The Middle to Upper Paleolithic transition: dating, stratigraphy, and isochronous markers

Accurate and precise dating is vital to our understanding of the Middle to Upper Paleolithic transition. There are, however, a number of uncertainties in the chronologies currently available for this period. We attempt to examine these uncertainties by utilizing a number of recent developments in the field. These include: the precise dating of the Campanian Ignimbrite (CI) tephra by 40Ar/39Ar; the tracing of this tephra to a number of deposits that are radiocarbon dated; the publication of revised radiocarbon calibration data for the period, showing a much better convergence with other available data than during the recent IntCal comparison; and a layer-counted ice-core chronology extending beyond 40,000cal BP. Our data comparisons suggest that a reasonable overall convergence between calibrated radiocarbon ages and calendar dates is possible using the new curves. Additionally, we suggest that charcoal-based radiocarbon ages, as well as bone-based radiocarbon determinations, require cautious interpretation in this period. Potentially, these issues extend far beyond the sites in this study and should be of serious concern to archaeologists studying the Middle to Upper Paleolithic. We conclude by outlining a strategy for moving the science forward by a closer integration of archaeology, chronology, and stratigraphy.     

Combined dendrochronological and radiocarbon dating of three Russian icons from the 15th–17th century

Dendrochronology is usually the only method of precise dating of unsigned art objects made on or of wood. It has a long history of application in Europe, however in Russia such an approach is still at an infant stage, despite its cultural importance. Here we present the results of dendrochronological and radiocarbon accelerated mass spectrometry (AMS) dating of three medieval icons from the 15th–17th century that originate from the North of European Russia and are painted on wooden panels made from Scots pines. For each icon the wooden panels were dendrochronologically studied and five to six AMS dates were made. Two icons were successfully dendro-dated whereas one failed to be reliably cross-dated with the existing master tree-ring chronologies, but was dated by radiocarbon wiggle-matching. Wiggle-matching of radiocarbon dates is the most promising method for dating Russian icons in the absence of a dense dendrochronological network. However, for this case uncertainties connected with the radiocarbon method have to be taken into account and further studies of these uncertainties must be undertaken by comparing dendro-dated and radiocarbon-dated wooden works of art. Our results, moreover, showed that in two cases art-historical dates were by five to ten decades older than the earliest possible time of the creation of the icons, based on dendrochronology.     

中国第四纪晚期孢粉记录整理

孢粉数据库是重建过去植被格局以及研究古气候变化和大气圈-生物圈-人类活动相互关系的基础,而孢粉取样信息的记录和整理是建立孢粉数据库的重要前提。该文在收集我国1960–2008年发表的孢粉研究文献的基础上,整理分析了第四纪晚期,尤其是2万年以来(全新世为主)全国孢粉采样点的信息,包括采样地点名称、详细采样位置、省份、采样点经纬度和海拔高度、样品类型、取样深度、孢粉样品数量、14C测年数量及年代记录、覆盖的时间段和参考文献。总结发现,我国目前共有2324个表土/湖泊表层花粉采样点和987个第四纪晚期的地层沉积剖面和钻孔,其中高质量的地层孢粉采样点714个。虽然我国以及部分国际上从事第四纪研究的科学家尽了最大努力开展中国疆域的孢粉学研究,但由于人力、物力以及地形条件的限制,在我国仍然存在部分孢粉采样的"地理空隙",比如北方和西北荒漠地区、青藏高原无人区、中南部山区和东部人类活动频繁区域。然而,该数据信息库的不断完善,将为中国第四纪孢粉数据库的建立奠定良好基础。     

Changes in the Radiocarbon Reservoir Age in Lake Xingyun,Southwestern China during the Holocene

Chronology is a necessary component of paleoclimatology. Radiocarbon dating plays a central role in determining the ages of geological samples younger than ca. 50 ka BP. However, there are many limitations for its application, including radiocarbon reservoir effects, which may cause incorrect chronology in many lakes. Here we demonstrate temporal changes in the radiocarbon reservoir age of Lake Xingyun, Southwestern China, where radiocarbon ages based on bulk organic matter have been reported in previous studies. Our new radiocarbon ages, determined from terrestrial plant macrofossils suggest that the radiocarbon reservoir age changed from 960 to 2200 years during the last 8500 cal a BP years. These changes to the reservoir effect were associated with inputs from either pre-aged organic carbon or ¹⁴C-depleted hard water in Lake Xingyun caused by hydrological change in the lake system. The radiocarbon reservoir age may in return be a good indicator for the carbon source in lake ecosystems and depositional environment.     

