Ka Climate Event Research Articles

Oasis civilization collapse under 3.9 ka climate event in Bactria, Central Asia

Central Asia played a significant role in the early exchange of civilizations across Eurasia. The arid climate, which makes the local ecology sensitive to climate change and the well-preserved archaeological remains, make Central Asia an ideal location for studying the mechanisms of interactions between civilization evolution and environmental change. This research presents archaeobotanical, palynological and stable isotope records from the Djarkutan site in southeastern Uzbekistan, which was occupied between 4100 and 3700 cal yr BP. Our research shows that in the Late Bronze Age, after 4000 yr BP, the local agricultural structure was highly complex. Pollen and stable isotope result indicate a sudden drought event occurred in the local area around 3900 yr BP, which had an impact on the local oasis agricultural system. Subsequently, this event promoted the migration of northern steppe populations into Central Asia, leading to the development of an agro-pastoral economy in the research area.

Uncovering Holocene climate fluctuations and ancient conifer populations: Insights from a high-resolution multi-proxy record from Northern Finland

A series of abrupt climate events linked to circum-North Atlantic meltwater forcing have been recognised in Holocene paleoclimate data. To address the paucity of proxy records able to characterise robustly the regional impacts of these events, we retrieved a sub-centennial resolution, well-dated core sequence from Lake Kuutsjärvi, northeast Finland. By analysing a range of paleo-environmental proxies (pollen, plant sedimentary ancient DNA, plant macrofossils, conifer stomata, and non-pollen palynomorphs), and supported with proxy-based paleotemperature and moisture reconstructions, we unravel a well-defined sequence of vegetation and climate dynamics over the early-to-middle Holocene. The birch-dominated pioneer vegetation stage was intersected by two transient tree-cover decrease events at 10.4 and 10.1 thousand years ago (ka), likely representing a two-pronged signal of the 10.3 ka climate event. Our data also show a clear signal of the 8.2 ka climate event, previously not well recorded in the European Arctic, with a collapse of the pine-birch forest and replacement by juniper developing in tight synchrony with Greenland isotopic proxies over 8.4–8.0 ka. Supported by climate modelling, severe winter cooling rather than summer might have been driving vegetation disruptions in the early Holocene. The Kuutsjärvi data indicate an early arrival of Norway spruce (Picea abies) by 9.2 ka (pollen, DNA, and stoma finds), as well as the first evidence for Holocene presence of larch (Larix) in Finland, with pollen finds dating to 9.6–5.9 ka.

Continuity and climate change: the Neolithic coastal settlement of Habonim North, Israel

ABSTRACTSedentary occupation of the southern Levantine coast spans from the Pre-Pottery Neolithic C to the Early Bronze Age Ib phase (c. 7000–3100 BC). Sites dating to the Early Pottery Neolithic (c. 6400–5500 BC) are scarce, however, potentially reflecting the effects of the 8.2ka climatic event. Here, the authors present the investigations at the submerged site of Habonim North off the Carmel Coast. Typological and radiocarbon dating indicate an Early Pottery Neolithic occupation and evidence for continuity of subsistence and economic strategies with both earlier and later Neolithic cultures. The results indicate the resilience of coastal communities in the face of significant climatic uncertainty and contribute to understanding human responses to environmental change.

The herding revolution in China under the impact of the 4.2 ka climate event

During the late fifth millennium BP, cattle and sheep were reintroduced into North China, then they were widespread adopted under the 4.2 ka climate event, which was associated with the rise of early states. With the synchronous exploitation of primary and secondary products, the herding revolution contributed to the cultural dynamics in North China.

