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1.
  • Alsos, Inger Greve, et al. (author)
  • Ancient sedimentary DNA shows rapid post-glacial colonisation of Iceland followed by relatively stable vegetation until the Norse settlement (Landnam) AD 870
  • 2021
  • In: Quaternary Science Reviews. - : Elsevier. - 0277-3791 .- 1873-457X. ; 259
  • Journal article (peer-reviewed)abstract
    • Understanding patterns of colonisation is important for explaining both the distribution of single species and anticipating how ecosystems may respond to global warming. Insular flora may be especially vulnerable because oceans represent severe dispersal barriers. Here we analyse two lake sediment cores from Iceland for ancient sedimentary DNA to infer patterns of colonisation and Holocene vegetation development. Our cores from lakes Torfdalsvatn and Nykurvatn span the last c. 12,000 cal yr BP and c. 8600 cal yr BP, respectively. With near-centennial resolution, we identified a total of 191 plant taxa, with 152 taxa identified in the sedimentary record of Torfdalsvatn and 172 plant taxa in the sedimentary record of Nykurvatn. The terrestrial vegetation at Torfdalsvatn was initially dominated by bryophytes, arctic herbs such as Saxifraga spp. and grasses. Around 10,100 cal yr BP, a massive immigration of new taxa was observed, and shrubs and dwarf shrubs became common whereas aquatic macrophytes became dominant. At Nykurvatn, the dominant taxa were all present in the earliest samples; shrubs and dwarf shrubs were more abundant at this site than at Torfdalsvatn. There was an overall steep increase both in the local accumulated richness and regional species pool until 8000 cal yr BP, by which time 3/4 of all taxa identified had arrived. The period 4500-1000 cal yr BP witnessed the appearance of a a small number of bryophytes, graminoids and forbs that were not recorded in earlier samples. The last millennium, after human settlement of the island (Landnam), is characterised by a sudden disappearance of Juniperus communis, but also reappearance of some high arctic forbs and dwarf shrubs. Notable immigration during the Holocene coincides with periods of increased incidence of sea ice, and we hypothesise that this may have acted as a dispersal vector. Thus, although ongoing climate change might provide a suitable habitat in Iceland for a large range of species only found in the neighbouring regions today, the reduction of sea ice may in fact limit the natural colonisation of new plant species.
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2.
  • Andersen, J. L., et al. (author)
  • Ice surface changes during recent glacial cycles along the Jutulstraumen and Penck Trough ice streams in western Dronning Maud Land, East Antarctica
  • 2020
  • In: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 249
  • Journal article (peer-reviewed)abstract
    • Reconstructing past ice-sheet surface changes is key to testing and improving ice-sheet models. Data constraining the past behaviour of the East Antarctic Ice Sheet are sparse, limiting our understanding of its response to past, present and future climate change. Here, we report the first cosmogenic multinuclide (Be-10, Al-26, Cl-36) data from bedrock and erratics on nunataks along the Jutulstraumen and Penck Trough ice streams in western Dronning Maud Land, East Antarctica. Spanning elevations between 741 and 2394 m above sea level, the samples have apparent exposure ages between 2 ka and 5 Ma. The highest-elevation bedrock sample indicates (near-) continuous minimum exposure since the Pliocene, with a low apparent erosion rate of 0.15 +/- 0.03 m Ma(-1), which is similar to results from eastern Dronning Maud Land. In contrast to studies in eastern Dronning Maud Land, however, our data show clear indications of a thicker-than-present ice sheet within the last glacial cycle, with a thinning of similar to 35-120 m during the Holocene (similar to 2-11 ka). Difficulties in separating suitable amounts of quartz from the often quartz-poor rock-types in the area, and cosmogenic nuclides inherited from exposure prior to the last deglaciation, prevented robust thinning estimates from elevational profiles. Nevertheless, the results clearly demonstrate ice-surface fluctuations of several hundred meters between the current grounding line and the edge of the polar plateau for the last glacial cycle, a constraint that should be considered in future ice-sheet model simulations.
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3.
  • Baykal, Yunus, et al. (author)
  • Detrital zircon U–Pb age analysis of last glacial loess sources and proglacial sediment dynamics in the Northern European Plain
  • 2021
  • In: Quaternary Science Reviews. - : Elsevier. - 0277-3791 .- 1873-457X. ; 274
  • Journal article (peer-reviewed)abstract
    • Loess deposits along the northern fringe of the European loess belt potentially record past changes in dust emission from areas proximal to former ice sheets. Recent chronologies from loess deposits across this region generally agree on greatly enhanced dust deposition rates when the Fennoscandian Ice Sheet reached its maximum extent during the late last glacial. However, uncertainties over the material's source and origin limit understanding of the causes of this enhanced dust activity. In particular, loess in southwestern Poland has been attributed to multiple origins, mainly involving glaciofluvial outwash plains along the Fennoscandian Ice Sheet margin and/or local sources in the mountainous areas of the Sudetes and Western Carpathians. Here we apply detrital zircon U–Pb age analyses for a large number of grains recovered from four loess samples taken from different stratigraphic units exposed at Biały Kościół in southwestern Poland, previously luminescence dated to MIS 4–2, to assess loess provenance as well as its temporal evolution during last glacial Fennoscandian Ice Sheet fluctuations. Furthermore, we analysed the detrital zircon U–Pb age spectra of five samples from potential source sediments to constrain the history of sediment recycling and mixing within the Northern European Plain prior to deflation and loess deposition. The broad range of zircon age components detected in the four loess samples suggests both Fennoscandian and closer Peri-Gondwanan proto-sources while a narrow, dominant Carboniferous age peak is consistent with sourcing from the local Strzelin Hills in the Sudetic foreland. However, the presence of both Fennoscandian and Peri-Gondwanan derived grains in samples from potential source sediments reveals that this mixture of sediment sources is widespread across the Northern European Plain, as a result of long-term glacial and fluvial reworking of cover sediments in the proglacial area throughout the Quaternary. Local rivers draining the Sudetic foreland transported this Fennoscandian-Peri-Gondwanan sediment mixture along with particles denuded from the Strzelin Hills, resulting in a nearby, temporally stable dust source for the Biały Kościół loess during MIS 4–2, while dust emission rates were substantially increased during the last glacial maximum. Given that our model for loess formation at Biały Kościół essentially involves sediment distribution via rivers prior to short distance aeolian transport, we infer that the proportion of northern ice sheet derived particles in European loess deposits is mainly controlled by the drainage pattern of major rivers in relation to Pleistocene ice margins where glaciofluvial sediment is abundant. Based on the presence of Fennoscandian derived zircon grains in European loess deposits, we constrain a southern limit of the influence of northern ice sheet dust sources along the central European highlands that currently divide drainage between the Northern European Plain and the Danube Basins.
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4.
  • Baykal, Yunus, et al. (author)
  • Eurasian Ice Sheet derived meltwater pulses and their role in driving atmospheric dust activity: Late Quaternary loess sources in SE England
  • 2022
  • In: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 296, s. 107804-107804
  • Journal article (peer-reviewed)abstract
    • The role of Quaternary ice sheet fluctuations in driving meltwater pulses and ocean circulation perturbations is widely acknowledged. What is less clear is the role of these processes in driving changes in past atmospheric dust activity, and possible wider links between dust and climate. Terrestrial windblown dust (loess) deposits along the northern fringe of the European loess belt potentially record past atmospheric dust emission from regions close to the former Eurasian Ice Sheet (EIS) and provide a means to evaluate the role of ice sheet fluctuations in the past dust cycle. Numerical loess chronologies across this region generally agree on greatly enhanced dust deposition rates during MIS 2, when the EIS reached its maximum extent. Yet, uncertainties over the sources of this material prevent understanding of the precise causes of this greatly enhanced atmospheric dustiness, and any potential link to ice sheet fluctuations and climate. In southeast England, loess accumulation dominantly occurred in two phases centered on 25–23.5 ka and 20–19 ka, matching the timing of coalescence of the Fennoscandian and British-Irish ice sheets and specifically advances and retreats of nearby ice lobes in the western North Sea. As such, these deposits provide an ideal test of the role of ice sheet fluctuations in atmospheric dust dynamics. Here we undertake such a test through a detailed provenance study of loess in southeast England and potential dust source sediments across the North Sea region. We group extensive new and published data sets of detrital zircon U–Pb ages from basement rocks and Cenozoic sediments in the North Sea area, which not only provide new insight into both loess source, but also the nature of sediment transport over NW Europe into the North Sea basin more widely. Multi-proxy evidence allows us to unambiguously identify ice sheet derived sediments in the exposed North Sea basin as the dominant source of loess in southeast England, while fluvial sediments delivered by rivers draining Continental Europe possibly contributed additional source material to the first loess accumulation phase. We propose that sudden retreats of the North Sea Lobe released substantial amounts of sediment rich meltwater into the southern North Sea and Channel basins, driving accelerated dust emission, loess deposition and provenance variability in NW Europe during MIS 2. Moreover, we propose that this model of dust activity driven by proglacial sediment availability may be applicable for EIS marginal regions more widely, even where resultant loess cover is rarely preserved due to extensive erosion and reworking along the ice marginal spillway. This implies the role of ice sheets in controlling wider dust emission may be underestimated. In addition to driving changes in ocean circulation through meltwater pulses, ice sheet dynamics in the Quaternary may have also driven substantial and abrupt changes in atmospheric dust activity. This mechanism may in part explain the coupling between dust and climate events widely seen in Quaternary dust sediment records and suggests a possible major role of high latitude dust emission in MIS 2 dustiness across Europe and beyond.
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5.
  • Belle, Simon (author)
  • Environmental drivers and abrupt changes of phytoplankton community in temperate lake Lielais Svetinu, Eastern Latvia, over the last Post-Glacial period from 14.5 kyr
  • 2021
  • In: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 263
  • Journal article (peer-reviewed)abstract
    • Understanding the long-term dynamics of ecological communities on the centuries-to-millennia scale is important for explaining the emergence of present-day biodiversity patterns and for predicting possible future scenarios. Fossil pigments and ancient DNA present in various sedimentary deposits can be analysed to study long-term changes in ecological communities. We analysed recent compilations of data, including fossil pigments, microfossils, and molecular inventories from the sedimentary archives, to understand the impact of gradual versus abrupt climate changes on the ecosystem status of a regional model lake over the last similar to 14.5 kyr. Such long and complete paleo-archives are scarce in North-Eastern Europe. The study site lies in a sensitive area, both climatically and in respect to vegetation. Namely the maritime-continentality line runs west to east in the central Baltic area to NE Europe and its south-north transect lies within the gradual decay of the nemoral forest into a boreal environment. Therefore, the selected location is an ideal sampling point to decipher long term environmental changes in the temperate climate zone. The main objective of the present study was to find out external factors influencing phototroph dynamics at temperate Lake Lielais Svetinu over the post-glacial period (similar to 14.5 kyr). We were able to model climate change together with vegetation change and the appearance of anthropogenic forcing, either as a gradual change or as abrupt events that influenced the phototrophs, which are keystone groups within the lacustrine ecosystem. Most interestingly, the gradual increase of species richness of phototrophs was linked to similar increase in fungal parasites of the same group - phototrophs. Abrupt climate change in the Late Glacial period caused abrupt events in the ecosystem but equally abrupt events were caused by gradual changes during the stable period of the Holocene Thermal Maximum (HTM). In addition, we highlight the increased frequency and degree of perturbation in pristine lakes due to low impact human activity over a larger region. Both observations demonstrate an impaired relationship between gradual external drivers and ecosystem response and apply to future scenarios of climate warming and increased human impact in north-eastern Europe. (C) 2021 The Authors. Published by Elsevier Ltd.
