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  • 1.
    Ampel, Linda
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Kylander, Malin E.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Steinthorsdottir, Margret
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Wohlfarth, Barbara
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Abrupt climate change and early lake development - the Lateglacial diatom flora at Hasseldala Port, southeastern Sweden2015In: Boreas, ISSN 0300-9483, E-ISSN 1502-3885, Vol. 44, no 1, p. 94-102Article in journal (Refereed)
    Abstract [en]

    The fossil diatom record from the Hasseldala Port palaeolake, southeastern Sweden, offers an excellent opportunity to investigate how past climatic shifts influenced catchment conditions and early lake development. The record, dating to between 13900 and 11200 cal. a BP, covers a climatically dynamic period, starting with deglaciation followed by oscillations between warmer and colder climate states. The stratigraphical changes in the fossil diatom assemblages show a trend of less open-water taxa and a successively more complex periphytic community as the lake shallows and the aquatic habitat structure develops. A diatom-based reconstruction of lake water pH indicates a natural acidification trend early in the record from 13900 to 12500 cal. a BP. From 12500 cal. a BP, coincident with the start of climate cooling, to 11300 cal. a BP this trend is disrupted and lake waters become more alkaline. A cooler and drier climate most likely resulted in reduced soil organic matter build-up as well as more frozen ground that impeded hydrological flow and decreased the input of dissolved organic matter and organic acids into the lake system. This study demonstrates the importance of the hydrological system as a link between terrestrial and aquatic ecosystems during early lake ontogeny.

  • 2.
    Berntsson, Annika
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Jansson, Krister
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Kylander, Malin E.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    De Vleeschouwer, François
    CNRS, EcoLab, Castanet Tolosan, France.
    Bertrand, Sebastien
    Ghent University.
    Late Holocene high precipitation events recorded in lake sediments and catchment geomorphology, Lake Vuoksjávrátje, NW SwedenManuscript (preprint) (Other academic)
    Abstract [en]

    In this paper, we highlight the importance of combining multi-proxy analysis of lake sediments with associated catchment geomorphology to better understand the late Holocene palaeoenvironmental evolution in a high latitude Alpine lake in N Sweden. Previous studies have suggested that such lakes may be highly sensitive to variations in catchment erosion and variations in precipitation, and that this sensitivity may influence ecologically-based reconstructions of past temperature changes. Here we have analysed lake sediments covering the last 5100 years from Lake Vuoksjávrátje in NW Sweden to identify different erosional regimes in the lake catchment and to identify sediment sources and lake sedimentary processes, which ultimately affect the palaeoecological record. Methods that were used include XRF core scanning, grain size analysis and geomorphological mapping, supported by previously published chironomid, total organic carbon and carbon/nitrogen data. From the integrated results we identify time intervals when increased amounts/intensity of precipitation altered sedimentation and lake catchment erosional processes. The most prominent event in our record occurred between 3090 and 2750 cal. a BP and is interpreted to be the result of excessive precipitation in relation to the 2.8 ka event. By combining the multi-proxy analysis of a lake sediment core with a detailed catchment characterisation it is possible to reach a better understanding of the processes active within the lake catchment, the factors governing the erosional regimes and the way these are recorded in lake sediments. For future palaeoclimatological research based on lake sediments we recommend increasing the integration of catchment geomorphology, sedimentology and palaeoecology.

  • 3.
    Berntsson, Annika
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Jansson, Krister N.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Kylander, Malin E.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    De Vleeschouwer, Francois
    Bertrand, Sebastien
    Late Holocene high precipitation events recorded in lake sediments and catchment geomorphology, Lake Vuoksjavratje, NW Sweden2015In: Boreas, ISSN 0300-9483, E-ISSN 1502-3885, Vol. 44, no 4, p. 676-692Article in journal (Refereed)
    Abstract [en]

    In this paper, we show the potential of combining multi-proxy analysis of lake sediments with catchment geomorphology to better understand palaeoenvironmental changes. Previous studies have suggested that alpine lakes in N Sweden may be highly sensitive to variations in catchment erosion and precipitation, and that this sensitivity may influence ecologically based reconstructions of past temperature changes. We analysed lake sediments covering the last 5100 years from the alpine Lake Vuoksjavratje in NW Sweden in order to identify different erosional regimes in the lake catchment, sediment sources and lake sedimentary processes, which ultimately affect the palaeoecological record. The measured proxies include elemental geochemistry from XRF core scanning, grain size, sediment accumulation rates, fraction of terrestrial organic carbon and geomorphological mapping, supported by previously published chironomid and total organic carbon data. From the integrated results we identified time intervals when increased intensity of precipitation altered sedimentation and lake catchment erosional processes. The most prominent event occurred c. 2900 cal. a BP and is interpreted to be the result of excessive precipitation, possibly related to the climatic shift towards cooler and wetter conditions referred to as the 2.8 ka event.

  • 4.
    Carugati, Gabriele
    et al.
    University of Insubria Department of Chemical and Environmental Science 22100 Como Italy.
    Rauch, Sebastien
    Chalmers University of Technology Water Environment Technology, Department of Civil and Environmental Engineering .
    Kylander, Malin E.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Experimental assessment of a large sample cell for laser ablation-ICP-MS, and its application to sediment core micro-analysis2010In: Mikrochimica Acta, ISSN 0026-3672, E-ISSN 1436-5073, Vol. 170, no 1-2, p. 39-45Article in journal (Refereed)
    Abstract [en]

    The coupling of laser ablation (LA) to inductively coupled plasma-mass spectrometry (ICP-MS) enables the direct analysis of solid samples with micrometric resolution. Analysis is often restricted to relatively small samples owing to the dimensions of conventional ablation cells. Here, we assess the performance of a large rectangular, commercially-available sample cell which enables analysis over a 10.2 x 5.2 cm(2) area. Comparison with the conventional cell shows a small to moderate performance decrease for the large cell resulting from the dilution of ablated particles in a larger volume with a 4-31% lower signal output and longer signal tailings. The performance of this cell is however sufficient for the determination of both major and trace elements in many kinds of samples. The applicability of the large cell LA-ICP-MS setup was demonstrated by the determination of Al, Si, Mn, Fe, Cu, Zn Pb and U in sediment core sections at a resolution of 0.6 mm. Detection limits for sediment analysis were 7 mg Al kg(-1), 68 mg Si kg(-1), 0.5 mg Mn kg(-1), 20 mg Fe kg(-1), 0.2 mg Cu kg(-1), 0.3 mg Zn kg(-1), 0.08 mg Pb kg(-1) and 0.003 mg U kg(-1). Cyclic patterns, which would have been overlooked by conventional analysis at cm resolution, were observed in analysed sediments. This study demonstrates the potential of LA-ICP-MS in environmental analysis, with the large sample cell setup offering the possibility to analyse a wider range of samples without sectioning.

