Latest Research Papers

Our sources include The Journal of Quaternary Science (John Wiley & Sons Ltd) published on behalf of the QRA, The Boreas Collegium (John Wiley & Sons Ltd), Quaternary Science Reviews (Elsevier) and the Earth and Planetary Science News (Elsevier).

Latest Research Papers

Our sources include The Journal of Quaternary Science (John Wiley & Sons Ltd) published on behalf of the QRA, The Boreas Collegium (John Wiley & Sons Ltd), Quaternary Science Reviews (Elsevier) and the Earth and Planetary Science News (Elsevier).

A multiproxy record of the Younger Holsteinian Oscillation (YHO) in the Ossówka profile, eastern Poland

Jerzy Nitychoruk, Krzysztof Bińka, Elwira Sienkiewicz, Marcin Szymanek, Marta Chodyka, Michał Makos, Hans Ruppert, Alina Tudryn

19/02/2018

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The laminated lacustrine succession at Ossówka in eastern Poland, which is largely the equivalent of MIS 11c, is amongst the best-developed sites in Europe that cover this time period. Close inspection of the depth interval between 35.0 and 42.5 m in a 55-m-long core shows an environmental...

The laminated lacustrine succession at Ossówka in eastern Poland, which is largely the equivalent of MIS 11c, is amongst the best-developed sites in Europe that cover this time period. Close inspection of the depth interval between 35.0 and 42.5 m in a 55-m-long core shows an environmental crisis at a depth of 40.95 m that lasted approximately 800 years and resulted in almost complete extinction of fir (Abies) from the communities existing at that time. Geochemical analyses reveal a simultaneous increase in sulphur in the deposits and a change in stable carbon and oxygen isotope ratios towards higher values, as well as a significant increase in the thickness of the laminae (up to 5 mm). Diatom studies show a clear increase in benthic diatoms in this interval, implying a decrease in water level. However, the predominance of such forms was probably caused by the elimination of planktonic diatoms by invasive blooms of Tetraedron, rather than lower lake levels, evidence of which was not noted in the pollen spectra. Hence, all these changes in the lake may have been triggered by the destruction of fir trees, the gradual decomposition of dead trunks and some inconspicuous geomorphological disturbances caused by wind throw. They resulted in a supply of micronutrients to the basin, an increase in varve thickness and rapid oscillations in the abundance and composition of algae and changes in the geochemical status of the lake. Rapid and significant drops in winter temperatures appear to be responsible for the extinction of fir. Alternatively, late frost in spring or hot and dry summers may have affected microsporophyll growth and the fir physiology as known from extant Abies populations. This environmental crisis, which is termed the Younger Holsteinian Oscillation (YHO), is noted at only a few sites. At Dethlingen (Germany), where hornbeam communities disappear at that time, a drop in summer temperatures is suggested to have been the driving force. We suggest that, at Ossówka, a drop in winter temperatures, late frost, or summer drought at the very start of the YHO are possible causes of the near-extinction of fir.

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Early Holocene NW-W winds reconstructed from small dune fields, central Sweden

Martin Bernhardson, Helena Alexanderson

14/02/2018

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Five small dune fields were investigated in central Sweden in the field and by using LiDAR-based remote sensing. The chronology of the dunes was determined using optically stimulated luminescence (OSL) dating. Most of the OSL ages indicate dune formation close to the time of deglaciation in...

Five small dune fields were investigated in central Sweden in the field and by using LiDAR-based remote sensing. The chronology of the dunes was determined using optically stimulated luminescence (OSL) dating. Most of the OSL ages indicate dune formation close to the time of deglaciation in this area of Sweden (11–10 cal. ka BP) and later sand drift events appear to have been uncommon, suggesting that most of the dune fields have been stable since their formation and throughout the Holocene. This makes them a valuable archive of past sand drift events and palaeowind directions, even though the dune fields are small compared to most other investigated dune fields around the world. The dunes are primarily of a transverse or parabolic type, and their orientation suggests formation by westerly or northwesterly winds. The local topography appears to have had little control over the formation of the dunes, suggesting that the dunes can be used as a proxy of regional wind directions. All dune fields in this study are linked to glacifluvial deposits that provide spatially and volumetrically limited sources of sand.

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The Hilina Pali palaeomagnetic excursion and possible self-reversal in the loess from western Ukraine

Jerzy Nawrocki, Andriy Bogucki, Maria Łanczont, Tomasz Werner, Karol Standzikowski, Magdalena Pańczyk

12/02/2018

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A loess-palaeosol succession from the last glacial cycle was palaeomagnetically studied in the Rivne abandoned brickyard (western Ukraine). Two samples of undisturbed loess from the same depth of parallel sections display steep negative inclinations. These reversed directions in the loess dated...

A loess-palaeosol succession from the last glacial cycle was palaeomagnetically studied in the Rivne abandoned brickyard (western Ukraine). Two samples of undisturbed loess from the same depth of parallel sections display steep negative inclinations. These reversed directions in the loess dated at c. 18 ka may possibly be correlated with the Hilina Pali palaeomagnetic excursion. This is the first occurrence of the Hilina Pali in a loess sediment. Unfortunately, the loess with negative inclination does not form any continuous layer that could be suitable for studies of detailed features of geomagnetic field inversion. Another six samples from an illuvial horizon of the Holocene soil also showed negative inclinations and strongly deviated declinations. This part of the section does not represent, however, any palaeomagnetic excursion. The anomalous magnetization in maghemite- and titanomagnetite-rich sediment results most probably from self-reversal remagnetization. A new insight into palaeomagnetic excursions noted in loess, especially in its parts affected by pedogenic processes, is recommended.

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Active retreat of a Late Weichselian marine-terminating glacier: an example from Melasveit, western Iceland

Thorbjörg Sigfúsdóttir, Ívar Örn Benediktsson, Emrys Phillips

31/01/2018

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Large and complete glaciotectonic sequences formed by marine-terminating glaciers are rarely observed on land, hampering our understanding of the behaviour of such glaciers and the processes operating at their margins. During the Late Weichselian in western Iceland, an actively retreating...

Large and complete glaciotectonic sequences formed by marine-terminating glaciers are rarely observed on land, hampering our understanding of the behaviour of such glaciers and the processes operating at their margins. During the Late Weichselian in western Iceland, an actively retreating marine-terminating glacier resulted in the large-scale deformation of a sequence of glaciomarine sediments. Due to isostatic rebound since the deglaciation, these formations are now exposed in the coastal cliffs of Belgsholt and Melabakkar-Ásbakkar in the Melasveit district, and provide a detailed record of past glacier dynamics and the inter-relationships between glaciotectonic and sedimentary processes at the margin of this marine-terminating glacier. A comprehensive study of the sedimentology and glaciotectonic architecture of the coastal cliffs reveals a series of subaquatic moraines formed by a glacier advancing from Borgarfjörður to the north of the study area. Analyses of the style of deformation within each of the moraines demonstrate that they were primarily built up by ice-marginal/proglacial thrusting and folding of marine sediments, as well as deposition and subsequent deformation of ice-marginal subaquatic fans. The largest of the moraines exposed in the Melabakkar-Ásbakkar section is over 1.5 km wide and 30 m high and indicates the maximum extent of the Borgarfjörður glacier. Generally, the other moraines in the series become progressively younger towards the north, each designating an advance or stillstand position as the glacier oscillated during its overall northward retreat. During this active retreat, glaciomarine sediments rapidly accumulated in front of the glacier providing material for new moraines. As the glacier finally receded from the area, the depressions between the moraines were infilled by continued glaciomarine sedimentation. This study highlights the dynamics of marine-terminating glaciers and may have implications for the interpretation of their sedimentological and geomorphological records.

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The Holocene expansion of grassland in northern Europe reconstructed from molluscan assemblages

Salomé Granai, Nicole Limondin-Lozouet

30/01/2018

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From the synthesis of the malacological data collected from 12 sites in the large flood-plain of the Seine basin, three main environmental stages have been reconstructed. During the first half of the Holocene, forest environments are prevalent (Seine 1). As early as c. 6.5 cal. ka BP, the...

From the synthesis of the malacological data collected from 12 sites in the large flood-plain of the Seine basin, three main environmental stages have been reconstructed. During the first half of the Holocene, forest environments are prevalent (Seine 1). As early as c. 6.5 cal. ka BP, the first evidence of woodland clearance is observed (Seine 2) and, from c. 3.4 cal. ka BP, the lowlands were largely cleared of trees and are dominated by grassland (Seine 3). This three-stage development of environmental conditions is consistent with the environmental developments reconstructed from molluscan successions in England, Germany, Luxembourg, Switzerland, Poland, the Czech Republic and Slovakia. Our results highlight anthropogenic disturbance as the key factor in the openness of the Holocene landscape and pinpoint the period between c. 3.6 and c. 2.8 cal. ka BP as a transitional phase of this large-scale environmental change.

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A temporary glacier-surge ice-dammed lake, Braganzavågen, Svalbard

Astrid Lyså, Eiliv A. Larsen, Fredrik Høgaas, Maria A. Jensen, Martin Klug, Lena Rubensdotter, Witold Szczuciński

17/01/2018

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A prominent thrust-moraine system formed in the inner van Mijenfjorden, Svalbard, during a surge event in a tributary fjord, creating a large temporary lake. Based on geomorphological, sedimentological, stratigraphical and chronological data, the lake began to form shortly after 648–551 cal....

A prominent thrust-moraine system formed in the inner van Mijenfjorden, Svalbard, during a surge event in a tributary fjord, creating a large temporary lake. Based on geomorphological, sedimentological, stratigraphical and chronological data, the lake began to form shortly after 648–551 cal. a BP. At its maximum, the lake covered an estimated area of 77 km2 with a water volume of 1.2 km3. Lake sediment up to 80 cm thick was rapidly deposited on top of terrestrial and marine sediments. At its maximum extent, the short-lived lake was the largest of any known Holocene lake in Svalbard. Modern river discharge would fill the lake to its highest shoreline at 23 m a.s.l. in only one season. Drainage was stepwise, as evidenced by four shorelines and abandoned drainage channels. This study has taken advantage of a unique suite of data available for such an ice-dammed lake. The results demonstrate the power of a multidisciplinary approach for recognizing lake events in the geological record, which is essential given the low preservation potential of such sediments.

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A pre-LGM sandur at Fiskarheden in NW Dalarna, central Sweden – sedimentology and glaciotectonic deformation

Anne-Cécile Flindt, Ívar Örn Benediktsson, Helena Alexanderson, Per Möller

11/01/2018

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The Fiskarheden quarry, situated in NW Dalarna, central Sweden, reveals thick coarse-grained sediments of Scott type facies association representing a sandur deposited in an ice-proximal proglacial environment. Optically Stimulated Luminescence (OSL) dating of the sandur sediments suggests a...

The Fiskarheden quarry, situated in NW Dalarna, central Sweden, reveals thick coarse-grained sediments of Scott type facies association representing a sandur deposited in an ice-proximal proglacial environment. Optically Stimulated Luminescence (OSL) dating of the sandur sediments suggests a pre-Last Glacial Maximum (LGM) age. Most acquired ages are pre-Saalian (>200 ka) and we regard each of these ages to represent non/poorly bleached sediment except for one small-aliquot OSL age of 98±6 ka. This age comes from the top surface of an arguably well-bleached sand bed deposited on the lee-side of a braid-bar, putting the sandur build-up into the Early Weichselian. Large-scale glaciotectonic structures show an imbricate thrust fan involving both ductile and brittle deformation. The deformation was from the WNW, which largely coincides with the formative trend of the predominating streamlined terrain and Rogen moraine tracts surrounding Fiskarheden. It is suggested that the deformation of the sandur sediments took place when the advancing glacier approached and pushed its own proglacial outwash sediment, during an ice-marginal oscillation either at the inception of one of the Early Weichselian glaciations in the area, or during a general ice retreat amid a deglacial phase. The Fiskarheden sandur deposits are covered by a subglacial traction till deposited from the NE/NNE. This direction corresponds with younger streamlined terrain flowsets cross-cutting the older NNW–SSE system and probably represents deglaciation in the area following the LGM. This study will add to the understanding of the formation and deformation of Pleistocene sandur successions and their relationship to past ice-sheet behaviour.

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Chronostratigraphy and spatial distribution of magnetic sediments in the Chukchi and Beaufort seas since the last deglaciation

Charles-Edouard Deschamps, Guillaume St-Onge, Jean-Carlos Montero-Serrano, Leonid Polyak

12/12/2017

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Palaeomagnetic investigation of three sediment cores from the Chukchi and Beaufort Sea margins was performed to better constrain the regional chronostratigraphy and to gain insights into sediment magnetic properties at the North American Arctic margin during the Holocene and the preceding...