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6.
  • Belle, Simon (author)
  • Food availability and temperature optima shaped functional composition of chironomid assemblages during the Late Glacial-Holocene transition in Northern Europe
  • 2021
  • In: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 266
  • Journal article (peer-reviewed)abstract
    • Non-biting midges (Chironomidae) are the most diverse and abundant invertebrate group in boreal lakes and are strongly responsive to climate change, thus they are a valuable palaeoecological proxy for studying aquatic biodiversity response in the face of climate change. Here, we aim to decipher the influence of climate-induced changes on temporal patterns in chironomid assemblages. We apply a novel approach combining traditional taxon-based analysis and species-trait framework to subfossil chironomid assemblages in a sediment core covering the Late Glacial-Holocene transition in Northern Europe. We produce pollen-based July and January temperature reconstructions to characterize past climate fluctuations that show a distinct Early Holocene warming for continuous 1700 years with considerably greater warming in winter (ca. 10 degrees C) than summer (ca. 4 degrees C) temperature. Overall, chironomid taxonomic changes were mainly induced by the temperature tolerances and optima of species, as temporal dynamics showed agreement with temperature reconstructions. Our results suggest that vegetation dynamics could also play a role in structuring chironomid assemblages by selecting taxa with the highest ability to exploit available food resources, thus potentially confounding chironomid-based summer climate reconstructions. We demonstrate that the study of the hidden chironomid functional composition could help to identify secondary drivers and thus strengthen the reliability of climate reconstruction based on subfossil chironomids. (C) 2021 Elsevier Ltd. All rights reserved.
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7.
  • Bird, Anna, et al. (author)
  • A constant Chinese Loess Plateau dust source since the late Miocene
  • 2020
  • In: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 227
  • Journal article (peer-reviewed)abstract
    • The Pliocene-Pleistocene boundary marks a major change in global climate and East Asian monsoon dynamic. However, the role of the global atmospheric dust-cycle over this time is unclear; in particular the degree to which changes in the dust cycle influenced climate change, were driven by climate change, and how these processes interacted. Chinese loess records past dust-cycle history and the influences of aridification and monsoon circulation over the last 40 Ma. Previous work on the Chinese Loess Plateau argue over whether changes in dust source occur at the Pliocene-Pleistocene boundary, or at 1.2 Ma, despite these intervals marking major shifts in monsoon dynamics. We present Sr, Nd and Hf isotope data from multiple sites and show that dust source largely remains unchanged across these boundaries. Shifts in geochemistry are due to changes in grain-size and weathering. While the transport pathway (river, deserts, direct aeolian) is unclear, these tracer isotopes show that dust was dominantly sourced from the Northern Tibetan Plateau, with some input from the local bedrock. This shows that a major established and constant dust source on the Tibetan Plateau has been active and unchanged since late Miocene, despite dramatically changing climate conditions. Changes in loess accumulation are a function of climate change in Tibetan Plateau source regions rather than effects from increased aridification over the Pliocene-Pleistocene boundary.
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8.
  • Boethius, Adam, et al. (author)
  • Mesolithic Scandinavian foraging patterns and hunting grounds targeted through laser ablation derived 87Sr/86Sr ratios at the Early-Mid Holocene site of Huseby Klev on the west coast of Sweden
  • 2022
  • In: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 293
  • Journal article (peer-reviewed)abstract
    • Mobility is one of the most fundamental aspects of a foraging society. Since prehistoric mobility is often difficult to identify in the archaeological record, our understanding is largely based on comparison with ethnographic communities. In recent years the application of 87Sr/86Sr isotope analysis has, however, greatly broadened our knowledge of mobility in the past. Despite this, few studies have been undertaken on faunal remains to explore their mobility patterns and infer human exploitation patterns with more precision. In this contribution we sampled 28 mammal teeth from three different occupation phases at the Early to Mid-Holocene coastal site of Huseby Klev, Sweden. We first established the local baseline for seven geographical areas in the region surrounding Huseby Klev. Then, by applying laser ablation-multi collector-inductively coupled plasma-mass spectrometry to the selected teeth, we identified the likely origins of a range of terrestrial and marine fauna, and the possible human mobility patterns required in their exploitation. Overall, our results demonstrate that the prehistoric communities inhabiting Huseby Klev undertook both short- and long-distance forays for the exploitation of particular species. By relating inferences on hunting grounds, derived from strontium isotope data, to zooarchaeological evidence from the site and ethnographic human mobility patterns, we establish and discuss the prerequisites for landscape utilization. Lastly, we demonstrate that glacial meltwater may have temporally affected the local oceanic Sr ratios – suggesting significantly increased soil and bedrock weathering may influence the Sr values in aquatic ecosystems and, consequently, should be considered in such regions and at times of melting glaciers. By applying the method to additional sites and assemblages in the future, our understanding of prehistoric mobility will be greatly enhanced.
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9.
  • Chawchai, Sakonvan, et al. (author)
  • Hydroclimate variability of central Indo-Pacific region during the Holocene
  • 2021
  • In: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 253
  • Journal article (peer-reviewed)abstract
    • Here we present a decadal-resolved hydroclimate record covering the past 11 thousand years based on δ18O data of three stalagmites from Klang Cave (TK) on the Thai-Malay Peninsula, southern Thailand. The δ18O values indicate wetter conditions/more rainfall during the early Holocene from 11 to 7 thousand years before present (kyr BP). A large increase of 2‰ in δ18O is observed from 7.0 to 6.0 kyr BP, indicating a millennial drying period followed by drought conditions between 6.0 and 5.2 kyr BP. After a long hiatus (5.2–2.7 kyr BP), δ18O data show a millennium-long trend toward dry conditions. An abrupt positive change of 0.8–1.0‰ in δ18O is noticed between 8.29 and 8.17 kyr BP, reflecting the 8.2-ka event; however, the amplitude of the δ18O shift is much smaller comparing to that of the event of 6.0–5.2 kyr BP. On orbital time-scales, the TK record agrees with insolation-dominated speleothem records in the Asian-Australian monsoon realm. Noticeable inconsistencies among records in the Southeast Asia region (between 8°N and 4°N–8°S) have been documented on multi-centennial scales. Lower δ18O values are likely associated with the mean position of the Intertropical Convergence Zone (ITCZ). A new reconstruction of Holocene ITCZ shifts index within the central Indo-Pacific region, based on stalagmite δ18O records from Klang Cave (8°N) and Liang Luar Cave (8°S), shows that the ITCZ played an important role in hydroclimate variability in the Asian-Australian monsoon regions. The southward shift of the ITCZ in the central Indo-Pacific region, controlled by the interhemispheric extratropical insolation gradient, may strongly correlate with the El Niño-Southern Oscillation (ENSO) activities in the Holocene.
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10.
  • Chen, Jie, et al. (author)
  • Northwestward shift of the northern boundary of the East Asian summer monsoon during the mid-Holocene caused by orbital forcing and vegetation feedbacks
  • 2021
  • In: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 268
  • Journal article (peer-reviewed)abstract
    • The East Asian summer monsoon (EASM) northern boundary is a critical indicator of EASM variations. Movement of the boundary is modulated by both the EASM and the mid-latitude westerlies. Here, we use the Earth system model EC-Earth to quantify the contribution of orbital forcing and vegetation feedbacks in modulating the movement of EASM northern boundary. The results show that the simulated EASM northern boundary during the mid-Holocene shifts by a maximum of ∼213 km northwestward due to orbital forcing. When the model was coupled with a dynamic vegetation module LPJ-GUESS, the northern boundary shifts further northwestward by a maximum of ∼90 km, indicating the importance of vegetation feedbacks. During the mid-Holocene, temperature increased in the mid-latitude during the boreal summer due to insolation, leading to increased meridional air temperature differences (MTDs) over the region north of 45°N and to decreased MTDs to the south. The changes in the temperature gradient weakened the East Asian Westly Jet (EAWJ) and displaced it northward, resulting in an earlier transition of the Meiyu stage and a more prolonged Midsummer stage. The northward movement of EAWJ, combined with the enhanced southerly moisture flow from South China, caused more precipitation in North China and eventually to a northwestward shift of the northern boundary of the EASM. The coupled dynamic vegetation module LPJ-GUESS simulated more grassland and less forest over Northeast Asia during the mid-Holocene. The increased surface albedo tended to lower the temperature in the region, and further enhanced the MTDs in mid-latitude East Asia, leading to the further northward movement of the EAWJ and a northwestward shift of the EASM northern boundary. Although the simulated vegetation distribution in several regions may be not accurate, it reflects the substantial contribution of climate-vegetation interaction on modulating the EASM.
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11.
  • Dalton, April S., et al. (author)
  • Deglaciation of the north American ice sheet complex in calendar years based on a comprehensive database of chronological data: NADI-1
  • 2023
  • In: QUATERNARY SCIENCE REVIEWS. - 0277-3791 .- 1873-457X. ; 321
  • Journal article (peer-reviewed)abstract
    • The most recent deglaciation of the North American Ice Sheet Complex (NAISC: comprising the Innuitian, Cordilleran, and Laurentide ice sheets) offers a broad perspective from which to analyze the timing and rate of ice retreat, deglacial sea-level rise, and abrupt climate change events. Previous efforts to portray the retreat of the NAISC have been focused largely on minimum-limiting radiocarbon ages and ice margin location(s) tied to deglacial landforms that were not, for the most part, chronologically constrained. Here, we present the first version of North American Deglaciation Isochrones (NADI-1) spanning 25 to 1 ka in calendar years before present. Key new features of this work are (i) the incorporation of cosmogenic nuclide data, which offer a direct constraint on the timing of ice recession; (ii) presentation of all data and time-steps in calendar years; (iii) optimal, minimum, and maximum ice extents for each time-step that are designed to capture uncertainties in the ice margin position, and; (iv) extensive documentation and justification for the placement of each ice margin. Our data compilation includes 2229 measurements of Be-10, 459 measurements of Al-26 and 35 measurements of Cl-36 from a variety of settings, including boulders, bedrock surfaces, cobbles, pebbles, and sediments. We also updated a previous radiocarbon dataset (n = 4947), assembled luminescence ages (n = 397) and gathered uranium-series data (n = 2). After scrutiny of the geochronological dataset, we consider >90% of data to be reliable or likely reliable. Key findings include (i) a highly asynchronous maximum glacial extent in North America, occurring as early as 27 ka to as late as 17 ka, within and between ice sheets. In most marine realms, extension of the ice margin to the continental shelf break at 25 ka is somewhat speculative because it is based on undated and spatially scattered ice stream and geomorphic evidence; (ii) detachment of the Laurentide and Cordilleran ice sheets took place gradually via southerly and northerly 'unzipping' of the ice masses, starting at 17.5 ka and ending around 14 ka; (iii) the final deglaciation of Hudson Bay began at 8.5 ka, with the collapse completed by 8 ka. The maximum extent of ice during the last glaciation occurred at 22 ka and covered 15,470,000 km(2). All North American ice sheets merged at 22 ka for the first time in the Quaternary. The highly asynchronous Last Glacial Maximum in North America means that our isochrones (starting at 25 ka) capture ice advance across some areas, which is based on limited evidence and is therefore somewhat speculative. In the Supplementary Data, the complete NADI-1 chronology is available in PDF, GIF and shapefile format, together with additional visualizations and spreadsheets of geochronological data. The NADI-1 shapefiles are also available at https://doi.org/10.5281/zenodo.8161764.
