale Industry’ of Level 3B. Overall, the shifts in lithic technology previously considered to be shared between Mumba and Nasera rockshelters are not temporally aligned, emphasizing the possibility that intra-site variability was the norm throughout the Late Pleistocene in eastern Africa.

Authenticity and credibility aware detection of adverse drug events from social media

ObjectivesAdverse drug events (ADEs) are among the top causes of hospitalization and death. Social media is a promising open data source for the timely detection of potential ADEs. In this paper, we study the problem of detecting signals of ADEs from social media. MethodsDetecting ADEs whose drug and AE may be reported in different posts of a user leads to major concerns regarding the content authenticity and user credibility, which have not been addressed in previous studies. Content authenticity concerns whether a post mentions drugs or adverse events that are actually consumed or experienced by the writer. User credibility indicates the degree to which chronological evidence from a user's sequence of posts should be trusted in the ADE detection. We propose AC-SPASM, a Bayesian model for the authenticity and credibility aware detection of ADEs from social media. The model exploits the interaction between content authenticity, user credibility and ADE signal quality. In particular, we argue that the credibility of a user correlates with the user's consistency in reporting authentic content. ResultsWe conduct experiments on a real-world Twitter dataset containing 1.2 million posts from 13,178 users. Our benchmark set contains 22 drugs and 8089 AEs. AC-SPASM recognizes authentic posts with F1 – the harmonic mean of precision and recall of 80%, and estimates user credibility with precision@10 = 90% and NDCG@10 – a measure for top-10 ranking quality of 96%. Upon validation against known ADEs, AC-SPASM achieves F1 = 91%, outperforming state-of-the-art baseline models by 32% (p < 0.05). Also, AC-SPASM obtains precision@456 = 73% and NDCG@456 = 94% in detecting and prioritizing unknown potential ADE signals for further investigation. Furthermore, the results show that AC-SPASM is scalable to large datasets. ConclusionsOur study demonstrates that taking into account the content authenticity and user credibility improves the detection of ADEs from social media. Our work generates hypotheses to reduce experts’ guesswork in identifying unknown potential ADEs.

Authenticity and credibility aware detection of adverse drug events from social media

ObjectivesAdverse drug events (ADEs) are among the top causes of hospitalization and death. Social media is a promising open data source for the timely detection of potential ADEs. In this paper, we study the problem of detecting signals of ADEs from social media. MethodsDetecting ADEs whose drug and AE may be reported in different posts of a user leads to major concerns regarding the content authenticity and user credibility, which have not been addressed in previous studies. Content authenticity concerns whether a post mentions drugs or adverse events that are actually consumed or experienced by the writer. User credibility indicates the degree to which chronological evidence from a user's sequence of posts should be trusted in the ADE detection. We propose AC-SPASM, a Bayesian model for the authenticity and credibility aware detection of ADEs from social media. The model exploits the interaction between content authenticity, user credibility and ADE signal quality. In particular, we argue that the credibility of a user correlates with the user's consistency in reporting authentic content. ResultsWe conduct experiments on a real-world Twitter dataset containing 1.2 million posts from 13,178 users. Our benchmark set contains 22 drugs and 8089 AEs. AC-SPASM recognizes authentic posts with F1 – the harmonic mean of precision and recall of 80%, and estimates user credibility with precision@10 = 90% and NDCG@10 – a measure for top-10 ranking quality of 96%. Upon validation against known ADEs, AC-SPASM achieves F1 = 91%, outperforming state-of-the-art baseline models by 32% (p < 0.05). Also, AC-SPASM obtains precision@456 = 73% and NDCG@456 = 94% in detecting and prioritizing unknown potential ADE signals for further investigation. Furthermore, the results show that AC-SPASM is scalable to large datasets. ConclusionsOur study demonstrates that taking into account the content authenticity and user credibility improves the detection of ADEs from social media. Our work generates hypotheses to reduce experts’ guesswork in identifying unknown potential ADEs.