  • 5.
    Chawchai, Sakonvan
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Chabangborn, Akkaneewut Nut
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Kylander, Malin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Loewemark, L.
    Mörth, Carl-Magnus
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Blaauw, M.
    Klubseang, W.
    Reimer, P. J.
    Fritz, S. C.
    Wohlfarth, Barbara
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Lake Kumphawapi - an archive of Holocene palaeoenvironmental and palaeoclimatic changes in northeast Thailand2013In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 68, p. 59-75Article in journal (Refereed)
    Abstract [en]

    The long-term climatic and environmental history of Southeast Asia, and of Thailand in particular, is still fragmentary. Here we present a new C-14-dated, multi-proxy sediment record (TOC, C/N, CNS isotopes, Si, Zr, K, Ti, Rb, Ca elemental data, biogenic silica) for Lake Kumphawapi, the second largest natural lake in northeast Thailand. The data set provides a reconstruction of changes in lake status, groundwater fluctuations, and catchment run-off during the Holocene. A comparison of multiple sediment sequences and their proxies suggests that the summer monsoon was stronger between c. 9800 and 7000 cal yr BP. Lake status and water level changes around 7000 cal yr BP signify a shift to lower effective moisture. By c. 6500 cal yr BP parts of the lake had been transformed into a peatland, while areas of shallow water still occupied the deeper part of the basin until c. 5400-5200 cal yr BP. The driest interval in Kumphawapi's history occurred between c. 5200 and 3200 cal yr BP, when peat extended over large parts of the basin. After 3200 cal yr BP, the deepest part of the lake again turned into a wetland, which existed until c. 1600 cal yr BP. The observed lake-level rise after 1600 cal yr BP could have been caused by higher moisture availability, although increased human influence in the catchment cannot be ruled out. The present study highlights the use of multiple sediment sequences and proxies to study large lakes, such as Lake Kumphawapi in order to correctly assess the time transgressive response to past changes in hydroclimate conditions. Our new data set from northeast Thailand adds important palaeoclimatic information for a region in Southeast Asia and allows discussing Holocene monsoon variability and ITCZ movement in greater detail.

  • 6. Chawchai, Sakonvan
    et al.
    Kylander, Malin E.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Chabangborn, Akkaneewut
    Löwemark, Ludvig
    Wohlfarth, Barbara
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Testing commonly used XRF core scanning based proxies for organic rich lake sediments and peat2016In: Boreas, ISSN 0300-9483, E-ISSN 1502-3885, Vol. 45, no 1, p. 180-189Article in journal (Refereed)
    Abstract [en]

    X-ray fluorescence (XRF) core scanning has become widely available for geological studies during the last decade. The data obtained from XRF core scanning, however, may be strongly influenced by the amount of organic matter, water content, density and porosity of the sediment matrix. In this study we discuss the usefulness of XRF core scanning to distinguish different kinds of organic-rich sediments and peat based on examples from tropical Lakes Kumphawapi and Nong Leng Sai in Thailand. We examined how sedimentary factors influence XRF core scanning analyses by comparing elemental and scattering ratios to lithological changes and quantitative LOI, TOC, biogenic silica (BSi) and grain-size values. Our comparison suggests that the (inc/coh) scattering ratio is of limited use as an indicator for variations in LOI and TOC in peaty gyttja or peat. In Lake Kumphawapi's sediments, Si/Ti ratios reflect clastic input associated with grain-size variations rather than BSi contents. The Ti-normalized ratios of Si, Zr, Sr, K and Rb are linked to mineral input and associated grain-size variations. We conclude that XRF core scanning of organic-rich tropical lake sediments and peat is useful to infer palaeoenvironmental conditions. However, XRF core scanning data does not stand-alone and needs to be underpinned by additional proxies.

  • 7. Diaz Somoano, Mercedes
    et al.
    Kylander, Malin
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Martínez-Tarazona, MR
    Suarez-Ruiz, I
    López Antón, M
    Kober, B
    Ferrat, Marion
    Weiss, Dominik
    Stable Lead Isotope Compositions In Selected Coals From Around The World And Implications For Present Day Aerosol Source Tracing2009In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 43, no 4, p. 1078-1085Article in journal (Refereed)
    Abstract [en]

    The phasing out of leaded gasoline in many countries around the world at the end of the last millennium has resulted in a complex mixture of lead sources in the atmosphere. Recent studies suggest that coal combustion has become an important source of Pb in aerosols in urban and remote areas. Here, we report lead concentration and isotopic composition for 59 coal samples representing major coal deposits worldwide in an attempt to characterize this potential source. The average concentration in these coals is 35 μg Pb g−1, with the highest values in coals from Spain and Peru and the lowest in coals from Australia and North America. The 206Pb/207Pb isotope ratios range between 1.15 and 1.24, with less radiogenic Pb in coals from Europe and Asia compared to South and North America. Comparing the Pb isotopic signatures of coals from this and previous studies with those published for Northern and Southern Hemisphere aerosols, we hypothesize that coal combustion might now be an important Pb source in China, the eastern U.S., and to some extent, in Europe but not as yet in other regions including South Africa, South America, and western U.S. This supports the notion that “old Pb pollution” from leaded gasoline reemitted into the atmosphere or long-range transport (i.e., from China to the western U.S.) is important. Comparing the isotope ratios of the coals, the age of the deposits, and Pb isotope evolution models for the major geochemical reservoirs suggests that the PbIC in coals is strongly influenced by the depositional coal forming environment.

  • 8.
    Finné, Martin
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Kylander, Malin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Boyd, Meighan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Sundqvist, Hanna S.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Löwemark, Ludvig
    Can XRF scanning of speleothems be used as a non-destructive method to identify paleoflood events in caves?2015In: International Journal of Speleology, ISSN 0392-6672, E-ISSN 1827-806X, Vol. 44, no 1, p. 17-23Article in journal (Refereed)
    Abstract [en]

    We have developed a novel, quick and non-destructive method for tracing flood events in caves through the analysis of a stalagmite thick section with an XRF core scanner. The analyzed stalagmite has multiple horizons of fine sediments from past flood events intercalated with areas of cleaner calcite. Flood events detected from the elemental XRF core scanning data show good agreement with the position of flood horizons identified in petrographic thin sections. The geochemical composition of the individual flood layers shows that in certain cases the clay horizons had a distinct geochemical fingerprint suggesting that it may be possible to distinguish individual flood layers based on their geochemistry. This presents the possibility for using flood events as marker horizons to chronologically tie different speleothems in a cave to each other.

  • 9. Gallagher, K
    et al.
    Bodin, T
    Sambridge, M
    Weiss, D
    Kylander, Malin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Large, David
    Inference of abrupt changes in noisy geochemical records using transdimensional changepoint models2011In: Earth and Planetary Science Letters, ISSN 0012-821X, E-ISSN 1385-013X, Vol. 311, no 1-2, p. 182-194Article in journal (Refereed)
    Abstract [en]

    We present a method to quantify abrupt changes (or changepoints) in data series, represented as a function of depth or time. These changes are often the result of climatic or environmental variations and can be manifested in multiple datasets as different responses, but all datasets can have the same changepoint locations/timings. The method we present uses transdimensional Markov chain Monte Carlo to infer probability distributions on the number and locations (in depth or time) of changepoints, the mean values between changepoints and, if required, the noise variance associated with each dataset being considered. This latter point is important as we generally will have limited information on the noise, such as estimates only of measurement uncertainty, and in most cases it is not practical to make repeat sampling/measurement to assess other contributions to the variation in the data. We describe the main features of the approach (and describe the mathematical formulation in supplementary material), and demonstrate its validity using synthetic datasets, with known changepoint structure (number and locations of changepoints) and distribution of noise variance for each dataset. We show that when using multiple data, we expect to achieve better resolution of the changepoint structure than when we use each dataset individually. This is conditional on the validity of the assumption of common changepoints between different datasets. We then apply the method to two sets of real geochemical data, both from peat cores, taken from NE Australia and eastern Tibet. Under the assumption that changes occur at the same time for all datasets, we recover solutions consistent with those previously inferred qualitatively from independent data and interpretations. However, our approach provides a quantitative estimate of the relative probability of the inferred changepoints, allowing an objective assessment of the significance of each change.