Palaeomagnetic investigation of three sediment cores from the Chukchi and Beaufort Sea margins was performed to better constrain the regional chronostratigraphy and to gain insights into sediment magnetic properties at the North American Arctic margin during the Holocene and the preceding deglaciation. Palaeomagnetic analyses reveal that the sediments under study are characterized by low-coercivity ferrimagnetic minerals (magnetite), mostly in the pseudo-single domain grain-size range, and by a strong, stable, well-defined remanent magnetization (MAD <5°). Age models for these sediment cores were constrained by comparing their palaeomagnetic secular variations (inclination, declination and relative palaeointensity) with previously published and independently dated sedimentary marine records from the study area. The magnetostratigraphical age models were verified by AMS radiocarbon dating tie points, tephrochronology and 210Pb-based sedimentation rate estimate. The analysed cores 01JPC, 03PC and 02PC span c. 6000, 10 500 and 13 500 cal. a BP, respectively. The estimated sedimentation rates were stable and relatively high since the deglaciation in cores 01JPC (60 cm ka−1) and 03PC (40–70 cm ka−1). Core 02PC shows much lower Holocene sedimentation rates with a strong decrease after the deglaciation from ~60 to 10–20 cm ka−1. Overall, this study illustrates the usefulness of palaeomagnetism to improve the dating of late Quaternary sedimentary records in the Arctic Ocean.

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Late Pleistocene and early Holocene drainage events in the eastern Fehmarn Belt and Mecklenburg Bight, SW Baltic Sea

Christoph Heinrich, Sarah Anders, Klaus Schwarzer

11/12/2017

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The Fehmarn Belt is a key area for the Late Pleistocene and Holocene development of the Baltic Sea as it was a passage for marine and fresh water during its different stages. The pre-Holocene geological development of this area is presented based on the analysis of seismic profiles and...

The Fehmarn Belt is a key area for the Late Pleistocene and Holocene development of the Baltic Sea as it was a passage for marine and fresh water during its different stages. The pre-Holocene geological development of this area is presented based on the analysis of seismic profiles and sedimentary gravity cores. Late Pleistocene varve sediments of the initial Baltic Ice Lake were identified. An exceptionally thick varve layer, overlain by a section of thinner varves with convolute bedding in turn covered by undisturbed varves with decreasing thicknesses is found in the Fehmarn Belt. This succession, along with a change in varve geochemistry, represents a rapid ice-sheet withdrawal and increasingly distal sedimentation in front of the ice margin. Two erosional unconformities are observed in the eastern Mecklenburg Bight, one marking the top of the initial Baltic Ice Lake deposits and the second one indicating the end of the final Baltic Ice Lake. These unconformities join in Fehmarn Belt, where deposits of the final Baltic Ice Lake are missing due to an erosional hiatus related to a lake-level drop during its final drainage. After this lake-level drop, a lowstand environment represented by river deposits developed. These deposits are covered by lake marls of Yoldia age. Tilting of the early glacial lake sediments indicates a period of vertical movements prior to the onset of the Holocene. Deposits of the earliest stages of the Baltic Sea have been exposed by ongoing erosion in the Fehmarn Belt at the transition to the Mecklenburg Bight.

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Late Quaternary landscape evolution in a region of stable postglacial relative sea levels, British Columbia central coast, Canada

Jordan B. R. Eamer, Daniel H. Shugar, Ian J. Walker, Christina M. Neudorf, Olav B. Lian, Jennifer L. Eamer, Jordan Bryce, Libby Biln

07/12/2017

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After retreat of the Cordilleran Ice Sheet (CIS) and subsequent glacio-isostatic adjustment of the central coast of British Columbia (BC), Canada, a complex coastline emerged as relative sea level rapidly reached equilibrium and maintained stability over the end of the Late Pleistocene and...

After retreat of the Cordilleran Ice Sheet (CIS) and subsequent glacio-isostatic adjustment of the central coast of British Columbia (BC), Canada, a complex coastline emerged as relative sea level rapidly reached equilibrium and maintained stability over the end of the Late Pleistocene and Holocene. This study provides a late Quaternary reconstruction of the landscape evolution of a geographically distinct location on the central BC coast, northwest Calvert Island, which experienced a re-advance of the CIS near the end of the Late Pleistocene and minimal subsequent relative sea-level change. Geomorphological observations from LiDAR imagery, sedimentological and palaeoecological evidence from exposures, cores and shovel pits, and a robust luminescence and 14C-based chronology spanning the last 15 000 years are used to reconstruct the landscape of northwest Calvert Island following CIS retreat. A single-aliquot regenerative dose protocol that was developed specifically for luminescence dating of the sediments on Calvert Island was utilized in this study. Localized proglacial sedimentation was linked to the glacial re-advance experienced at the end of the Late Pleistocene. Extensive coastal reconfiguration (e.g. rapid shoreline progradation of >1 m a−1) occurred in the absence of extensive RSL change, which was the main driver of coastal change elsewhere along the BC coast. Changes in climate, small magnitude changes in RSL, and fire all probably played a role in isolated aeolian landform development and stabilization in the study area. An important contribution of this study is the documentation of the multi-disciplinary approach for reconstructing palaeogeography, using multiple geochronological methods, micro- and macro-sedimentology, the palaeoecology inferred from both macro and microfossils (e.g. diatoms and foraminifers), stratigraphy, field mapping and remote sensing. In addition, these findings inform our understanding of the drivers of coastal sedimentary processes, particularly in the temperate coastal rainforest region of BC, and the role that fire may play in those processes. Coastal palaeogeography studies in the region will become increasingly important as discoveries of Late Pleistocene human habitation along the coastal migration route continue to be documented.

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Spatial analysis of cirques from three regions of Iceland: implications for cirque formation and palaeoclimate

Heather A. Ipsen, Sarah M. Principato, Rachael E. Grube, Jessica F. Lee

21/11/2017

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This study is a quantitative analysis of cirques in three regions of Iceland: Tröllaskagi, the East Fjords and Vestfirðir. Using Google Earth and the National Land Survey of Iceland Map Viewer, we identified 347 new cirques on Tröllaskagi and the East Fjords region, and combined these data...

This study is a quantitative analysis of cirques in three regions of Iceland: Tröllaskagi, the East Fjords and Vestfirðir. Using Google Earth and the National Land Survey of Iceland Map Viewer, we identified 347 new cirques on Tröllaskagi and the East Fjords region, and combined these data with 100 cirques previously identified on Vestfirðir. We used ArcGIS to measure length, width, aspect, latitude and distance to coastline of each cirque. Palaeo-equilibrium-line altitudes (palaeo-ELAs) of palaeo-cirque glaciers were calculated using the altitude-ratio method, cirque-floor method and minimum-point method. The mean palaeo-ELA values in Tröllaskagi, the East Fjords and Vestfirðir are 788, 643 and 408 m a.s.l, respectively. Interpolation maps of palaeo-ELAs demonstrate a positive relationship between palaeo-ELA and distance to coastline. A positive relationship between palaeo-ELA and latitude is observed on Vestfirðir, a negative relationship is observed on Tröllaskagi and no statistically significant relationship is present on the East Fjords. The modal orientation of cirques on Tröllaskagi and Vestfirðir is northeast, while orientation of cirques in the East Fjords is north. Palaeo-wind reconstructions for the LGM show that modal aspect is aligned with the prevailing north-northeast wind directions, although aspect measurements demonstrate wide dispersion. Cirque length is similar on Tröllaskagi and the East Fjords, but cirques are approximately 200 m shorter in Vestfirðir. Cirque widths are similar in all three regions. Comparisons with a global data set show that cirques in Iceland are smaller and more circular than cirques in other regions of the world. Similar to glaciers in Norway and Kamchatka, our results demonstrate that access to a moisture source is a key parameter in determining palaeo-ELAs in Iceland. Temperatures interpreted from palaeo-ELA depressions suggest that these cirques may have been glaciated as recently as the Little Ice Age.

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Re-assessment of the age and depositional origin of the Paviland Moraine, Gower, south Wales, UK

Richard A. Shakesby, John F. Hiemstra, Bernd Kulessa, Adrian J. Luckman

17/11/2017

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The Bristol Channel, including onshore areas, is critical for reconstructing Pleistocene glacial limits in southwest Britain. Debate about the precise regional southern limits of Devensian (Oxygen Isotope Stage (OIS) 2) and Anglian (OIS 12) glaciations has recently been rekindled. The Paviland...

The Bristol Channel, including onshore areas, is critical for reconstructing Pleistocene glacial limits in southwest Britain. Debate about the precise regional southern limits of Devensian (Oxygen Isotope Stage (OIS) 2) and Anglian (OIS 12) glaciations has recently been rekindled. The Paviland Moraine (Llanddewi Formation), Gower, south Wales is conventionally regarded as Anglian in age. Its ‘old’ age has been based on reported highly weathered clasts, a subdued morphology and ‘field relationships’ to fossil beach sediments of now disputed age(s). Relatively little about its sedimentary characteristics has been previously published. This paper: (i) presents new sedimentological evidence including lithofacies analysis, XRF analysis and electrical resistivity tomography (ERT) of sediment cores and electrical resistivity of a tied 3D field grid; (ii) re-assesses the proposed ‘old’ age; (iii) suggests a likely depositional origin; and (iv) discusses implications for regional glacial dynamics and future research priorities. The sediments comprise mostly dipping glacigenic diamict units containing mainly Welsh Coalfield erratics. The location and subdued moraine morphology are attributed to the hydrological influence of the underlying limestone, the local topography and ice-sheet behaviour rather than to long-term degradation. Moraine formation is attributed mainly to sediment gravity flows that coalesced to produce an ice-frontal apron. Neither geochemical data nor clasts indicate prolonged subaerial weathering and in-situ moraine sediments are restricted to a limestone plateau above and inland of fossil beach sediments. We recommend rejecting the view that the moraine represents the only recognized OIS 12 deposit in Wales and conclude that instead it marks the limit of relatively thin Last Glacial Maximum (LGM) ice in west Gower. This requires revision of the accepted view of a more restricted LGM limit in the area. We suggest that substrate hydrological conditions may be a more influential factor in moraine location and form than is currently acknowledged.

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Chronology of a lacustrine core from Lake Linggo Co using a combination of OSL, 14C and 210Pb dating: implications for the dating of lacustrine sediments from the Tibetan Plateau

Gang Hu, Chaolu Yi, Jiafu Zhang, Guirong Cao, Baolin Pan, Jinhua Liu, Tao Jiang, Shuangwen Yi, Dehong Li, Jianwei Huang

15/11/2017

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Vast palaeolakes once occupied the Qinghai-Tibetan Plateau (TP). Analyses of the sedimentary records of these lakes could potentially provide an extensive dating archive. Many previously constructed age-depth models simulating lacustrine cores have been principally based on radiocarbon (14C)...

Vast palaeolakes once occupied the Qinghai-Tibetan Plateau (TP). Analyses of the sedimentary records of these lakes could potentially provide an extensive dating archive. Many previously constructed age-depth models simulating lacustrine cores have been principally based on radiocarbon (14C) dating. However, such dating could have been hampered by the so-called ‘lake reservoir effect’ (LRE) and the reworking of lakebed sediments, resulting in inaccurate 14C age-depth models and limiting interpretations of existing lacustrine palaeoclimatic records. Lake Linggo Co is located on the central TP, in one of the coldest and most arid regions of Tibet. We dated a 9.87-m-long lacustrine core extracted from the lakebed at a water depth of ~60 m using a combination of 210Pb, 14C and optically stimulated luminescence (OSL) techniques. Some 14C ages showed significant age reversals; all the 14C ages were much older than the 210Pb and OSL ages for the same depths. This could possibly be attributed to the presence of old, inherited carbon, causing the inherited 14C age to appear unstable during the deposition period. The 210Pb and OSL ages were roughly concordant, and were also consistent with the stratigraphical succession. We therefore suggest that 14C dating may, on its own, be inadequate for accurate dating of lacustrine sediment sites on the TP, and that the OSL method should also be applied in order to evaluate the reliability of any 14C ages. With this approach, we constructed an age-depth model, revealing sedimentation rates of 1.7, 0.8, 6.8 and 0.6 mm a−1 between 0–1.9, 1.9–4.2, 4.2–4.4 and 4.4–9.4 ka, respectively.

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Provenance signatures and changes of the southwestern sector of the Barents Ice Sheet during the last deglaciation

Ekaterina Kaparulina, Juho Junttila, Kari Strand, Juha P. Lunkka

07/11/2017

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Southwestern Barents Sea sediments contain important information on Lateglacial and Holocene environmental development of the area, i.e. sediment provenance characteristics related to ice-flow patterns and ice drifting from different regional sectors. In this study, we present investigations of...