Can magmatic zircon be distinguished from hydrothermal zircon by trace element composition? The effect of mineral inclusions on zircon trace element composition

Mineral inclusions, e.g., apatite, titanite, monazite, K-feldspar, are common in magmatic zircons. Although many studies mention that light rare earth element (LREE) contents of zircons could be compromised by an analytical artefact of the accidental sampling of mineral inclusions, how and to what degree these inclusions influence analysis of zircon composition is still not well constrained. Here we report U–Pb ages and trace element abundances for zircon crystals, where apatite and K-feldspar inclusions are observed, from diorite porphyry in the Weibao deposit, East Kunlun Mountains, Northern Tibetan Plateau. Although zircon morphological and chronological evidence consistently advocates a magmatic origin without undergoing significant hydrothermal alteration, 7 of 15 analytical spots show LREE-enriched patterns and low Ce/Ce* ratios which are comparable to those for published “hydrothermal” zircon. Quantitative modelling in this study manifests that these LREE-enriched patterns and low Ce/Ce* ratios can be achieved with only 0.1 to 2 vol% contamination from sub-micrometer apatite inclusions, which in practice are hard to monitor under the LA–ICP–MS (normally with large pit diameter and depth) and conventional microscopes. Titanite, monazite, xenotime, and allanite have similar roles to apatite, and LREE contents of zircon can be significantly elevated with only 0.05 vol% contamination from these inclusions. We therefore suggest that the widely used geochemical discrimination criteria for magmatic and hydrothermal zircon, e.g., (Sm/La)N vs. La and Ce/Ce* vs. (Sm/La)N diagrams and the degree of Ce anomalies, are ambiguous since they are extremely susceptible to contamination by mineral inclusions, and that within single samples only Ce4+/Ce3+ values calculated from zircons of low LREE values probably represent the oxidation state of magmas.

Impressões de um passado incógnito. Dos vestígios da memória pessoal à memória histórica entre o século XIX e o século XX em Portugal

O presente artigo tem como ponto de partida a investigação sobre a árvore genealógica de uma das autoras, impulsionada pelos relatos na primeira pessoa transmitidos por uma tia-avó. Tal transferência rica, embora difusa, de indícios de um passado que remonta ao início do século XX em Portugal, constituiu uma oportunidade para estender a recolha a outros antepassados a partir de variados tipos de arquivo. A esta memória oral, que exterioriza as emoções e factos numa mescla pessoal e afetivamente modelada, justapõem-se os registos materiais, visuais e documentais. Nestes incluem-se objetos nostálgicos, fotografias de família e registos paroquiais de batismos, casamentos e óbitos, provenientes de diversos arquivos distritais. O resgate de memórias dispersas, que até à data permaneceram na penumbra entre gerações, trouxe à tona eventos enigmáticos e significativos em Portugal. Tais como a migração e radicação em meados do século XIX de várias famílias espanholas de Badajoz na Amareleja, ou o terramoto de Benavente de 1909 presenciado pelos bisavós paternos de uma das autoras, documentado pelo fotógrafo Joshua Benoliel, fornecendo uma visão humanista e intimista sobre a catástrofe. Da reconstituição histórica, manifesta na teia de ligações entre fotografias e textos, motivada por imagens mentais que começam a recuperar a sua forma sugerida pelas pistas e achados coletados, esboçam-se narrativas simultâneas alicerçadas em evidências genealógicas, cronológicas e geográficas. Nesta oscilação entre a esfera pessoal e coletiva, alicerçada em metodologias do domínio da História e dos Estudos Visuais, procura-se refletir sobre as possibilidades de tangibilização da memória, as migrações entre diferentes locais e o que permanece de referência emocional do local de origem, como são transferidas entre gerações as memórias pessoais, como reconstituir memórias esparsas e como a partir de memórias pessoais é possível enquadrar uma memória coletiva.