  • 10. Hansson, Sophia V.
    et al.
    Rydberg, Johan
    Kylander, Malin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Gallagher, Kerry
    Bindler, Richard
    Evaluating paleoproxies for peat decomposition and their relationship to peat geochemistry2013In: The Holocene, ISSN 0959-6836, E-ISSN 1477-0911, Vol. 23, no 12, p. 1666-1671Article in journal (Refereed)
    Abstract [en]

    The past decade has seen a rapid increase in interest in the biogeochemical record preserved in peat, particularly as it relates to carbon dynamics and environmental change. Importantly, recent studies show that carbon dynamics, that is, organic matter decomposition, can influence the record of atmospherically derived elements such as halogens and mercury. Most commonly, bulk density, light transmission, or carbon/nitrogen (C/N) ratios are used as a proxy to qualitatively infer the degree of decomposition in peat, but do these three proxies reflect the same patterns? Furthermore, how do each of these proxies relate to other geochemical data? To address these questions, we analyzed bulk density, light transmission, and C/N ratios, as well as multielement geochemistry (wavelength-dispersive x-ray fluorescence (WD-XRF)), in three hummock cores (70 cm in length, c. 500 years) from an ombrotrophic Swedish bog. To compare the proxies, we applied principal component analysis (PCA) to identify how the proxies relate to and interact with the geochemical matrix. This was coupled with changepoint modeling to identify and compare statistically significant changes for each proxy. Our results show differences between the proxies within and between cores, indicating each responds to a different part of the decomposition process. This is supported by the PCA, where the three proxies fall on different principal components. Changepoint analysis also showed that the inferred number of changepoints and their depths vary for each proxy and core. This suggests that decomposition is not fully captured by any one of these commonly used proxies, and thus, more than one proxy should be included.

  • 11.
    Helmens, Karin F.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Salonen, J. Sakari
    Plikk, Anna
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Engels, Stefan
    Valiranta, Minna
    Kylander, Malin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Brendryen, Jo
    Renssen, Hans
    Major cooling intersecting peak Eemian Interglacial warmth in northern Europe2015In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 122, p. 293-299Article in journal (Refereed)
    Abstract [en]

    The degree of climate instability on the continent during the warmer-than-present Eemian Interglacial (around ca. 123 kyr ago) remains unsolved. Recently published high-resolution proxy data from the North Atlantic Ocean suggest that the Eemian was punctuated by abrupt events with reductions in North Atlantic Deep Water formation accompanied by sea-surface temperature cooling. Here we present multiproxy data at an unprecedented resolution that reveals a major cooling event intersecting peak Eemian warmth on the North European continent. Two independent temperature reconstructions based on terrestrial plants and chironomids indicate a summer cooling of the order of 2-4 degrees C. The cooling event started abruptly, had a step-wise recovery, and lasted 500-1000 yr. Our results demonstrate that the common view of relatively stable interglacial climate conditions on the continent should be revised, and that perturbations in the North Atlantic oceanic circulation under warmer-than-present interglacial conditions may also lead to abrupt and dramatic changes on the adjacent continent.

  • 12. Johnson, Mark D.
    et al.
    Kylander, Malin E.
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Casserstedt, Lovise
    Wiborgh, Hanna
    Björck, Svante
    Varved glaciomarine clay in central Sweden before and after the Baltic Ice Lake drainage: a further clue to the drainage events at Mt Billingen2013In: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 135, no 3-4, p. 293-307Article in journal (Refereed)
    Abstract [en]

    Glaciomarine clay found west of Mt Billingen, central Sweden, contains two distinct varve units separated by a sand layer that we interpret to be sediment deposited in the North Sea during the catastrophic drainage of the Baltic Ice Lake (BIL). The lower varve series was deposited proximal to the retreating ice margin and consists of varves that grade upward from gray to red. The upper varve series was deposited after the drainage event when fresh water within the Baltic basin flowed westward north of Billingen; the upper varves grade from red to gray. Grain size, elemental composition (determined by X-ray fluorescence (XRF)), iron and organic-carbon content vary within each varve, with values that grade upward through each varve, but with a sharp contact with the overlying varve. The two varve units differ from each other, with the lower sequence being coarser and the upper containing a higher iron and organic-carbon content. We attribute the differences between pre- and post-drainage varves to reflect changes in distance to the ice margin and provenance. The stratigraphy at the site suggests that the BIL drainage lasted <1 year. Lithostratigraphic correlations to the Lake Langen basin west of Mt Billingen support the idea of glacier ice in the Langen basin during the drainage and a retreat and advance of the ice sheet during Allerod and Younger Dryas, including the possibility of an earlier, Allerod drainage.

  • 13.
    Kylander, Malin
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Ampel, Linda
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Veres, Daniel
    Wohlfarth, Barbara
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    High‐Resolution XRF Core Scanning Analysis of Les Echets (France) Sedimentary Sequence: New Insights from Chemical Proxies2011In: Journal of Quaternary Science, ISSN 1099-1417, Vol. 26, no 1, p. 109-117Article in journal (Refereed)
    Abstract [en]

    The Les Echets sediment sequence has recently been the subject of a high-resolution, multi-proxy study which revealed shifts in lake productivity linked to Greenland stadials and interstadials over the last 40 kyr (Wohlfarth et al., 2008. Rapid ecosystem response to abrupt climate changes during the last glacial period in western Europe, 40-16 ka. Geology 36:407-410). Here we present new elemental data for this sequence as acquired using an XRF core scanning system which provides in situ high-resolution, continuous, multi-element analyses. It was found that the strength of associations between the studied elements (Ti, Rb, K, Zr, Si, Ca, Sr, Mn and Fe) varied over time with changes in lake status which are ultimately driven by changes in climate. Increases in fine grained, detrital input (as indicated by Ti, Rb, K and Zr/Rb) overlap with independently established periods of lower lake productivity and are interpreted to represent more arid conditions. Several of these arid periods are coincident with low diatom concentrations and the timing of Heinrich events H4, H3 and H2. The duration of the environmental impacts linked to the H events varied based on the proxy used with the elemental data (Ti and Zr/Rb) estimating shorter events than the diatom data. Periods of lower detrital input and coarser grain sizes agreed in time with periods of higher lake productivity. The elemental data provides new insight into hydrological changes and related sediment processes within the catchment, and highlights the need for multi-element and multi-proxy approaches when reconstructing climate change using lacustrine sediment sequences. 