Vegetation reconstruction of the Agro Pontino and Fondi basin (central Italy) before and after the Bronze Age eruption of Somma-Vesuvius (c. 1900 BCE)

In the research project The Avellino Event: Cultural and Demographic Effects of the Great Bronze Age Eruption of Mount Vesuvius, the recording of local and regional changes in the vegetation of the landscapes of the Agro Pontino and the Fondi basin (southern Lazio, Italy) before and after the Bronze Age eruption of Somma-Vesuvius (c. 1900 BCE) was central to answer the project’s central question, which revolved around the nature of the distal effects of this high-magnitude eruption on the conditions of living for the Bronze Age human population inhabiting these landscapes. If adverse effects of the ash fall in these areas were minor, the Agro Pontino and the Fondi basin, located about 125 km north of the Vesuvius, could well have been the refuge area people might have fled to in their attempts to escape the pyroclastic flows that eventually would bury parts of Campania around the Vesuvius below a thick layer of tephra. If adverse effects of the ash fall were major, the situation might, likewise, have led to changes in vegetation but could have resulted in a decline in human and animal presence due to toxicity, for instance. In both scenarios, either population growth due to in-migration or population decline due to environmental impact, we expected to see changes in the vegetation record in the period during which the Avellino Event occurred. To test our hypotheses, we performed archaeobotanical research, using pollen and macro-remains, on stratified soil sequences from test pits in the Agro Pontino and the Fondi basin containing the Avellino tephra layers, thereby guaranteeing sound chronological control. (The research revealed the presence of other known distal tephras as well.) Contrary to our expectations, the research did not provide proof of any significant changes in the vegetation around the date of the Avellino Event, nor did it provide any strong signs of human impact on these landscapes in the longer term before and after the distal ash fall, thereby indicating low population levels during the final part of the Early Bronze Age (EBA) and the initial phase of the Middle Bronze Age. Although this finding about human impact is an important outcome, it is not the only finding. The archaeobotanical research provided the project with high-resolution information on the vegetation and environmental conditions in the Agro Pontino and the Fondi basin for the duration of the Bronze Age. This, in combination with the physical-geographical data collected during the project, added significantly to our ability to perform detailed palaeogeographical reconstruction of the Agro Pontino and the Fondi basin. In addition, it increased our understanding of how the landscape had been settled during the Bronze Age (Sevink et al. 2022; Attema et al. in press). A final spin-off consisted of possible new information on the 4.2 ka climatic event that impacted Italy during later prehistory, as reflected in the pollen diagrams presented.

Sudden disappearance of yew (Taxus baccata) woodlands from eastern England coincides with a possible climate event around 4.2 ka ago

Tree-ring chronologies form the backbone of high-resolution palaeoclimatology. However, their number declines drastically prior to medieval times, and only a few such records worldwide extend back to the mid-Holocene. Here, we present a collection of more than 400 subfossil yew (Taxus baccata L.) trees excavated from near sea-level peat-rich sediments in the Fenland region of eastern England. The well-preserved yew trunks are between two and eight metres long, often exhibit adventitious root layers, and contain up to 400 rings of highly irregular growth. Combined dendrochronological and radiocarbon dating resulted in two tree-ring width chronologies that comprise 36 and 32 trees, span 413 and 418 years, exhibit mean inter-series correlations (Rbar) of 0.50 and 0.51, and were provisionally dated to 5225−4813 (±4) and 4612−4195 (±6) years cal BP. Together with a total of 63 radiocarbon dates (14C), our subfossil tree-ring evidence suggests that yew establishment (or onset of preservation) began ∼5250 years cal BP and resulted in extensive climax forests between 5200 and 4200 years cal BP. A first stage of yew decline ∼4800−4600 years cal BP was possibly caused by oxygen deprivation from soil wetting, whereas yew disappearance ∼4200 years cal BP is suggested to have been triggered by marine inundation as a consequence of rapid sea-level rise. Both phases of yew decline in eastern England coincide with marked reductions in subfossil oak and pine from peatbogs in Ireland, Germany and the Netherlands. Our results emphasise the potential to develop a dendrochronological network in coastal England for better understanding of larger-scale climate and environmental changes during the mid-Holocene, including the still debated 4.2 ka climate event. Moreover, we expect our subfossil yew chronologies to facilitate the dating of local archaeological remains, refine sea-level reconstructions around the British Isles, and contribute to the international radiocarbon calibration curve IntCal.

