Chronometric Framework Research Articles

Pleistocene landscape evolution in the Avon valley, southern Britain: Optical dating of terrace formation and Palaeolithic archaeology

This paper presents the first comprehensive Optically Stimulated Luminescence dating programme from a sequence of Pleistocene river terraces in the Avon valley (Wiltshire-Hampshire-Dorset), southern Britain. These results offer the most complete chronometric framework for Pleistocene landscape evolution and Palaeolithic occupation in the Avon valley, allowing for the first time: (1) an assessment of the timing of terrace formation and landscape evolution, (2) the dating of hominin presence in the area, and (3) an investigation of the relationship between terrace formation and Quaternary climatic change. Analysis of 25 samples collected from terraces 10 and 7 to 4 show that the middle Avon terraces formed in response to the main Pleistocene climatic oscillations (Marine Isotope Stages (MIS) 10, 8, 6) and that fluvial mechanisms changed through time, resulting in three different types of terrace architecture. The highest and oldest deposits are compound terraces deposited during the Early Pleistocene before the Mid Pleistocene Transition. The middle reach of the valley is characterised by well-developed strath terraces overlain with thick fluvial deposits, reflecting the greater degree of incision in response to the increased amplitude of climate cycles in the Middle Pleistocene. The youngest deposits in the confined modern floodplain represent cut-and-fill terraces deposited after MIS5e. The results indicate that the two main Palaeolithic sites in the area, Milford Hill and Woodgreen, date to between at least MIS 10 and 8 with a pre-MIS 10 human occupation at a third main site at Bemerton. This is significant because the sites date to a period previously associated with a decline in hominin presence in Britain. The dating of the Avon valley terrace sequence highlights the complex nature of terrace formation during the Pleistocene and the need to critically reassess the chronological understanding of these fluvial archives in southern Britain. This research demonstrates that with a detailed and multidisciplinary approach shifts in hominin landscape use can be discovered, providing new information on hominin behavioural change during the Pleistocene.

Holocene palaeoenvironmental changes in the Thar Desert: An integrated assessment incorporating new insights from aeolian systems

Due to the scarcity of geochemical and palaeoecological proxies in drylands, dunes have often been used as geoproxies for late Quaternary palaeoenvironmental reconstruction, with chronologies commonly provided by luminescence dating. Owing to their widespread occurrence and location in a monsoonal regime, dunes in the Thar Desert in South Asia act as important archives of past landscape change. Previous reviews have assimilated dune age data from the Thar and suggested a temporally and spatially complex record of sediment accumulation over the last ∼70 ka. New luminescence age data presented in this study and from recent dunefield based investigations demonstrate a stronger Holocene record of dune building in parts of the Thar than previously suggested.In this study, the Accumulation Intensity (AI) methodology is applied to new and old data sets, providing records of dune accumulation that can be analysed alongside other palaeoenvironmental records. AI analysis demonstrates the significance of Holocene dune accumulation in the Thar landscape, with accumulation peaks observed between ∼12 and ∼8 ka, centred around ∼7, ∼5 and ∼3.5 ka, and in last two millennia. The strengthening of the Indian Summer Monsoon remains a significant influence on widespread dune accumulation in the early Holocene, but dunefields have also shown diverse and spatially intensive responses to sediment supply and anthropogenic disturbances during the late Holocene. Additionally, aeolian-fluvial sequences associated with the Ghaggar-Hakra palaeochannel along the northern margin of the Thar also display dynamic geomorphic behaviour during the Holocene. The integration and interpretation of the AI data with published, highly resolved geochemical proxies of palaeoclimate, shows a complex relationship between geoproxy and geochemical records. We suggest that process studies of geomorphologic systems and their diverse responses to the same environmental stimuli must be given due consideration before deriving palaeoenvironmental interpretations. Despite the presence of over a hundred Holocene dune records from the Thar, there still remains marked spatial and temporal gaps. Further intensive investigations of distinct dunefields with a strong chronometric framework and geomorphological grasp are required to gain significant insights into wider Thar landscape and palaeoenvironmental dynamics.