  • 14.
    Kylander, Malin
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Bindler, Richard
    Cortizas, Antonio Martinez
    Gallagher, Kerry
    Mörth, Carl-Magnus
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Rauch, Sebastien
    A novel geochemical approach to paleorecords of dust deposition and effective humidity: 8500 years of peat accumulation at Store Mosse (the Great Bog), Sweden2013In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 69, p. 69-82Article in journal (Refereed)
    Abstract [en]

    Both bog surface wetness and atmospheric dust deposition are intricately linked to changes in the hydrological cycle and pairing these types of records at the same site provides complementary information. Here a peat core from Store Mosse in southern Sweden covering the last 8500 years was used to make a high-resolution paleoclimate reconstruction based on a combination of bog development, colourimetric humification and inorganic geochemistry data. The coupling of Principal Component Analysis with changepoint modelling allowed for precise linking of changes in bog surface wetness and dust deposition records. A long-term trend towards warm (and possibly wet) conditions starts ca 8150 cal yr BP and culminates with the most pronounced conditions from 6900 to 6600 cal yr BP. The most significant arid period at Store Mosse occurred between 6500 and 5600 cal yr BP during which dust deposition was significantly higher. Wetter conditions dominate from 5500 to 4980 cal yr BP as the transition from the Hypsithermal and into the Neoglacial is made. After a shift to drier conditions, humification enters a more stable period that lasts from 4525 until 3200 cal yr BP. It is during this time that the first possible anthropogenic dust signals occur at ca 4200 cal yr BP. From 3200 cal yr BP to present humification generally shows a long-term decline moving towards wetter conditions. The main exceptions are during the transition from the Neoglacial to Roman Warm Period which is registered as a significantly wetter period and two dry periods recorded 2365 to 2155 cal yr BP and 1275-1105 cal yr BP. In general, the observed changes agree well with regional records of effective humidity and temperature. The high temporal resolution of the Store Mosse record reveals that palaeoclimatic change over the last 8500 years in southern Sweden has had a complex and variable structure.

  • 15.
    Kylander, Malin
    et al.
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Coulter, Sarah
    Klimaschewski, Andrea
    Wohlfarth, Barbara
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    A New Micro-Analytical Technique for the Identification of Tephra Layers in Sediments2008Conference paper (Other (popular science, discussion, etc.))
    Abstract [en]

    Tephrochronology uses material emitted during volcanic eruptions as isochronous markers for linking paleoclimatic records. Cryptotephra (i.e., those tephra not visible to the naked eye) layers can be as little as one to two shards thick while the shards themselves can be smaller than 10 m. The methods used to locate cryptotephra are often time consuming and laborious (e.g., sieving and point counting, density separation techniques) and in some cases may not be applicable (e.g., magnetic susceptibility of tephra may not differ from the sediment). XRF is a well-established analytical tool that has recently taken a new direction with the introduction of core scanning systems. The ITRAX XRF core scanning system is non-destructive, can acquire continuous data for a broad range of elements in situ in both marine and lacustrine sediments as well as take radiographic images. We test the possibility of screening sediment cores to flag the potential location of cryptotephra layers thereby eliminating lengthy laboratory work and saving on often precious sample. The method was tested by seeding a sediment core with tephra shards in layers of increasing thickness and then scanning the core with the ITRAX. The method was then further tested on sequences from two different sites: Hässeldala Port in Southern Sweden where up to 5 different cryptotephra have been detected and Lake Pechora from Russia which has several visible tephra layers. We show that using the ITRAX it is possible to locate most tephra layers without using any sample and within a minimal amount of time (a 1 m core can be analyzed reasonably in 12 hours and it requires essentially no sample preparation).

  • 16.
    Kylander, Malin E.
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Martinez-Cortizas, A.
    Bindler, Richard
    Kaal, Joeri
    Sjöström, Jenny K.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Hansson, Sophia V.
    Silva-Sanchez, Noemi
    Greenwood, Sarah L.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Gallagher, Kerry
    Rydberg, Johan
    Mörth, Carl-Magnus
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Rauch, Sebastien
    Mineral dust as a driver of carbon accumulation in northern latitudes2018In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, article id 6876Article in journal (Refereed)
    Abstract [en]

    Peatlands in northern latitudes sequester one third of the world's soil organic carbon. Mineral dusts can affect the primary productivity of terrestrial systems through nutrient transport but this process has not yet been documented in these peat-rich regions. Here we analysed organic and inorganic fractions of an 8900-year-old sequence from Store Mosse (the Great Bog) in southern Sweden. Between 5420 and 4550 cal yr BP, we observe a seven-fold increase in net peat-accumulation rates corresponding to a maximum carbon-burial rate of 150 g C m(-2) yr(-1) -more than six times the global average. This high peat accumulation event occurs in parallel with a distinct change in the character of the dust deposited on the bog, which moves from being dominated by clay minerals to less weathered, phosphate and feldspar minerals. We hypothesize that this shift boosted nutrient input to the bog and stimulated ecosystem productivity. This study shows that diffuse sources and dust dynamics in northern temperate latitudes, often overlooked by the dust community in favour of arid and semi-arid regions, can be important drivers of peatland carbon accumulation and by extension, global climate, warranting further consideration in predictions of future climate variability.

  • 17.
    Kylander, Malin E.
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Martinez-Cortizas, Antonio
    Bindler, Richard
    Greenwood, Sarah L.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Mörth, Carl-Magnus
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Rauch, Sebastien
    Potentials and problems of building detailed dust records using peat archives: An example from Store Mosse (the Great Bog), Sweden2016In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 190, p. 156-174Article in journal (Refereed)
    Abstract [en]

    Mineral dust deposition is a process often overlooked in northern mid-latitudes, despite its potential effects on ecosystems. These areas are often peat-rich, providing ample material for the reconstruction of past changes in atmospheric deposition. The highly organic (up to 99% in some cases) matrix of atmospherically fed mires, however, makes studying the actual dust particles (grain size, mineralogy) challenging. Here we explore some of the potentials and problems of using geochemical data from conservative, lithogenic elements (Al, Ga, Rb, Sc, Y, Zr, Th, Ti and REE) to build detailed dust records by using an example from the 8900-yr peat sequence from Store Mosse (the Great Bog), which is the largest mire complex in the boreo-nemoral region of southern Sweden. The four dust events recorded at this site were elementally distinct, suggesting different dominant mineral hosts. The oldest and longest event (6385-5300 cal yr BP) sees a clear signal of clay input but with increasing contributions of mica, feldspar and middle-REE- rich phosphate minerals over time. These clays are likely transported from a long-distance source (< 100 km). While dust deposition was reduced during the second event (5300-4370 cal yr BP), this is the most distinct in terms of its source character with [Eu/Eu*] UCC revealing the input of plagioclase feldspar from a local source, possibly active during this stormier period. The third (2380- 2200 cal yr BP) and fourth (1275-1080 cal yr BP) events are much shorter in duration and the presence of clays and heavy minerals is inferred. Elemental mass accumulation rates reflect these changes in mineralogy where the relative importance of the four dust events varies by element. The broad changes in major mineral hosts, grain size, source location and approximated net dust deposition rates observed in the earlier dust events of longer duration agree well with paleoclimatic changes observed in northern Europe. The two most recent dust events are much shorter in duration, which in combination with evidence of their local and regional character, may explain why they have not been seen elsewhere.