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12.
  • Dehasque, Marianne, et al. (author)
  • Combining Bayesian age models and genetics to investigate population dynamics and extinction of the last mammoths in northern Siberia
  • 2021
  • In: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 259
  • Journal article (peer-reviewed)abstract
    • To understand the causes and implications of an extinction event, detailed information is necessary. However, this can be challenging when working with poorly resolved paleontological data sets. One approach to increase the data resolution is by combining different methods. In this study, we used both radiocarbon and genetic data to reconstruct the population history and extinction dynamics of the woolly mammoth in northern Siberia. We generated 88 new radiocarbon dates and combined these with previously published dates from 626 specimens to construct Bayesian age models. These models show that mammoths disappeared on the eastern Siberian mainland before the onset of the Younger Dryas (12.9–11.7 ky cal BP). Mammoths did however persist in the northernmost parts of central and western Siberia until the early Holocene. Further genetic results of 131 high quality mitogenomes, including 22 new mitogenomes generated in this study, support the hypothesis that mammoths from, or closely related to, a central and/or west- Siberian population recolonized Wrangel Island over the now submerged northern Siberian plains. As mammoths became trapped on the island due to rising sea levels, they lived another ca. 6000 years on Wrangel Island before eventually going extinct ca. 4000 years ago.
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13.
  • Dominguez-Rodrigo, M., et al. (author)
  • Earliest Acheulian paleolandscape reveals a 1.7 million-year-old megasite at Olduvai Gorge (Tanzania)
  • 2023
  • In: Quaternary Science Reviews. - 0277-3791 .- 1873-457X. ; 316
  • Journal article (peer-reviewed)abstract
    • FLK West (Bed II, Olduvai Gorge) contains the oldest association of Acheulian stone tools and exploitation of fauna (including megafauna) by hominins in the Pleistocene. Recently, the FLK West paleolandscape has been intensively studied, unveiling a spatial association between archaeological materials and hydrothermal resources. A new type of landscape use by hominins has also been documented around the area where the penecontemporaneous FLK West and HWK site complex were formed, resulting in an array of habitats spanning thousands of square meters covered with large amounts of lithic artefacts. Here, we show how the intensive use of certain environments by hominins resulted in these megasites, in which hominins engaged in a variety of activities, complementary to those performed at discrete archaeological clusters like FLK West. Despite using these habitats redundantly as quarries, hominins performed extensive core reduction of several types of raw materials indicating a dexterity and careful planning undocumented in earlier periods. Here, we also show how palaeoecological reconstructions must be based on fine-scale geological analyses, given the palimpsestic nature of both geological and anthropogenic processes. The research reported here also uncovered an additional unknown source of metamorphic rocks for hominins at Olduvai, which questions a large part of previous modeling based on hominin provisioning exclusively at Naibor Soit. We also show that the manufacture of handaxes was slightly older than documented at FLK West and that they occur in isolation on the landscape in addition to being clustered at sites. This implies that at the beginning of the Acheulian, hominins were not only using and discarding handaxes at specific loci, but they also transported these tools for various activities across the landscape as part of their strategized adaptation to those environments. The occurrence of these intensively-used megasites hints at some territorial behaviors by early Acheulian hominins.
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14.
  • Drobyshev, Igor (author)
  • Temperature and fire controls on vegetation dynamics in Northern Ural (Russia) boreal forests during the Holocene based on brGDGT and pollen data
  • 2023
  • In: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 305
  • Journal article (peer-reviewed)abstract
    • Boreal vegetation is influenced by multiple factors such as climate and fire, but interactions between long-and short-term effects of climate upon fire activity are complex and remain poorly studied, especially in Eurasia. To understand the relationships between climate, fire and vegetation in Eurasia, we reconstruct the climate changes during the Holocene for the western section of the Northern Urals re-gion, in the southern part of the Republic of Komi. We relate these temperature reconstructions to pollen and charcoal records from the same region (Yaksha site, Republic of Komi, Russia). We use here a combined approach based on pollen and molecular biomarkers (branched Glycerol Dialkyl Glycerol Tetraethers or brGDGTs) to provide independent estimates of past temperatures. Our objectives were: (1) to understand the relationships between climate, fire, vegetation and human activity during the Holo-cene at the local scale of Yaksha and (2) to provide a robust regional-scale climatic reconstruction of the southern part of the Republic of Komi. Our study shows that climate had a major influence on the regional vegetation between 10,000 and 4000 cal Yr BP. Subsequently, fire activity had a joint and growing impact on vegetation dynamics between 4000 and 600 cal Yr BP. Finally, from 600 until the present (2016 CE), human presence and activities had a greater impact on the fire regime and vegetation than earlier in time, and combined with climate to influence the dynamics of the boreal forest. At the regional scale of the Republic of Komi and the local scale of Yaksha, the Holocene Thermal Maximum was detected between 6800 and 4000 cal Yr BP, using pollen-based temperature estimates but at 4000 cal Yr BP using brGDGT calibrations applied from the literature. These results are consistent with evidence from neighboring regions in the Eurasian boreal biome which were studied for different proxies (pollen, chironomids), and also with reference to climate models (General Circulation Models).(c) 2023 Elsevier Ltd. All rights reserved.
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15.
  • Dulfer, Helen E., et al. (author)
  • Reconstructing the advance and retreat dynamics of the central sector of the last Cordilleran Ice Sheet
  • 2022
  • In: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 284
  • Journal article (peer-reviewed)abstract
    • The advance of the Cordilleran Ice Sheet (CIS) towards its Last Glacial Maximum (LGM) configuration and its subsequent retreat remain poorly understood. We use the glacial landform record to determine ice dynamics for the central sector of the CIS in northern British Columbia, Canada, beneath the LGM ice divide. We classify seventy ice-flow indicator flowsets based on morphology, elevation, orientation and cross-cutting relationships into one of three stages, whereby stage 1 is oldest and stage 3 youngest. Combined with ice-contact geomorphology, our reconstruction highlights complex changes in ice flow over time as a result of ice divide migrations through the LGM and deglacial phases. The orientation and distribution of landforms indicates active post-LGM ice retreat westward through the Cassiar and Omineca mountains. We map the regional distribution of independent mountain glaciers, ice caps, and ice fields that regrew during a cooling event in the Late Glacial and show that some of these readvance glaciers were subsequently overrun by advancing outlet glaciers of the CIS. We use the cross-cutting relationship between readvance glaciers and CIS outlet glaciers and available chronological data to reconstruct the eastern CIS margin during the Late Glacial for the first time.
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16.
  • Dögg Eddudottir, Sigrun, et al. (author)
  • Landscape change in the Icelandic highland : A long-term record of the impacts of land use, climate and volcanism
  • 2020
  • In: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 240
  • Journal article (peer-reviewed)abstract
    • Agriculture has been practiced in Iceland since settlement (landnam; AD 877). This has caused changes in vegetation communities, soil erosion, desertification and loss of carbon stocks. Little data exist regarding vegetation and ecosystems in the Icelandic highland before landnam and therefore the impact of land use over time is poorly understood. The objectives of the study are to examine the timing, nature and causes of land degradation in the highland of Northwest Iceland. Specifically, to determine the resilience of the pre-landnam highland environment to disturbances (i.e. climate cooling and volcanism) and whether land use pressure was of sufficient magnitude to facilitate ecosystem change. A sediment core was taken from the highland lake Galtabol. A chronology for the core was constructed using known tephra layers and radiocarbon dated plant macrofossils. Pollen analysis (vegetation), coprophilous fungal spores (proxy for grazing), and sediment properties (proxies for erosion) were used to provide a high-resolution, integrated vegetation and paleoenvironmental reconstruction. The pre-landnam environment showed resilience to climate cooling and repeated tephra fall. Soon after landnam the vegetation community changed and instability increased, indicated by changes in sediment properties. The pollen and spore record suggest introduction of grazing herbivores into the area after landnam. Following landnam, indicators of soil erosion appear in the sediment properties. Intensification of soil erosion occurred during the 17th century. The Galtabol record clearly demonstrates what can happen in landscapes without adequate management of natural resources and underestimation of landscape sensitivity. Introduction of land use resulted in changes in vegetation communities, loss of resilience and onset of increased soil erosion. Paleoenvironmental reconstructions may inform future decisions on management of the highland by providing baselines for natural variability in the pre-landmim environment.
  •  
17.
  • Ehnvall, Betty, et al. (author)
  • Landscape constraints on mire lateral expansion
  • 2023
  • In: Quaternary Science Reviews. - : Elsevier. - 0277-3791 .- 1873-457X. ; 302
  • Journal article (peer-reviewed)abstract
    • Little is known about the long-term expansion of mire ecosystems, despite their importance in the global carbon and hydrogeochemical cycles. It has been firmly established that mires do not expand linearly over time. Despite this, mires are often assumed to have expanded at a constant rate after initiation simply for lack of a better understanding. There has not yet been a serious attempt to determine the rate and drivers of mire expansion at the regional, or larger spatial scales. Here we make use of a natural chronosequence, spanning the Holocene, which is provided by the retreating coastline of Northern Sweden. By studying an isostatic rebound area we can infer mire expansion dynamics by looking at the portion of the landscape where mires become progressively scarce as the land becomes younger. Our results confirms that mires expanded non-linearly across the landscape and that their expansion is related to the availability of suitably wet areas, which, in our case, depends primarily on the hydro-edaphic properties of the landscape. Importantly, we found that mires occupied the wettest locations in the landscape within only one to two thousand years, while it took mires three to four thousand years to expand into slightly drier areas. Our results imply that the lateral expansion of mires, and thus peat accumulation is a non-linear process, occurring at different rates depending, above all else, on the wetness of the landscape.
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18.
  • Farjon, Aljos, et al. (author)
  • Early Pleistocene conifer macrofossils from Happisburgh, Norfolk, UK, and their environmental implications for early hominin occupation
  • 2020
  • In: Quaternary Science Reviews. - : Elsevier. - 0277-3791 .- 1873-457X. ; 232
  • Journal article (peer-reviewed)abstract
    • Continuing coastal erosion in the vicinity of Happisburgh in north Norfolk has revealed archaeological sites documenting early human presence during at least two episodes in the Early and early Middle Pleistocene. At Happisburgh 3, the oldest archaeological site in northern Europe (approximately 900,000 years old) finds include at least 80 flint artefacts and human footprints associated with abundant, well-preserved organic remains. The deposits consist of gravels and estuarine sands and silts contained within a complex of channels, which accumulated in the estuary of a large river, probably the ancestral River Thames. The environmental remains reflect a slow-flowing tidal river, at the limit of tidal influence, and a grassland valley bordered by conifer-dominated woodland. Analyses of the pollen, wood, cones and leaves have identified a diversity of coniferous taxa, with some unexpected central and southern European elements (Pinus mugo ssp. mugo, Pinus mugo ssp. rotundata and Juniperus thurifera) indicating a type of coniferous woodland no longer present in Europe today. Here we present the conifer finds and their environmental implications. A new multi-proxy consensus palaeoclimate reconstruction, using conifer and beetle mutual climatic ranges, confirms and refines previous indications of a more continental climate than today, with significantly colder winters. These results provide a new perspective for understanding the climate and environment encountered by Early Pleistocene hominins at the northernmost limit of their range.