Obliterative cholangiopathy in acquired cystic biliary atresia type III after cyst perforation: a case report

BackgroundIn biliary atresia, the disease process of obliterative cholangiopathy may begin in the perinatal period; however, no chronological evidence exists on how the cholangiopathy progresses to biliary obliteration.This is the first acquired case with the final diagnosis of type III cystic biliary atresia with an extrahepatic biliary cyst which showed the progression of obliterative cholangiopathy in chronological order after birth.Case presentationAn 81-day-old girl presented with acute abdominal distress due to bilious peritonitis caused by biliary cyst perforation, for which she underwent emergency biliary drainage. Postoperative images showed a dilated common bile duct and hepatic ducts bilaterally, with flow of the contrast medium to the duodenum through the dilated common bile duct. Biochemistry of the bile collected during and after the operation revealed elevated levels of pancreatic enzymes in the bile from the gallbladder. The patient was diagnosed as having a congenital choledochal cyst and underwent laparotomy at 120 days of age which revealed that she had pancreaticobiliary maljunction. The biliary cyst was resected at the narrow portion just above the junction with the main pancreatic duct. During dissection up to the hepatic hilum, we found that the hilar hepatic ducts were bilaterally replaced by fibrous tissue and were obstructed, leading to a diagnosis of type III a1, μ biliary atresia. The fibrous tissue was excised, and hepatic portoenterostomy was performed according to the Kasai procedure. The patient’s postoperative course was uneventful and the jaundice resolved within 1 month. She has had normal liver function tests with no episode of cholangitis for 3 years after discharge.ConclusionsWe demonstrated the process of acquired type III biliary atresia in a patient with cystic biliary atresia and biliary cyst perforation. To the best of our knowledge, this is the first case of acquired cystic biliary atresia showing chronological progression of the course of obliterative cholangiopathy, providing a better understanding of the development of type III biliary atresia as an acquired disease.

Patagonian ash on sub‐Antarctic South Georgia: expanding the tephrostratigraphy of southern South America into the Atlantic sector of the Southern Ocean

ABSTRACTFingerprinting non‐visible volcanic ash (cryptotephra) enables precise dating and time synchronization of palaeoclimate archives. Recent analytical advances allow us to strengthen and expand existing tephrostratigraphical frameworks and harness the full potential of this powerful geochronological tool. Here, we present geochemical (electron microprobe) and chronological (14C) evidence to show that ash found in a peat section on the sub‐Antarctic island of South Georgia correlates to the ∼2950 cal a BP Alpehué eruption of the Chilean Sollipulli volcano. This discovery marks the first tephra fingerprint on South Georgia and expands the recently refined tephrostratigraphy of Patagonia ∼3000 km into the Southern Ocean. As deposition of this tephra horizon coincides with a major shift in regional atmospheric conditions, future finds may yield information on the spatiotemporal pattern of Southern Ocean climate dynamics.

Evidence for Middle Bronze Age Chronology and Synchronisms in the Levant: A Response to Höflmayer et al. 2016

In a recent article published in the Bulletin of the American Schools of Oriental Research 375, Felix Höflmayer and his colleagues present a set of radiocarbon data from Tell el-Burak on the Lebanese coast and claim that these data argue for dating the early phase of the Middle Bronze Age in the Levant (Middle Bronze Age IIA/I) between ca. 2000 and the early 18th century B.C. Considering these radiocarbon dates, the authors assert that the low chronology for this period suggested by Manfred Bietak, based on archaeological evidence from Tell el-Dabʿa, should be raised by roughly 120 years. The aim of this article is to show that ceramic and glyptic evidence from Egypt and the Levant firmly support the low chronology and historical synchronisms proposed by Bietak.