  • 18.
    Kylander, Malin E.
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Plikk, Anna
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Rydberg, Johan
    Löwemark, Ludvig
    Salonen, J. Sakari
    Fernández-Fernández, María
    Helmens, Karin
    Stockholm University, Faculty of Science, Department of Physical Geography.
    New insights from XRF core scanning data into boreal lake ontogeny during the Eemian (Marine Isotope Stage 5e) at Sokli, northeast Finland2018In: Quaternary Research, ISSN 0033-5894, E-ISSN 1096-0287, Vol. 89, no 1, p. 352-364Article in journal (Refereed)
    Abstract [en]

    Biological proxies from the Sokli Eemian (Marine Isotope Stage 5e) paleolake sequence from northeast Finland have previously shown that, unlike many postglacial records from boreal sites, the lake becomes increasingly eutrophic over time. Here, principal components (PC) were extracted from a high resolution multi-element XRF core scanning dataset to describe minerogenic input from the wider catchment (PC1), the input of S, Fe, Mn, and Ca-rich detrital material from the surrounding Sokli Carbonatite Massif (PC2), and chemical weathering (PC3). Minerogenic inputs to the lake were elevated early in the record and during two abrupt cooling events when soils and vegetation in the catchment were poor. Chemical weathering in the catchment generally increased over time, coinciding with higher air temperatures, catchment productivity, and the presence of acidic conifer species. Abiotic edaphic processes play a key role in lake ontogeny at this site stemming from the base cation- and nutrient-rich bedrock, which supports lake alkalinity and productivity. The climate history at this site, and its integrated effects on the lake system, appear to override development processes and alters its long-term trajectory.

  • 19.
    Kylander, Malin
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Klaminder, Jonatan
    Department of Ecology and Environmental Sciences, Umeå University .
    Bindler, Richard
    Department of Ecology and Environmental Sciences, Umeå University.
    Weiss, Dominik
    Department of Earth Science and Engineering, Imperial College London.
    Natural lead isotope variations in the atmosphere2010In: Earth and Planetary Science Letters, ISSN 0012-821X, E-ISSN 1385-013X, Vol. 290, no 1-2, p. 44-53Article in journal (Refereed)
    Abstract [en]

    Stable lead (Pb) isotope data from pre-contamination peat sections has the potential to contribute to our understanding of earth system processes (e.g., atmospheric circulation, erosion, volcanic activity) in the past. Key questions arise however. Can the Pb isotopes archived in peat records be used for assessing aerosol dynamics on a hemispheric scale or do they mainly reflect inputs from local soils? What natural Pb sources are important and do contributions vary over time? In order to answer these questions we have synthesized all available Pb isotope data from pre-contamination peat sections in Europe, Australia, North America and South America. We specifically examine the spatial and temporal variability of the Pb isotope records and identify regionally important trends and Pb sources.

    A pooling of all available pre-contamination peat data generated an average natural 206Pb/207Pb background ratio of 1.21±0.05 (2σ, n=300)(206Pb/204Pb= 18.90±0.86, 207Pb/204Pb= 15.66±0.10 and 208Pb/204Pb= 38.74±0.57, n=207). The majority of the records showed limited temporal and compositional agreement, suggesting that the peat record receives mainly inputs from local (<10 km) and/or regional (10-500 km) sources. Three-isotope plots also support local and regional control and evidence a wide natural spread at some sites, particularly those located in radiogenic geological settings. A temporally synchronous isotope excursion to values between 1.16-1.18 at sites across Europe ca 4000-3000 B.C. was detected, however. While usually associated with anthropogenic sources, there are indeed natural aerosols having 206Pb/207Pb signatures as low as 1.16 as evidenced in several peat and ice core records globally. Three-isotope plots suggest that this unlikely to be a signal of mineral dust contributions, which tend to have 206Pb/207Pb ratios ≥1.19, but rather sourced to volcanic emissions. These results stress caution when using estimates of the upper continental crust to constrain natural Pb sources in, e.g., mixing equations. Considering the strong influence from local and regional sources on Pb-containing aerosols in the peat record, the assessment of aerosol dynamics at lower latitudes is likely best achieved using a compliment of archives rather than just polar ice cores, for example. 

  • 20.
    Kylander, Malin M
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Klaminder, Jonatan
    Wohlfarth, Barbara
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Loewemark, Ludvig
    Geochemical responses to paleoclimatic changes in southern Sweden since the late glacial: the Hasseldala Port lake sediment record2013In: Journal of Paleolimnology, ISSN 0921-2728, E-ISSN 1573-0417, Vol. 50, no 1, p. 57-70Article in journal (Refereed)
    Abstract [en]

    There is a relatively good understanding of the paleoenvironmental changes that have occurred in southern Sweden since the Late Glacial. A main exception, however, is the sedimentary response of lacustrine systems during this period of rapid climate shifts. To address this, high-resolution X-ray fluorescence core scanning, Total Organic Carbon (TOC), C/N and delta C-13 analyses were made on a core from Hasseldala Port, a paleolake in the region. Site-specific geochemical analyses documented variations in silicate inputs (Zr/Ti, Si/Ti, K/Ti and K/Rb), productivity (TOC, Ca/Ti and Sr/Ti), as well as redox conditions in the sediment (delta C-13, Mn/Ti and Fe/Ti), which were then linked to the regional climatic framework. During the Bolling/Older Dryas sediment accumulation was at its highest, particularly prior to colonization by terrestrial vegetation, and hydrological transport dominated. No clear signal of the Older Dryas was detected in the elemental chemistry. The Allerod was a period of relatively constant sediment accumulation, with the exception of during the Gerzensee oscillation when rates increased. There is evidence for increased within-lake and -catchment productivity and a change in silicate source during parts of the Allerod. As opposed to other records from the region, constant sediment accumulation rates were found during the Younger Dryas. Other proxies also suggest that this was a rather static period at Hasseldala Port. A gradual change in productivity and hydrological activity was observed from 12,000 cal year BP. The Preboreal section is rather short but the geochemical response was similar to that seen during other periods with milder climate conditions. The geochemical record archived in the sediments at Hasseldala Port was found to be the integrated result of physical erosion, landscape and soil development, vegetation changes, basin hydrology and moisture and temperature variations and it fills an important information gap in our understanding of the geochemical response of lake sediments to past climate change.

  • 21.
    Kylander, Malin M
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Lind, Ewa M
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Wastegård, Stefan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Löwemark, Ludvig
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Recommendations for using XRF core scanning as a tool in tephrochronology2012In: The Holocene, ISSN 0959-6836, E-ISSN 1477-0911, Vol. 22, no 3, p. 371-375Article in journal (Refereed)
    Abstract [en]

    X-ray fluorescence (XRF) core scanning is a relatively new arrangement of a classic analytical technique which allows for non-destructive, in situ XRF analysis of sediment cores from submillimetre resolution upwards. In this contribution we explore the use of XRF core scanning for tephrochronology based on the analysis of three gyttja-rich sediment cores from the Faroe Islands. Using a combination of optical and radiographic images, analytical parameters and elemental profiles (Si, K, Ca, Ti, Mn, Fe, Sr and Zr), higher concentration basaltic tephra layers (>1000 shards/cm3) were positively identified. The XRF core scanning did not capture the lower concentration (<850 shards/cm3) rhyolitic layers found in the core. The elemental data generated for the detected tephra layers using XRF core scanning was not comparable to individual shard analysis by electron microprobe. We recommend using XRF core scanning for tephra screening in order to localize depths for high-resolution subsampling and to avoid depths where sediment mixing has caused tailing/mixing of the tephra signal. At the studied site the basaltic Saksunarvatn ash as well as a tephra belonging to the Askja-S/10 ka eruption were identified.