  •  
19.
  • Fietz, Susanne, et al. (author)
  • Terrestrial temperature evolution of southern Africa during the late Pleistocene and Holocene: Evidence from the Mfabeni Peatland
  • 2023
  • In: Quaternary Science Reviews. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0277-3791 .- 1873-457X. ; 299
  • Journal article (peer-reviewed)abstract
    • The scarcity of suitable high-resolution archives, such as ancient natural lakes, that span beyond the Holocene, hinders long-term late Quaternary temperature reconstructions in southern Africa. Here we target two cores from Mfabeni Peatland, one of the few long continuous terrestrial archives in South Africa that reaches into the Pleistocene, to generate a composite temperature record spanning the last similar to 43 kyr. The Mfabeni Peatland has previously been proven suitable for temperature and hydrological reconstructions based on pollen and geochemical proxies. Here we use branched glycerol dialkyl glycerol tetraethers (brGDGTs) preserved in the Mfabeni peatland to derive a new quantitative air temperature record for south-east Africa. Our temperature record generally follows global trends in temperature and atmospheric CO2 concentrations, but is decoupled at times. Annual air temperatures during Marine Isotope Stage (MIS) 3 were moderately high (c. 20.5 degrees C), but dropped by c. 5 degrees C during the Last Glacial Maximum, reaching a minimum at c.16-15 ka. Asynchronous with local insolation, this cooling may have resulted from reduced sea surface temperatures linked to a northward shift in the Southern Hemisphere westerly winds. Concurrent with the southward retreat of the westerlies, and increasing sea surface temperatures offshore, warming from minimum temperatures (c. 15.0 degrees C) to average Holocene temperatures (c. 20.0 degrees C) occurred across the deglaciation. This warming was briefly but prominently interrupted by a millennial-scale cooling event of c. 3 degrees C at c. 2.4 ka, concurrent with a sudden change in hydrological conditions. The average Holocene temperatures of c. 20.0 degrees C were similar to those reconstructed for MIS 3, but after the 2.4 ka cooling period, air temperatures in the Mfabeni peat recovered and steadily increased towards the present. In summary, our record demonstrates that land temperature in eastern South Africa is highly sensitive to global drivers as well as nearby sea surface temperatures. (C) 2022 Elsevier Ltd. All rights reserved.
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20.
  • Glueder, Anna, et al. (author)
  • Calibrated relative sea levels constrain isostatic adjustment and ice history in northwest Greenland
  • 2022
  • In: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 293
  • Journal article (peer-reviewed)abstract
    • Relative Sea Levels (RSLs) derived primarily from marine bivalves near Petermann Glacier, NW Greenland, constrain past regional ice-mass changes through glacial isostatic adjustment (GIA) modeling. Oxygen isotopes measured on bivalves corrected for shell-depth habitat and document changing meltwater input. Rapid RSL fall of up to 62 m/kyr indicates ice loss at or prior to ∼9 ka. Transition to an RSL stillstand starting at ∼6 ka reflects renewed ice-mass loading followed by further mass loss over the past few millennia. GIA simulations of rapid early RSL fall suggest a low regional upper-mantle viscosity. Early loss of grounded ice tracks atmospheric warming and pre-dates the eventual collapse of Petermann Glacier's floating ice tongue near ∼7 ka, suggesting grounding zone stabilization during early phases of deglaciation. We hypothesize mid-Holocene regrowth of regional ice caps in response to cooling and increased precipitation, following loss of the floating shelf ice. Remnants of these ice caps remain present but are now melting.
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21.
  • Glykou, Aikaterini, et al. (author)
  • Reconstructing the ecological history of the extinct harp seal population of the Baltic Sea
  • 2021
  • In: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 251
  • Journal article (peer-reviewed)abstract
    • The harp seal (Pagophilus groenlandicus), today a subarctic species with breeding populations in the White Sea, around the Jan Mayen Islands and Newfoundland, was a common pinniped species in the Baltic Sea during the mid- and late Holocene. It is puzzling how an ice dependent species could breed in the Baltic Sea during the Holocene Thermal Maximum (HTM), and it remains unclear for how long harp seals bred in the Baltic Sea and when the population became extirpated. We combined radiocarbon dating of harp seal bones with zooarchaeological, palaeoenvironmental and stable isotope data to reconstruct the harp seal occurrence in the Baltic Sea. Our study revealed two phases of harp seal presence and verifies that the first colonization and establishment of a local breeding population occurred within the HTM. We suggest that periods with very warm summers but cold winters allowed harp seals to breed on the ice. Human pressure, salinity fluctuations with consequent changes in prey availability and competition for food resources, mainly cod, resulted in physiological stress that ultimately led to a population decline and local extirpation during the first phase. The population reappeared after a long hiatus. Final extinction of the Baltic Sea harp seal coincided with the Medieval Warm Period. Our data provide insights for the first time on the combined effects of past climatic and environmental change and human pressure on seal populations and can contribute with new knowledge on ongoing discussions concerning the impacts of such effects on current arctic seal populations.
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22.
  • Gravgaard Askjær, Thomas, et al. (author)
  • Multi-centennial Holocene climate variability in proxy records and transient model simulations
  • 2022
  • In: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 296
  • Journal article (peer-reviewed)abstract
    • Variability on centennial to multi-centennial timescales is mentioned as a feature in reconstructions of the Holocene climate. As more long transient model simulations with complex climate models become available and efforts have been made to compile large proxy databases, there is now a unique opportunity to study multi-centennial variability with greater detail and a large amount of data than earlier. This paper presents a spectral analysis of transient Holocene simulations from 9 models and 120 proxy records to find the common signals related to oscillation periods and geographic dependencies and discuss the implications for the potential driving mechanisms. Multi-centennial variability is significant in most proxy records, with the dominant oscillation periods around 120–130 years and an average of 240 years. Spectra of model-based global mean temperature (GMT) agree well with proxy evidence with significant multi-centennial variability in all simulations with the dominant oscillation periods around 120–150 years. It indicates a comparatively good agreement between model and proxy data. A lack of latitudinal dependencies in terms of oscillation period is found in both the model and proxy data. However, all model simulations have the highest spectral density distributed over the Northern hemisphere high latitudes, which could indicate a particular variability sensitivity or potential driving mechanisms in this region. Five models also have differentiated forcings simulations with various combinations of forcing agents. Significant multi-centennial variability with oscillation periods between 100 and 200 years is found in all forcing scenarios, including those with only orbital forcing. The different forcings induce some variability in the system. Yet, none appear to be the predominant driver based on the spectral analysis. Solar irradiance has long been hypothesized to be a primary driver of multi-centennial variability. However, all the simulations without this forcing have shown significant multi-centennial variability. The results then indicate that internal mechanisms operate on multi-centennial timescales, and the North Atlantic-Arctic is a region of interest for this aspect.
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23.
  • Jacobson, Matthew, et al. (author)
  • Speleothem records from western Thailand indicate an early rapid shift of the Indian summer monsoon during the Younger Dryas termination
  • 2024
  • In: Quaternary Science Reviews. - 0277-3791 .- 1873-457X. ; 330
  • Journal article (peer-reviewed)abstract
    • Mainland Southeast Asia experiences complex and variable hydroclimatic conditions, mainly due to its location at the intersection of Asian monsoon subsystems. Predicting future changes requires an in-depth understanding of paleoclimatic conditions that is currently hindered by a paucity of records in some regions. In this paper, we present the first speleothem stable isotope records from western Thailand detailing the Bølling-Allerød interstadial, Younger Dryas termination, and early- to mid-Holocene period. We find evidence of higher precipitation during the Bølling-Allerød (14,321-12,824 years before present (1950: BP)) compared to a Younger Dryas termination that starts 11,702-11,674 BP, has a rapid shift centered on 11,660-11,641 BP, and ends 11,603-11,589 BP. In addition, our records show Holocene monsoon intensity peaking at 8250 BP or before, a multi-millennia delay from the Northern Hemisphere summer insolation peak, followed by a trend to drier conditions until at least 750 BP. Assessment of the timing of the Younger Dryas termination in paleoclimate records across Southeast Asia reveals an earlier shift of the Indian Summer Monsoon to global climate shifts when compared to East Asian Summer Monsoon records. The causes of this are currently unknown. Some potentially important aspects include: an Indian Summer Monsoon influence on East Asian Summer Monsoon strength via the Indian Ocean Dipole climate pattern, the role of the Tibetan Plateau in monsoon dynamics, and exposure of the Sundaland shoreline. More high-resolution paleoclimate records, especially on the pathway of Indian Summer Monsoon to East Asian Summer Monsoon, are required for further discussion on the mechanisms controlling the differences between climate regimes.
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24.
  • Jennings, Anne, et al. (author)
  • Modern and early Holocene ice shelf sediment facies from Petermann Fjord and northern Nares Strait, northwest Greenland
  • 2022
  • In: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 283
  • Journal article (peer-reviewed)abstract
    • Based on sediment cores and geophysical data collected from Petermann Fjord and northern Nares Strait, NW Greenland, an Arctic ice shelf sediment facies is presented that distinguishes sub and pro ice shelf environments. Sediment cores were collected from sites beneath the present day Petermann Ice Tongue (PIT) and in deglacial sediments of northern Nares Strait with a focus on understanding the glacial and oceanographic history over the last 11,000 cal yr BP. The modern sub ice shelf sediment facies in Petermann Fjord is laminated and devoid of coarse clasts (IRD) due to strong basal melting that releases debris (debris filtering) from the basal ice at the grounding zone driven by buoyant subglacial meltwater and entrained Atlantic Water. Laminated sediments in the deep basin proximal to the gounding zone comprise layers of fine mud formed by suspension settling from turbid meltwater plumes (plumites) interrupted by normally graded very fine sand to medium silt layers with sharp basal contacts and rip-up clasts of mud, interpreted as turbidites. An inner fjord sill limits distribution of sediment gravity flows from the grounding zone to the deep inner fjord basin, such that sites on the inner sill and beyond the ice tongue largely only comprise plumites. Bioturbation and foraminiferal abundances increase with distance from the grounding zone. The benthic foraminiferal species, Elphidium clavatum is absent beneath the ice tongue, but dominant in the turbid meltwater influenced environment beyond the ice tongue. The very sparse IRD in sediments beneath the PIT and in the fjord beyond the PIT derives mainly from englacial debris in the ice tongue, side valley glaciers, rock falls from the steep fjord walls and sea ice.We use the modern ice shelf sediment facies characteristics to infer the past presence of ice shelves in northern Nares Strait using analyses of sediment cores from several cruises (OD1507, HLY03, 2001LSSL, RYDER19). On bathymetric highs, bioturbated mud with dispersed IRD overlies a 10–15 m thick, distinctly laminated silt and clay unit with rare coarse clasts and sparse foraminifera which forms a sediment drape of nearly uniform thickness. We interpret these laminated sediments to represent glaciomarine deposition by meltwater plumes emanating from ice streams that terminated in floating ice shelves. IRD layers, shifts in sediment composition (qXRD, MS and XRF) and faunal assemblage changes in the laminated unit document periods of ice-shelf instability sometimes, but not always, coupled with grounding zone retreat. Our deglacial reconstruction, including ice shelves, begins ∼10.7 cal ka BP, with confluent ice streams grounded in Hall Basin fronted by the Robeson Channel ice shelf. Ice shelf breakup and grounding zone retreat to relatively stable grounding zones at Kennedy Channel and the mouth of Petermann Fjord was accomplished by 9.4 cal ka BP when the Hall Basin ice shelf was established. This ice shelf broke up and reformed once prior to the final break up at 8.5 to 8.4 cal ka BP marking ice stream collapse, separation of Greenland and Innuitian ice sheets, and the opening of Nares Strait for Arctic-Atlantic throughflow. The Petermann ice shelf remained in Hall Basin until the Petermann Glacier retreated from the fjord mouth ∼7.1 cal ka BP. The resilience of these northern ice streams to strong early Holocene insolation and subsurface Atlantic Water advection is attributed to their northern aspect, buttressing by narrow passages, and high ice flux from the Greenland Ice Sheet (GIS).