Vertebral Bomb Radiocarbon Suggests Extreme Longevity in White Sharks

Conservation and management efforts for white sharks (Carcharodon carcharias) remain hampered by a lack of basic demographic information including age and growth rates. Sharks are typically aged by counting growth bands sequentially deposited in their vertebrae, but the assumption of annual deposition of these band pairs requires testing. We compared radiocarbon (Δ¹⁴C) values in vertebrae from four female and four male white sharks from the northwestern Atlantic Ocean (NWA) with reference chronologies documenting the marine uptake of ¹⁴C produced by atmospheric testing of thermonuclear devices to generate the first radiocarbon age estimates for adult white sharks. Age estimates were up to 40 years old for the largest female (fork length [FL]: 526 cm) and 73 years old for the largest male (FL: 493 cm). Our results dramatically extend the maximum age and longevity of white sharks compared to earlier studies, hint at possible sexual dimorphism in growth rates, and raise concerns that white shark populations are considerably more sensitive to human-induced mortality than previously thought.     

Palynological richness and evenness: insights from the taxa accumulation curve

Palynology provides the opportunity to make inferences on changes in diversity of terrestrial vegetation over long time scales. The often coarse taxonomic level achievable in pollen analysis, differences in pollen production and dispersal, and the lack of pollen source boundaries hamper the application of diversity indices to palynology. Palynological richness, the number of pollen types at a constant pollen count, is the most robust and widely used diversity indicator for pollen data. However, this index is also influenced by the abundance distribution of pollen types in sediments. In particular, where the index is calculated by rarefaction analysis, information on taxonomic richness at low abundance may be lost. Here we explore information that can be extracted from the accumulation of taxa over consecutive samples. The log-transformed taxa accumulation curve can be broken up into linear sections with different slope and intersect parameters, describing the accumulation of new taxa within the section. The breaking points may indicate changes in the species pool or in the abundance of high versus low pollen producers. Testing this concept on three pollen diagrams from different landscapes, we find that the break points in the taxa accumulation curves provide convenient zones for identifying changes in richness and evenness. The linear regressions over consecutive samples can be used to inter- and extrapolate to low or extremely high pollen counts, indicating evenness and richness in taxonomic composition within these zones. An evenness indicator, based on the rank-order-abundance is used to assist in the evaluation of the results and the interpretation of the fossil records. Two central European pollen diagrams show major changes in the taxa accumulation curves for the Lateglacial period and the time of human induced land-use changes, while they do not indicate strong changes in the species pool with the onset of the Holocene. In contrast, a central Swedish pollen diagram shows comparatively little change, but high richness during the early Holocene forest establishment. Evenness and palynological richness are related for most periods in the three diagrams, however, sections before forest establishment and after forest clearance show high evenness, which is not necessarily accompanied by high palynological richness, encouraging efforts to separate the two.     