  • 22.
    Kylander, Malin
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Potucek, Martina
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Bindler, Richard
    Wohlfarth, Barbara
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Using Peatlands as Archives of Dust Deposition: A Preliminary Record from Southern Sweden2010In: European Geosciences Union: General Assembly 2010, 2010, p. 2677-Conference paper (Refereed)
    Abstract [en]

    Our understanding of the complex role that mineral dust and its feedbacks play in the Earth's climate system is limited by its highly variable nature in space and time and a lack of data reflecting this variability. Paleorecords of dust provide a means by which we can examine the response of dust over time under very different climatic conditions. These records also supply the data (dust deposition rates, grain size, mineralogy and provenance) necessary to validate models of the dust cycle. Ombrotrophic peat is hydrologically isolated and therefore, like ice, records atmospheric deposition alone. Peatlands have a wide distribution globally, particularly in formerly glaciated regions, and are established environmental archives which provide continuous, high-resolution, datable records of atmospheric deposition and climate change. The use of peat for reconstructing dust deposition has been demonstrated, but as yet, not systematically examined. Their use as an archive of dust deposition must be further tested before they can be used to improve on the relatively poor spatial coverage of current terrestrial dust records (e.g., loess, lake sediments, dune building records). We present here a first focussed effort to reconstruct past changes in dust deposition through loss on ignition (LOI), bulk density, humification and inorganic geochemistry data using a peat sequence from Store Mosse in southern Sweden. This deposit has been studied previously and reveals a record that extends back some 5000 years. LOI data, in combination with elemental chemistry of the samples, aids in identifying those depths where the observed signal is atmospheric in source only. Humification analyses and bulk density are used as a proxy for surface wetness and allows for the linking of broader climatic changes (precipitation, evaporation, temperature) with fluctuations in dust deposition rates and changes in grain character (grain size, surface roughness). The inorganic geochemistry provides a means to quantify dust deposition as well as make a first attempt at source tracing of the deposited materials; this is important in terms of reconstructing changes in paleo wind regimes. Past variations in aeolian activity in Scandinavia are relatively unknown. Dune building records from Denmark and elsewhere around Europe show several periods of inland sand invasion and dune building during the Holocene. These are linked to cooler and stormier climates caused by shifts in the North Atlantic Oscillation and/or movement of the polar front. We compare the dust deposition record from Store Mosse with available dune building records and records of storminess from the region in order to make a preliminary assessment of the use of peatlands as paleo records of dust deposition.

  • 23.
    Kylander, Malin
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Wastegård, Stefan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Lind Mettävainio, Ewa
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Löwemark, Ludvig
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Wohlfarth, Barbara
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    The Itrax and organic rich sediments: Tephrochronologyand humification2010Conference paper (Refereed)
    Abstract [en]

    Holocene records of climate change can be derived from organic rich sediments such as peats (with organic contents >99%) and gyttja rich lake sediments. While the performance of the Itrax is generally negatively affected by higher organic matter contents, we are currently developing two separate Itrax applications for such sediments.

    Tephras are an important part of establishing good chronologies for Holocene sequences. Tephras can vary in thickness from a few centimeters to a few shards thick. Finding crypotephra (i.e., those tephra not visible to the naked eye) is a time consuming process involving tedious sub-sampling and density separations. In order to improve the efficiency of tephra extraction we are developing a method to ‘screen’ sediment cores for tephra. Using small step sizes (<1 mm), we identify areas where changes in the sample matrix (signaled through changes in the mean standard error) and elemental chemistry suggest the possible presence of tephra. These ‘target depths’ are then sub-sampled at a higher resolution (1 cm vs. 5 cm) for tephra extraction. To date we have tested three different sites and shard counts made at target depths shows that the Itrax can successfully locate both rhyolitic and basaltic tephra layers. In those cores with visible tephra, we are also testing the possibility of using major element concentrations from Itrax scans to make preliminary identifications of tephra layers through their elemental fingerprints. The Itrax generated plots are tested for accuracy by comparing them against conventional electron microprobe analyses of traditionally extracted tephra shards.

    Humification analyses reflect the level of decomposition of an organic deposit which in itself signals changes in evaporation/precipitation and temperature regimes, and by extension, paleo-climate. At present humification is measured through leaching of samples and the use of a colorimeter. We are developing the use of the Itrax to capture major changes in humification by using the ratio of coherent to incoherent scattering.

  • 24.
    Kylander, Malin
    et al.
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Weiss, Dominik
    Kober, Bernd
    Two high resolution terrestrial records of atmospheric Pb deposition from New Brunswick, Canada, and Loch Laxford, Scotland2009In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 407, no 5, p. 1644-1657Article in journal (Refereed)
    Abstract [en]

    Environmental archives like peat deposits allow for the reconstruction of both naturally and anthropogenically forced changes in the biogeochemical cycle of Pb and the quantification of past and present atmospheric Pb pollution. Records of atmospheric Pb deposition from pre-industrial times however, are lacking.

                    In a publication by Weiss et al. (2002) Pb isotope data measured by Q-ICP-MS and TIMS, concentration and enrichment data was presented for sites in eastern Canada (PeW1) and northwestern Scotland (LL7c), dating to 1586 A.D and 715 A.D., respectively. Here we re-analyse these same cores for Pb isotopes by MC-ICP-MS thereby acquiring 204Pb data and improving on the original data in terms of resolution and temporal coverage. Significant differences were found between the Q-ICP-MS/TIMS and MC-ICP-MS measurements, particularly at PeW1. These discrepancies are attributed to the problematic presence of organic matter during sample preparation and analysis compounded by the heterogeneity of the organic compounds that survived sample preparation steps. The precision and accuracy of Pb isotopes in complex matrices like peat is not always well estimated by industrial standards like NIST-SRM 981 Pb.

                    Lead pollution histories at each site were constructed using the MC-ICP-MS data. The entire LL7c record is likely subject to some amount of anthropogenic pollution. Contributions from local mining were detected in Medieval times. Later, coal use and mining in Scotland, Wales and England became important. After industrialization (ca. 1885 A.D.) contributions from Broken Hill type ores and hence, leaded petrol, dominate atmospheric Pb signatures right up to modern times. At PeW1 anthropogenic impacts are first distinguishable in the late 17th century with the mining and use of local coal. After industrialization (ca. 1810 A.D.), coal and petrol are the main Pb sources. A comprehensive estimate of the natural atmospheric background 206Pb/207Pb signature in eastern Canadian aerosols is made with a value of ~1.19.

