New developments in Pleistocene art

Research on Pleistocene art is a dynamic and thriving area. Many new advances and discoveries have been made since the last major review of this topic.¹ Indeed, thanks to the introduction of direct dating and detailed analysis of pigments, the last few years can arguably be described as the most exciting and most important phase in Ice Age art studies since such art was first discovered and validated.     

The assessment of 210Pb data from sites with varying sediment accumulation rates

The last few years have seen a dramatic growth in the use of ²¹⁰Pb sediment dating. Despite this, considerable doubt still surrounds the nature of the processes by which ²¹⁰Pb is deposited in lake sediments, and this has lead to a situation where there is a choice of dating models offering different interpretations of ²¹⁰Pb data. In assessing ²¹⁰Pb data it is therefore essential to first of all determine whether data is consistent with the assumptions of the dating model, and to then compare the ²¹⁰Pb chronology with independent dating evidence. We have tested ²¹⁰Pb data from a wide variety of sites, and our calculations indicate that the crs (constant rate of ²¹⁰Pb supply) model provides a reasonably accurate chronology when the total ²¹⁰Pb contents of cores from neighbouring locations are comparable.     

Radionuclide dating of the recent sediments of Blelham Tarn

Lake sediments of the last 1000 years provide a unique record of environmental changes. Methods of dating this record are reviewed and discussed. Sediments of the last 20 years, which are of particular biological significance because of their record of man-made changes in lakes (including enrichment and pollution) have been dated successfully by the distribution within them of the fallout product ¹³⁷Cs, present in the atmosphere since 1954 and reaching a peak of supply in 1963. The structured pattern shown by the curve for ¹³⁷Cs concentration in most sediments investigated indicates that faunal mixing of the surface muds does not destroy the vertical stratification of the sediment profile. Sediments up to 120 years old have been dated by a lead isotope technique, and the results of this proved consistent with both ¹³⁷Cs dating and with palaeomagnetic dating where this was possible. Theoretical considerations of the application of radiocarbon dating to organic material of 18th and 19th century date are reviewed. Results of application of these radionuclide techniques to the sediments of a small lake, Blelham Tarn, near Windermere, are presented. Evidence from ¹³⁷Cs and ²¹⁰Pb dating of profiles from several different positions within the lake shows that the depth of the annual increment to the sediments varies by a factor of × 2 from place to place. The concentration within the sediment of chemical and biological variables shows no significant variation from one position to another; therefore calculated values for amounts of each variable included within unit area of the annual increment depend primarily on the thickness of this at the site chosen, and so cannot be directly related to the rates of supply of, for example, pollen grains or total organic matter, and so to rates of productivity. Results from nine ¹⁴C dates on material 400–1000 years old, when correlated with analyses for pollen and sediment composition, demonstrate the profound effects of agricultural practices in the catchment (assumed to be deforestation and ploughing) in disturbing the orderly transfer to lake sediments of material eroded from the catchment.     

A 14C age calibration curve for the last 60 ka: the Greenland-Hulu U/Th timescale and its impact on understanding the Middle to Upper Paleolithic transition in Western Eurasia

This paper combines the data sets available today for ¹⁴C-age calibration of the last 60 ka. By stepwise synchronization of paleoclimate signatures, each of these sets of ¹⁴C-ages is compared with the U/Th-dated Chinese Hulu Cave speleothem records, which shows global paleoclimate change in high temporal resolution. By this synchronization we have established an absolute-dated Greenland-Hulu chronological framework, against which global paleoclimate data can be referenced, extending the ¹⁴C-age calibration curve back to the limits of the radiocarbon method. Based on this new, U/Th-based Greenland_Hulu chronology, we confirm that the radiocarbon timescale underestimates calendar ages by several thousand years during most of Oxygen Isotope Stage 3. Major atmospheric ¹⁴C variations are observed for the period of the Middle to Upper Paleolithic transition, which has significant implications for dating the demise of the last Neandertals. The early part of “the transition” (with ¹⁴C ages > 35.0 ka ¹⁴C BP) coincides with the Laschamp geomagnetic excursion. This period is characterized by highly-elevated atmospheric ¹⁴C levels. The following period ca. 35.0-32.5 ka ¹⁴C BP shows a series of distinct large-scale ¹⁴C age inversions and extended plateaus. In consequence, individual archaeological ¹⁴C dates older than 35.0 ka ¹⁴C BP can be age-calibrated with relatively high precision, while individual dates in the interval 35.0-32.5 ka ¹⁴C BP are subject to large systematic age-‘distortions,’ and chronologies based on large data sets will show apparent age-overlaps of up to ca. 5,000 cal years. Nevertheless, the observed variations in past ¹⁴C levels are not as extreme as previously proposed (“Middle to Upper Paleolithic dating anomaly”), and the new chronological framework leaves ample room for application of radiocarbon dating in the age-range 45.0-25.0 ka ¹⁴C BP at high temporal resolution.     