Southwestern Barents Sea sediments contain important information on Lateglacial and Holocene environmental development of the area, i.e. sediment provenance characteristics related to ice-flow patterns and ice drifting from different regional sectors. In this study, we present investigations of clay, heavy minerals, and ice-rafted debris from three sediment cores obtained from the SW Barents Sea. The sediments studied are subglacial/glaciomarine to marine in origin. The core sequences were divided into three lithostratigraphical units. The lowest, Unit 3, consists of laminated glaciomarine sediments related to regional deglaciation. The overlying Unit 2 is a diamicton, dominated by mud and oversized clasts. Unit 2 reflects a more ice-proximal glaciomarine sedimentary environment or even a subglacial depositional environment; its deposition may indicate a glacial re-advance or stillstand during an overall retreat. The uppermost Unit 1 consists of Holocene marine sediments and current-reworked sedimentary material with a relatively high carbonate content. A significant proportion of the sedimentary material could be derived from Svalbard and transported by sea ice or icebergs to the Barents Sea during the late deglacial phase. The Fennoscandian sources and local Mesozoic strata from the bottom of the Barents Sea are the likely provenances of sediments deposited during the deglacial and ice re-advance phases. Bottom currents and sea-ice transport were the main mechanisms influencing sedimentation during the Holocene. Our results indicate that the provenance areas can be reliably related to certain ice-flow sectors and transport mechanisms in the deglaciated Barents Sea.

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Tunnel valley deposits from the southern North Sea – material provenance and depositional processes

Antonio Benvenuti, Branimir Šegvić, Andrea Moscariello

26/10/2017

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This study offers new insights into the origin and depositional history of the mixture of sediments infilling one of the largest offshore, northward-orientated, clinoform-structured, tunnel valleys (TVs) of Elsterian age in the southern North Sea (SNS). Specifically, the study sheds light on...

This study offers new insights into the origin and depositional history of the mixture of sediments infilling one of the largest offshore, northward-orientated, clinoform-structured, tunnel valleys (TVs) of Elsterian age in the southern North Sea (SNS). Specifically, the study sheds light on the provenance of TV deposits based on K-Ar dating of illite, QEMSCAN® heavy mineral assemblage study, and U-Pb and fission track dating on single grains of apatite. Early Pleistocene substrate and the TV infill demonstrate provenance from the Scandinavian and Baltic realms as well as from Renish central Europe and the Alps. Prior to Elsterian glaciation fluvial transport to the SNS increasingly switched from Baltic sources to a more central European influence. However, based on similar provenance of both the substrate and TV infill, the episode of subglacial tunnel valley formation interrupted this central European influence. Glacial erosional processes associated with the expansion of the Elsterian ice sheet to the SNS reworked a large amount of sediment from the Early Pleistocene deposits of the SNS. The sediment was eventually deposited as the tunnel valley infill. Taking into account a high uncertainty related to the facies of TV sedimentary infill, which thus far has been inferred from seismic reflection surveys only, this study offers the first comprehensive set of data on the composition and provenance of the offshore Elsterian TV sediment.

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Carbon accumulation in Dahu Swamp in the eastern Nanling Mountains (south China) and its implications for hydroclimatic variability over the past 47 000 years

Zhiqiang Wei, Wei Zhong, Shengtan Shang, Jibin Xue, Jun Ouyang, Chan Zhu, Lixue Tian, Yu Chen, Bin Chen

25/10/2017

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Wetlands act as persistent natural carbon sinks over long time scales. Understanding the response of these carbon reservoirs to climate change is critical to assessing potential climate feedbacks. We conducted a study of an 860-cm-long sediment core in Dahu Swamp in south China to determine how...

Wetlands act as persistent natural carbon sinks over long time scales. Understanding the response of these carbon reservoirs to climate change is critical to assessing potential climate feedbacks. We conducted a study of an 860-cm-long sediment core in Dahu Swamp in south China to determine how the carbon accumulation rate (CAR) has varied as a function of palaeohydrology and palaeoclimate over the past 47 000 years. From an orbital time scale, our results show that the CAR in Dahu Swamp is relatively low in the wet periods of Marine Isotope Stage 3 (MIS 3) (mean: 46.7 gC m−2 a−1) and MIS 1 (mean: 28.2 gC m−2 a−1), compared to the dry periods of MIS 2 (mean: 59.9 gC m−2 a−1). At centennial and millennial scales, the highest CARs of Dahu Swamp mainly occur in organic-rich silt or clay (gyttja) layers, which correspond to the relatively dry climate (e.g. c. 48 000–41 000, c. 33 000–32 000, c. 15 800–14 900 and c. 4400–4250 cal. a BP). The CAR of Dahu Swamp is mainly controlled by local hydrological variations that are closely related to the East Asian summer monsoon (EASM) intensity, which may be co-influenced by orbitally induced summer insolation forcing and internal feedback processes (e.g. Atlantic Meridional Overturning Circulation and El Niño/Southern Oscillation). Based on comparison with the CARs in monsoonal regions of China, we consider that precipitation may be the key factor for wetland CAR in EASM areas, whereas temperature is more important in Qinghai–Tibetan Plateau regions under Indian summer monsoon influence. The CAR of Dahu Swamp provides valuable records of wetland carbon accumulation dynamics in subtropical monsoon regions, which contradict the traditional patterns in global northern wetlands.

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Late Holocene stable isotopic (δ13C and δ15N) records of lacustrine organic matter in Guangdong Province, south China, and their palaeoenvironmental implications

Wei Zhong, Zhiqiang Wei, Shengtan Shang, Yu Chen, Susu Ye, Xiaowen Tang, Chan Zhu, Jun Ouyang, Jibin Xue

23/10/2017

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This study presents the results of TOC/TN (C/N) ratio, δ13C and δ15N analyses of lake sedimentary organic matter (OM) from the Hedong section, western Guangdong Province in south China, with the objective to reveal the history of hydrological and ecological variations in the region influenced...

This study presents the results of TOC/TN (C/N) ratio, δ13C and δ15N analyses of lake sedimentary organic matter (OM) from the Hedong section, western Guangdong Province in south China, with the objective to reveal the history of hydrological and ecological variations in the region influenced by both the Indian summer monsoon (ISM) and East Asian summer monsoon (EASM). Variations in δ13C and δ15N of sedimentary OM may be closely related to past climatic conditions, which results in variations in surface runoff, lake level, allochthonous and autochthonous sources of OM, and lake productivity. Based on the interpretation of these proxies, four periods, i.e. 4370–4100, 3700–2900, 2400–2100 and 1900–900 cal. a BP, are characterized by low lake level, weakened surface runoff and deteriorated status of terrestrial and aquatic ecosystems, whereas the periods 4100–3700, 2900–2400, 2100–1900 and 900–600 cal. a BP are dominated by high lake level, strengthened surface runoff, and flourishing terrestrial and aquatic plants. A remarkable positive correlation between the δ13C values of the section and the ENSO number record obtained from the tropical Pacific implies that the impact of the ISM is greater than that of the EASM in the study area. The abnormal correspondence between the δ13C and solar activity reconstructed from 10Be and 14C records in GRIP ice-core occurred from 1500–800 and particularly from 4200–4000 cal. a BP, suggesting that these two cool and dry intervals may be caused by stronger volcanic activities that are recorded in the GISP2 and Dome C ice-cores. This study reveals that changes in solar insolation and solar activity, as well as changes in oceanic–atmospheric circulation (e.g. the ENSO intensity) and intensive volcano eruptions may have exerted influence on late Holocene climate variability in the study area.

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Holocene permafrost history and cryostratigraphy in the High-Arctic Adventdalen Valley, central Svalbard

Stefanie Cable, Bo Elberling, Aart Kroon

20/10/2017

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This paper presents the history and cryostratigraphy of the upper permafrost in the High-Arctic Adventdalen Valley, central Svalbard. Nineteen frozen sediment cores, up to 10.7 m long, obtained at five periglacial landforms, were analysed for cryostructures, ice, carbon and solute contents,...

This paper presents the history and cryostratigraphy of the upper permafrost in the High-Arctic Adventdalen Valley, central Svalbard. Nineteen frozen sediment cores, up to 10.7 m long, obtained at five periglacial landforms, were analysed for cryostructures, ice, carbon and solute contents, and grain-size distribution, and were 14C- and OSL-dated. Spatial variability in ice and carbon contents is closely related to the sedimentary history and mode of permafrost aggradation. In the valley bottom, saline epigenetic permafrost with pore ice down to depths of 10.7 m depth formed in deltaic sediments since the mid-Holocene; cryopegs were encountered below 6 m. In the top 1 to 5 m, syngenetic and quasi-syngenetic permafrost with microlenticular, lenticular, suspended and organic-matrix cryostructures developed due to loess and alluvial sedimentation since the colder late Holocene, which resulted in the burial of organic material. At the transition between deltaic sediments and loess, massive ice bodies occurred. A pingo developed where the deltaic sediments reached the surface. On hillslopes, suspended cryostructure on solifluction sheets indicates quasi-syngenetic permafrost aggradation; lobes, in contrast, were ice-poor. Suspended cryostructure in eluvial deposits reflects epigenetic or quasi-syngenetic permafrost formation on a weathered bedrock plateau. Landform-scale spatial variations in ground ice and carbon relate to variations in slope, sedimentation rate, moisture conditions and stratigraphy. Although the study reveals close links between Holocene landscape evolution and permafrost history, our results emphasize a large uncertainty in using terrain surface indicators to infer ground-ice contents and upscale from core to landform scale in mountainous permafrost landscapes.

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A chronology of environmental changes in the Lake Vättern basin from deglaciation to its final isolation

Henrik Swärd, Matt O'Regan, Svante Björck, Sarah L. Greenwood, Malin E. Kylander, Carl-Magnus Mörth, Christof Pearce, Martin Jakobsson

20/10/2017

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During and after deglaciation, Lake Vättern developed from a proglacial lake situated at the westernmost rim of the Baltic Ice Lake (BIL), into a brackish water body connecting the North Sea and the Baltic Sea, and finally into an isolated freshwater lake. Here we present geochemical and...

During and after deglaciation, Lake Vättern developed from a proglacial lake situated at the westernmost rim of the Baltic Ice Lake (BIL), into a brackish water body connecting the North Sea and the Baltic Sea, and finally into an isolated freshwater lake. Here we present geochemical and mineralogical data from a 70-m composite sediment core recovered in southern Lake Vättern. Together with a radiocarbon age model of this core, we are able to delineate the character and timing of the different lake stages. In addition to a common mineralogical background signature seen throughout the sediment core, the proglacial sediments bear a calcite imprint representing ice-sheet transported material from the limestone bedrock that borders the lake basin in the northeast. The proglacial fresh to brackish water transition is dated to 11 480±290 cal. a BP and is in close agreement with other regional chronologies. The brackish period lasted c. 300 years and was followed by a c. 1600 year freshwater period before the Vättern basin became isolated from the Initial Littorina Sea. Decreasing detrital input, increasing δ13C values and the appearance of diatoms in the upper 15 m of the sediment succession are interpreted as an overall increase in biological productivity. This mode of sedimentation continues until the present and is interpreted to mark the final isolation of the lake at 9530±50 cal. a BP. Consequently, the isolation of Lake Vättern was not an outcome of the Ancylus Lake regression, but rather because of ongoing continental uplift in the early Littorina period.

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Perspective of landscape change following early settlement (landnám) in Svalbarðstunga, northeastern Iceland

Natasha Roy, James Woollett, Najat Bhiry, Guillaume Haemmerli, Véronique Forbes, Reinhard Pienitz

20/10/2017

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A series of peat monoliths was collected from Hjálmarvík, Kúðá and Bægístaðir, three abandoned farm sites located on a transect extending from the coast to 18 km inland in the Svalbarðstunga region (northeastern Iceland) in order to document the impact of human occupation and patterns...

A series of peat monoliths was collected from Hjálmarvík, Kúðá and Bægístaðir, three abandoned farm sites located on a transect extending from the coast to 18 km inland in the Svalbarðstunga region (northeastern Iceland) in order to document the impact of human occupation and patterns of land use on landscape change and vegetation. Svalbarðstunga is of considerable interest because of the geographical and ecological features that distinguish it from other regions of Iceland, in particular by the more direct influence of the cold East Greenland Current (EGC). Plant and insect macrofossils and diatoms identified in peat monoliths provided proxy indicators of human settlement and land use that in some cases corroborate, and in others expand upon, existing archaeological and historical dates. Based on the presence of ecofacts (calcined bones, fish bones and charcoal), synanthropic insects and some anthropogenic plant-indicators (e.g. weeds), we showed that there was a consistent occupation and use of the coastal site of Hjálmarvík since AD 970. At Kúðá, the scenario is quite different. Two periods of occupation or land use were identified: from prior to c. AD 960 to 1190 and from c. AD 1650 to 1870. In the 15th and into the 16th centuries, the decrease in the deposition of traces of fuel wastes around the inland farm sites (Kúðá and Bægístaðir) suggests that they were used much less frequently. The decline of such proxies for human occupation occurred shortly before the occurrence of the coldest conditions from the 16th to the 17th centuries as well as prior to the V1477 eruption, suggesting that these natural factors may not have been the primary or unique driver of changing modes of tenancy. A scenario of famine-related depopulation would have played a significant role in this decrease in the human impact on vegetation.