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25.
  • Jiangzuo, Qigao, et al. (author)
  • A dwarf sabertooth cat (Felidae: Machairodontinae) from Shanxi, China, and the phylogeny of the sabertooth tribe Machairodontini
  • 2022
  • In: Quaternary Science Reviews. - Amsterdam : Elsevier. - 0277-3791 .- 1873-457X. ; 284, s. 107517-107517
  • Journal article (peer-reviewed)abstract
    • The tribe Machairodontini is a major lineage of felid sabertooth cats that flourished in the late Cenozoic and included the top predators in the ecosystem of that time. As top predators members of the tribe had a profound influence on the paleoenvironment, yet the evolution and diversification of this tribe are unclear due to a lack of comprehensive revision and phylogenetic study. Here we describe a new dwarfed ecomorph of Machairodontini, Taowu liui gen. et sp. nov., from the Early Pleistocene of northern China,and carry out the best sampled phylogeny of the subfamily to date. Our analyses support that the African Mio-Pleistocene Lokotunjailurus represents an early divergent group, convergent with the Amphimachairodus-Homotheriina lineage in dental traits. The derived Pliocene to Pleistocene subtribe Homotheriina originated in Africa, from Adeilosmilus gen. nov. kabir or very a closely related taxon. Taowu liui gen. et sp. nov. belongs to a sister clade to Homotheriina. The Plio-Pleistocene Homotheriina of theNew World belong to a monophyletic group in which Ischyrosmilus-Xenosmilus show a gradual adaptation to handling slow and powerful prey, whereas the true Homotherium only appeared after theMiddle Pleistocene, in a separate intercontinental dispersal event.
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26.
  • Jones, Samantha E., et al. (author)
  • Lake and crannog : A 2500-year palaeoenvironmental record of continuity and change in NE Scotland
  • 2022
  • In: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 285
  • Journal article (peer-reviewed)abstract
    • Wetland environments have been important resources for human habitation since prehistoric times and in parts of northern Europe these have witnessed the construction of artificial islet settlements, known as ‘crannogs’ in Scotland and Ireland. This paper presents a high-resolution multi-proxy palaeoenvironmental study from the Loch of Leys, Aberdeenshire, Scotland, the site of a recently excavated crannog that provides a chronological context for its inhabitation. The combined datasets demonstrate that the first occupation from AD 20–210 coincided not only with a transitional phase from lake to wetland (mire) but also with the timing of the first major Roman campaigns in northeast Scotland. Techniques including microfossil analysis, geochemistry, IR-spectroscopy and physical properties integrated with archaeological and historical records have helped to better define both natural changes that took place in the wetland environment and human activity (agriculture, fires, metal working) spanning the Roman Iron Age through to the present. This has allowed a better understanding of the responses of existing Iron Age communities to Roman military activity (e.g. through continuity or change in land use) as well as the resources exploited in frontier zones during the Roman and post Roman eras. This has wider significance not just for Scotland but also for other parts of Europe that had similar frontiers and conflict zones during the Roman period.
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27.
  • Kalliokoski, Maarit, et al. (author)
  • A Holocene tephrochronological framework for Finland
  • 2023
  • In: Quaternary Science Reviews. - 0277-3791 .- 1873-457X. ; 312
  • Journal article (peer-reviewed)abstract
    • Regional tephrochronological frameworks serve as dating and correlating tools that enable critical assessment of the validity of single cryptotephra findings. In this study, our aim was to construct an outline for a Finnish Holocene tephra framework by investigating 12 peatlands and one lake site for presence of cryptotephra. As a result, glass shards from 19 individual tephras were geochemically characterized and correlated to their source volcanoes in Iceland and Alaska. Fifteen of these tephras were identified in Finland for the first time. The oldest identified cryptotephra in the Finnish environmental records is the 7 ka Hekla 5 tephra, and the youngest one is the Askja 1875. The identification of two Alaskan tephras (White River Ash eastern lobe and Aniakchak tephra) in Finland demonstrates an opportunity for intercontinental tephra correlations. The first Finnish Holocene tephrochronology presented here reveals a great potential for using tephrochronology as a dating method in Finland and is expected to aid in future cryptotephra research in the region. Additionally, the cryptotephra findings in this study help to refine the dispersal areas of several Holocene tephras. 
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28.
  • Katrantsiotis, Christos, et al. (author)
  • Seasonal variability in temperature trends and atmospheric circulation systems during the Eemian (Last Interglacial) based on n-alkanes hydrogen isotopes from Northern Finland
  • 2021
  • In: Quaternary Science Reviews. - Amsterdam : Elsevier. - 0277-3791 .- 1873-457X. ; 273, s. 107250-107250
  • Journal article (peer-reviewed)abstract
    • The Last Interglacial warm period, the Eemian (ca. 130-116 thousand years ago), serves as a reference for projected future climate in a warmer world. However, there is a limited understanding of the seasonal characteristics of interglacial climate dynamics, especially in high latitude regions. In this study, we aimto provide new insights into seasonal trends in temperature and moisture source location, linked to shifts in atmospheric circulation patterns, for northern Fennoscandia during the Eemian. Our study is based on the distribution and stable hydrogen isotope composition (dD) of n-alkanes in a lake sediment sequence from the Sokli paleolake in NE Finland, placed in a multi-proxy framework. The dD values of predominantly macrophyte-derived mid-chain n-alkanes are interpreted to reflect lake water dD variability influenced by winter precipitation dD (dDprec), ice cover duration and deuterium (D)-depleted meltwater. The dD values of terrestrial plant-derived long-chain n-alkanes primarily reflect soil water dD variability modulated by summer dDprec and by the evaporative enrichment of soil and leaf water. The dDprec variability in our study area is mostly attributed to the temperature effect and the moisture source location linked to the relative dominance between D-depleted continental and polar air masses and Denriched North Atlantic air masses. The biomarker signal further corroborates earlier diatom-based studies and pollen-inferred January and July temperature reconstructions from the same sediment sequence. Three phases of climatic changes can be identified that generally follow the secular variationsin seasonal insolation: (i) an early warming trend succeeded by a period of strong seasonality (ii) a midoptimum phase with gradually decreased seasonality and cooler summers, and (iii) a late climatic instability with a cooling trend. Superimposed on this trend, two abrupt cooling events occur in the early and late Eemian. The Sokli dD variability is generally in good agreement with other North Atlantic and Siberian records, reflecting major changes in the atmospheric circulation patterns during the Eemian as a response to orbital and oceanic forcings.
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29.
  • Kirkeng Jørgensen, Erlend, et al. (author)
  • Source-sink dynamics drove punctuated adoption of early pottery in Arctic Europe under diverging socioecological conditions
  • 2023
  • In: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 299
  • Journal article (peer-reviewed)abstract
    • What drives the adoption of pottery amongst prehistoric foragers in high-latitude environments? Following the long-running interests of archaeology in explaining the origin and dispersal of new technologies, recent years have seen growing efforts to understand what drove the emergence and expansion of early hunter-gatherer pottery use across northern Eurasia. However, many regional dimensions to this continental-scale phenomenon remain poorly understood. Initial pottery adoption has often been explained as a generic cultural response to warming climates and the growing diversity of food resources, yet resolving challenges of food security during seasonal shortfalls or general climatic downturns may have provided alternative motivations. It is also becoming clear that many regions experienced more complex patterns of pottery adoption and that many resist simplistic monocausal interpretations. In this paper we deploy a Human Ecodynamics framework to examine what drove the punctuated adoption of two early pottery traditions into Arctic Maritime Europe, which were separated by a multi-millennial ceramic hiatus – Early Northern Comb Ware (ENCW) and Asbestos Tempered Ware (ATW). Our multi-proxy approach involves the revision of pottery chronologies to clarify the timing and ecological context for each dispersal, combined with analysis of technological and functional dimensions of the ceramic traditions to understand the contrasting social organization of these technologies. Our results confirm that ENCW expanded at a time of increased locational investment and ecological abundance in the region, while ATW spread in a series of smaller and more intermittent waves in the context of a major ecological downturn and alongside a return to a high-mobility lifestyle. Finally, we use the concept of “source-sink dynamics” to suggest that both dispersals were driven by the same underlying process. This involved major climatic fluctuations triggering small-scale population transfers from lake and riverine settings of western Russia, Finland and the Eastern Baltic region via interior areas and through to the Arctic Norwegian coastline, a persistent process that is also well-documented in later historical periods. Our results highlight the crucial importance of bridging-scale case studies as these have the “unsettling” potential to highlight deeper problems of equifinality. In this case, they reveal that two broadly similar material traditions spread into the same regions, albeit in the context of strikingly different environmental and behavioural conditions.
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30.
  • Kleman, Johan, et al. (author)
  • Age and duration of a MIS 3 interstadial in the Fennoscandian Ice Sheet core area-Implications for ice sheet dynamics
  • 2021
  • In: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 264
  • Journal article (peer-reviewed)abstract
    • Previous assumptions of continuous ice cover of the core area of the Fennoscandian Ice Sheet, from Marine Isotope Stage 4 (ca. 70 ka) to the end of MIS 2 (ca. 12 ka), have been challenged by the discovery of several sites in central and northern Scandinavia with interstadial sediments of assumed MIS 3 age. The sequences have often been dated by Optically Stimulated Luminescence (OSL) and dates of around 55 ka are present at most sites, indicating ice-free conditions at this time. There is less consensus about the timing of the build-up and advance of the last (Late Weichselian) ice sheet after this ice-free stage. To address the duration of MIS 3 ice-free conditions in central Scandinavia, we reviewed available dating evidence. At the few sites where multiple OSL dates are available, ages indicate around 15 ka of ice-free conditions. Two studies employing cosmogenic nuclide dating of preserved interstadial ground surfaces both indicate a 20 ka long period of ice-free conditions during the last ice-free period before the Holocene. Our interpretation is that central Scandinavia became ice-free around 55 ka and remained so until c. 35 ka, when the Scandinavian Ice Sheet started to expand once again. Expansion started from a small-sized remnant ice sheet, or from separate remnant ice caps in Norway. Available data limits the size of any Scandinavian ice sheet remnant surviving the MIS 3 interstadial to less than 1 m of global sea-level equivalent.