Dendrochronology improves understanding of the charcoal production history

Charcoal piles have become a frequent subject of research in recent years as a better understanding of past human activities in forests is sought. The age of charcoal piles is usually determined by radiocarbon dating; dendrochronology is rarely used because of the small size of preserved charcoal remains and the insufficient number of visible tree rings. This paper presents the potential for dendrochronological and ¹⁴C method in research into charcoal piles. From 14 charcoal-burning sites in the Czech Republic, 214 pieces of charcoal were anatomically identified at the genus level and dendrochronologically analysed. Our results show that fir dominated in these charcoal remains, followed by oak, beech, spruce and pine. With an overall dendrochronological dating success of 24 %, fir charcoal was dated most often (65 %) with measurable tree rings ranging from 14 to 90. The oldest charcoals were dendrochronologically dated to summer 1682 CE; conversely, the youngest had end dates in the second half of the 19th century. The relatively poor dating success of oak charcoal very likely resulted from the use of branches for charcoal production rather than tree trunks. Based on an analysis of selected charcoal samples, we confirm that radiocarbon dating provided a very wide range of dates in the post-1650 CE period and the use of the wiggle-matching method was usually challenging because of short TRW series. Based on samples with preserved waney edges, we conclude that charcoal was more commonly made from wood felled in the summer than in the winter. Despite the relatively low level of success of dendrochronological dating, it seems more effective for dating charcoal than the ¹⁴C method, especially with samples from the last 350 years.     

Electron spin resonance dating in paleoanthropology

Many archeological and paleoanthropological sites cannot be dated by well established and common dating techniques such as uranium series (U-series) or argon-argon (⁴⁰Ar/³⁹Ar) because of the lack of materials that are suitable for these techniques. Most sites, however, contain bones and teeth, and the latter can be used to obtain electron spin resonance (ESR) age estimates. The theoretical age range of ESR dating accuracy lies between a few thousand and more than a million years. In practice, continuing uranium accumulation increases the uncertainty of ESR age assessments in such a way that most age assignments beyond 300,000 years are very uncertain.     

Uranium series dating in paleoanthropology

Many hominid and archaeological sites contain materials that were formed or deposited synchronously with the site and can be dated by uranium-series methods, principally ²³⁰Th/²³⁴U dating. The range of the method is approximately 350,000 years. U-series dating yields most accurate results when applied to chemically precipitated calcium carbonate, which occurs in stalagmitic layers, travertines, and lacustrine limestones. Materials such as bone and shell are less reliable. Using mass spectrometry (MS), a precision of ±1% is attainable, whereas conventional alpha counting optimally gives a precision of ±5%. Mass spectrometric dating requires smaller samples, potentially allowing determination of ante quem dates for calcite coatings on hominid fossils and associated faunal skeletons.     

40Ar/39Ar dating in paleoanthropology and archeology

The potassium-argon (K-Ar) dating method has been widely used over the past 40 years to provide radioisotopic age control of hominid/hominoid evolutionary time scales. The wide appeal of the technique to paleoanthropology and archeology has been, in part, a result of its broad time range of applicability, from materials as young as a few thousand years old to an essentially unbounded upper age limit. Another reason for its appeal is the many geological circumstances in which datable materials are found. Beginning about two decades ago and accelerating into this decade, however, the conventional K-Ar technique has given way to ⁴⁰Ar/³⁹Ar dating as the method of preference. This technique is not only more precise and accurate when dating ideal materials, but also permits excellent ages to be obtained from situations that often stymie the conventional K-Ar technique, such as dating of contaminated tuffs and altered rocks. © 1998 Wiley-Liss, Inc.     