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Mid-Holocene frozen ground in China from PMIP3 simulations

Yeyi Liu, Dabang Jiang

05/10/2017

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Extensive degradation of frozen ground in the mid-Holocene is widely assumed on the basis of sparse proxy data. Here, the simulated soil temperature from the Paleoclimate Modelling Intercomparison Project Phase 3 is used to address this issue over China. By comparing with the results of a...

Extensive degradation of frozen ground in the mid-Holocene is widely assumed on the basis of sparse proxy data. Here, the simulated soil temperature from the Paleoclimate Modelling Intercomparison Project Phase 3 is used to address this issue over China. By comparing with the results of a preindustrial (0 ka, baseline) simulation, we show that frozen ground in the mid-Holocene (6 ka) simulation is degraded mainly in northeast China and on the northern Tibetan Plateau. The change follows closely orbitally induced variations in insolation. Quantitatively, permafrost area reduces by 0.02×106 km2 in northeast China in response to an orbitally induced increase in boreal summer insolation but increases by 0.08×106 km2 on the southern Tibetan Plateau due to local summer cooling. Changing values of active layer thickness vary greatly amongst different locations. On average, they are 3 and 4 cm thicker than the preindustrial values in northeast China and on the Tibetan Plateau, respectively. No degradation in seasonally frozen ground is detected over China as a whole. Regionally, its coverage increases by 0.21×106 km2 near the middle and lower reaches of the Yangtze River valley. In addition, the maximum depth of seasonal frost penetration is on average 8.5 cm deeper than preindustrial values due to widespread winter cooling. The changes in frozen ground are consistent amongst models. However, the models disagree with proxy data in terms of not only the changes in frozen ground but also climate. Further modelling improvements and adequate proxy data are both needed to fill in the gaps between models and the data in our knowledge of the mid-Holocene frozen ground.

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Phytolith reference study for identifying vegetation changes in the forest−grassland region of northeast China

Guizai Gao, Dongmei Jie, Yong Wang, Lidan Liu, Hongyan Liu, Dehui Li, Nannan Li, Jichen Shi, Chengcheng Leng

18/09/2017

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To provide a basis for tracing changes in vegetation and tree cover density, we studied the phytoliths of 129 common temperate plant species, and extracted the phytoliths from 75 surface soil samples from sites in grassland, forest−grassland ecotone and forest habitats in northeast China....

To provide a basis for tracing changes in vegetation and tree cover density, we studied the phytoliths of 129 common temperate plant species, and extracted the phytoliths from 75 surface soil samples from sites in grassland, forest−grassland ecotone and forest habitats in northeast China. From the analysis of shapes and morphological parameters of the plant samples, we developed a reference data set of herbaceous and woody phytoliths, and subsequently identified 21 herbaceous and 13 woody phytolith types in the surface soil samples. To test the reliability of soil phytolith analysis for distinguishing forest, grassland and the forest−grassland ecotone, we used principal components analysis (PCA) and discriminant analysis (DA) to summarize the soil phytolith assemblage characteristics of the different ecosystems. The results show that the grassland and forest samples are characterized by abundant herbaceous and woody phytoliths, respectively; and that forest−grassland ecotone habitats are characterized by low abundances of blocky polyhedral, multifaceted epidermal and sclereid phytoliths. In general, the surface soil phytolith assemblages can reliably differentiate samples from forest, grassland and the forest−grassland ecotone, with up to 92% of the samples classified correctly. We also tested the reliability of phytolith indices (W/G (1), W/G (2), W/G (3)) for discriminating different vegetation types in our study area, and found that W/G (2) was the most reliable index and corresponded well with the species inventory data. The W/G values for grassland ranged from 0 to 0.3, from 0.3 to 0.6 for the forest−grassland ecotone, and exceeded 0.6 for forest. We conclude that our study provides reliable analogues for phytolith assemblages from palaeoecological contexts, which can be used to reconstruct shifts in forest−grassland ecotones and vegetation succession in temperate areas.

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Palaeoceanographic evolution of the SW Svalbard shelf over the last 14 000 years

Maciej M. Telesiński, Joanna E. Przytarska, Beata Sternal, Matthias Forwick, Witold Szczuciński, Magdalena Łącka, Marek Zajączkowski

18/09/2017

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The palaeoceanographic evolution of the SW Svalbard shelf west of Hornsund over the last 14 000 years was reconstructed using benthic foraminiferal assemblages, stable oxygen and carbon isotopes, and grain-size and ice-rafted debris data. The results reveal the complexity of the feedbacks...

The palaeoceanographic evolution of the SW Svalbard shelf west of Hornsund over the last 14 000 years was reconstructed using benthic foraminiferal assemblages, stable oxygen and carbon isotopes, and grain-size and ice-rafted debris data. The results reveal the complexity of the feedbacks influencing the shelf environment: the inflow of Atlantic and Arctic waters (AW and ArW, respectively), and the influence of sea ice and tidewater glaciers. The inflow of subsurface AW onto the shelf gradually increased with the first major intrusion at the end of the Bølling-Allerød. During the Younger Dryas, the shelf was affected by fresh water originating from sea ice and glacier discharge. Glaciomarine conditions prevailed until the earliest Holocene with the intense deliveries of icebergs and meltwater from retreating glaciers and the occasional penetration of AW onto the shelf. Other major intrusions of AW occurred before and after the Preboreal oscillation (early Holocene), which resulted in more dynamic and open-water conditions. Between 10.5 and 9.7 cal. ka BP, the shelf environment transformed from glaciomarine to open marine conditions. Between c. 9.7 and 6.1 cal. ka BP the AW advection reached its maximum, resulting in a highly dynamic and productive environment. At c. 6.1 cal. ka BP, the inflow of AW onto the Svalbard shelf decreased due to the intensification of the Greenland Gyre and the subduction of AW under the sea-ice-bearing ArW. Bioproductivity decreased over the next c. 5500 years. During the Little Ice Age, bioproductivity increased due to favourable conditions in the marginal sea-ice zone despite the effects of cooling. The renewed advection of AW after AD 1850 started the climate warming trend observed presently. Our findings show that δ18O can be used to reconstruct the dominances of different water-masses and, with some caution, as a proxy for the presence of sea ice in frontal areas over the northwestern Eurasian shelves.

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Elemental geochemistry of freshwater snail shells: palaeolimnology of a Holsteinian (MIS 11) deposit from eastern Poland

Marcin Szymanek

18/09/2017

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The elemental shell chemistry of two freshwater snails, Viviparus diluvianus (Kunth) and Valvata piscinalis (Müller) was studied for palaeoenvironmental purposes. The shells were collected from lake sediments from five Holsteinian (Marine Isotope Stage 11) sites in eastern Poland (Ossówka,...

The elemental shell chemistry of two freshwater snails, Viviparus diluvianus (Kunth) and Valvata piscinalis (Müller) was studied for palaeoenvironmental purposes. The shells were collected from lake sediments from five Holsteinian (Marine Isotope Stage 11) sites in eastern Poland (Ossówka, Hrud II, Roskosz, Ortel Królewski and Szymanowo) and analysed for Ca, Mg, Sr, Mn and Fe. The Fe/Mn molar ratio was used as a redox indicator, with lower values (and high Mn concentrations) pointing to suboxic conditions. These occurred in the beginning of the Taxus zone and during the transition between the Taxus and Pinus-Larix zones at Ortel Królewski, and in the Holsteinian thermal maximum (Carpinus-Abies zone) at Roskosz Lake. Strongly reducing conditions, indicated by increased Fe and Fe/Mn values, prevailed at Ortel Królewski palaeolake in the middle of the Taxus zone, in the Pinus-Larix zone and in the upper part of the Roskosz sequence. Indicators of anoxia correlate with eutrophic conditions, enhanced productivity and oxygen consumption due to organic matter decay. The most distinct environmental changes in the records are comparable to other central and northern European records and to the main climatic oscillations during the Holsteinian, inferred from palynological, malacological and isotopic data.

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Holocene environmental history of the Ångermanälven Estuary, northern Baltic Sea

Jonathan P. Warnock, Thorsten Bauersachs, Ulrich Kotthoff, Hauke-Tom Brandt, Elinor Andrén

12/09/2017

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The Baltic Sea has experienced a complex geological history, with notable swings in salinity driven by changes to its connection with the Atlantic and glacio-isostatic rebound. Sediments obtained during International Ocean Drilling Program Expedition 347 allow the study of the effects of these...

The Baltic Sea has experienced a complex geological history, with notable swings in salinity driven by changes to its connection with the Atlantic and glacio-isostatic rebound. Sediments obtained during International Ocean Drilling Program Expedition 347 allow the study of the effects of these changes on the ecology of the Baltic in high resolution through the Holocene in areas where continuous records had not always been available. Sites M0061 and M0062, drilled in the Ångermanälven Estuary (northern Baltic Sea), contain records of Holocene-aged sediments and microfossils. Here we present detailed records of palaeoecological and palaeoenvironmental changes to the Ångermanälven Estuary inferred from diatom, palynomorph and organic-geochemical data. Based on diatom assemblages, the record is divided into four zones that comprise the Ancylus Lake, Littorina Sea, Post-Littorina Sea and Recent Baltic Sea stages. The Ancylus Lake phase is initially characterized as oligotrophic, with the majority of primary productivity in the upper water column. This transition to a eutrophic state continues into the Initial Littorina Sea stage. The Initial Littorina Sea stage contains the most marine phase recorded here, as well as low surface water temperatures. These conditions end before the Littorina Sea stage, which is marked by a return to oligotrophic conditions and warmer waters of the Holocene Thermal Maximum. Glacio-isostatic rebound leads to a shallowing of the water column, allowing for increased benthic primary productivity and stratification of the water column. The Medieval Climate Anomaly is also identified within Post-Littorina Sea sediments. Modern Baltic sediments and evidence of human-induced eutrophication are seen. Human influence upon the Baltic Sea begins c. 1700 cal. a BP and becomes more intense c. 215 cal. a BP.

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Holocene glacial evolution of Mohnbukta in eastern Spitsbergen

Anne E. Flink, Peter Hill, Riko Noormets, Nina Kirchner

24/08/2017

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Submarine geomorphology is one of the main tools for understanding past fluctuations of tidewater glaciers. In this study we investigate the glacial history of Mohnbukta, on the east coast of Spitsbergen, Svalbard, by combining multibeam-bathymetric data, marine sediment cores and remote...

Submarine geomorphology is one of the main tools for understanding past fluctuations of tidewater glaciers. In this study we investigate the glacial history of Mohnbukta, on the east coast of Spitsbergen, Svalbard, by combining multibeam-bathymetric data, marine sediment cores and remote sensing data. Presently, three tidewater glaciers, Heuglinbreen, Königsbergbreen and Hayesbreen calve into Mohnbukta. Hayesbreen surged at the end of the Little Ice Age, between 1901 and 1910. The submarine landform assemblage in Mohnbukta contains two large transverse ridges, interpreted as terminal moraines, with debrisflow lobes on their distal slopes and sets of well-preserved geometric networks of ridges, interpreted as crevasse-squeeze ridges inshore of the moraines. The arrangement of crevasse-squeeze ridges suggests that both landform sets were produced during surge-type advances. The terminus position of the 1901–1910 Hayesbreen surge correlates with the inner (R.2) terminal moraine ridge suggesting that the R.1 ridge formed prior to 1901. Marine sediment cores display 14C ages between 5700–7700 cal. a BP derived from benthic foraminifera, from a clast-rich mud unit. This unit represents pre-surge unconsolidated Holocene sediments pushed in front of the glacier terminus and mixed up during the 1901 surge. An absence of retreat moraines in the deeper part of the inner basin and the observation of tabular icebergs calving off the glacier front during retreat suggest that the front of Hayesbreen was close to flotation, at least in the deeper parts of the basin. As the MOH15-01 core does not penetrate into a subglacial till and the foraminifera in the samples were well preserved, the R.1 ridge is suggested to have formed prior to the deposition of the foraminifera. Based on these data we propose that a surge-type advance occurred in Mohnbukta in the early Holocene, prior to 7700 cal. a BP, which in turn indicates that glaciers can switch to and from surge mode.