Pb–Pb chronometry and the early Solar System

Of the long-lived chronometric systems, only the dual decay of 238U and 235U to 206Pb and 207Pb, respectively, have appropriate half-lives to resolve the ages of meteorites and their components formed in the first 5Myr of the Solar System. This paper reviews the theory and methods behind this chronometer, offers criteria to critically evaluate Pb–Pb ages and presents a summary of the current state and immediate future of the chronometry of the early Solar System. We recognize that there is some debate over the age of the Solar System, but conclude that an age of 4567.30±0.16Ma based on four CAIs dated individually by the same method in two different laboratories is presently the best constrained published value. We further conclude that nebular chondrules dated by the Pb–Pb method require that they formed contemporaneously with CAIs and continued to form for at least ∼4Myr, a conclusion that implies heterogeneous distribution of the short-lived 26Al nuclide in the protoplanetary disk. Planetesimals were already forming by ∼1Myr after CAI formation, consistent with their growth predominantly through the accretion of chondrules. Nebular chondrule formation was completed by ∼5Myr after CAI formation when the impact-generated Cba chondrules formed after the disk was cleared of gas and dust. We note that the absolute age of the Solar System or any single early Solar System object is not fundamental to any significant scientific question and that it is important only to know the correct relative ages of objects being used to piece together the formation history of the Solar System. As such, we point out the risks inherent in comparing Pb–Pb ages produced by different approaches in different laboratories at the level of the internal errors of individual ages. Until a cross-calibration exercise using synthetic and natural standards establishes the reproducibility between laboratories, only ages from a single laboratory, or between laboratories having demonstrated concordance, can provide a reliable relative chronometric framework for the formation and evolution of the early Solar System.

Geochronological reconsideration of the eastern European key loess section at Stayky in Ukraine

Abstract. Event-stratigraphical correlations between regional terrestrial sedimentary archives and marine or ice-core records that provide climate history are highly desirable for a deeper understanding of the effects of global climate change. However, such correlations are not simple, as the terrestrial records tend to be floating and fragmentary, and usually show varying sedimentation rates. Therefore, a reliable chronometric framework is a prerequisite for any event stratigraphy involving terrestrial archives. We propose that the age model underlying the event-stratigraphical approach for the eastern European key loess section at Stayky in Ukraine needs revision. Here we explore why it is unlikely that the Middle Pleniglacial Vytachiv Soil developed during Greenland interstadial (GIS) 8, and why the embryonic soils in the upper part of the Upper Pleniglacial part of the loess section most likely post-date the Heinrich 2 event. As a consequence, the revised age-model challenges the earlier suggested correlation of the suite of incipient soils above the Vytachiv Soil with Greenland Interstadials, which was supposed to start with GIS7 but for which matching from after GIS5 seems more likely. The revised chronology suggests that the transition from Middle to Upper Pleniglacial environmental conditions at the eastern European key section occurred during the final phase of marine isotope stage (MIS) 3. Thus, the picture appears to be in accordance with that of the western European key section at Nussloch. This points to a common driver of palaeo-environmental change in both regions, such as early late glacial maximum (LGM) advances of the Arctic ice shield or changes of the North Atlantic circulation and sea-ice distribution associated with changes in the palaeowind field relevant to aeolian loess deposition and soil formation. To test and substantiate the alternative age model, more chronologies for well-stratified loess sections throughout the European loess belt are required.

Six Decades of Radiocarbon Dating in New World Archaeology

Radiocarbon (14C) dating provided New World archaeological research with the first continent-wide common chronometric scale that transcended the mostly relative site- and region-specific chronological sequences that had been assembled during the preceding century of fieldwork.14C data continue to play a critical role in establishing a chronometric framework for the 5-century-long debate concerning the timing of the initial peopling of the New World. Other issues where14C results have been of particular importance include the origins and development of New World agriculture and determination of the relationship between the Western and Classic Maya long-count calendar. The introduction of a third-generation measurement technology of accelerator mass spectrometry (AMS) beginning in the late 1970s has provided a means of obtaining analyses on milligram and microgram amounts of carbon permitting more detailed critical approaches to increasing the accuracy of14C values on certain sample types—particularly human skeletal materials. It also provided a more effective means of allowing greater dating precision in situations where such data had an important bearing on the validity of inferences about the rates of cultural evolutionary change in New World societies.