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31.
  • Koriche, Sifan A., et al. (author)
  • What are the drivers of Caspian Sea level variation during the late Quaternary?
  • 2022
  • In: Quaternary Science Reviews. - : Elsevier. - 0277-3791 .- 1873-457X. ; 283
  • Journal article (peer-reviewed)abstract
    • Quaternary Caspian Sea level variations depended on geophysical processes (affecting the opening and closing of gateways and basin size/shape) and hydro-climatological processes (affecting water balance). Disentangling the drivers of past Caspian Sea level variation, as well as the mechanisms by which they impacted the Caspian Sea level variation, is much debated. In this study we examine the relative impacts of hydroclimatic change, ice-sheet accumulation and melt, and isostatic adjustment on Caspian Sea level change. We performed model analysis of ice-sheet and hydroclimate impacts on Caspian Sea level and compared these with newly collated published palaeo-Caspian sea level data for the last glacial cycle. We used palaeoclimate model simulations from a global coupled ocean-atmosphere-vegetation climate model, HadCM3, and ice-sheet data from the ICE-6G_C glacial isostatic adjustment model. Our results show that ice-sheet meltwater during the last glacial cycle played a vital role in Caspian Sea level variations, which is in agreement with hypotheses based on palaeo-Caspian Sea level information. The effect was directly linked to the reorganization and expansion of the Caspian Sea palaeo-drainage system resulting from topographic change. The combined contributions from meltwater and runoff from the expanded basin area were primary factors in the Caspian Sea transgression during the deglaciation period between 20 and 15 kyr BP. Their impact on the evolution of Caspian Sea level lasted until around 13 kyr BP. Millennial scale events (Heinrich events and the Younger Dryas) negatively impacted the surface water budget of the Caspian Sea but their influence on Caspian Sea level variation was short-lived and was outweighed by the massive combined meltwater and runoff contribution over the expanded basin. (c) 2022 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
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32.
  • Kylander, Malin E., 1977-, et al. (author)
  • Storm chasing : Tracking Holocene storminess in southern Sweden using mineral proxies from inland and coastal peat bogs
  • 2023
  • In: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 299, s. 107854-
  • Journal article (peer-reviewed)abstract
    • Severe extratropical winter storms are a recurrent feature of the European climate and cause widespread socioeconomic losses. Due to insufficient long-term data, it remains unclear whether storminess has shown a notable response to changes in external forcing over the past millennia, which impacts our ability to project future storminess in a changing climate. Reconstructing past storm variability is essential to improving our understanding of storms on these longer, missing timescales. Peat sequences from coastal ombrotrophic bogs are increasingly used for this purpose, where greater quantities of coarser grained beach sand are deposited by strong winds during storm events. Moving inland however, storm intensity decreases, as does sand availability, muting potential paleostorm signals in bogs. We circumvent these issues by taking the innovative approach of using mid-infrared (MIR) spectral data, supported by elemental information, from the inorganic fraction of Store Mosse Dune South (SMDS), a 5000-year-old sequence from a large peatland located in southern Sweden. We infer past changes in mineral composition and thereby, the grain size of the deposited material. The record is dominated by quartz, whose coarse nature was confirmed through analyses of potential local source sediments. This was supported by further mineralogical and elemental proxies of atmospheric input. Comparison of SMDS with within-bog and regionally relevant records showed that there is a difference in proxy and site response to what should be similar timing in shifts in storminess over the-100 km transect considered. We suggest the construction of regional storm stacks, built here by applying changepoint modelling to four transect sites jointly. This modelling approach has the effect of reinforcing signals in common while reducing the influence of random noise. The resulting Southern Sweden-Storm Stack dates stormier periods to 4495-4290, 3880-3790, 2885-2855, 2300-2005, 1175-1065 and 715-425 cal yr BP. By comparing with a newly constructed Western Scotland-Storm Stack and proximal dune records, we argue that regional storm stacks allow us to better compare past storminess over wider areas, gauge storm track movements and by extension, increase our understanding of the drivers of storminess on centennial to millennial timescales.
  •  
33.
  • Költringer, Chiara, et al. (author)
  • Palaeoenvironmental implications from Lower Volga loess - Joint magnetic fabric and multi-proxy analyses
  • 2021
  • In: Quaternary Science Reviews. - : Elsevier. - 0277-3791 .- 1873-457X. ; 267, s. 107057-
  • Journal article (peer-reviewed)abstract
    • Magnetic fabric (MF) investigations complemented by geochemical and grain surface analyses of the understudied and controversial marine isotope stage (MIS) 5 b, 4 and 3 loess deposits in the Lower Volga region, Russia show that the material has been transported and deposited by wind and to a large extent experienced post-depositional reworking. Grain surface features suggest that the material was glacially ground and fluvially transported prior to final aeolian deposition as loess. Secondary magnetic fabrics in the loess reveal pedogenic and cryogenic processes and a generally cold environment with brief shifts to warmer climate during late MIS 5 and MIS 3. Palaeowind reconstructions derived from preserved primary aeolian MF, indicate locally influenced westerly and north-westerly flow as part of a wider scale westerly wind pattern, similar to modern day winter conditions. We suggest that the climate of the last glacial in the Northern Caspian Lowland was cold and dry, with higher windspeeds and less variability during MIS 4 compared to MIS 3.
  •  
34.
  • Ljungqvist, Fredrik Charpentier, et al. (author)
  • Ranking of tree-ring based hydroclimate reconstructions of the past millennium
  • 2020
  • In: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 230
  • Journal article (peer-reviewed)abstract
    • © 2019 The Authors To place recent hydroclimate changes, including drought occurrences, in a long-term historical context, tree-ring records serve as an important natural archive. Here, we evaluate 46 millennium-long tree-ring based hydroclimate reconstructions for their Data Homogeneity, Sample Replication, Growth Coherence, Chronology Development, and Climate Signal based on criteria published by Esper et al. (2016) to assess tree-ring based temperature reconstructions. The compilation of 46 individually calibrated site reconstructions includes 37 different tree species and stem from North America (n = 29), Asia (n = 10); Europe (n = 5), northern Africa (n = 1) and southern South America (n = 1). For each criterion, the individual reconstructions were ranked in four groups, and results showed that no reconstruction scores highest or lowest for all analyzed parameters. We find no geographical differences in the overall ranking, but reconstructions from arid and semi-arid environments tend to score highest. A strong and stable hydroclimate signal is found to be of greater importance than a long calibration period. The most challenging trade-off identified is between high continuous sample replications, as well as a well-mixed age class distribution over time, and a good internal growth coherence. Unlike temperature reconstructions, a high proportion of the hydroclimate reconstructions are produced using individual series detrending methods removing centennial-scale variability. By providing a quantitative and objective evaluation of all available tree-ring based hydroclimate reconstructions we hope to boost future improvements in the development of such records and provide practical guidance to secondary users of these reconstructions.
  •  
35.
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36.
  • Ma, Zhaoying, et al. (author)
  • Mineralogical and magnetic variations of periglacial loess in SE Tibet reveal mid-Pleistocene expansion of Tibetan glacial activity
  • 2024
  • In: Quaternary Science Reviews. - : Elsevier. - 0277-3791 .- 1873-457X. ; 330
  • Journal article (peer-reviewed)abstract
    • The formation and evolution of the cryosphere on the Tibetan Plateau is of great significance in understanding the Earth's carbon and climatic system. Periglacial loess deposits in southeastern Tibet offer a means to constrain this history as they contain critical information on glacial grinding and frost shattering processes in high-altitude mountain regions through time, which yield lithogenic fractions of largely loess silts and sands. Based on combined analyses of lithogenic magnetic properties and mineralogical composition, here we find that increasing high mountain production and supply of fresh detrital components since the mid-Pleistocene climate transition (MPT, 1.2–0.7 Ma) led to a substantial increase of the lithogenic susceptibility and decrease in chemical weathering intensity of periglacial loess in southeastern Tibet. The agreement of these findings with similar results from eolian loess on the northern margins of the Tibetan Plateau suggests a plateau-wide glacier expansion during the MPT. Enhanced glacial erosion and freeze-thaw activities occurred in the high-altitude mountain regions of the plateau during the MPT, thereby providing vast amounts of fresh detritus for the formation of loess deposits. High and constant values of lithogenic magnetic parameters in the loess deposits after 0.7–0.6 Ma further indicate that the Middle Pleistocene is a critical period for the establishment of modern-like glacial and periglacial landforms on the Tibetan Plateau. Our results further suggest that enhanced Quaternary glaciation in SE Tibet occurred earlier than in the north, which we attribute to climate cooling combined with regional seasonal snowline lowering. As such, a close relationship exists between global climate changes, development of pan-Tibetan glaciations, and large-scale dust emission.
  •  
37.
  • Madurell-Malapeira, Joan, et al. (author)
  • First small-sized Dinofelis: Evidence from the Plio-Pleistocene of North Africa
  • 2021
  • In: Quaternary Science Reviews. - Amsterdam : Elsevier. - 0277-3791 .- 1873-457X. ; 265
  • Journal article (peer-reviewed)abstract
    • We describe small-sized specimens of the metailurine felid Dinofelis from a new Plio-Pleistocene site in North Africa. Dinofelis is a genus of saber-toothed cats mainly recorded from East and South Africa with numerous leopard to jaguar-sized species. The described specimens, clearly smaller than all the other African Dinofelis, resemble isolated remains from the Late Pliocene of France and the Early Pleistocene of Africa. Present evidence suggests that our form represents a new species and/or new lineage of Dinofelis, smaller and probably occupying a different ecological niche compared to the previously known members of the genus, and thus it adds complexity to the high intraspecific competition among large carnivorans in the Plio-Pleistocene of Africa.
  •  
38.