Validation of yellowedge grouper, <Emphasis Type="Italic">Epinephelus flavolimbatus</Emphasis>, age using nuclear bomb-produced radiocarbon

Age validation and estimates of longevity of yellowedge grouper (Epinephelus flavolimbatus) from the Gulf of Mexico (GOM) are needed to inform fishery management decisions. Yellowedge grouper sagittal otoliths (n = 100) were collected, aged using conventional means, and cores were submitted for radiocarbon (¹⁴C) measurement. Radiocarbon values of yellowedge grouper otoliths were compared to established radiocarbon chronologies in the region to validate the age and ageing methodology of this species. The yellowedge grouper chronology displayed a similar sigmoidal trend as previously published chronologies. In addition to the core analysis, multiple areas on otolith sections from eight specimens were analyzed for Δ¹⁴C to validate age estimates for fish born prior to the ¹⁴C increase. Our results indicate that yellowedge grouper live longer than previously reported (minimum of 40 years based on radiocarbon measurements). The validated ageing methodology supported an estimated maximum longevity of 85 years and established that yellowedge grouper have the longest lifespan currently known for any species of grouper in the GOM. Results also indicate a depth-age interaction in that material extracted from adult otolith sections assigned to post-bomb dates exhibited lower Δ¹⁴C values than cores (juvenile material) assigned to the same post-bomb dates. This finding is likely explained by lower ¹⁴C levels reported from water masses at deeper depths (>100 m) which are inhabited by adults.     

The European Pollen Database: past efforts and current activities

Pollen stratigraphies are the most spatially extensive data available for the reconstruction of past land-cover change. Detailed knowledge of past land-cover is becoming increasingly important to evaluate the present trends in, and drivers of, vegetation composition. The European Pollen Database (EPD) was established in the late 1980s and developed in the early 1990s to provide a structure for archiving, exchanging, and analysing Quaternary pollen data from Europe. It provides a forum for scientists to meet and engage in collaborative investigations or data analysis. In May 2007 several EPD support groups were developed to assist in the task of maintaining and updating the database. The mapping and data accuracy work group (MADCAP) aims to produce an atlas of past plant distributions as detected by pollen analyses in Europe, in order to meet the growing need for this data from palaeoecologists and the wider scientific community. Due to data handling problems in the past, a significant number of EPD datasets have errors. The initial task of the work group, therefore, was a systematic review of pollen sequences, in order to identify and correct errors. The EPD currently (January 2009) archives 1,032 pollen sequences, of which 668 have age-depth models that allow chronological comparison. Many errors have been identified and corrected, or flagged for users, most notably errors in the pollen count data. The application of spatial analyses to pollen data is related to the number of data points that are available for analysis. We therefore take this opportunity to encourage the submission of pollen analytical results to the EPD or other relevant pollen databases. Only in this way will the scientific community be able to gain a better understanding of past vegetation dynamics.     

Use of stored carbon reserves in growth of temperate tree roots and leaf buds: analyses using radiocarbon measurements and modeling

Characterizing the use of carbon (C) reserves in trees is important for understanding regional and global C cycles, stress responses, asynchrony between photosynthetic activity and growth demand, and isotopic exchanges in studies of tree physiology and ecosystem C cycling. Using an inadvertent, whole-ecosystem radiocarbon (¹⁴C) release in a temperate deciduous oak forest and numerical modeling, we estimated that the mean age of stored C used to grow both leaf buds and new roots is 0.7 years and about 55% of new-root growth annually comes from stored C. Therefore, the calculated mean age of C used to grow new-root tissue is ∼0.4 years. In short, new roots contain a lot of stored C but it is young in age. Additionally, the type of structure used to model stored C input is important. Model structures that did not include storage, or that assumed stored and new C mixed well (within root or shoot tissues) before being used for root growth, did not fit the data nearly as well as when a distinct storage pool was used. Consistent with these whole-ecosystem labeling results, the mean age of C in new-root tissues determined using 'bomb-¹⁴C' in three additional forest sites in North America and Europe (one deciduous, two coniferous) was less than 1–2 years. The effect of stored reserves on estimated ages of fine roots is unlikely to be large in most natural abundance isotope studies. However, models of root C dynamics should take stored reserves into account, particularly for pulse-labeling studies and fast-cycling roots (<1 years).     