What Happened in the Summer ofa.d. 122? Hadrian on the British Frontier — Archaeology, Epigraphy and Historical Agency

AbstractIn the summer ofa.d.122, Hadrian (a.d.117–38) visited Britain as part of his first major journey. It is broadly accepted that the construction of Hadrian's Wall was inaugurated on this occasion. Following recent advances in Upper Germany where thelimespalisade is now known to have been under construction when Hadrian visited the province, this paper re-examines the various strands of evidence for the early chronology of the Wall. It is argued that work started well beforea.d.122 and that it was in fact the ‘fort decision’ which resulted from the imperial visit. The revised sequence offers a fresh perspective on several classic Wall problems and prepares the ground for a new understanding of unique features like the milecastles and Vallum.

Thermoluminescence dating of stalactitic calcite from the early Palaeolithic occupation at Tongamdong site

There are several archaeological sites in the Taedong river basin around Pyongyang. Recently, the Palaeolithic Tongamdong site was newly unearthed in this area. This contribution presents the first thermoluminescence (TL) dating for the Palaeolithic sequence at the Tongamdong site, recently excavated by Human Evolution Research Office, Faculty of History, Kim Il Sung University, Democratic People's Republic of Korea. Tens of stone tools and thousands of vertebrate fossils were discovered within the sediments of the site. The Palaeolithic sequence from Tongamdong site in Sunchon City, South Pyongan Province, contains six stratified archaeological levels. The archaeological level 4 and 5 consist of many fossil bones and several stone tools. Two stalactite samples from level 4 and three from level 5 were dated by thermoluminescence. Comparison of calcite dates by thermoluminesence with the previous reference dates (ESR and relative dates) from the site was carried on successfully. The calcite dating results are in good agreement with those of the chronological evidence. A range of the estimated ages is between 699 and 813 ka for the five dates, a mean age-estimate of 754.6 ka is summarised. These ages are close to that of electron spin resonance (ESR) dating with tooth fossils of rhinoceros (704 ka) and horse (881 ka) respectively excavated from archaeological level 5 and 4 of Tongamdong site sediments. Relative ages from animal fossil bones discovered in the sediments of Tongamdong site are the early Middle Pleitoscene of the Quaternary.

The sedimentary evolution of Yangtze River delta since MIS3: A new chronology evidence revealed by OSL dating

Abstract The Yangtze River delta, one of the largest tide-dominated deltas in the world, is a valuable archive for studying the land-sea interaction. Previous investigations have mainly focused on the Holocene Yangtze River delta initiation and the coastal dynamics in response to sea level changes based on analysis of the stratigraphic and sedimentologic evidences. However, the detailed depositional history of the Yangtze River delta prior to Holocene is still poorly understood owing to a deficiency of accurate absolute chronologies. In this study, a 60-m-long core (EGQD14) was drilled in the front edge of modern Yangtze River deltaic plain. The sedimentary features were analyzed based on the data of sediment particle size composition, colors, textures and intra-structure description; a total of 20 sediment samples were collected from this core for optically stimulated luminescence (OSL) dating. The single aliquot regenerative dose (SAR) protocol was applied to fine (4–11 μm in diameter) and coarse (63–100 μm or 100–200 μm) grained quartz extracts to determine their equivalent dose (De). The bleaching levels of different grain-sized fractions were investigated. We found that 63–100 μm grains and fine grains are generally well-bleached, and are appropriate for establishing the chronology of the studying core. However, ages of 100–200 μm grains appear to be problematic as potential feldspar contamination, revealed by remarkable infrared (IR) depletion ratios as low as to 0.3. Thus, ages derived only from 4–11 μm and 63–100 μm fractions were used for the reconstruction of chronological framework. The sedimentary history of the Yangtze River delta since the Marine Isotope Stage 3 (MIS3) was inferred by combination of a 50-ka spanning stratigraphic sequence of the EGQD14 core with previously investigated sedimentary stratigraphy in the study area. This study provided a new chronological evidence of the Yangtze River delta sedimentary evolution over the last ∼50 ka, which generally underwent the terrestrial fluvial, floodplain, tidal flat, estuary-neritic, deltaic and modern Yangtze River delta plain sedimentary environments.