Paleolimnological evidence of change in a shallow, hypereutrophic lake: Upper Klamath Lake, Oregon, USA

Sediment cores were collected from Upper Klamath Lake in October, 1998 and analyzed for ²¹⁰Pb, ¹⁴C, ¹⁵N, N, P, C, Ti, Al, diatoms, Pediastrum, and cyanobacterial akinetes. These results were used to reconstruct changes in water quality in Upper Klamath Lake over the last 150 years. The results showed that there was substantial mixing of the upper 10 cm of sediment, representing the previous 20 to 30 years. However, below that, ²¹⁰Pb activity declined monotonically, allowing reasonable dating for the period from about 1850 to 1970. The sediment accumulation rates (SAR) showed a substantial increase in the 20th century. The increase in SAR corresponded with increases in erosional input from the watershed as represented by the increases in sediment concentrations of Ti and Al. The upper 20 cm of sediment, representing the last 150 years, also showed increases in C, N, P, and ¹⁵N. The increases in nutrient concentrations may be affected to various degrees by diagenetic reactions within the sediments, although the changes in concentrations also were marked by changes in the N:P ratio and in a qualitative change in the source of N as reflected in increasing δ¹⁵N. The diatoms showed modest changes in the 20th century, with increases in Asterionella formosa, Stephanodiscus hantzschii, and S. parvus. Pediastrum, a green alga, was well-preserved in the sediments and exhibited a sharp decline in relative abundance in the upper sediments. Total cyanobacteria, as represented by preserved akinetes, exhibited only minor changes in the last 1000 years. However, Aphanizomenon flos-aquae, a taxon which was formerly not present in the lake 150 years ago, but that now dominates the summer phytoplankton, has shown major increases over the past 100 years. The changes in sediment composition are consistent with activities including timber harvest, drainage of wetlands, and agricultural activities associated with livestock grazing, irrigated cropland, and hydrologic modifications.     

Accumulation and attrition of peat soils in the Australian Alps: Isotopic dating evidence

Bog peat soils have been accumulating at Wellington Plain peatland, Victoria, Australia for the last 3300 years. Now, dried peat soils are common adjacent to bog peats. The ¹⁴C basal age of dried peat is not different from the ¹⁴C basal age of bog peat, which supports the theory that dried peat formed from bog peat. A novel application of ²¹⁰Pb dating links the timing of this change with the introduction of livestock to Wellington Plain in the mid‐1800s. Physical loss of material appears to have been the dominant process removing material as bog peats drained to form dried peats, as indicated by the mass balances of carbon and lead. This research has implications for the post‐fire and post‐grazing restoration of bogs in Victoria's Alpine National Park, and the contribution of peat soils to Australia's carbon emissions.     

Postcranial remains and the origin of modern humans

The nature, timing, and location of the origin of modern humans has been the subject of intense controversy for the last 15 years.^1–4 Genetic data and new radiometric dates for key fossils that lie beyond the range of radiocarbon dating have substantially added to the knowledge derived from the fossil evidence documenting the transition from archaic to modern humans. These new data, however, have failed to resolve the problem in its entirety. Most authorities now accept that Africa played an important, and probably central, role in the origin of modern humans.^7–13 The genetic evidence seems to be particularly emphatic that an African population that existed between 200,000 and 100,000 years ago (100 ka) is ancestral to all living humans.^6,7 Controversy still surrounds the question of how much, if at all, archaic humans from outside of Africa, such as Neandertals, late archaic Chinese hominins such as Jinniushan, and the Indonesian Ngandong hominins, may have contributed to the morphological and genetic diversity present in living populations and the morphology of the earliest fossils of modern humans.¹⁰     

Radiocarbon dating: The continuing revolution

Radiocarbon (¹⁴C) dating, now in its fifth decade of general use, continues to be the most widely employed method of inferring chronometric age for late Pleistocene and Holocene age materials recovered from archeological contexts. Over the last decade, several technical advances in ¹⁴C studies have provided contexts for a number of significant applications in archeology that were previously either not possible or not practical. These include the extension of the calibrated ¹⁴C time scale into the late Pleistocene and the development of accelerator mass spectrometry (AMS). The contribution of AMS-based ¹⁴C values to the critical evaluation of archeological data is illustrated by considering the problems of dating early plant domestication in the Near East and Mesoamerica, New World Paleoindian human skeletal materials, and European Upper Paleolithic and Mesolithic materials.     