Optical dating of perennially frozen deposits associated with preserved ancient plant and animal DNA in north-central Siberia

We present chronological constraints on a suite of permanently frozen fluvial deposits which contain ancient DNA (aDNA) from the Taimyr Peninsula of north-central Siberia. The luminescence phenomenology of these samples is first discussed, focusing on the optically stimulated luminescence (OSL) decay curve characteristics, thermoluminescence (TL) properties, and signal compositions of quartz from these previously unstudied deposits. Secondly, we assess the suitability of these samples for OSL dating and present the OSL chronologies obtained using both single-grain and multi-grain equivalent dose (De) measurements. The results of our analyses reveal a large amount of inter-aliquot variability in OSL decay curve shape that is directly related to differences in the size of the 280°C TL peak and the associated slowly bleached ‘S2’ OSL component. Longer OSL stimulation durations are adopted in the De measurement procedure to prevent the progressive build-up of slowly bleached signal components throughout successive single-aliquot regenerative-dose (SAR) measurement cycles. The use of low preheat temperatures in the SAR procedure also reduces the deleterious effects of these slowly bleached signal components. The resultant single-grain and multi-grain OSL chronologies obtained using this approach are stratigraphically consistent and are in close agreement with independently established 14C ages at our sites. The findings of this research reveal the potential of OSL dating as a means of providing a reliable chronometric framework for sedimentary aDNA records in permafrost environments.

No Systematic Early Bias to Mediterranean14C Ages: Radiocarbon Measurements from Tree-Ring and Air Samples Provide Tight Limits to Age Offsets

Existing data and theory do not support a recent assertion that upwelling of old carbon has led to systematically 100–300 yr too old radiocarbon ages for the Mediterranean region. Similarly, the prehistoric tree-ring record produced over 3 decades by the Aegean Dendrochronology Project is shown to provide robust, well-replicated data, contrary to a recent unfounded assertion.14C and dendrochronology provide an accurate and precise chronometric framework for the Mediterranean region.

野尻湖立が鼻遺跡第１０次発掘出土の骨器

The first excavation at Tategahana, on the shore of Lake Nojiri, was carried out in 1962; since then, excavations have been undertaken ten times. On the occasion of the 10th excavation season in 1987, the total number of excavated items reached 7, 872. They include 755 archaeological items, 1, 931 mammalian fossil items, 98 lithic artifacts and 23 bone artifacts which were mainly made of bones of the Naumann elephant (Palaeoloxodon naumanni).The Nojiri-ko Formation is divided into three members, Lower, Middle and Upper, with marked unconformities between them. Furthermore, each member is subdivided into three or four parts. On the basis of radiocarbon dating and both palaeontological and archaeological studies, the chronometric framework of the Nojiri-ko Formation can be attributed as follows: the Lower Member represents 50, 000-30, 000y.B.P., the Middle Member represents 30, 000-25, 000y.B.P., and the Upper Member represents 25, 000-10, 000y.B.P.The present paper focuses on bone tools including a cleaver, flakes, a spiral flake and chips made of Naumann elephant bones from Middle Member I (26, 100±2, 070y.B.P. 14C, GaK-7789), giving a description of morphological characteristics and attempting to reconstruct the manufacturing processes of bone tools. The most remarkable tool from this layer is a bone cleaver which coincides well morpho-typologically with the definition of a stone cleaver. Our discussion compares the cleaver with other examples of bone cleavers from Anaguni, Central Italy, and Lang/Ferguson, South Dakota. The characteristics of secondary flaking technique for the bone cleaver, together with a bone “point” excavated in the 5th excavation season, were discussed in comparison with the flaking technique expressed among lithic industries from Cultural Layers IX and X in the Musashino Upland area of Tokyo.The distribution pattern of the bone tool assemblage, including two refitted bone items, on the horizon of Middle Nojiri-ko Member I implies that the elephant hunters had also made bone tools in the process of kill-butchering.

Stratigraphic context of fossil hominids from the Omo group deposits: northern Turkana Basin, Kenya and Ethiopia.

The chronometric framework developed for Plio-Pleistocene deposits of the northern Turkana Basin is reviewed in light of recent advances in lithostratigraphy, geochemical correlation, paleomagnetic stratigraphy, and isotopic dating. The sequence is tightly controlled by 20 precise ages on volcanic materials. These ages are internally consistent but are at variance with estimates for the boundaries of the magnetic polarity time scale by about 0.07 my. This discrepancy can be only partially resolved at present. Based on the established chronometric framework and stratigraphic sequences, depositional ages can be estimated for significant marker beds. These ages can in turn be used to constrain the 449 hominid specimens thus far reported from the basin. Ages for most hominid specimens can be estimated with a precision of +/- 0.05 my. In addition, the chronometric framework will be applicable to other paleontological collections, archeological excavations, and future discoveries in the basin.