  • Marquer, Laurent, et al. (author)
  • Pollen-based reconstruction of Holocene land-cover in mountain regions : Evaluation of the Landscape Reconstruction Algorithm in the Vicdessos valley, northern Pyrenees, France
  • 2020
  • In: Quaternary Science Reviews. - : Elsevier. - 0277-3791 .- 1873-457X. ; 228, s. 1-15
  • Research review (peer-reviewed)abstract
    • Long-term perspectives on climate- and human-induced shifts in plant communities and tree line in mountains are often inferred from fossil pollen records. However, various factors, such as complex patterns of orographic wind fields and abundant insect-pollinated plants in higher altitudes, make pollen-based reconstruction in mountain regions difficult. Over the last decade the Landscape Reconstruction Algorithm (LRA) - a model-based approach in reconstruction of vegetation - has been successfully applied in various parts of the globe. However, evaluation of its effectiveness in mountain ranges is still limited. The present study assesses the extent to which the LRA approach helps quantify the local changes in vegetation cover at Vicdessos valley in northern French Pyrenees as a case study. In the study area well-dated sediment cores are available from eight bogs and ponds, 6-113 m in radius, located above the current tree line. We first use a simple simulation experiment to evaluate the way how pollen records from "landscape islands" (mountain tops and plateaus) would represent local vegetation and to clarify important factors affecting the LRA-based reconstruction in a mountainous region. This study then uses pollen records from these sites and vegetation and land-cover data both within a 50-km radius around the Vicdessos valley and within a 2-km radius from each site for evaluation of the REVEALS- and LOVE-based reconstruction of the regional and local plant cover, respectively, in the LRA approach. The land-cover data are complied for coniferous trees, broadleaved trees and non-forested areas from the CORINE and historical maps in three time windows: 1960-1970, 1990-2000 and 2000-2013. Major findings are as follows. (1) Accuracy of the regional vegetation estimates affects the reliability of the LRA-based reconstruction of vegetation within a 2-km radius; use of the CORINE data as input to the LOVE model improves reliability of the results over the use of the REVEALS-based estimates of regional vegetation. This implies that a systematic selection of pollen data only from sites above the tree line is problematic for estimating regional vegetation, and thus the entire LRA process. (2) Selection of the dispersal models for pollen transport (i.e. the Langrangian Stochastic Model vs. Gaussian Plume Model) does not affect significantly the LRA-based estimates at both the regional and local scales in the study area. (3) The LRA approach improves the pollen-based reconstruction of local vegetation compared to pollen percentage alone in northern Pyrenees. Although further empirical and simulation studies are necessary, our results emphasize the importance of site selection for the LRA-based reconstruction of vegetation in mountain regions. (C) 2019 Elsevier Ltd. All rights reserved.
  •  
39.
  •  
40.
  • Marwan, Norbert, et al. (author)
  • Nonlinear time series analysis of palaeoclimate proxy records
  • 2021
  • In: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 274
  • Journal article (peer-reviewed)abstract
    • Identifying and characterising dynamical regime shifts, critical transitions or potential tipping points in palaeoclimate time series is relevant for improving the understanding of often highly nonlinear Earth system dynamics. Beyond linear changes in time series properties such as mean, variance, or trend, these nonlinear regime shifts can manifest as changes in signal predictability, regularity, complexity, or higher-order stochastic properties such as multi-stability. In recent years, several classes of methods have been put forward to study these critical transitions in time series data that are based on concepts from nonlinear dynamics, complex systems science, information theory, and stochastic analysis. These include approaches such as phase space-based recurrence plots and recurrence networks, visibility graphs, order pattern-based entropies, and stochastic modelling. Here, we review and compare in detail several prominent methods from these fields by applying them to the same set of marine palaeoclimate proxy records of African climate variations during the past 5 million years. Applying these methods, we observe notable nonlinear transitions in palaeoclimate dynamics in these marine proxy records and discuss them in the context of important climate events and regimes such as phases of intensified Walker circulation, marine isotope stage M2, the onset of northern hemisphere glaciation and the mid-Pleistocene transition. We find that the studied approaches complement each other by allowing us to point out distinct aspects of dynamical regime shifts in palaeoclimate time series. We also detect significant correlations of these nonlinear regime shift indicators with variations of Earth's orbit, suggesting the latter as potential triggers of nonlinear transitions in palaeoclimate. Overall, the presented study underlines the potentials of nonlinear time series analysis approaches to provide complementary information on dynamical regime shifts in palaeoclimate and their driving processes that cannot be revealed by linear statistics or eyeball inspection of the data alone. 
  •  
41.
  • McMichael, C. N. H., et al. (author)
  • 30,000 years of landscape and vegetation dynamics in a mid-elevation Andean valley
  • 2021
  • In: Quaternary Science Reviews. - : Elsevier. - 0277-3791 .- 1873-457X. ; 258
  • Journal article (peer-reviewed)abstract
    • The mid-elevation settings of the Andes are important biodiversity hotspots, yet little is known of their long-term ecology or environmental change. Here, we assess 30,000 years of landscape and vegetation dynamics on an alluvial terrace located in a mid-elevation valley of the Ecuadorian Andes (Campo Libre). We used loss-on-ignition and particle size analysis to reconstruct past river dynamics, charcoal analysis to reconstruct past fire regimes, and phytolith analysis to reconstruct vegetation change through time. Our results show that Campo Libre was a part of the active floodplain system of the Quijos River until 18,000 cal yr BP. The biggest vegetation change in vegetation at Campo Libre occurred ca. 13,000 cal yr BP, when the site warmed and dried, transforming the swampy alluvial terrace into a palm forest. As Ho-locene precipitation increased, the site transformed back into a swamp around 7500 cal yr BP, and it remained that way until maize agriculture began around 4600 cal yr BP. Local and regional fires were absent from the system until regional fires were detected ca. 3300 cal yr BP. By ca. 2700 cal yr BP, maize cultivation became frequent and regular. Climate, tectonic activity, and the human history have shaped the modern vegetation around Campo Libre, although during different periods of the Holocene. Our results demonstrate the ability of phytoliths to reconstruct vegetation change through time, and show that the mid-elevation Andean valley systems were highly dynamic over the last 30,000 years.
  •  
42.
  • Ni, S., et al. (author)
  • Last interglacial seasonal hydroclimate in the North Sea–Baltic Sea region
  • 2023
  • In: Quaternary Science Reviews. - 0277-3791 .- 1873-457X. ; 312
  • Journal article (peer-reviewed)abstract
    • The Last Interglacial (LIG) experienced substantial changes in seasonal insolation compared with the present day, which may have affected the hydrography and water-mass exchange in the North Sea and Baltic Sea region. Here we investigate the effects of solar radiation and greenhouse gas (GHG) forcing on the regional climate by analyzing model simulations of the LIG (127 ka BP), pre-industrial (PI, 1850 CE), and present-day (PD, 1990 CE) climates. We also interpret the reconstructed seasonal bottom water conditions using benthic foraminifera and geochemistry data. Our simulations reveal that during the LIG, the Baltic Sea region (including the Kattegat and the Danish Straits) experienced more saline and colder bottom waters than those in the PD, in agreement with the reconstruction data. This can be attributed to lower GHG levels and enhanced water exchange of cooler, saline North Sea water into the Baltic Sea during the LIG. The thermocline was stronger during the summer months in the LIG, mainly due to the higher sea surface temperature (SST) compared to that of the PD resulting from increased summer insolation. Further, the temperature anomalies (LIG–PD) show significant inverse correlations with the precipitation–minus–evaporation (P–E) at the Baltic Sea entrance. However, the P–E balance appears to have had minimal impact on salinity changes in the North Sea, the Baltic Proper, and the open sea area. Our findings indicate that monthly surface and bottom water salinity anomalies of LIG-PI exhibit strong positive correlations with the North Atlantic Oscillation (NAO) anomalies in the Baltic entrance region. During the LIG, a more positive phase of the NAO index in autumn played a crucial role in wind-driven major inflows and led to more intensive water exchange in the North Sea–Baltic Sea region compared to the late Holocene.
  •  
43.
  • Organista, Elia, et al. (author)
  • A taphonomic analysis of PTK (Bed I, Olduvai Gorge) and its bearing on the interpretation of the dietary and eco-spatial behaviors of early humans
  • 2023
  • In: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 300
  • Journal article (peer-reviewed)abstract
    • Here, we present a thorough taphonomic analysis of the 1.84 million-year-old site of Phillip Tobias Korongo (PTK), Bed I, Olduvai Gorge. PTK is one of the new archaeological sites documented on the FLK Zinj paleolandscape, in which FLK 22 level was deposited and covered by Tuff IC. Therefore, PTK is pene-contemporary with these sites: FLK Zinj, DS, AMK and AGS. The occurrence of these sites within a thin clay unit of ∼20 cm, occupying not only the same vertically discrete stratigraphic unit, but also the same paleosurface, with an exceptional preservation of the archaeological record in its primary depositional locus, constitutes a unique opportunity to explore early hominin behavioral diversity at the most limited geochronological scale possible. The Olduvai Bed I sites have been the core of behavioral modelling for the past half a century, and the newly discovered sites, excavated with 21st century technology, will increase significantly our understanding of early human adaptive patterns. Here, we present PTK as another assemblage where faunal resources were acquired by hominins prior to any carnivore, and where stone-tool assisted bulk defleshing was carried out. The abundance of juvenile individuals extends our understanding, as in Kanjera (Kenya), about the hunting skills of early Homo sensu lato. The increasing number of sites, where bulk defleshing of small and medium-sized carcasses took place is underscoring the importance of meat in the diets of some of the early hominins, and their patterned use of the space for food processing and consumption. The patterning emerging has a profound importance for the evolution of some of the features that have traditionally been used to identify the behavior of the genus Homo.
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44.
  • Petrini, Michele, et al. (author)
  • Simulated last deglaciation of the Barents Sea Ice Sheet primarily driven by oceanic conditions
  • 2020
  • In: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 238
  • Journal article (peer-reviewed)abstract
    • The Barents Sea Ice Sheet was part of an interconnected complex of ice sheets, collectively referred to as the Eurasian Ice Sheet, which covered north-westernmost Europe, Russia and the Barents Sea during the Last Glacial Maximum (around 21 ky BP). Due to common geological features, the Barents Sea component of this ice complex is seen as a paleo-analogue for the present-day West Antarctic Ice Sheet. Investigating key processes driving the last deglaciation of the Barents Sea Ice Sheet represents an important tool to interpret recent observations in Antarctica over the multi-millennial temporal scale of glaciological changes. We present results from a perturbed physics ensemble of ice sheet model simulations of the last deglaciation of the Barents Sea Ice Sheet, forced with transient atmospheric and oceanic conditions derived from AOGCM simulations. The ensemble of transient simulations is evaluated against the databased DATED-1 reconstruction to construct minimum, maximum and average deglaciation scenarios. Despite a large model/data mismatch at the western and eastern ice sheet margins, the simulated and DATED-1 deglaciation scenarios agree well on the timing of the deglaciation of the central and northern Barents Sea. We find that the simulated deglaciation of the Barents Sea Ice Sheet is primarily driven by the oceanic forcing, with prescribed eustatic sea level rise amplifying the ice sheet sensitivity to sub-shelf melting over relatively short intervals. Our results highlight that the sub-shelf melting has a very strong control on the simulated grounding-line flux, showing that a slow, gradual ocean warming trend is capable of triggering sustained grounded ice discharge over multi-millennial timescales, even without taking into account marine ice sheet or ice cliff instability.
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45.