Dendroarchaeology at Lake Ohrid: 5th and 2nd millennia BCE tree-ring chronologies from the waterlogged site of Ploča Mičov Grad,North Macedonia

On the prehistoric site of Ploča Mičov Grad (Ohrid, North Macedonia) on the eastern shore of Lake Ohrid a total of 799 wooden elements were recorded from a systematically excavated area of nearly 100 square metres. Most of them are pile remains made of round wood with diameters up to almost 40 cm. A comprehensive dendrochronological analysis allows the construction of numerous well-replicated tree-ring chronologies for different species. High agreements between the chronologies prove that oak, pine, juniper, ash and hop-hornbeam can be crossdated. The chronologies are dated by means of radiocarbon dates and modelling using wiggle matching. An intensive settlement phase is attested for the middle of the 5th millennium BCE. Further phases follow towards the end of the 5th millennium BCE and in the 2nd millennium around 1800, 1400 and 1300 BCE. Furthermore, the exact, relative felling dates allow first insights into the minimum duration of the settlement phases, which lie between 17 and 87 years. The multi-centennial chronologies presented in this study can be used as a first robust dating basis for future research in the numerous not yet dated prehistoric lake shore settlements of the region with excellently preserved wooden remains.     

Tree-ring and varve scales combined,c. 13500 B.C. to A.D. 1977

Varve chronologies are of several kinds but glacial varves respond to summer temperature and fluvial varves to summer rainfall.Tree-ring chronologies near the timberline respond to summer temperature but European oak chronologies respond to summer rainfall.Certain global features of the weather of the summer season, notably the Biennial Index, are therefore parameters that can be used for cross-dating both varves and tree-rings in different continents.Characteristic curves for different parameters in the Late Glacial (Zones Ia, Ib and II) and in the past thousand years are presented. A moisture curve is given for the North European Plain (200 B.C.–A.D. 1100). A conversion chart for tree-rings and radiocarbon dates is extended back into the Late Glacial on the tentative assumption that the radiocarbon error was about 950 years at the beginning of the Holocene (III/IV), i.e. that 10300 b.p. should be 11250 B.P. or 9300 B.C.Supplementary sources of information useful in obtaining approximate dates include: (a) palaeomagnetism; (b) tephrochronology and X-ray analysis; (c) cycle analysis; (d) climatic peculiarities associated with specific radiocarbon centuries; (e) X-ray analysis of specific varves; and (f) new methods of varve-analysis.The varve-series used for the Late Glacial, if the author's cross-dating between North America and Scandinavia is acceptable, constitute a floating chronology of about 4000 years. Given approximate ¹⁴C dates for any long series of varves or tree-rings in one part of the world, it is now possible to obtain cross-dating with any other long series in another part of the world, and it will be easy to replace the tentative ‘950-year’ error by a precise figure determined from a combined varve and tree-ring scale extending back from the present day to (say) the zero of Sauramo's scale for varves in Finland. In the meantime the ‘950’ is mnemonically convenient, as this would make the year on the B.C. scale one thousand less than the year on the b.p. scale.     

Species clustering and New Zealand quaternary climate

This paper uses the relative frequencies of occurrence of various types of pollen and spores to indicate the comparative temperatures under which Quaternary sediments accumulated in several locations in New Zealand. The application of association measures, and cluster and discriminant function analysis to such information is described and discussed.The analyses show that the types may be divided into groups whose members vary little with locality or with the statistical methods used to establish them. This stability suggests that anomalous dispersion effects are not a major influence. For some of these groups there is a similarity between the present-day climate of known pollen or spore sources and those of the corresponding groups at the time of deposition. The significant groups are used to summarise the results in pollen diagrams which are compared with similar diagrams for the discriminant function. It is also shown that the methods described assist in locating zone boundaries in a series of samples taken from a bore hole.The results obtained are relevant to the interpretation of samples in which southern beech (Nothofagus fusca type) is the most abundant tree pollen.     