  • 25. Large, David
    et al.
    Spiro, Baruch
    Ferrat, Marion
    Shopland, Maria
    Kylander, Malin
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Gallagher, Kerry
    Li, X
    Chengde, S
    Possnert, G
    Gan, Z
    Darling, WG
    Weiss, Dominik
    The influence of climate, hydrology and permafrost on Holocene peat accumulation at 3500 m on the Eastern Qinghai-Tibetan Plateau2009In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 28, no 27-28, p. 3303-3314Article in journal (Refereed)
    Abstract [en]

    Peatland of the eastern Qinghai–Tibetan Plateau lies at the convergence of the East Asian and Indian monsoon systems in eastern Asia. To understand the evolution of this peatland and its potential to provide new insights into the Holocene evolution of the East Asian monsoon a 6 m peat core was collected from the undisturbed central part of a peat deposit near Hongyuan. The age-depth profile was determined using 16 14C-AMS age dates, the peat analysed for a range of environmental variables including carbon, nitrogen and hydrogen concentration, bulk density, δ13C and the associated spring water analysed for hydrogen and oxygen isotopes. The age-depth profile of the recovered peat sequence covers the period from 9.6 to 0.3 kyr BP and is linear indicating that the conditions governing productivity and decay varied little over the Holocene. Using changes in carbon density, organic carbon content and its δ13C, cold dry periods of permafrost characterised by low density and impeded surface drainage were identified. The low δ18O and δD values of the spring water emanating around the peat deposit, down to −13.8 and −102‰ (VSMOW), respectively, with an inverse relationship between electrical conductivity and isotopic composition indicate precipitation under colder and drier conditions relative to the present day. In view of the current annual mean air temperature of 1 °C this suggests conditions in the past have been conducive to permafrost. Inferred periods of permafrost correspond to independently recognised cold periods in other Holocene records from across China at 8.6, 8.2–7.8, 5.6–4.2, 3.1 and 1.8–1.5 kyr BP. The transition to a cold dry climate appears to be more rapid than the subsequent recovery and cold dry periods at Hongyuan are of longer duration than equivalent cold dry periods over central and eastern China. Light–dark banding peat on a scale of 15–30 years from 9.6 to 5.5 kyr BP may indicate a strong influence of decadal oscillations possibly the Pacific Decadal Oscillation and a potential link between near simultaneous climatic changes in the northwest Pacific, ENSO, movement of the Intertropical Convergence Zone and the East Asian Monsoon.

  • 26.
    Lind, Ewa
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Kylander, Malin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Olsen, Jesper
    Aarhus University.
    Lacustrine response to short rapid climate shifts during Late Younger Dryas-Early Holocene in Central Norway, registred by XRF and stable isotopesManuscript (preprint) (Other academic)
    Abstract [en]

    There is relatively good knowledge about the climate and the deglaciation pattern during the Late Glacial-Early Holocene transitionin Norway. The origin and mechanisms behind the short, rapid climate shifts that occurred during this period are however notwell known. In this context climate studies in this region can contribute to our understanding of climate patterns. Our specificobjectives in this study were to compare the geochemical response of lake sediments during Late Younger Dryas-Early Holoceneto the general picture of deglaciation in Central Norway and also to evaluate if the Preboreal oscillation (PBO), the Erdalen events,the 9.3 and 8.2 ka cal BP could be detected, superimposed on the general Late Glacial-Early Holocene climate. To address this; highresolutionXRF fluorescence core-scanning, Total organic carbon (TOC), carbon/nitrogen (C/N), stable isotopes of carbon andnitrogen (δ13C, δ15N) and total nitrogen (TN) were made on a palaeolake core from Grønlia fen situated on the Fosen peninsula,Central Norway. The reconstructed Late Younger Dryas-Early Holocene climate from the Grønlia record was noteworthily similarto other reconstructions from the region. The Younger Dryas-Preboreal transition was dated to c. 11 420 cal a BP and five climateshifts were identified in the Early Holocene; c. 11 190 cal a BP, 10 500 cal a BP, 10 200 cal a BP, 9900 cal a BP and 9250 cal a BP.

  • 27. Ljung, Karl
    et al.
    Holmgren, Sofia
    Kylander, Malin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Sjolte, Jesper
    Van der Putten, Nathalie
    Kageyama, Masa
    Porter, Charles T.
    Björck, Svante
    The last termination in the central South Atlantic2015In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 123, p. 193-214Article in journal (Refereed)
    Abstract [en]

    Lake sediments and peat deposits from two basins on Nightingale Island (37 degrees S), in the Tristan da Cunha archipelago, South Atlantic, have been analyzed. The studies were focused on the time period 16.2-10.0 cal ka BP, determined by 36 C-14 dates from the two sequences. A wide variety of proxies were used, including pollen and diatom analyzes, biogenic silica content, C and N analyzes, stable isotopes (C-13 and N-15), elemental concentrations and magnetic susceptibility measurements, to detect environmental changes that can be related to shifts of the circulation belts of the Southern Ocean. In addition, climate model simulations were carried out. We find that the sediments are underlain by a >2 cal ka BP long hiatus, possibly representing a dried-out lake bed. The climate simulations corroborate that the area might have been exposed to arid conditions as a consequence of the Heinrich I event in the north and a southward displacement of the ITCZ. The development on the island after 16.2 cal ka BP is determined by the position of the Subtropical Front (STF) and the Southern Hemisphere Westerlies (SHW). The period 16.2-14.75 cal ka BP was characterized by varying influence from SHW and with STF situated south of Tristan da Cunha, ending with a humidity peak and cooler conditions. The stable conditions 14.7-14.1 cal ka BP with cool and fairly arid conditions imply that STF and SHW were both north of the islands during the first part of the Antarctic Cold Reversal. The most unstable period, 14.1-12.7 cal ka BP, indicates incessant latitudinal shifts of the zonal circulation, perhaps related to climate variability in the Northern Hemisphere and bipolar seesaw mechanisms as the strength of the Atlantic Meridional Overturning Circulation (AMOC) varied. At 12.7 cal ka BP the Holocene warming began with a gradually drier and warmer climate as a result of a dampened AMOC during the Younger Dryas cooling in the north with ITCZ, STF and SHW being displaced southwards. Peak warming seems to have occurred in the earliest part of the Holocene, but this period was also characterized by humidity shifts, possibly an effect of retraction and expansion phases of SHW during AMOC variations in the north.

  • 28.
    Löwemark, Ludvig
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Chen, H. -F
    Yang, T. -N
    Kylander, Malin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Yu, E. -F
    Hsu, Y. -W
    Lee, T. -Q
    Song, S. -R
    Jarvis, S.
    Normalizing XRF-scanner data: A cautionary note on the interpretation of high-resolution records from organic-rich lakes2011In: Journal of Asian Earth Sciences, ISSN 1367-9120, E-ISSN 1878-5786, Vol. 40, no 6, p. 1250-1256Article in journal (Refereed)
    Abstract [en]

    X-ray fluorescence (XRF) scanning of unlithified, untreated sediment cores is becoming an increasingly common method used to obtain paleoproxy data from lake records. XRF-scanning is fast and delivers high-resolution records of relative variations in the elemental composition of the sediment. However, lake sediments display extreme variations in their organic matter content, which can vary from just a few percent to well over 50%. As XRF scanners are largely insensitive to organic material in the sediment, increasing levels of organic material effectively dilute those components that can be measured, such as the lithogenic material (the closed-sum effect). Consequently, in sediments with large variations in organic material, the measured variations in an element will to a large extent mirror the changes in organic material. It is therefore necessary to normalize the elements in the lithogenic component of the sediment against a conservative element to allow changes in the input of the elements to be addressed. In this study we show that Al, which is the lightest element that can be measured using the Wax XRF-scanner, can be used to effectively normalize the elements of the lithogenic fraction of the sediment against variations in organic content. We also show that care must be taken when choosing resolution and exposure time to ensure optimal output from the measurements.