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Late Quaternary glaciation of the northern Urals: a review and new observations

Valery I. Astakhov

24/08/2017

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This is a synthesis of the glacial history of the northern Urals undertaken using published works and the results of geological surveys as well as recent geochronometric and remote sensing data. The conclusions differ from the classical model that considers the Urals as an important source of...

This is a synthesis of the glacial history of the northern Urals undertaken using published works and the results of geological surveys as well as recent geochronometric and remote sensing data. The conclusions differ from the classical model that considers the Urals as an important source of glacial ice and partly from the modern reconstructions. The principal supporting evidence for the conventional model – Uralian erratics found on the adjacent plains – is ambiguous because Uralian clasts were also delivered by a thick external ice sheet overriding the mountains during the Middle Pleistocene. Alternative evidence presented in this paper indicates that in the late Quaternary the Ural mountains produced only valley glaciers that partly coalesced in the western piedmont to form large piedmont lobes. The last maximum glaciation occurred in the Early Valdaian time at c. 70–90 ka when glacial ice from the Kara shelf invaded the lowlands and some montane valleys but an icecap over the mountains was not formed. The moraines of the alpine glaciation are preserved only beyond the limits of the Kara ice sheet and therefore cannot be younger than MIS 4. More limited glaciation during MIS 2 generated small alpine moraines around the cirques of the western Urals (Mangerud et al. 2008: Quaternary Science Reviews 27, 1047). The largest moraines of Transuralia were probably produced by the outlet glaciers of a Middle Pleistocene ice sheet that formed on the western plains and discharged across the Polar Urals. The resultant scheme of limited mountain glaciation is possibly also applicable as a model for older glacial cycles.

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An 810-year history of cold season temperature variability for northern Poland

Daniel Balanzategui, Antje Knorr, Karl-Uwe Heussner, Tomasz Wazny, Wolfgang Beck, Michał Słowiński, Gerhard Helle, Allan Buras, Martin Wilmking, Ernst Van Der Maaten, Tobias Scharnweber, Isabel Dorado-Liñán, Ingo Heinrich

24/08/2017

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Scots pine (Pinus sylvestris L.) is a widely used tree species in European dendroclimatology studies due to its common distribution across much of the continent. Almost all studies find radial growth strongly related to summer temperature, a result reflecting site selection at high...

Scots pine (Pinus sylvestris L.) is a widely used tree species in European dendroclimatology studies due to its common distribution across much of the continent. Almost all studies find radial growth strongly related to summer temperature, a result reflecting site selection at high elevation/latitude environments where trees grow at their ecophysiological limits. Due to the amount of attention spent on these sites there is a geographical and seasonal bias in temperature reconstructions based upon tree-ring proxies in Europe. To overcome the limited availability of tree-ring data in temperate lowlands, we present a northern Poland ring-width chronology developed from living and historic Scots pine material with a strong common growth signal going back to AD 1200. Investigations into climate-growth relationships found year-to-year ring-width variability to be more strongly correlated to cold season temperature (November to April) prior to the growing season than summer temperatures during tree-ring formation. Based on this relationship it was possible to reconstruct cold season temperature conditions for the last 810 years. Spatial field correlations with gridded instrumental records indicated that the reconstruction provides relevant cold season temperature information across the land regions bordering the North Atlantic Ocean and Baltic Sea, lowlands and uplands of western and central Europe, and the eastern and central interior of Russia. Despite an unsuccessful attempt to find a stationary relationship with the North Atlantic Oscillation, comparisons with several cold season temperature reconstructions confirmed the long-term connection between our reconstructed temperature series for northern Poland and the wider area.

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Holocene development and permafrost history in sub-arctic peatlands in Tavvavuoma, northern Sweden

Anna Britta Kristina Sannel, Liljen Hempel, Alexander Kessler, Vilmantas Pr≐skienis

17/08/2017

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Under changing climatic conditions permafrost peatlands can play an important role in the global carbon budget through permafrost carbon feedbacks and shifts in carbon assimilation. To better predict future dynamics in these ecosystems an increased understanding of their Holocene carbon and...

Under changing climatic conditions permafrost peatlands can play an important role in the global carbon budget through permafrost carbon feedbacks and shifts in carbon assimilation. To better predict future dynamics in these ecosystems an increased understanding of their Holocene carbon and permafrost history is needed. In Tavvavuoma, northern Sweden, we have performed detailed analyses of vegetation succession and geochemical properties at six permafrost peatland sites. Peatland initiation took place around 10 000 to 9600 cal. a BP, soon after retreat of the Fennoscandian Ice Sheet, and the peatlands have remained permafrost-free fens throughout most of the Holocene. At the four sites that showed a continuous accumulation record during the late Holocene radiocarbon dating of the shift from wet fen to dry bog vegetation, characteristic of the present permafrost peatland surface, suggests that permafrost developed at around 600–100 cal. a BP. At the other two sites peat accumulation was halted during the late Holocene, possibly due to abrasion, making it more difficult to imply the timing of permafrost aggradation. However also at these sites there are no indications of permafrost inception prior to the Little Ice Age. The mean long-term Holocene carbon accumulation rate at all six sites was 12.3±2.4 gC m−2 a−1 (±SD), and the mean soil organic carbon storage was 114±27 kg m−2.

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02/01/2018

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Jens Esmark's mountain glacier traverse 1823 − the key to his discovery of Ice Ages

Geir Hestmark

22/05/2017

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The discovery of Ice Ages is one of the most revolutionary advances made in the Earth sciences. In 1824 Danish-Norwegian geoscientist Jens Esmark published a paper stating that there was indisputable evidence that Norway and other parts of Europe had previously been covered by enormous glaciers...

The discovery of Ice Ages is one of the most revolutionary advances made in the Earth sciences. In 1824 Danish-Norwegian geoscientist Jens Esmark published a paper stating that there was indisputable evidence that Norway and other parts of Europe had previously been covered by enormous glaciers carving out valleys and fjords, in a cold climate caused by changes in the eccentricity of Earth's orbit. Esmark and his travel companion Otto Tank arrived at this insight by analogous reasoning: enigmatic landscape features they observed close to sea level along the Norwegian coast strongly resembled features they observed in the front of a retreating glacier during a mountain traverse in the summer of 1823. Which glacier they observed up close has however remained a mystery, and thus an essential piece of information in the story of this discovery has been missing. Based on previously unknown archive sources, supplemented by field study, I here identify the key locality as the glacier Rauddalsbreen. This is the northernmost outlet glacier from Jostedalsbreen, the largest glacier in mainland Europe. Here the foreland exposed by glacier retreat since the Little Ice Age maximum around AD 1750 contains a rich collection of glacial deposits and erosional forms. The point of enlightenment is more precisely identified to be a specific moraine and its distal sandur at 61°53′26″N, 7°26′43″E. In memory of Esmark's travel companion who possibly was the first to realise the analogy, it is proposed to name this moraine Otto Tank's Moraine, a pendant to the already famous Esmark Moraine at Forsand by the sea.

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BRITICE Glacial Map, version 2: a map and GIS database of glacial landforms of the last British–Irish Ice Sheet

Chris D. Clark, Jeremy C. Ely, Sarah L. Greenwood, Anna L. C. Hughes, Robert Meehan, Iestyn D. Barr, Mark D. Bateman, Tom Bradwell, Jenny Doole, David J. A. Evans, Colm J. Jordan, Xavier Monteys, Xavier M. Pellicer, Michael Sheehy

29/08/2017

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During the last glaciation, most of the British Isles and the surrounding continental shelf were covered by the British–Irish Ice Sheet (BIIS). An earlier compilation from the existing literature (BRITICE version 1) assembled the relevant glacial geomorphological evidence into a freely...

During the last glaciation, most of the British Isles and the surrounding continental shelf were covered by the British–Irish Ice Sheet (BIIS). An earlier compilation from the existing literature (BRITICE version 1) assembled the relevant glacial geomorphological evidence into a freely available GIS geodatabase and map (Clark et al. 2004: Boreas 33, 359). New high-resolution digital elevation models, of the land and seabed, have become available casting the glacial landform record of the British Isles in a new light and highlighting the shortcomings of the V.1 BRITICE compilation. Here we present a wholesale revision of the evidence, onshore and offshore, to produce BRITICE version 2, which now also includes Ireland. All published geomorphological evidence pertinent to the behaviour of the ice sheet is included, up to the census date of December 2015. The revised GIS database contains over 170 000 geospatially referenced and attributed elements – an eightfold increase in information from the previous version. The compiled data include: drumlins, ribbed moraine, crag-and-tails, mega-scale glacial lineations, glacially streamlined bedrock (grooves, roches moutonnées, whalebacks), glacial erratics, eskers, meltwater channels (subglacial, lateral, proglacial and tunnel valleys), moraines, trimlines, cirques, trough-mouth fans and evidence defining ice-dammed lakes. The increased volume of features necessitates different map/database products with varying levels of data generalization, namely: (i) an unfiltered GIS database containing all mapping; (ii) a filtered GIS database, resolving data conflicts and with edits to improve geo-locational accuracy (available as GIS data and PDF maps); and (iii) a cartographically generalized map to provide an overview of the distribution and types of features at the ice-sheet scale that can be printed at A0 paper size at a 1:1 250 000 scale. All GIS data, the maps (as PDFs) and a bibliography of all published sources are available for download from: https://www.sheffield.ac.uk/geography/staff/clark_chris/britice.

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The Lateglacial to early Holocene tephrochronological record from Lake Hämelsee, Germany: a key site within the European tephra framework

Gwydion Jones, Christine S. Lane, Achim Brauer, Siwan M. Davies, Renée Bruijn, Stefan Engels, Aritina Haliuc, Wim Z. Hoek, Josef Merkt, Dirk Sachse, Falko Turner, Friederike Wagner-Cremer

27/04/2017

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Here we present the results of a detailed cryptotephra investigation through the Lateglacial to early Holocene transition, from a new sediment core record obtained from Lake Hämelsee, Germany. Two tephra horizons, the Laacher See Tephra (Eifel Volcanic Field) and the Saksunarvatn Ash...

Here we present the results of a detailed cryptotephra investigation through the Lateglacial to early Holocene transition, from a new sediment core record obtained from Lake Hämelsee, Germany. Two tephra horizons, the Laacher See Tephra (Eifel Volcanic Field) and the Saksunarvatn Ash (Iceland), have been previously described in this partially varved sediment record, indicating the potential of the location as an important Lateglacial tephrochronological site in northwest Europe. We have identified three further tephra horizons, which we correlate to: the c. 12.1 ka BP Vedde Ash (Iceland), the c. 11 ka BP Ulmener Maar tephra (Eifel Volcanic Field) and the c. 10.8 ka BP Askja-S tephra (Iceland). Three additional cryptotephra deposits have been found (locally named HÄM_T1616, HÄM_T1470 and HÄM_T1456-1455), which cannot be correlated to any known eruption at present. Geochemical analysis of the deposits suggests that these cryptotephras most likely have an Icelandic origin. Our discoveries provide age constraints for the new sediment records from Lake Hämelsee and enable direct stratigraphical correlations to be made with other tephra-bearing sites across Europe. The new tephrostratigraphical record, within a partially varved Lateglacial sediment record, highlights the importance of Lake Hämelsee as a key site within the European tephra lattice.

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The timing and consequences of the blockage of the Humber Gap by the last British−Irish Ice Sheet

Mark D. Bateman, David J. A. Evans, David H. Roberts, Alicia Medialdea, Jeremy Ely, Chris D. Clark

15/05/2017

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The eastern England terrestrial glacial sequences are critical to the spatial and temporal reconstruction of the last British−Irish Ice sheet (BIIS). Understanding glacial behaviour in the area of the Humber Gap is key as its blockage by ice created extensive proglacial lakes. This paper maps...

The eastern England terrestrial glacial sequences are critical to the spatial and temporal reconstruction of the last British−Irish Ice sheet (BIIS). Understanding glacial behaviour in the area of the Humber Gap is key as its blockage by ice created extensive proglacial lakes. This paper maps the glacial geomorphology of the Humber Gap region to establish for the first time the extent and thickness of the North Sea Lobe (NSL) of the BIIS. Findings establish the westerly maximal limit of the NSL. Ten new luminescence ages from across the region show the initial Skipsea Till advance to the maximal limits occurred regionally at c. 21.6 ka (Stage 1) and retreated off-shore c. 18 ka (Stage 2). Punctuated retreat is evident in the south of the region whilst to the immediate north retreat was initially rapid before a series of near synchronous ice advances (including the Withernsea Till advance) occurred at c. 16.8 ka (Stage 3). Full withdrawal of BIIS ice occurred prior to c. 15 ka (Stage 4). Geomorphic mapping and stratigraphy confirms the existence of a proto Lake Humber prior to Stage 1, which persisted to Stage 3 expanding eastward as the NSL ice retreated. It appears that proglacial lakes formed wherever the NSL encountered low topography and reverse gradients during both phases of both advance and retreat. These lakes may in part help explain the dynamism of parts of the NSL, as they initiated ice draw down and associated streaming/surging. The above record of ice-dammed lakes provides an analogue for now off-shore parts of the BIIS where it advanced as a number of asynchronous lowland lobes.