Radiocarbon and dendrochronology

The radiocarbon dating method relies on calibration through an independent dating method. Dendrochronology is an ideal partner of radiocarbon, because tree-rings are close-to-perfect archives of the atmospheric ¹⁴C level, and the tree-ring time scale can be built beyond doubt with high replication. Over the past 30 years, several stages of ¹⁴C calibration data sets have been constructed from the work of tree-ring laboratories in Europe and North America. This process is outlined and the present state is documented. In turn, ¹⁴C age fluctuations, caused mainly by helio-magnetic changes, can be used to anchor floating tree-ring sections to the calendar scale with a precision of a few decades.     

The Temporal Distribution and Carbon Storage of Large Oak Wood in Streams and Floodplain Deposits

We used tree-ring dating and ¹⁴C dating to document the temporal distribution and carbon storage of oak (Quercus spp.) wood in trees recruited and buried by streams and floodplains in northern Missouri, USA. Frequency distributions indicated that oak wood has been accumulating in Midwest streams continually since at least the late Pleistocene, about 14,000 calibrated radiocarbon years before present (cal. BP). The median residence time of an oak bole in the study streams was 3,515 years (n = 200). More than 30% of sampled oak wood entered the floodplain sediments and stream waters within the last 1,000 years, though very few samples dated to the last 150 years. Temporal variability in the record of oak recruitment to streams suggests a potentially strong influence from shifts in climate and fluvial processes, although other possible influences are addressed. Recent human impacts on streams have altered the dynamics of oak input and sequestered carbon with unknown long-term consequences. The long duration of carbon storage (mean age = 1,960 years) in this waterlogged environment appears to be strongly limited by decreasing wood density resulting from reductions in cell wall thickness. Lack of evidence of biotic degradation may imply that wood loss is largely due to abiotic hydrolyses. These findings document a continuous and long-term form of carbon storage that is sensitive to changes in climate and anthropogenic alteration of fluvial processes.     

26Al/10Be Burial Dating of Xujiayao-Houjiayao Site in Nihewan Basin,Northern China

The Xujiayao-Houjiayao site in Nihewan Basin is among the most important Paleolithic sites in China for having provided a rich collection of hominin and mammalian fossils and lithic artifacts. Based on biostratigraphical correlation and exploratory results from a variety of dating methods, the site has been widely accepted as early Upper Pleistocene in time. However, more recent paleomagnetic analyses assigned a much older age of ∼500 ka (thousand years). This paper reports the application of ²⁶Al/¹⁰Be burial dating as an independent check. Two quartz samples from a lower cultural horizon give a weighted mean age of 0.24 ± 0.05 Ma (million years, 1σ). The site is thus younger than 340 ka at 95% confidence, which is at variance with the previous paleomagnetic results. On the other hand, our result suggests an age of older than 140 ka for the site’s lower cultural deposits, which is consistent with recent post-infrared infrared stimulated luminescence (pIR-IRSL) dating at 160–220 ka.     

Late Quaternary vegetation history at Stracciacappa (Rome, central Italy)

The pollen diagram from Stracciacappa (Sabatini volcanic complex, Rome) provides a record of vegetational and climatic change spanning the last 60000 years, which is the time since when volcanic activity in the crater came to an end. The chronological framework of the sediment core is set by five AMS and three conventional radiocarbon dates; the mean sedimentation rate obtained by radiocarbon measurements was used to extrapolate the age of the record beyond the reach of ¹⁴C dating. The sequence from Stracciacappa provides results of fundamental importance for the understanding of the vegetational changes which occurred during the last pleniglacial period in central Italy, and it can be considered as a reference pollen record for the regional biostratigraphic characterization of this period. The site shows a high climatic sensitivity, particularly highlighted by the development of some pleniglacial oscillations with woodland, which interrupted the succession of steppe and grassland vegetational formations typical of the glacial periods. Unfortunately, due to sedimentation problems and alteration of the top level sediments, the Holocene is only recorded in part. Only for one millennium, from ca. 8300 to 7200 uncalb.p., was a real forest expansion characterized by over 90% arboreal pollen found.     