High-resolution quantitative vegetation reconstruction in the North China Plain during the early-to-middle Holocene using the REVEALS model

Understanding the process and pattern of vegetation succession during the early-to-middle Holocene can yield valuable information for better predicting future vegetation evolution. In this study, we investigated the humidity evolution pattern in the North China Plain (NCP) during the early-to-middle Holocene by employing principal component analysis on 93 fossil spectra. Furthermore, by integrating the Regional Estimates of Vegetation Abundance from Large Sites (REVEALS) model, we quantitatively reconstructed the process of vegetation succession and discussed vegetation response to climate change events. Our results indicate that the sample scores of the first principal component axis (PCA axis 1) exhibited a consistent negative bias, implying a gradual rise in regional humidity. The quantitatively reconstructed tree coverage was found to be lower than the uncorrected pollen proportions, while the coverage of herb plants showed a significant increase compared to their respective pollen percentages. In the early and middle Holocene, the vegetation of the NCP succeeded from meadow steppe (10,000 ∼ 8,100 cal yr B.P.) to meadow steppe with pine woodland patches (8,100 ∼ 7,100 cal yr B.P.), then to pine forest (7,100 ∼ 5,300 cal yr B.P.). The quantitatively reconstructed vegetation exhibited the most pronounced response to 8.2 ka climate event, with Asteraceae emerging as the dominant taxa. Furthermore, we conducted a comprehensive analysis of the impact of the 8.2 ka climate event on vegetation in northern China, identifying four distinct types of vegetation feedback: (1) negligible alterations in vegetation, (2) expansion of steppe or desert steppe, (3) proliferation of temperate tree species, and (4) augmentation of meadow steppe.

The magnitude and source of meltwater forcing of the 8.2 ka climate event constrained by relative sea-level data from eastern Scotland

The 8.2 ka climate event is the most significant North Atlantic cooling event during the Holocene. Freshwater pulses from the melting Laurentide Ice Sheet draining into the North Atlantic Ocean are commonly thought to be its cause by perturbing the Atlantic Meridional Overturning Circulation. The timing, magnitude and number of freshwater pulses, however, remain uncertain. This is problematic for predicting future climate scenarios because it prevents rigorous testing of coupled ocean–atmosphere climate models against an otherwise excellent test case of climate effects of meltwater inputs into the North Atlantic. To address this knowledge gap, we present a high-resolution relative sea-level record from the Ythan Estuary, Scotland, spanning the centuries leading into the 8.2 ka climate event. The results show a ‘sea-level event’ with two distinct stages between 8,530 and 8,240 cal yr BP when rates of sea-level rise departed from the background rates of around 2 mm yr-1 and reached around 13 mm yr-1 and 4 mm yr-1, respectively. The maximum probable magnitude of local sea-level rise during the stages was 1.67 and 0.41 m, which equate to barystatic magnitudes of 2.39 and 0.58 m respectively after considering the geographic location relative to the source.For the first time, we demonstrate that Lake Agassiz-Ojibway drainage alone is insufficient to explain the large volumes of North Atlantic freshwater input, and that the collapse of the Hudson Bay Ice Saddle appears to have been the main source of meltwater in to the North Atlantic. By comparing the Ythan sea-level record with other sources of evidence, we hypothesise that an initial thinning of the Laurentide Ice Sheet enabled subglacial drainage of Lake Agassiz and subsequent collapse of the Hudson Bay Ice Saddle. This was followed by the terminal drainage of Lake Agassiz completing a sequence of events that likely forced the shift in the Atlantic Meridional Overturning Circulation and hence the 8.2 ka climate event.