Holocene vegetation of the Van area: palynological and chronological evidence from Söğütlü, Turkey

Evidence of the terrestrial pollen precipitation in the Van area, obtained from the marsh of Söütlü, is compared with the lacustrine record from Lake Van, eastern Turkey. The radiocarbon chronology of the vegetation history of the Van area is compared with that from varve counting. The first method produced the most probable results, supported by palynological investigations in other parts of Turkey and Iran. The combination of radiocarbon dating and palynological correlation dates the sediments of Lake Van 1100 to 2200 years older than the varve dating.The indicator value of Cerealia-type pollen as evidence of prehistoric agriculture is discussed and compared with results from observations on modern crops. In the present study, Cerealia-type pollen may have been produced by wild grasses growing in the marsh.     

Palynology of peat sections from Spitsbergen covering the last few centuries

Peat sections, measuring up to 40 cm, from four areas of Spitsbergen were studied for pollen and spores; the results are presented as pollen concentration diagrams. Dated parts of the sections cover approximately the last three to thirteen centuries. In one section, an increasing rate of peat accumulation is suggested by a decreasing trend in concentrations of long-distance transported pollen and spores and by radiocarbon dates; in the other three sections there are no indications of the existence of phases differing in peat-accumulation rates. In two sections a local development is recorded from dry peat-forming vegetation relatively rich in vascular-plant species into wet peat-forming vegetation poor in vascular-plant species. The two other sections represent wet peat-forming vegetation relatively poor in vascular-plant species throughout the recorded period.     

A probabilistic approach to the use of pollen indicators for plant attributes and biomes: an application to European vegetation at 0 and 6 ka

Aim This paper presents a probabilistic method for the characterization of pollen taxa using attributes, and for the reconstitution of past biomes. The probabilities are calculated on the basis of European floristic and pollen databases sufficiently large and exhaustive to provide robust estimates. Location The analysis is based on data from approximately 1000 sites throughout Europe. Method We use all the pollen data from the European Pollen Database (EPD), which contains about 50 000 pollen assemblages distributed across Europe and covering the period from the Last Glacial Maximum to the present. Using existing floras, each pollen taxon has been characterized by allocating one or more modes of several attributes, chosen according to the biogeography and phenology of the taxon. With this information, conditional probabilities are defined, representing the chance of a given attribute mode occurring in a given pollen spectrum, when the taxa assemblage is known. The concept of co‐occurrence is used to provide a greater amount of information to compensate for difficulties in the identification of pollen grains, allowing a better interpretation when there is little diversity in the pollen assemblage. Results The method has been validated using a dataset of modern samples against existing methods of biome classification and remote sensing data. An application is proposed in which the new method is used to produce biomes for pollen data 6000 years ago. This confirms previous results showing an extension of the deciduous forest to the north, east and south, explained by milder winters in western and northern Europe, and cooler and wetter climate in the Mediterranean region. Conclusion The results show the new method to be efficient, reliable and flexible and to be an improvement over the previous method of biomization. They will be used to test simulations of earth system models running on periods with climate significantly different from the present day, enabling a robust test of the validity of applying these models to the future.     

A deep dig––hindsight on Holocene vegetation composition from ancient environmental DNA

Want a glimpse at past vegetation? Studying pollen and other plant remains, which are preserved for example in lake sediments or mires for thousands of years, allows us to document regional occurrences of plant species over radiocarbon‐dated time series. Such vegetation reconstructions derived from optical analyses of fossil samples are inherently incomplete because they only comprise taxa that contribute sufficient amounts of pollen, spores, macrofossil or other evidences. To complement optical analyses for paleoecological inference, molecular markers applied to ancient DNA (aDNA) may help in disclosing information hitherto inaccessible to biologists. Parducci et al. (2013) targeted aDNA from sediment cores of two lakes in the Scandes Mountains with generic primers in a meta‐barcoding approach. When compared to palynological records from the same cores, respective taxon lists show remarkable differences in their compositions, but also in quantitative representation and in taxonomic resolution similar to a previous study (Jørgensen et al. 2012). While not free of assumptions that need critical and robust testing, notably the question of possible contamination, this study provides thrilling prospects to improve our knowledge about past vegetation composition, but also other organismic groups, stored as a biological treasure in the ground.     