The use of fallout 137Cs and 239,240Pu for dating of lake sediments

The distribution of ¹³⁷Cs and ^239,240Pu in sediment core samples of the Finnish lakes Laukunlampi, Lovojärvi and Pääjärvi were determined. The sediment samples were collected using dry ice and liquid nitrogen freezing methods. The sediments of these lakes are annually laminated. A clear maximum concentration of ¹³⁷Cs and ^239,240Pu was found in sediment layers formed during 1962–1964, the years of maximum fallout, and the middle of the 1950's can be estimated from the ¹³⁷Cs and ^239,240Pu profiles. The highest concentrations, 11 500 and 820 pCi kg^–1 dry wt for ¹³⁷Cs and ^239,240Pu, respectively, were found in the sediment of Laukunlampi. The vertical distribution was similar for ¹³⁷Cs and ^239,240Pu in the lakes investigated. A slight migration of ^239,240Pu and ¹³⁷Cs was found and the migration of ¹³⁷Cs seems to be higher than that of ^239,240Pu. The advantages of ¹³⁷Cs dating method are rapidity and simplicity. ^239,240Pu is preferable when the sample size is small. The agreement found between ¹³⁷Cs and ^239,240Pu dates and the annual laminae show that these fallout radio isotopes can be used for dating sediments formed during the past 25 years.     

Remains of a Pliocene Mammut borsoni (Hays, 1834) (Proboscidea,Mammalia), from Milia (Grevena,W. Macedonia,Greece)

A partial skeleton of the mastodont Mammut borsoni (Hays, 1834) (Proboscidea), was excavated from Pliocene deposits at Milia — Grevena, W. Macedonia, in 1996–1999. The skeleton includes substantial portions of the skull — maxillary area — with left and right molar series (M² + M³); with the longest upper tusks ever found in Greece (4.39 m); the most complete mandible with left and right molar series (M₂ + M₃) and two lower incisor tusks, as well as post-cranial skeleton. It represents a very large adult of about 40 years in age. The high age of the finding is partly corroborated by ESR dating studies of tooth enamel, indicating an age probably beyond the upper dating range of this technique (approx. 800 000 years). The evolutionary position of this specimen among mammutids is also discussed.     

Cosmogenic 10Be as a potential dating tool in peat

Because ombrotrophic peat bogs receive inputs of water, nutrients, pollutants, and xerobiotic materials solely from the atmosphere, and accumulate organic matter vertically, dated peat cores can provide a historical record of deposition. We propose a novel method for accurately determining dates of peat, based on cosmogenic ¹⁰Be. In a laboratory study, we document limited post-depositional mobility of atmospherically-deposited Be, a requisite for ¹⁰Be dating. We provide an example of how the ²¹⁰Pb-dated upper portion of a peat core can be used to back-calculate a site-specific ¹⁰Be deposition rate, which can then be used to estimate dates for peat throughout a core, and also discuss limitations to the application of cosmogenic ¹⁰Be to the dating of peat deposits.     

渝东南近100年石笋灰度变化及气候环境意义

以采自重庆市酉阳自治县天坑洞的石笋TK22-1为研究对象,利用~(230)Th测年、~(210)Pb测年和石笋纹层等计年法建立了近100年来高分辨率、精确定年的石笋灰度序列,并与器测气象资料对比,重建了渝东南近100年的气候环境变化历史,进一步明确石笋灰度指示的气候环境意义。研究结果显示,石笋TK22-1灰度值与当地年平均温度呈显著的正相关关系,与年平均湿度、降雨天数呈显著的反相关关系,这表明温度和湿度等气候条件是驱动石笋灰度值变化的主要因素。渝东南岩溶槽谷区属于生态环境脆弱区,薄层土壤对降水的储存能力较弱,水分是主导土壤湿度变化的主要因素之一。当降水量和地表湿度较大时,雨水在土壤中滞留时间较少、下渗速度加快,水岩作用减弱,土壤水中溶解的有机质和杂质浓度降低,最终在石笋表面结晶出较为纯净的方解石矿物,进而使石笋灰度值降低;反之亦然。当温度较高时地表蒸发量较大,地表及土壤中湿度较小,水在土壤和石灰岩地层中滞留时间长,土壤中有机质和CO_2的释放量增加,洞穴滴水中有机质和杂质浓度升高,导致石笋中方解石结构疏松、杂质较多,石笋灰度值较高;反之亦然。重庆东南岩溶槽谷区近100年期间的干旱事件与石笋TK22-1灰度序列有较好的对应关系,干旱事件发生的年代对应着石笋灰度峰值,即当地降水减少,发生伏旱时,石笋灰度值升高,进一步表明土壤湿度和水岩作用是影响石笋灰度值变化的主要因素。