Hydroclimatic variation over central China during the 4.2 ka event and its implications for cultural transformation

The 4.2 ka climate event, which marks the start of the late Holocene (Meghalayan), is linked to disruption to human cultures across a wide belt from the eastern Mediterranean to the Yangtze River Valley. Here we present a high-resolution stalagmite δ13C record for the middle Yangtze Valley from 4.4 to 3.0 ka BP, and identify two humid pulses and two dry episodes associated with the 4.2 ka event. Similar hydroclimate fluctuations associated with the 4.2 ka event also occur in the Chinese Loess Plateau and Central Plains of China, and may be at least partly responsible for the decline of the Neolithic culture in these regions. Although the 4.2 ka event marks the internationally recognised boundary between the middle and late Holocene, our stalagmite-based evidence shows that regime shift in hydrological variability occurred at ∼3.5 ka BP in the middle Yangtze Valley. Regime shift correlates with inflection points of temperature in the extratropical Northern Hemisphere and tropical El Niño Southern Oscillation (ENSO) systems, indicating teleconnections between local and global climate change at this time. Following regime shift, precipitation fluctuated with a larger amplitude. Two dry events and one humid rebound event correspond to the early, late, and middle phases of the Shang Dynasty, respectively. In summary, we propose that frequent climatic alternations and their increased amplitudes impacted late Holocene cultural evolution in China.

Mid- to late Holocene vegetation response to relative sea-level fluctuations recorded by multi-proxy evidence in the Subei Plain, eastern China

Reconstructing Holocene changes in regional sea level is useful for understanding future sea-level scenarios. In this paper we examined the sedimentology, pollen, foraminifera, and organic matter properties of a well-dated profile from the Subei Basin that spans the last 6.7 ka. By integrating our findings with the archaeological record, we investigated mid- to late Holocene vegetation responses to relative sea-level fluctuations and considered the impact of climatic variations on cultural development. In the middle Holocene, the rapid and abrupt expansion of salt marsh vegetation (Chenopodiaceae, Cyperaceae, and Poaceae) suggests a relative rise in sea level. From 5.7 to 4.2 cal ka BP, lowland swamps were settled by Neolithic communities, as indicated by peak levels of microscopic charcoal and a significant rise in herbaceous pollen species, such as Cyperaceae, Typha, Myriophyllum, and Poaceae. From 4.2 to 3.7 cal ka BP, a major increase in Chenopodiaceae abundance and a δ13C excursion were observed along with a decrease in Cyperaceae and Poaceae levels, which revealed that human activity significantly decreased following the 4.2 ka climate event. Evidence suggests that the area under investigation experienced a relatively high sea level between 6.7 and 6.0 ka, a relative decrease in sea level between 6.0 and 5.7 ka, a steady sea-level condition between 5.7 and 4.2 ka, and gradual replacement by a freshwater marsh between 5.7 and 4.2 ka. The pollen and δ13 C records demonstrate that the relative sea level rose quickly from 4.2 to 3.7 ka, which could correspond to the 4.2 ka event. Enhanced El Niño-Southern Oscillation (ENSO) variance and intense climatic events in eastern China were the driving forces behind the mid-late Holocene relative sea-level shift. The rise in relative sea level eventually led to the collapse of the Qingdun and Jiangzhuang sites in the Subei Basin. Our results provide independent vegetation evidence of the simultaneous changes in relative sea level and variations in climate.