  • Rasmussen, Christian F., et al. (author)
  • High-resolution OSL dating of loess in Adventdalen, Svalbard : Late Holocene dust activity and permafrost development
  • 2023
  • In: Quaternary Science Reviews. - 0277-3791 .- 1873-457X. ; 310
  • Journal article (peer-reviewed)abstract
    • There is considerable uncertainty over the nature and causes of Holocene dust activity in the Arctic, and its links to climatic changes. Loess deposits act as near-source archives of dust deposition and provide a means to address these uncertainties. Here we develop a fully independent age model for a loess core taken in Adventdalen, Svalbard, based on 136 quartz luminescence ages taken at 2 cm intervals. This represents the most detailed luminescence dating analysis undertaken to date on a sedimentary archive. Extensive laboratory tests and stratigraphic consistency indicate that the quartz luminescence ages are reliable. Together with grain size and cryostratigraphic analyses, as well as stratigraphic investigation of an adjacent loess exposure, the exceptional detail of the chronology combined with Bayesian age modelling uniquely allows changes in loess accumulation rates, particle size and permafrost development to be reconstructed over the last 3000 yrs on 101–103 yr timescales. The results show that loess deposition was mostly continuous over this interval, albeit with a short period of reworking or non-aeolian sedimentation during the Little Ice Age. Permafrost development in the loess is dominantly syngenetic, with ice contents increasing with depth. There is considerable variability in loess mass accumulation rate over the late Holocene, with peaks occurring during the last 250 yrs, as well as at 750–900, 1050–1200, 1400–1600, 1900–2450 and possibly 2700–3000 a. These peaks generally coincide with increased coarse silt deposition, potentially suggesting a link with greater wind activity. However, the peaks also seem to coincide with possible warm phases on Svalbard, which would rather imply that temperature-driven sediment availability in glaciofluvial source areas is the main control on dustiness in Adventdalen. In any case, the rates of loess deposition in the Adventdalen core are exceptionally high globally (up to 0.35 cm yr−1/2900 g m−2 yr−1 sedimentation and mass accumulation rates, respectively), and if representative of wider patterns across Svalbard, may suggest that the archipelago is a more important high latitude dust source than previously realised.
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46.
  • Ratcliffe, Joss (author)
  • Rapid carbon accumulation in a peatland following Late Holocene tephra deposition, New Zealand
  • 2020
  • In: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 15
  • Journal article (peer-reviewed)abstract
    • Contemporary measurements of carbon (C) accumulation rates in peatlands around the world often show the C sink to be stronger on average than at times in the past. Alteration of global nutrient cycles could be contributing to elevated carbon accumulation in the present day. Here we examine the effect of volcanic inputs of nutrients on peatland C accumulation in Moanatuatua Bog, New Zealand, by examining a high-resolution Late Holocene C accumulation record during which powerful volcanic eruptions occurred, depositing two visible rhyolitic tephra layers (Taupo, 232 ± 10 CE; Kaharoa, 1314 ± 12 CE). Carbon accumulation rates since c. 50 CE, well before any human presence, increased from a background rate of 23 g C m−2 yr−1 up to 110 g C m−2 yr−1 following the deposition of the Taupo Tephra, and 84 g C m−2 yr−1 following the deposition of the Kaharoa Tephra. Smaller but nevertheless marked increases in C accumulation additionally occurred in association with the deposition of three andesitic-dacitic cryptotephras (each ≤ ∼1 mm thick) of the Tufa Trig Formation between the Taupo and Kaharoa events. These five periods of elevated C uptake, especially those associated with the relatively thick Taupo and Kaharoa tephras, were accompanied by shifts in nutrient stoichiometry, indicating that there was greater availability of phosphorus (P) relative to nitrogen (N) and C during the period of high C uptake. Such P was almost certainly derived from volcanic sources, with P being present in the volcanic glass at Moanatuatua, and many of the eruptions described being associated with the local deposition of the P rich mineral apatite. We found peatland C accumulation to be tightly coupled to N and P accumulation, suggesting nutrient inputs exert a strong control on rates of peat accumulation. Nutrient stoichiometry indicated a strong ability to recover P within the ecosystem, with C:P ratios being higher than most other peatlands in the literature. We conclude that nutrient inputs, deriving from volcanic eruptions, have been very important for C accumulation rates in the past. Therefore, the elevated nutrient inputs occurring in the present day could offer a more plausible explanation, as opposed to a climatic component, for observed high contemporary C accumulation in New Zealand peatlands.
  •  
47.
  • Razmjooei, Mohammad J., et al. (author)
  • Revision of the Quaternary calcareous nannofossil biochronology of Arctic Ocean sediments
  • 2023
  • In: Quaternary Science Reviews. - : Elsevier. - 0277-3791 .- 1873-457X. ; 321
  • Journal article (peer-reviewed)abstract
    • Despite extensive chronological studies, the relationship between the age and sub-seafloor depth of Arctic Ocean sediments remains ambiguous. This prevents confident identification of paleoceanographic changes in the Arctic during the Quaternary. Currently, age-depth models derived from uranium-series decay in Arctic sediments diverge by hundreds of thousands of years compared to those built on known evolutionary appearances and extinctions of calcareous nannoplankton, a group of globally valuable age-markers. Here we report on highresolution biostratigraphic analysis of late Quaternary sediments in six cores from the central Arctic Ocean (CAO). We applied paired light microscope (LM) and scanning electron microscope (SEM) imaging to improve nannofossil diagnosis. We argue that low abundances and poor preservation have led to misidentification of the true stratigraphic depth of the critical Pleistocene nannofossil bio-events that have underpinned age models for many Arctic sedimentary records for decades. The revised calcareous nannofossil biochronology provides a radically different geochronological framework for CAO sediments - indicating that what had previously been identified as Marine Isotope Stage (MIS) 7 (191-243 ka) in many sedimentary records is older than MIS 12 (424-478 ka). Furthermore, it suggests that previously inferred sub-stages of MIS 5 could represent full interglacial periods rather than interstadials. The results help reconcile the different dating approaches and provide a transformative step towards resolving the disparity in Quaternary Arctic age-depth models, bringing us one step closer to accurate paleoceanographic reconstructions based on sediment cores.
  •  
48.
  • Regnéll, Carl, et al. (author)
  • Ice-dammed lakes and deglaciation history of the Scandinavian Ice Sheet in central Jämtland, Sweden
  • 2023
  • In: Quaternary Science Reviews. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0277-3791 .- 1873-457X. ; 314
  • Journal article (peer-reviewed)abstract
    • Extensive glacial lakes dammed in the Scandinavian Mountains during the retreat of the last Scandinavian Ice Sheet were first hypothesised over a century ago. Here, using high-resolution LiDAR, we report >4500 relict shorelines, deltas and palaeo-channels related to ice-dammed lakes over a -30 000 km2 area of central Jämtland, west-central Sweden. Shorelines occur as flights on the valley sides, a consequence of sequential lowering of palaeo-lake levels during ice margin retreat and lower threshold outlets becoming ice-free. Based on the extent and elevation of shorelines, we identify requisite lake-damming ice-margin positions and lake drainage outlets, and we reconstruct the coupled evolution of ice-dammed lakes and the retreating ice margin. Beginning as a series of smaller ice-dammed lakes along the Swedish-Norwegian border, draining westward across the present-day water divide and into the Atlantic Ocean, the lakes successively coalesced during eastward ice margin retreat to form water bodies covering 1000s of km2 with 10s of km-long calving margins. Ultimately, the lake system coalesced into a single lake: the Central Jämtland Ice Lake, which exceeded 3500 km2 in area and 360 km3 in volume. Eventually, the damming ice-margin split in two, resulting in a large (-200 km2) catastrophic glacial lake outburst flood (GLOF) that reversed the drainage of the entire lake system from the west to an eastern outlet draining to the Baltic basin. We present new radiocarbon ages for one lake drainage event prior to the eastward outburst flood and, together with previously published deglacial ages and local varve records, we suggest that the region was possibly deglaciated within just 350 years, sometime between 10.5 and 9.2 cal ka BP. We tentatively correlate the penultimate drainage of the Central Jämtland Ice Lake to the zero-varve of the Swedish Time Scale, a drainage varve at Döviken, eastern Jämtland, raising the tantalising prospect of using the evolution of the ice-dammed lake system to tie the varve-based Swedish Time Scale to the radiocarbon timescale with a new programme of radiocarbon dating in central Jämtland. 
  •  
49.
  • Rosentau, A., et al. (author)
  • A Holocene relative sea-level database for the Baltic Sea
  • 2021
  • In: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 266
  • Journal article (peer-reviewed)abstract
    • We present a compilation and analysis of 1099 Holocene relative shore-level (RSL) indicators located around the Baltic Sea including 867 relative sea-level data points and 232 data points from the Ancylus Lake and the following transitional phase. The spatial distribution covers the Baltic Sea and near-coastal areas fairly well, but some gaps remain mainly in Sweden. RSL data follow the standardized HOLSEA format and, thus, are ready for spatially comprehensive applications in, e.g., glacial isostatic adjustment (GIA) modelling. We apply a SQL database system to store the nationally provided data sets in their individual form and to map the different input into the HOLSEA format as the information content of the individual data sets from the Baltic Sea area differs. About 80% of the RSL data is related to the last marine stage in Baltic Sea history after 8.5 ka BP (thousand years before present). These samples are grouped according to their dominant RSL tendencies into three clusters: regions with negative, positive and complex (transitional) RSL tendencies. Overall, regions with isostatic uplift driven negative tendencies dominate and show regression in the Baltic Sea basin during the last marine stage. Shifts from positive to negative tendencies in RSL data from transitional regions show a mid-Holocene highstand around 7.5-6.5 ka BP which is consistent with the end of the final melting of the Laurentide Ice Sheet. Comparisons of RSL data with GIA predictions including global ICE-5G and ICE-6G_C ice histories show good fit with RSL data from the regions with negative tendencies, whereas in the transitional areas in the eastern Baltic, predictions for the mid-Holocene clearly overestimate the RSL and fail to recover the midHolocene RSL highstand derived from the proxy reconstructions. These results motivate improvements of ice-sheet and Earth-structure models and show the potential and benefits of the new compilation for future studies. (C) 2021 The Authors. Published by Elsevier Ltd.
  •  
50.
  • Schenk, Frederik, et al. (author)
  • Floral evidence for high summer temperatures in southern Scandinavia during 15-11 cal ka BP
  • 2020
  • In: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 233
  • Journal article (peer-reviewed)abstract
    • The global climate transition from the Lateglacial to the Early Holocene is dominated by a rapid warming trend driven by an increase in orbital summer insolation over high northern latitudes and related feedbacks. The warming trend was interrupted by several abrupt shifts between colder (stadial) and warmer (interstadial) climate states following instabilities of the Atlantic Meridional Overturning Circulation (AMOC) in response to rapidly melting ice sheets. The sequence of abrupt shifts between extreme climate states had profound impacts on ecosystems which make it challenging to reliably quantify state variables like July temperatures within a non-analogue climate envelope. For Europe, there is increasing albeit inconclusive evidence for higher stadial summer temperatures than initially thought. Here we present a comprehensive floral compilation of plant macrofossils from lake sediment cores of 15 sites from S-Scandinavia covering the period similar to 15 to 11 ka BP. We find evidence for a continued presence of plant species indicating high July temperatures throughout the last deglaciation. The presence of hemiboreal plants in close vicinity to the southern margin of the Fennoscandian Ice Sheet implies a strong thermal summer forcing for the rapid ice sheet melt. Consistent with some recent studies, we do not find evidence for a general stadial summer cooling, which indicates that other reasons than summer temperatures caused drastic setbacks in proxy signals possibly driven by extreme winter cooling and/or shorter warm seasons.
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