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Holocene lake sediments from the Faiyum Oasis in Egypt: a record of environmental and climate change

Leszek Marks, Alaa Salem, Fabian Welc, Jerzy Nitychoruk, Zhongyuan Chen, Maarten Blaauw, Abdelfattah Zalat, Aleksandra Majecka, Marcin Szymanek, Marta Chodyka, Anna Tołoczko-Pasek, Qianli Sun, Xiaoshuang Zhao, Jun Jiang

10/05/2017

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The Qarun Lake in the Faiyum Oasis (Egypt) provides a unique record of Holocene environmental and climate change in an arid area largely devoid of fossil proxy records. Multiple lithological, palaeontological and geochemical proxies and 32 radiocarbon dates from the 26-m-long core FA-1 provide...

The Qarun Lake in the Faiyum Oasis (Egypt) provides a unique record of Holocene environmental and climate change in an arid area largely devoid of fossil proxy records. Multiple lithological, palaeontological and geochemical proxies and 32 radiocarbon dates from the 26-m-long core FA-1 provide a time series of the lake's transformation. Our results confirm that a permanent lake appeared in the Holocene at c. 10 cal. ka BP. The finely laminated lake sediments consist of diatomite, in which diatoms and ostracods together with lower concentrations of ions indicate a freshwater environment at the end of the early and middle Holocene. This freshwater supply was closely associated with regular inflows of the Nile water during flood seasons, when the Intertropical Convergence Zone (ITCZ) migrated northwards in Africa, although it has probably never reached the Faiyum Oasis. Local rainfall, possibly connected with a northern atmospheric circulation, may have been important during winter. Several phases in the lake's evolution are recognized, represented by oscillations between deep open freshwater conditions during more humid climate and shallow fresh to brackish water during drier episodes. After a long freshwater phase, the lake setting has become more brackish since c. 6.2 cal. ka BP as indicated by diatoms and increasing contents of evaporite ions in the sediment. This clearly shows that since that time the lake has occasionally become partly desiccated. This is a result of reduced discharge of the Nile. In the late Holocene the lake was mostly brackish and then gradually turned into a saline lake. This natural process was interrupted about 2.3 cal. ka BP when a man-made canal facilitated water inflow from the Nile. The examined FA-1 core can be used as a reference age model of climate change in the Holocene and its impact on the development and decline of ancient civilizations in northeastern Africa.

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A revised stratigraphical framework for the Quaternary deposits of the German North Sea sector: a geological-geotechnical approach

Mark Coughlan, Matthias Fleischer, Andrew J. Wheeler, Daniel A. Hepp, Dierk Hebbeln, Tobias Mörz

10/05/2017

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Using extensive data sets from three separate areas in the German North Sea sector, consisting of seismic grids, cores and in-situ cone penetration tests (CPT), we have established a revised stratigraphical framework for the mid to late Quaternary deposits of the German North Sea sector. This...

Using extensive data sets from three separate areas in the German North Sea sector, consisting of seismic grids, cores and in-situ cone penetration tests (CPT), we have established a revised stratigraphical framework for the mid to late Quaternary deposits of the German North Sea sector. This framework consists of four regional unconformities and 15 other local unconformities derived from seismic profiles. Using these unconformities, along with lithological and geotechnical data, it was possible to define and correlate 14 major units and 21 subunits within the framework. The Quaternary cover in the area is characterized by a variety of environmental settings ranging from glacial terrestrial and fluvial to lacustrine as well as brackish and marine environments with associated erosion, reworking and deposition. The complexity of Quaternary deposits within the area is explained by its history of repeated ice advances interrupted by marine transgressions and exposed periglacial landscapes. Within the framework, eight buried tunnel valleys and two shallow buried river valleys are identified from seismic profiles with four phases of tunnel valley generation inferred. These phases of tunnel valley generation are associated with the Elsterian (three) and Saalian (one) glacial stages. Infill of these tunnel valleys consists of glaciofluvial sands, thick sequences of marine and lacustrine fine-grained sediments and some reworked till remnants. Elsewhere, extensive tabular units have formed consisting of marine and fluvial sediments. We compare this new stratigraphy with previous stratigraphies for the German North Sea sector, attribute informal stratigraphical names and offer preliminary correlations with established stratigraphies from other sectors of the North Sea.

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A multiproxy macrofossil record of Eemian palaeoenvironments from Klaksvík, the Faroe Islands

Ole Bennike, Lars Hedenäs, Geoffrey Lemdahl, Peter Wiberg-Larsen

03/05/2017

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Studies of interglacial successions are critical to our understanding of the environmental history of an area. Analyses of macrofossil remains of plants and invertebrates from Eemian sediments exposed in a coastal cliff section at Borðoyarvík near Klaksvík, Bordoy, northeastern Faroe...

Studies of interglacial successions are critical to our understanding of the environmental history of an area. Analyses of macrofossil remains of plants and invertebrates from Eemian sediments exposed in a coastal cliff section at Borðoyarvík near Klaksvík, Bordoy, northeastern Faroe Islands, indicate that the sediments accumulated in a coastal lagoon. The fossil flora comprises tree birch Betula sect. Albae and we suggest that birch forests were found locally at sheltered sites in the area. Tree birch also occurred on the islands during the mid-Holocene. The only other woody plant recovered from the Eemian deposit is the dwarf-shrub Empetrum nigrum, which is common on the islands today. Remains of herbaceous plants are rare but include Viola, Ajuga, Myosotis, Urtica dioica and Ranunculus. The bryophyte flora is species-rich and most of the fragments belong either to stream species or to species of humid or wet habitats. The fossil flora and fauna also comprise a number of freshwater species that probably lived in an oligotrophic lake and in streams in the catchment of the lagoon. The climate during deposition of the lagoonal sediments was similar to the Holocene oceanic climate of the Faroe Islands. The study adds to our understanding of Eemian environments in the North Atlantic region and helps to fill a knowledge gap about the history of the flora and fauna of the Faroe Islands, which is of biogeographical importance.

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A multi-proxy palaeoenvironmental and geochronological reconstruction of the Saalian-Eemian-Weichselian succession at Klein Klütz Höved, NE Germany

Michael Kenzler, Henrik Rother, Heiko Hüneke, Peter Frenzel, Jaqueline Strahl, Sumiko Tsukamoto, Yan Li, Stefan Meng, Julia Gallas, Manfred Frechen

15/05/2017

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Here we present a multi-proxy investigation of the Klein Klütz Höved (KKH) coastal cliff section in northeastern Germany, involving lithofacies analysis, micromorphology, micropalaeontology, palynology and luminescence dating of quartz and feldspar. We subdivide the local stratigraphy into...

Here we present a multi-proxy investigation of the Klein Klütz Höved (KKH) coastal cliff section in northeastern Germany, involving lithofacies analysis, micromorphology, micropalaeontology, palynology and luminescence dating of quartz and feldspar. We subdivide the local stratigraphy into three depositional phases. (i) Following a Saalian advance (MIS 6) of the Scandinavian Ice Sheet, the penultimate deglaciation (Termination II) at the site occurred between c. 139 and 134 ka, leading to the establishment of a braided river system and lacustrine basins under arctic-subarctic climate conditions. (ii) In the initial phase of the Eemian interglacial lacustrine deposits were formed, containing warm-water ostracods and a pollen spectrum indicating gradual expansion of woodlands eventually containing thermophile deciduous forest elements. A correlation of the local pollen assemblages with Eemian reference records from central Europe suggests that fewer than 750 years of the last interglacial period are preserved at KKH. The occurrence of brackish ostracods dates the onset of the Eemian marine transgression at the section at c. 300–750 years after the beginning of the last interglacial period. (iii) Directly above the Eemian record a ~10-m-thick sedimentary succession of MIS 2 age was deposited, implying a significant hiatus of c. 90 ka encompassing the time from middle and upper MIS 5e to late MIS 3. During the Late Weichselian, KKH featured a depositional shift from (glacio-)lacustrine to subglacial to recessional terminoglacial facies, with the first documented Weichselian ice advance post-dating 20±2 ka. Overall, the KKH section represents an exceptional sedimentary archive for palaeoenvironmental reconstructions, covering the period from the Saalian glaciation and subsequent Termination II to the early Eemian and Late Weichselian. The results refine the existing palaeogeographical and geochronological models of the late Quaternary history in the southwestern Baltic Sea area and allow correlations with other reference records in a wider area.

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High-latitude vegetation and climate changes during the Mid-Pleistocene Transition inferred from a palynological record from Lake El'gygytgyn, NE Russian Arctic

Wenwei Zhao, Pavel E. Tarasov, Anatoly V. Lozhkin, Patricia M. Anderson, Andrei A. Andreev, Julie A. Korzun, Martin Melles, Ekaterina Y. Nedorubova, Volker Wennrich

22/05/2017

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A continuous pollen record from Lake El'gygytgyn (northeastern Russian Arctic) provides detailed information concerning the regional vegetation and climate history during the Mid-Pleistocene Transition (MPT), between 1091 ka (end of Marine Isotope Stage (MIS) 32) and 715 ka (end of MIS 18)....

A continuous pollen record from Lake El'gygytgyn (northeastern Russian Arctic) provides detailed information concerning the regional vegetation and climate history during the Mid-Pleistocene Transition (MPT), between 1091 ka (end of Marine Isotope Stage (MIS) 32) and 715 ka (end of MIS 18). Pollen-based qualitative vegetation reconstruction along with biome reconstruction indicate that the interglacial regional vegetation history during the MPT is characterized by a gradual replacement of forest and shrub vegetation by open herbaceous communities (i.e. tundra/cold steppe). The pollen spectra reveal seven vegetation successions that have clearly distinguishable glacial-interglacial cycles. These successions are represented by the intervals of cold deciduous forest (CLDE) biome scores changing from high to low, which are basically in phase with the variations of obliquity from maxima to minima. The dominating influence of obliquity forcing on vegetation successions contradicts with the stronger power of eccentricity, as demonstrated by the result of wavelet analysis based on landscape openness reconstruction. This discrepancy shows that a single index is insufficient for catching signals of all the impacting factors. Comparisons with vegetation and environmental changes in the Asian interior suggest that global cooling during the MPT was probably the key force driving long-term aridification in the Arctic region. The accelerated aridification after MIS 24–22 was probably caused by the additional effect of the Tibetan Plateau uplift, which played an important role on intensification of the Siberian High and westerly jet systems.

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Glacial advance, occupation and retreat sediments associated with multi-stage ice-dammed lakes: north-central Alberta, Canada

Jessica M. Slomka, Daniel J. Utting

08/05/2017

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Ice sheets that advance upvalley, against the regional gradient, commonly block drainage and result in ice-dammed proglacial lakes along their margins during advance and retreat phases. Ice-dammed glacial lakes described in regional depositional models, in which ice blocks a major lake outlet,...

Ice sheets that advance upvalley, against the regional gradient, commonly block drainage and result in ice-dammed proglacial lakes along their margins during advance and retreat phases. Ice-dammed glacial lakes described in regional depositional models, in which ice blocks a major lake outlet, are often confined to basins in which the glacial lake palaeogeographical position generally remains semi-stable (e.g. Great Lakes basins). However, in places where ice retreats downvalley, blocking regional drainage, the palaeogeographical position and lake level of glacial lakes evolve temporally in response to the position of the ice margin (referred to here as ‘multi-stage’ lakes). In order to understand the sedimentary record of multi-stage lakes, sediments were examined in 14 cored boreholes in the Peace and Wabasca valleys in north-central Alberta, Canada. Three facies associations (FAI–III) were identified from core, and record Middle Wisconsinan ice-distal to ice-proximal glaciolacustrine (FAI) sediments deposited during ice advance, Late Wisconsinan subglacial and ice-marginal sediments (FAII) deposited during ice-occupation, and glaciolacustrine sediments (FAIII) that record ice retreat from the study area. Modelling of the lateral extent of FAs using water wells and gamma-ray logs, combined with interpreted outlets and mapped moraines based on LiDAR imagery, facilitated palaeogeographical reconstruction of lakes and the identification of four major retreat-phase lake stages. These lake reconstructions, together with the vertical succession of FAs, are used to develop a depositional model for ice-dammed lakes during a cycle of glacial advance and retreat. This depositional model may be applied in other areas where meltwater was impounded by glacial ice advancing up the regional gradient, in order to understand the complex interaction between depositional processes, ice-marginal position, and supply of meltwater and sediment in the lake basin. In particular, this model could be applied to decipher the genetic origin of diamicts previously interpreted to record strictly subglacial deposition or multiple re-advances.