Antipodal pattern of millet and rice demography in response to 4.2 ka climate event in China

The response of population and agriculture to abrupt climate events remains a matter of heated debates, especially the societal collapses related to the 4.2 ka event. Long-term interaction between regional demography and millet-rice agriculture in China provide a unique opportunity to study this issue. Here using a newly database of radiocarbon dates and archaeobotanical data spanning the Neolithic-Bronze Age from different regions in China, we address the response and resilience of demography and agriculture to the 4.2 ka event. Regional populations show an antipodal pattern of boom in north and northwest (NW) and bust in south and southeast (SE) China during 4300–3500 cal a BP. This pattern coincided with the prosperity and breakdown of millet and rice agricultures contemporaneously, respectively. Our study reveals that drought-induced enlargement of farmland and trans-Eurasian cultural exchange promoted the sustainability of millet agriculture and population in NW China, and combined effects of cooling and flooding events and social crises caused a decline in rice agriculture and population in SE China. The diverse response and resilience of human societies to the 4.2 ka event has been attributed to both climatic anomalies and cultural exchange across different regions. In sum, the complex societies with high stratification and hierarchies were more vulnerable to abrupt climate events than low stratified societies open to exchanges during the middle to late Holocene.

Holocene climate events and associated land use changes in the eastern coast of India: Inferences from the Chilika Lagoon

The Holocene arid events and related societal responses are important scientific inquiries due to concerns about their reoccurrences in the future. In the Indian subcontinent, significant number of studies have focussed on understanding the Holocene aridification events at 8.2 and 4.2 ka. Despite these studies, high resolution palaeoclimatic records from the eastern India during Holocene, particularly around the above-mentioned aridification events are lacking. In this study, we present high resolution Holocene palaeoclimate records reconstructed based on geochemical and isotopic data from the Chilika Lagoon located in the east coast of India. A 130 cm long sediment core, retrieved from the southern end of the lagoon, revealed a continuous sedimentation history between 8.49 and 0.99 ka. The variations in organic carbon isotopic compositions, total organic carbon contents, along with major and trace element abundances suggested a strong effect of 8.2 dry event and a shift in chemical weathering at around 4.2 ka in the eastern coast of India. Additionally, a strong warm climate anomaly was observed at 1.2 ka. Interestingly, higher sedimentation rates were observed post 4.2 ka, which potentially indicated a significant change in settlement dynamics and human interventions. It appears that the eastern coast of India experienced human migration and surge in agricultural practices similar to that in northwest India after the 4.2 ka climatic event. It is likely that people relocated themselves, which eventually increased the pastoral activities in newly occupied lands. Consequently, enhanced land use and land cover changes accelerated soil erosion in the region leading to higher sedimentation rate in the lagoon.

Climate disaster and the resilience of local maritime networks: Two examples from the Aegean Bronze Age

This paper investigates changing patterns of maritime small-world networks among the Cycladic islands of the southern Aegean Sea in the context of two climate disasters in the Bronze Age (ca. 3200 BCE - 1100 BCE): the 4.2 ka event at the end of the Early Bronze Age and the eruption of Thera in the late 17th century BCE in the Late Bronze Age. The 4.2 ka event is a period where changing environmental conditions — including landscape degradation, deforestation, and increased drought — correlate with drastically reduced maritime connectivity and increased settlement isolation. Previous archaeological study of the eruption of the Theran volcano (Santorini) has shown the persistence of regional-scale communication networks for a period of up to a century after the eruption. This paper examines the effect of the eruption on local-scale maritime networks. The archaeological study of both climate events is complicated by chronological discrepancies and, in the case of the 4.2 ka event, reliance on indirect environmental data.This paper addresses the questions: a) what effect did these two climate disasters have on small-world maritime networks in the Bronze Age Cyclades, and b) how did the island inhabitants adapt within a context of disruptive environmental phenomena? GIS modeling reveals that small-world networks in the Early Bronze Age Cyclades were substantially altered in the face of the 4.2 ka climate event, while in response to the eruption of Thera, small-world networks were resilient. Variables influencing the differing network responses include the temporality of the climate disasters, the availability of the sail as a technology of resilience, and varying environmental and social vulnerabilities.