The potential of intra-annual density information for crossdating of short tree-ring series

The crossdating of tree-ring series is typically based on tree-ring width sequences, which is a crude abstraction of the growth signal stored in tree rings. In contrast, intra-annual wood density data allows a much more detailed comparison of wood growth processes and new measurement techniques scale well to measure large amounts of samples. Thus, chronologies of intra-annual densitometric curves can be built. Here, we investigate to what extent intra-annual wood density information can improve crossdating. We evaluate different approaches on a data set of Norway spruce trees (Picea abies) and compare the results to standard methods that are based on ring width or maximum density. Our results show that intra-annual densitometric data indeed increases crossdating success rate notably for short tree ring series that cover less than 25 years.     

桃花粉低温和超低温保存方法比较研究

桃(Prunus persica(L.)Batsch)是我国重要的无性繁殖作物种质资源,目前主要保存于3个国家无性繁殖作物种质圃。随着以茎尖、花粉、休眠芽为保存载体的超低温保存技术的发展,超低温保存已成为无性繁殖作物重要备份保存方式。本研究以15份桃种质花粉为研究对象,开展含水量、回湿处理和保存温度(4℃低温保存和液氮超低温保存)对保存后花粉离体萌发率的影响研究。研究结果:明确了桃种质花粉超低温保存的含水量;揭示了回湿处理对部分桃种质花粉超低温保存产生显著影响;超低温保存后花粉离体萌发率最高可达83%;4℃低温保存和超低温保存比较研究结果表明,超低温保存4年后14份桃种质花粉离体萌发率仍可保持30%以上,11份桃种质花粉离体萌发率与保存前花粉离体萌发率相比无显著变化甚至显著提高,而4℃低温保存的花粉离体萌发率降至0。该研究为国家种质库建立花粉规模化超低温保存提供技术支撑。     

Late Würm and early Holocene in the mountains of northwest Iberia: biostratigraphy,chronology and tree colonization

Northwest Iberia (Spain and Portugal) is a large and complex territory which is currently considered a contact border between two different biogeographical regions, the Eurosiberian and the Mediterranean. Such complexity is clearly influenced by several main factors, namely the winding mountain ranges of this region and their position on the peninsula, which result in several markedly different environments coexisting within distances of only a few kilometres apart, such as extremely oceanic or continental climates and high mountain areas or inland basins. This intricacy might also be reflected in the postglacial palaeoecological reconstructions which have been made for different mountain areas of northwest Iberia. Several isolated pollen diagrams from key sites in the area which have been published during the last decades have been questioned, because they show tendencies or chronologies apparently incompatible with global dynamics affecting the North Atlantic. In this paper we explore the possible integration of the biostratigraphies and chronologies of several selected pollen sites in this region. Northwest Iberia as a whole has been firstly divided into several more homogeneous biogeographical units, and high quality pollen sequences from each unit were selected to obtain reconstructions of local dynamics at each site and also approximations of the regional tendencies in each unit. Subsequently, the correlation between the different regional tendencies and their coherence in relation to the global climatic models performed for the North Atlantic is discussed.     

Vegetation history of Lago Battaglia (eastern Gargano coast,Apulia, Italy) during the middle-late Holocene

A pollen and charcoal record from Gargano (southern Italy) provides new information on the vegetation history and environmental change in southern Italy during the middle to late Holocene. The chronological framework is provided by six AMS radiocarbon dates carried out on plant macroremains. Pollen diagrams record a Mediterranean vegetation along the coastland and a stable mixed oak forest at higher elevations between ca. 5900 and 4200 cal b.p. A sharp and dramatic fall of tree pollen concentrations and a change in fire frequencies occurred from approximately 4200 cal b.p. suggesting a climate change towards drier conditions. This event is coherent with regional and extra-regional palaeoclimatic records that suggest that a mid-Holocene dry period was experienced in southern Italy, southern Spain, and perhaps further afield. Human impact on vegetation seems to have occurred since about 2700 cal b.p.