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Subarctic Front migration at the Reykjanes Ridge during the mid- to late Holocene: evidence from planktic foraminifera

Kerstin Perner, Matthias Moros, Eystein Jansen, Antoon Kuijpers, Simon R. Troelstra, MAARTIN A. Prins

29/05/2017

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Expansion of fresh and sea-ice loaded surface waters from the Arctic Ocean into the sub-polar North Atlantic is suggested to modulate the northward heat transport within the North Atlantic Current (NAC). The Reykjanes Ridge south of Iceland is a suitable area to reconstruct changes in the mid-...

Expansion of fresh and sea-ice loaded surface waters from the Arctic Ocean into the sub-polar North Atlantic is suggested to modulate the northward heat transport within the North Atlantic Current (NAC). The Reykjanes Ridge south of Iceland is a suitable area to reconstruct changes in the mid- to late Holocene fresh and sea-ice loaded surface water expansion, which is marked by the Subarctic Front (SAF). Here, shifts in the location of the SAF result from the interaction of freshwater expansion and inflow of warmer and saline (NAC) waters to the Ridge. Using planktic foraminiferal assemblage and concentration data from a marine sediment core on the eastern Reykjanes Ridge elucidates SAF location changes and thus, changes in the water-mass composition (upper ˜200 m) during the last c. 5.8 ka BP. Our foraminifer data highlight a late Holocene shift (at c. 3.0 ka BP) in water-mass composition at the Reykjanes Ridge, which reflects the occurrence of cooler and fresher surface waters when compared to the mid-Holocene. We document two phases of SAF presence at the study site: from (i) c. 5.5 to 5.0 ka BP and (ii) c. 2.7 to 1.5 ka BP. Both phases are characterized by marked increases in the planktic foraminiferal concentration, which coincides with freshwater expansions and warm subsurface water conditions within the sub-polar North Atlantic. We link the SAF changes, from c. 2.7 to 1.5 ka BP, to a strengthening of the East Greenland Current and a warming in the NAC, as identified by various studies underlying these two currents. From c. 1.5 ka BP onwards, we record a prominent subsurface cooling and continued occurrence of fresh and sea-ice loaded surface waters at the study site. This implies that the SAF migrated to the southeast of our core site during the last millennium.

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Untangling natural and anthropogenic multi-element signatures in archaeological soils at the Ikirahak site, Arctic Canada

Don H. Butler, Peter C. Dawson

10/05/2017

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Multi-element archives housed within archaeological soils and sediments are useful for identifying ancient human activities invisible to routine methodologies. These records, however, are rarely studied in the Canadian Arctic. Contributing to this area of research, we address the fundamental...

Multi-element archives housed within archaeological soils and sediments are useful for identifying ancient human activities invisible to routine methodologies. These records, however, are rarely studied in the Canadian Arctic. Contributing to this area of research, we address the fundamental issue of isolating natural and anthropogenic multi-element signatures in archaeological soils from the region. We specifically investigated the element record in the soil system at the Ikirahak site, a Taltheilei hunter-gatherer camp in southern Nunavut that was established roughly 2000 years ago. Ikirahak soils displayed high potential for the preservation of anthropogenic element additions. This owes to the fine textures, high cation adsorbance capacities and acidic pH levels of the local soils, as well as the absence of processes such as brunification and solifluction. Multi-element characterization was accomplished using x-ray fluorescence and inductively coupled plasma - mass spectroscopy. Several locations with anomalous concentrations were pinpointed using enrichment factors. Natural and anthropogenic signals were untangled using categorical principal components analysis of a mixed quantitative/qualitative data set comprised of the element concentrations and contextual information such as the presence of specific archaeological materials, organic matter content, and vegetation communities. Results indicated that enrichments in CaO, P2O5, Ba, Fe2O3, MnO, Cu and Sc across the site relate to the disposal of burned refuse that was produced in pit-house hearths. Concentrations of Li, Na, K, Rb and Cs (alkali metals), Mg and Sr (alkaline earths), Ti, V, Cr, Ni, Zn, Y, Zr, Nb, Mo and Hf (transition metals), Al, Ga and Pb (post-transition metals), and La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu (rare earths) were linked to esker and lacustrine parent sediments.

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Glacial landsystems, retreat dynamics and controls on Loch Lomond Stadial (Younger Dryas) glaciation in Britain

Hannah L. Bickerdike, Colm Ó Cofaigh, David J. A. Evans, Chris R. Stokes

29/05/2017

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Glacial geomorphology relating to the Loch Lomond Stadial (Younger Dryas) in Britain is used to construct five glacial landsystem models. These landsystems lie on a continuum of increasing ice thickness and decreasing topographic control and typify the principal styles of glaciation during the...

Glacial geomorphology relating to the Loch Lomond Stadial (Younger Dryas) in Britain is used to construct five glacial landsystem models. These landsystems lie on a continuum of increasing ice thickness and decreasing topographic control and typify the principal styles of glaciation during the stadial. The landsystems comprise: the cirque/niche glacier landsystem, the alpine icefield landsystem, the lowland piedmont lobe landsystem, the plateau icefield landsystem and the icecap landsystem. Geomorphological features representing the icecap landsystem are present only at the centre of the West Highland Glacier Complex, which was flanked primarily by satellite alpine and plateau icefields. The cirque/niche glacier landsystem was present predominantly in areas that experienced conditions only marginally favourable for glacier development at peripheral sites. Three styles of glacier retreat are recorded by the geomorphology: active, two-phase and uninterrupted retreat. Of these, active retreat appears to be most widespread within the Loch Lomond Stadial limits. These retreat styles reflect a combination of climatic and topographic conditions, coupled with local factors influencing the preservation of landforms from which retreat dynamics can be inferred. Likewise, the distribution of landsystems was influenced by an interplay between topography and climate, with glacier formation being facilitated in locations where topographical conditions aided in the accumulation of snow. The pattern also supports the existence of previously recognized northward and eastward precipitation gradients across Britain during the stadial.

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Deglacial dynamics of the Vestfjorden – Trænadjupet palaeo-ice stream, northern Norway

Jan Sverre Laberg, Raymond S. Eilertsen, Gaute R. Salomonsen

18/05/2017

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Few well-dated records of the deglacial dynamics of the large palaeo-ice streams of the major Northern Hemisphere ice sheets are presently available, a prerequisite for an improved understanding of the ice-sheet response to the climate warming of this period. Here we present a transect of...

Few well-dated records of the deglacial dynamics of the large palaeo-ice streams of the major Northern Hemisphere ice sheets are presently available, a prerequisite for an improved understanding of the ice-sheet response to the climate warming of this period. Here we present a transect of gravity-core samples through Trænadjupet and Vestfjorden, northern Norway, the location of the Trænadjupet – Vestfjorden palaeo-ice stream of the NW sector of the Fennoscandian Ice Sheet. Initial ice recession from the shelf break to the coastal area (~400 km) occurred at an average rate of about 195 m a−1, followed by two ice re-advances, at 16.6–16.4 ka BP (the Røst re-advance) and at 15.8–15.6 ka BP (the Værøy re-advance), the former at an estimated ice-advance rate of 216 m a−1. The Røst re-advance has been interpreted to be part of a climatically induced regional cold spell while the Værøy re-advance was restricted to the Vestfjorden area and possibly formed as a consequence of internal ice-sheet dynamics. Younger increases in IRD content have been correlated to the Skarpnes (Bølling – Older Dryas) and Tromsø – Lyngen (Younger Dryas) Events. Overall, the decaying Vestfjorden palaeo-ice stream responded to the climatic fluctuations of this period but ice response due to internal reorganization is also suggested. Separating the two is important when evaluating the climatic response of the ice stream. As demonstrated here, the latter may be identified using a regional approach involving the study of several palaeo-ice streams. The retreat rates reported here are of the same order of magnitude as rates reported for ice streams of the southern part of the Fennoscandian Ice Sheet, implying no latitudinal differences in ice response and retreat rate for this ~1000 km2 sector of the Fennoscandian Ice Sheet (~60–68°N) during the climate warming of this period.

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Late Holocene palaeoproductivity changes: a multi-proxy study in the Norwegian Trench and the Skagerrak, North Sea

Irina Polovodova Asteman, Bjørg Risebrobakken, Matthias Moros, Anna Binczewska, Sławomir Dobosz, Eystein Jansen, Joanna Sławińska, Małgorzata Bąk

29/05/2017

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To detect climatic linkages between the Baltic Sea, the Skagerrak and the Nordic Seas, we present multi-proxy reconstructions covering the last 4500 years from three sediment cores taken in the Skagerrak and along the SW Norwegian margin. Foraminiferal assemblages at all three sites show a...

To detect climatic linkages between the Baltic Sea, the Skagerrak and the Nordic Seas, we present multi-proxy reconstructions covering the last 4500 years from three sediment cores taken in the Skagerrak and along the SW Norwegian margin. Foraminiferal assemblages at all three sites show a distinct change at c. 1700 years BP, associated with a transition from absence and rare occurrence of Brizalina skagerrakensis during c. 4500–2300 years BP to its subsequent abundance increase, suggesting a stronger influence of nutrient-rich water-masses during the last c. 1700 years. Increased nutrient availability, which probably stimulated higher primary productivity, is further supported by an increase in diatoms, total organic carbon and benthic foraminiferal species indicative of high productivity and carbon fluxes during the last c. 1700 years as compared to c. 4500–2300 years BP. The amplitude of the B. skagerrakensis signal is largest in the central Skagerrak and gradually becomes smaller towards the Norwegian Sea suggesting that the dominant source of the nutrient-rich water was the brackish outflow from the Baltic Sea. The generally lower abundances of planktonic foraminifera since c. 1700 years BP support the hypothesis of less saline surface water conditions in the Skagerrak. These results agree with other studies, which suggest a stronger Baltic outflow over the last 1700 years coinciding with a general cooling, increased wintertime westerlies bringing more winter precipitation to northern Europe, increased river runoff and higher frequency of floods. The increase in outflow also occurs during deposition of laminated sediments in the deep Baltic Sea. Leakage of dissolved inorganic phosphorus from anoxic sediments, as well as enhanced erosion due to deforestation in combination with higher runoff from Norway, coastal upwelling and more vigorous frontal dynamics may all have contributed to higher nutrient availability within the adjacent Skagerrak during the last 1700 years BP as compared to c. 4500–2300 years BP, when low productivity prevailed in the study area.

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Timing of fluvial sedimentation in the Upper Rhine Graben since the Middle Pleistocene: constraints from quartz and feldspar luminescence dating

Yan Li, Sumiko Tsukamoto, Manfred Frechen, Gerald Gabriel

26/06/2017

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The Heidelberg Basin (HDB) hosts one of the thickest Quaternary sediment successions in central Europe. To establish a reliable Middle and Upper Pleistocene chronology for a recently drilled core from the depocentre of the Heidelberg Basin, we applied multiple luminescence dating approaches,...

The Heidelberg Basin (HDB) hosts one of the thickest Quaternary sediment successions in central Europe. To establish a reliable Middle and Upper Pleistocene chronology for a recently drilled core from the depocentre of the Heidelberg Basin, we applied multiple luminescence dating approaches, including quartz optically stimulated luminescence (OSL), two feldspar post-IR IRSL protocols using second IR stimulation temperatures of 225 °C (pIRIR225) and 290 °C (pIRIR290), and two fading correction models. Relatively high anomalous fading was observed for both the pIRIR225 and pIRIR290 signals, with mean fading rates of 2.13±0.27 and 2.08±0.49%/decade, respectively. Poor dose recovery behaviour of the pIRIR290 signal suggests that the pIRIR290 ages are not reliable. The comparison of two fading correction methods for the K-feldspar ages indicates that the correction method proposed by Kars et al. (2008) Radiation Measurements 43, 786, yields reliable ages, whereas the dose-rate correction method proposed by Lamothe et al. (2003) Radiation Measurements 37, 493, does not. A chronology for the HDB is established using the quartz ages and reliable fading corrected feldspar pIRIR225 ages. Our chronology shows that the sediments in the upper Mannheim Formation were deposited during Marine Isotope Stage (MIS) 4 (c. 70 ka), constrained by two quartz ages in the upper 20 m of the core. Four fading corrected pIRIR225 ages of c. 400 ka show that the upper Ludwigshafen Formation was deposited during MIS 12–11, correlated with the Elsterian-Holsteinian stage. Two ages of 491±76 and 487±79 ka indicate that the Middle and Upper Ludwigshafen Formation were probably deposited during the Cromerian Complex. This luminescence chronology is consistent with palynological results. It also indicates that the IR-RF ages reported earlier are probably underestimated due to anomalous fading.