Searching for the 4.2 ka climate event at Lake Spore, Poland

Many regions around the world experienced abrupt climate change with far-reaching societal and environmental effects at ca. 4.2 cal. ka BP. As one of the most distinct climatic events of the last 11.7 ka, it has been used to establish the formal boundary between the mid- and late-Holocene. Although the 4.2 ka event was not pronounced in East-Central Europe, its exact impact on the area has yet to be evaluated. The aim of this paper is twofold: (1) to reconstruct the functioning of the selected lake and terrestrial ecosystems from northern Poland around the time of the 4.2 ka event, and (2) to disentangle the drivers of the recorded environmental changes (local factors vs. climate impact). We studied the sedimentary record of Lake Spore, focusing on the period between 3.8 and 4.5 cal. ka BP using numerous biotic and abiotic proxies, such as chironomids, cladocerans, pollen and spores, δ13Corg, δ15Norg, δ18Ocarb, δ13Ccarb, TOC/N, Fe, S, LOI550, and LOI950. The chironomid-derived reconstruction of mean July air temperature did not change during the 4.2 ka event. Pollen accumulation rate (PAR) data showed lower pollen production of some tree taxa during the period 4.0–4.25 cal. ka BP that is consistent with low PARs recorded for the corresponding period in the sediments of nearby (~75 km) Lake Suminko. This change might have occurred due to either regional-scale forest disturbance or cooler winters resulting from an exceptionally strong Siberian High during the 4.2 ka event. Distinct peaks of Fe and δ13Ccarb at 4.2 cal. ka BP likely record a pulse of podzolization. Although soil transformation processes were common in East-Central Europe after ca. 5 cal. ka BP due to general climate cooling, they could have been enhanced at Lake Spore during the 4.2 ka event, if winters were more severe. The δ13Corg, δ15Norg, TOC/N and δ18Ocarb records point to a water level rise after 4.2 cal. ka BP that most likely resulted from soil transformation in the catchment, not a change in effective precipitation. The composition of the terrestrial vegetation and the lake fauna and flora remained largely unaffected by the 4.2 ka event.

The emergence of hunter-gatherer pottery in the Urals and West Siberia: New dating and stable isotope evidence

The emergence of pottery among Stone Age hunter-gatherer societies of Eurasia constitutes one of the major open questions in Old World prehistory. Located halfway between the earliest Late Glacial cores of pottery production in East Asia, and Eastern Europe with forager ceramic starting around 6000 cal BC, the Urals and West Siberia are a key region in various scenarios currently under discussion. A lack of reliable absolute dates has been hindering an in-depth understanding of the temporal and spatial scales of the initial spread of the ceramic innovation. A Russian-German dating programme has now created a more reliable chronology of the early pottery phase, based on 28 AMS dates from across the study region. Taking freshwater reservoir effects into account, we can show that the earliest reliable evidence for pottery stems from the West Siberian forest steppes and Urals foothills, dating to the end of the 7th millennium cal BC. Over the following centuries, the innovation spread rapidly north into the taiga. Here, the early pottery horizon coincides with a unique set of innovations and intensification in the settlement system and the socio-economic sphere, including the appropriation of vast previously barely settled regions, the emergence of complex and even fortified settlements, and of ritual mounds. Pilot isotopic analyses of pottery charred crusts indicate diverse functions of the early vessels that were apparently not restricted to the processing of fish. The emerging wider picture indicates a surprisingly late, largely concurrent appearance of pottery in hunter-gatherer groups over extensive areas along the southern fringes of the taiga to both sides of the Urals at the end of the 7th millennium cal BC which is apparently not connected to the earlier, Late Pleistocene ceramic traditions in Trans-Baikalia and further East. Possible links to the 8.2 ka climatic event, other underlying triggers as well as the detailed chronology of these developments are still poorly understood and require further archaeological, biomolecular and typological studies.