The Asian hominidae

A variety of new chronometric, biostratigraphic and other data and a reanalysis of previous research indicates maximum ages of 0·1–1·3 m.y.a. for the earliest known Asian hominids. Most of the data suggest that the majority of known Asian hominids are less than 1·0 m.y.a. All of these hominids can be incorporated within the taxa Homo erectus or Homo sapiens . A new hyper-robust cranium which has been referred to “ Meganthropus ” is also discussed. The chronometric framework and morphological data reveal that the Asian hominid fossil record does not support “stasis” over a protracted period of time, but rather gradual change over a period of ca 1·0–0·7 million years.

Global sea level stratigraphy: An appraisal

Although Pleistocene sea level concepts were first developed in the Mediterranean Basin, research has been revolutionized during the past 15 years by massive dating programs applied in other world areas. reappraisal of four key sequences nonetheless shows that the chronometric framework is imperfect. As a result, available paleosea level traces continue to depend on deep-sea stratigraphy for confirmation rather than the reverse; they do not provide independent support for the Milankovitch radiation cycles, nor do they invite deductive-hypothetical ‘dating’ by means of such astronomical reconstructions. Inferred ‘initial’ sea levels, based on uplift assumptions or δ 18O determinations on coral and mollusca, show considerable divergence but broadly agree that sea levels assigned to isotope stages 5a and 5c were lower than today. Systematic studies should be expanded in environments that allow lithostratigraphic resolution of interdigitated marine and continental sediments, meticulously complemented by biostratigraphic work. Direct information on the complexity and significance of regressional hemicycles helps place sea level stages recorded by transgressive facies into a multidimensional context essential for comprehensive interpretation.

UCLA Radiocarbon Dates X

The measurements reported in this date list form the chronometric framework for obsidian hydration and trade studies in California (Ericson, 1975; 1977; 1978; 1981; Ericson et al, 1975; Singer and Ericson, 1977). All samples were analyzed as CO2 gas at close to 1 atm in a 7.5L proportional counter with three energy channels. Radiocarbon ages are based by convention on the 5568 ± 30 yr half-life. The biospheric standard is 95% the count rate of NBS oxalic acid for radiocarbon laboratories. Background is based on CO2 obtained from marble. Counter operation is checked against a historically dated wood sample from the funerary boat of Sesostris III, 1872 +4−8 BC (Hayes, 1962). All samples were subjected to accepted NaOH, HCl or other special chemical treatments to exclude contamination. No tree-ring calibration was applied to any of the samples listed.

Upper Palaeolithic Archaeology

A review article on the Upper Palaeolithic could attempt to do various things, but I think it could not successfully attempt to cover all recent developments in our understanding of specific Upper Palaeolithic sequences unless it were very long and accompanied by profuse artifact illustration. Upper Palaeolithic specialists will have such information at their disposal, and anthropologists with other interests are unlikely to profit from a systematic textbook-like treatment. [For those who wish an encapsulated presentation of Upper Palaeolithic prehistory, the best source is still, in my opinion, the relevant portion of Bordes's (11) text.] I have assumed that the most useful approach would be topical and that the number of topics discussed should be sufficiently small so that something of consequence could be said about each one. Eschewing various topics of equal relevance and importance to those I have chosen (e.g. the geochronologic and chronometric framework of the Upper Palaeolithic; recent developments in typological analysis, paleoecology, etc; widespread changes at the end of the Upper Palaeolithic and their relevance to the establishment of food-producing economies), I have restricted my consideration to two topics. Because of my own research interests (centered for the moment on the Chatelperronian of southwestern Europe) and because of its implications for teachers and scholars in other fields of anthropology, the principal topic of this article is the origins of the Upper Palaeolithic and how ideas about this have been changed by recent developments. The second topic, to which I give much shorter treatment, concerns some recently acquired information about ritual, notation, and symbol in the Upper Palaeolithic. These aspects of the culture of early modern man have, I believe, an interest for a broad spectrum of anthropologists caring little or nothing for the arcane intricacies of local archaeological sequences. It is my intention in this article to speak to anthropologists whose interests are