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Deglaciation and ice shelf development at the northeast margin of the Laurentide Ice Sheet during the Younger Dryas chronozone

Mark F. A. Furze, Anna J. Pieńkowski, Morgan A. McNeely, Robbie Bennett, Alix G. Cage

23/06/2017

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Core 2011804-0010 from easternmost Lancaster Sound provides important insights into deglacial timing and style at the marine margin of the NE Laurentide Ice Sheet (LIS). Spanning 13.2–11.0 cal. ka BP and investigated for ice-rafted debris (IRD), foraminifera, biogenic silica and total...

Core 2011804-0010 from easternmost Lancaster Sound provides important insights into deglacial timing and style at the marine margin of the NE Laurentide Ice Sheet (LIS). Spanning 13.2–11.0 cal. ka BP and investigated for ice-rafted debris (IRD), foraminifera, biogenic silica and total organic carbon, the stratigraphy comprises a lithofacies progression from proximal grounding line and sub-ice shelf environments to open glaciomarine deposition; a sequence similar to deposits from Antarctic ice shelves. These results are the first marine evidence of a former ice shelf in the eastern Northwest Passage and are consistent with a preceding phase of ice streaming in eastern Lancaster Sound. Initial glacial float-off and retreat occurred >13.2 cal. ka BP, followed by formation of an extensive deglacial ice shelf during the Younger Dryas, which acted to stabilize the retreating margin of the NE LIS until 12.5 cal. ka BP. IRD analyses of sub-ice shelf facies indicate initial high input from source areas on northern Baffin Island delivered to Lancaster Sound by a tributary ice stream in Admiralty Inlet. After ice shelf break-up, Bylot Island became the dominant source area. Foraminifera are dominated by characteristic ice-proximal glaciomarine benthics (Cassidulina reniforme, Elphidium excavatum f. clavata), complemented by advected Atlantic water (Cassidulina neoteretis, Neogloboquadrina pachyderma) and enhanced current indicators (Lobatula lobatula). The biostratigraphy further supports the ice shelf model, with advection of sparse faunas beneath the ice shelf, followed by increased productivity under open water glaciomarine conditions. The absence of Holocene sediments in the core suggests that the uppermost deposits were removed, most likely due to mass transport resulting from the site's proximity to modern tidewater glacier margins. Collectively, this study presents important new constraints on the deglacial behaviour of the NE Laurentide Ice Sheet, with implications for past ice sheet stability, ice-rafted sediment delivery, and ice−ocean interactions in this complex archipelago setting.

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Changes in the inflow of saline water into the Bornholm Basin (SW Baltic Sea) during the past 7100 years – evidence from benthic foraminifera record

Anna Binczewska, Matthias Moros, Irina Polovodova Asteman, Joanna Sławińska, Małgorzata Bąk

15/06/2017

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The Baltic Sea (~393 000 km2) is the largest brackish sea in the world and its hydrographic and environmental conditions are strongly dependent on the frequency of saline water inflows from the North Sea. To improve our understanding of the natural variability of the Baltic Sea ecosystem...

The Baltic Sea (~393 000 km2) is the largest brackish sea in the world and its hydrographic and environmental conditions are strongly dependent on the frequency of saline water inflows from the North Sea. To improve our understanding of the natural variability of the Baltic Sea ecosystem detailed reconstructions of past saline water inflow changes based on palaeoecological archives are needed. Here we present a high-resolution study of benthic foraminiferal assemblages accompanied by sediment geochemistry (loss on ignition, total organic carbon) and other microfossil data (ostracods and cladocerans) from a well-dated 8-m-long gravity core taken in the Bornholm Basin. The foraminiferal diversity in the core is low and dominated by species of Elphidium. The benthic foraminiferal faunas in the central Baltic require oxic bottom water conditions and salinities >11–12 PSU. Consequently, shell abundance peaks in the record reflect frequent saline water inflow phases. The first appearance of foraminiferal tests and ostracods in the investigated sediment core is dated to c. 6.9 cal. ka BP and attributed to the first inflows of saline and oxygenated bottom waters into the Bornholm Basin during the Littorina Sea transgression. The transgression terminated the Ancylus Lake phase, reflected in the studied record by abundant cladocerans. High absolute foraminiferal abundances are found within two time intervals: (i) c. 5.5–4.0 cal. ka BP (Holocene Thermal Maximum) and (ii) c. 1.3–0.75 cal. ka BP (Medieval Climate Anomaly). Our data also show three intervals of absent or low saline water inflows: (i) c. 6.5–6.0 cal. ka BP, (ii) c. 3.0–2.3 cal. ka BP and (iii) c. 0.5–0.1 cal. ka BP (Little Ice Age). Our study demonstrates a strong effect of saline and well-oxygenated water inflows from the Atlantic Ocean on the Baltic Sea ecosystem over millennial time scales, which is linked to the major climate transitions over the last 7 ka.

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Earliest Holocene deglaciation of the central Uummannaq Fjord system, West Greenland

William Philipps, Jason P. Briner, Ole Bennike, Avriel Schweinsberg, Casey Beel, Nathaniel Lifton

20/07/2017

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Uummannaq Fjord, West Greenland, held the Uummannaq Ice Stream system that drained an estimated ~6% of the Greenland Ice Sheet (GrIS) during the Last Glacial Maximum. Published ages for the final deglaciation in Uummannaq Fjord vary from as early as c. 9.8 ka to as late as c. 5.3 ka....

Uummannaq Fjord, West Greenland, held the Uummannaq Ice Stream system that drained an estimated ~6% of the Greenland Ice Sheet (GrIS) during the Last Glacial Maximum. Published ages for the final deglaciation in Uummannaq Fjord vary from as early as c. 9.8 ka to as late as c. 5.3 ka. Assessing this variability requires additional chronological controls to improve the deglaciation history of central West Greenland. Here, we combine 14C dating of lake sediment cores with cosmogenic 10Be exposure dating at sites adjacent to the present GrIS margin in the central-inland sector of the Uummannaq Fjord system. We find that ice retreated to or within the present GrIS margin at 10.8±0.2 ka (n = 6). Although this ‘final deglaciation’ to or within the present GrIS margin across the Uummannaq Fjord system varies from c. 10.8 to 5.3 ka, all chronologies indicate collapse from the continental shelf to the inner fjords at c. 11.0 ka, which occurred at a net retreat rate of 300–1100 m a−1. The Uummannaq Fjord system deglaciated c. 1000 years earlier than the major fjord system to the south, Disko Bugt. However, similarly rapid retreat rates of the two palaeo-ice stream systems suggest that their collapse may have been aided by high calving rates. The asynchronous deglaciation of the GrIS throughout the Uummannaq Fjord system probably relates to the influence of varying fjord geometry on marine glacier behaviour.

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Subglacial blowouts in western Canada: insights into extreme meltwater pressures and hydrofracturing

Paul L. Broughton

28/06/2017

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This study interprets deformations of indurated 10s of metres thick bedrock strata by subglacial meltwater pressures at maximum levels, resulting in types of hydrodynamic structures not previously recognized. The structures provide insights into the range of extreme pressures possible with the...

This study interprets deformations of indurated 10s of metres thick bedrock strata by subglacial meltwater pressures at maximum levels, resulting in types of hydrodynamic structures not previously recognized. The structures provide insights into the range of extreme pressures possible with the backup of meltwaters sufficient to deform multi-metre thick indurated beds, unlike elsewhere. Subglacial meltwater flows into the subsurface below the 50–100 m thick bitumen platform aquiclude of the Cretaceous Athabasca Oil Sands deposit were driven by the hydraulic head of the 1.5-km-thick Laurentide Ice Sheet. These meltwaters over-pressured the regional Devonian aquifer waters, but the low permeability of the aquifer below the site of the Muskeg River Mine was insufficient to accommodate the voluminous influxes of subglacial meltwater. The resulting meltwater flows backed-up, resulting in elevating aquifer pressures to maximum levels along the margins of the underlying Devonian Keg River reef mound and within water-saturated Cretaceous sand beds offset to the east. The meltwater pressure build to extreme levels hydrofractured strata at sites along the margins of the Keg River mound preconditioned by dissolution-induced subsidence in underlying salt beds. Release of the confining pressure upon withdrawal of the Laurentide Ice Sheet resulted in 45-m-high open blowout structures that punctured the bitumen platform at sites above the northern margin of the Keg River mound. Other blowout chimney sites above the southern margin of the mound were plugged because of insufficient pressure build to clear vents of all ejecta. Concurrently, pressured meltwater flows along the eastern margin resulted in dykes that cross-cut and buckled Devonian limestone beds. Some dykes extended into overlying water-saturated unconsolidated Cretaceous sand beds, channelling pressured water and hydroplastic mudflows that dissipated the extreme meltwater flow pressures and prevented puncturing of the overlying bitumen platform. These unusual deformation structures in western Canada resulted from catastrophic failure of hydrofractured rock zones responding to extreme meltwater pressures, in contrast to unconsolidated sediment deformations resulting from only moderately elevated meltwater pressures commonly observed elsewhere.

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The last deglaciation of the Norwegian Channel – geomorphology, stratigraphy and radiocarbon dating

Björn M. Morén, Hans Petter Sejrup, Berit O. Hjelstuen, Marianne V. Borge, Cathrina Schäuble

17/08/2017

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Based on high-resolution TOPAS acoustic data, bathymetric data sets and sediment cores from the Norwegian Channel, the last retreat of the Norwegian Channel Ice Stream has been investigated. Mapping of ice-marginal features such as grounding-zone wedges and terminal moraines off western Norway...

Based on high-resolution TOPAS acoustic data, bathymetric data sets and sediment cores from the Norwegian Channel, the last retreat of the Norwegian Channel Ice Stream has been investigated. Mapping of ice-marginal features such as grounding-zone wedges and terminal moraines off western Norway suggest that the retreat of the grounding line in this part of the channel was interrupted by frequent stillstands, whereas the channel south of the threshold at Jæren does not have crossing ice-marginal landforms. Three main seismic units have been identified, and, based on their seismic characteristics, in addition to study of sediment cores, these units are interpreted as till (U1), glacial marine sediment (U2) and Holocene hemipelagic sediment (U3). Based on new and published radiocarbon dates of the lower part of U2, combined with dates from the adjacent areas, it is concluded that the grounding line started to retreat from the shelf edge at about 19 ka and that the inner part of Skagerrak was ice free at 17.6 ka. This gives an average retreat rate of 450 m a−1, which is generally higher than mean retreat rates estimated for other palaeo-ice streams (15–310 m a−1).

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Stalagmites from western Thailand: preliminary investigations and challenges for palaeoenvironmental research

Sakonvan Chawchai, Guangxin Liu, Raphael Bissen, Kampanart Jankham, Warisa Paisonjumlongsri, Pitsanupong Kanjanapayont, Vichai Chutakositkanon, Montri Choowong, Santi Pailoplee, Xianfeng Wang

13/12/2017

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Locating suitable caves and stalagmites for palaeoenvironmental and palaeoclimatic studies can be challenging. Isotopic geochemical analyses, albeit commonly performed for palaeoclimatic reconstruction, are also time consuming and costly. Therefore, petrographic and non-destructive...

Locating suitable caves and stalagmites for palaeoenvironmental and palaeoclimatic studies can be challenging. Isotopic geochemical analyses, albeit commonly performed for palaeoclimatic reconstruction, are also time consuming and costly. Therefore, petrographic and non-destructive morphological studies on speleothems are desirable to facilitate sample selection for further analysis. In this study, 20 caves were surveyed in Ban Rai district, Uthai Thani province in western Thailand. After external physical observations in the field, three stalagmite samples were collected from Tham Nam Cave to test their potential for palaeoclimatic research. Firstly, the stalagmites were scanned by X-ray computed tomography (CT scanning) and subsequently the CT images were compared with petrographic inspections. Columnar fabrics show the highest density, whereas closed and open dendritic fabrics have medium and the lowest densities, respectively. Layers near the top and bottom of the three stalagmites were dated by U-Th mass spectrometric techniques. All three samples were deposited between c. 87 and c. 105 ka ago; therefore, they are probably the oldest stalagmites that have been reported so far from mainland Southeast Asia. However, their physical features indicate that all the samples have suffered from postdepositional dissolution, and are unlikely to be suitable for palaeoclimatic research. The internal dissolution feature of stalagmites, however, cannot be identified by visual inspection of uncut samples. We hereby argue that CT images are useful to characterize stalagmite petrography, in particular fabric, porosity and density. Such features can be used to select the ideal plane of a stalagmite for sectioning, to maximize the chances of robust climatic reconstruction.

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Corrigendum

05/12/2017

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