The 7.2 ka climate event: Evidence from high-resolution stable isotopes and trace element records of stalagmite in Shuiming Cave, Chongqing, China

Speleothem records have radically changed our understanding of the paleo Asian monsoon (AM), but explanations for Asian summer monsoon (ASM) variations in the Holocene period are usually based on single proxy records, such as oxygen isotope (δ18O). The application of multi-proxy records to the study of the forcing mechanism and internal structure of climate events is more comprehensive and accurate in the analysis of paleoclimates than using single proxy records. Therefore, a multi-proxy speleothem record of weak ASM events in 8.0–7.0 BP from Chongqing, which showed a dry southwestern China during weak ASM episodes, was reported. The analysis of multi-proxy records of SMY2 stalagmite indicated that the beginning of the ‘7.2 ka event’ was at 7.29 ± 0.03 ka BP, and its culmination was at 7.1 ± 0.04 ka BP. Thus, this event lasted nearly 200 a, and the main drought period lasted 50 a. Power spectrum analysis showed a significant 61 a cycle signal during the study period in the δ18O record of SMY2, which coincided with the Atlantic multidecadal oscillation activity (AMOC) cycle. This study demonstrates that the ASM during 8.0–7.0 ka BP is strongly correlated with the changes in solar activity and also sensitive to the southward shift of Intertropical Convergence Zone (ITCZ) and AMOC cycle.

Human-climate interactions since the neolithic period in Central Anatolia: Novel multi-proxy data from the Kureyşler area, Kütahya, Turkey

Sedimentological and paleoclimatological data from a fluvial infill retrieved from a series of cores taken across Kureyşler Valley, Kütahya, western Turkey, are compared alongside evidence for an almost unbroken record of human occupation in the area since Neolithic times. Recent salvage excavations in the valley exposed settlement remains from the Early Bronze Age and Late Byzantine periods with interfingering of archaeological and geological materials in the valley-fill, adding a wealth of information to the archaeological record in this region. Our geological data, constrained by seven radiocarbon dates from the sediment infill demonstrate that the earliest sediments were deposited during the Late Glacial (∼13.8 ka) under a cold and relatively dry climatic conditions with evidence of amelioration and increase in arboreal taxa from the Neolithic onwards. The occurrence of Cerealia-T and Apiaceae pollen is significant as an important indicator for anthropisation already present during the Epipaleolithic period (before 9 ka cal. BP). Also, the effects of 8.2 ka climatic event are clearly visible in our multi-proxy results. The onset of the Early Bronze Age settlements in the vicinity ∼ ca. 5.2 ka BP occurred alongside a climatic switch to warmer conditions recorded by a lithological change and a positive shift in isotopic data. The 4.2 ka event, present in records related to several Early Bronze Age (EBA) sites of Anatolia is also recorded in the Kureyşler Valley both in the pollen and δ18O records. In general, these results show that climate shifts occurred at the beginning and end of the EBA, as well as during the Neolithic and Chalcolithic and are to be compared with new archaeological data.

Multiproxy analyses of Lake Allos reveal synchronicity and divergence in geosystem dynamics during the Lateglacial/Holocene in the Alps

Palaeoenvironmental reconstructions of ecosystem responses to external forcing are generally limited by the difficulty of understanding the geosystem as a whole, because of the complex interactions between ecological compartments. Therefore, identifying which geosystem compartments or proxies co-vary is a prerequisite in unravelling the propagation of disturbances (e.g. climatic or anthropogenic) from one compartment to another. A multiproxy study of a continuous 13,500-year sedimentary profile cored in Lake Allos (European Alps, 2200 m a.s.l) was carried out on the basis of high-resolution sedimentological, geochemical, and botanical analyses, as well as determination of aquatic biotic proxies (diatoms, ostracods). These multiproxy datasets are rare at these high altitudes. Major changes occurred in the course of the palaeoenvironmental history of this alpine watershed at 12,000, 8600, 7200 and 3000 cal. BP. During the Holocene, two main transitions were recorded in all the ecological compartments (8600 and 3000 cal. BP), but the period 4500-3000 cal. BP stands out because of major changes that concerned only the lacustrine ecosystem. The frequent switches in lake level might correspond to the 4.2 ka climatic event. Proximity of this alpine lake to climatically-sensitive thresholds (ice-cover, thermal stratification, hydrological balance) may have amplified climatic signals in the lake ecosystem. This study illustrates the difficulties inherent to the use of common intra-Holocene stratigraphical limits, given that ecological compartments are likely to have different responses to forcing factors depending on the characteristics of the watershed and its capacity to accommodate disturbances.

Holocene climatic fluctuation and lithic technological change in northeastern Hokkaido (Japan)

In Japan, a body of archaeological assemblages with radiocarbon dates has been providing better understanding of relationship between lithic technology, pottery culture, settlement system, social change, and environment.This paper presented newly conducted radiocarbon dating on charred residue on potteries from Initial Jomon sites in northeastern Hokkaido. This work evidenced current pottery typological chronology and allows us to confirm diachronic lithic technological change associated with these potteries. Regarding the lithic technology, it became clear that lithic technological change into sophisticated blade technology suddenly occurred around 8400cal BP, then lasted for very short time period until 8000cal BP in northeastern Hokkaido, and that there was a clear technological gap between this sophisticated blade technology and the previous or subsequent simple flake technology. Since lithic raw material procurement strategy changed during this period, it is supposed that settlement system and foraging strategy might also be reorganized.According to the correspondence between duration of the sophisticated blade technology and global climatic fluctuation, it is likely that 8.2ka climatic event (maximum duration is roughly 8300–8050cal BP) was responsible for this sudden change of blade technology. At present, regional environmental change driven by this global climatic fluctuation is not evidenced yet, but there is enough possibility that sudden appearance of sophisticated blade technology might have been caused not only by simple population dynamics or diffusion, but by rapid change in environmental condition.

The timing of postglacial coastal adaptations in Eastern Iberia: A Bayesian chronological model for the El Collado shell midden (Oliva, Valencia, Spain)

El Collado is an open air site containing evidence of 14 burials and a shell midden archaeological deposit with different phases of human occupation dated to the Early Holocene. Previous studies have produced 14 radiocarbon dates using bone collagen samples from human burials. However, no attempt has been made to date the stratigraphic sequence to address the formation time of the shell midden and establish a chrono-stratigraphic framework for the study of bio-archaeological and cultural assemblages. We critically evaluate the available radiocarbon record of the site and present 6 new AMS radiocarbon dates on ungulate bones with anthropic fractures and bivalves from the three major stratigraphic horizons. Then, we integrate our results with previously published AMS radiocarbon determinations on human samples into a chronological Bayesian model, constraining the radiocarbon distributions with prior information about the samples stratigraphic provenance. Finally, we correlate the results of the chronological model with the regional archaeological sequence and the available data on coastal evolution at regional and local scales. The vertical distribution of the radiocarbon dates makes evident some stratigraphic disturbance caused by the repeated presence of pit graves, agricultural activities and low stratigraphic control of the excavation process. However, once the problematic determinations are identified as outliers, the remaining radiocarbon dates grouped according the major stratigraphic divisions, and the calibrated distributions modelled-constrained, the resulting Bayesian phase model reveal high agreement index (Ac = 103). The shell midden formation took place from the bottom of the sequence, spanning 1022–1965 calibrated years (CI 95.4%). The occupations documented at Phase 1 (Level IV) are dated to the Early Holocene (9828–9551 cal BP). The Phase 2 (Level II), encompass radiocarbon evidence of both burial and occupational activities dated to 9437 to 8477 cal BP, spanning 779–985 calibrated years (CI 95.4%). Finally, the Phase 3 (Level I) records Late Mesolithic occupations deposited between 8509 and 8391 cal BP for the start boundary and 8499–8060 cal BP for the end boundary (CI:95.4%). There are no individual radiocarbon dates during or postdating the chronological span of the 8.2 ka climatic event (8300–8140 cal BP).