  • 29. Martinez Cortizas, Antonio
    et al.
    Lopez-Merino, Lourdes
    Bindler, Richard
    Mighall, Tim
    Kylander, Malin E.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Early atmospheric metal pollution provides evidence for Chalcolithic/Bronze Age mining and metallurgy in Southwestern Europe2016In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 545, p. 398-406Article in journal (Refereed)
    Abstract [en]

    Although archaeological research suggests that mining/metallurgy already started in the Chalcolithic (3rd millennium BC), the earliest atmospheric metal pollution in SW Europe has thus far been dated to similar to 3500-3200 cal. yr. BP in paleo-environmental archives. A low intensity, non-extensive mining/metallurgy and the lack of appropriately located archives may be responsible for this mismatch. We have analysed the older section (>2100 cal. yr. BP) of a peat record from La Molina (Asturias, Spain), a mire located in the proximity (35-100 km) of mines which were exploited in the Chalcolithic/Bronze Age, with the aim of assessing evidence of this early mining/metallurgy. Analyses included the determination of C as a proxy for organic matter content, lithogenic elements (Si, Al, Ti) as markers of mineral matter, and trace metals (Cr, Cu, Zn, Pb) and stable Pb isotopes as tracers of atmospheric metal pollution. From similar to 8000 to similar to 4980 cal. yr. BP the Pb composition is similar to that of the underlying sediments (Pb 15 +/- 4 mu g g(-1); Pb-206/Pb-207 1.204 +/- 0.002). A sustained period of low Pb-206/Pb-207 ratios occurred from similar to 4980 to similar to 2470 cal. yr. BP, which can be divided into four phases: Chalcolithic (similar to 4980-3700 cal. yr. BP), Pb-206/Pb-207 ratios decline to 1.175 and Pb/Al ratios increase; Early Bronze Age (similar to 3700-3500 cal. yr. BP), Pb-206/Pb-207 increase to 1.192 and metal/Al ratios remain stable; Late Bronze Age (similar to 3500-2800 cal. yr. BP), Pb-206/Pb-207 decline to their lowest values (1.167) while Pb/Al and Zn/Al increase; and Early Iron Age (similar to 2800-2470 cal. yr. BP), Pb-206/Pb-207 increase to 1.186, most metal/Al ratios decrease but Zn/Al shows a peak. At the beginning of the Late Iron Age, Pb-206/Pb-207 ratios and metal enrichments show a rapid return to pre-anthropogenic values. These results provide evidence of regional/local atmospheric metal pollution triggered by the earliest phases of mining/metallurgy in the area, and reconcile paleo-environmental and archaeological records.

  • 30. Martinez Cortizas, Antonio
    et al.
    Lopez-Merino, Lourdes
    Bindler, Richard
    Mighall, Timothy
    Kylander, Malin M
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Atmospheric Pb pollution in N Iberia during the late Iron Age/Roman times reconstructed using the high-resolution record of La Molina mire (Asturias, Spain)2013In: Journal of Paleolimnology, ISSN 0921-2728, E-ISSN 1573-0417, Vol. 50, no 1, p. 71-86Article in journal (Refereed)
    Abstract [en]

    Extensive mining took place in Spain during the Iron Age and Roman times, although a detailed chronology is still lacking due to the inherent difficulties in dating mining structures. In this study we sampled and analyzed a core from La Molina mire in the Asturias region, northern Spain. Because more than 100 Roman mines have thus far been found within 20 km of the mire, our aim was to shed light on local mining history, which we can then compare to the wider narrative of early mining pollution in Spain. We focus on the section from similar to 500 BC to AD similar to 600, which has a high temporal resolution of 6-15 year per sample. Geochemical analyses included the determination of major, minor and trace lithogenic elements (Si, Al, Fe, Ti, Ga, Rb, Y, Zr, Th) as markers of mineral content of the peat, and trace metals/metalloids (Mn, Cu, Ni, As, Pb) as well stable Pb isotopes, as potential markers of atmospheric metal pollution. The use of principal components analysis enabled the identification of a dominant geogenic component and a secondary pollution component. The earliest pollution signal of the covered period was recorded by similar to 300 BC, coinciding with the late local Iron Age. Average Pb-206/Pb-207 ratios of samples with ages older than this date was 1.204 +/- A 0.002, while all samples with a younger age had a less radiogenic ratio. Based on the metal pollution component four phases were identified: I, similar to 500 to 300 BC; II, similar to 300 to 20 BC; III, similar to 20 BC-AD 480; IV, AD similar to 480 to 600. The lowest isotopic ratio and highest proportion of pollution Pb (Pb-206/Pb-207 ratio of 1.157 and 89 % of total accumulated Pb) was reached at peak Pb production during Roman times (AD similar to 180 to 340), indicating that this was the period of most intense metal contamination in the area over the studied period. It is remarkable that the La Molina record shows a more extended period (two centuries) of active mining in comparison with other areas in Iberia, and a pattern of repeated shifts in Pb pollution of short duration, which is likely related to the local history of exploitation and exhaustion of mines within the area.

  • 31.
    Plikk, Anna
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Helmens, Karin F.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Fernández-Fernández, María
    Kylander, Malin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Löwemark, Ludvig
    Risberg, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Salonen, J. Sakari
    Väliranta, Minna
    Weckström, Jan
    Development of an Eemian (MIS 5e) Interglacial palaeolake at Sokli (N Finland) inferred using multiple proxies2016In: Palaeogeography, Palaeoclimatology, Palaeoecology, ISSN 0031-0182, E-ISSN 1872-616X, Vol. 463, p. 11-26Article in journal (Refereed)
    Abstract [en]

    A 12 m long lacustrine record from Sokli, N Finland, was analyzed for diatoms, non-pollen palynomorphs, macrofossils, pollen and geochemistry in order to reconstruct the development of a high-latitude Eemian lake and investigate the influence of climatic and environmental changes on the lake ecosystem. Based on this multi-proxy dataset we distinguished five major lake phases in the lake's evolution. An initial minerogenic, glacio-lacustrine phase was followed by an organic-rich early Eemian lake phase characterized by anoxic bottom waters, high seasonality and rising nutrient levels. A long open water season, pronounced summer stratification and high productivity characterized the following early mid-Eemian lake phase, corresponding to the Eemian thermal maximum. During the late mid-Eemian lake phase decreasing water depths due to infilling and extensive mixing of the water column resulted in less stable summer stratification and decreased anoxia. The late-Eemian lake phase was characterized by shallow and dynamic conditions and a cooling climate. Superimposed on these general trends are two events characterized by colder and more arid conditions, that possibly match cold and arid events registered in palaeolimnological records on the European continent. In general, the multi-proxy record reflects a nutrient rich lake, where changes in mixing regime associated with climatic forcing and lake level changes asserted a major impact on the aquatic assemblages. The changes in the aquatic assemblages reflect the major patterns of climate change that took place during the Eemian in northern Europe; i.e. a rapid warming and high seasonality during the early Eemian, decreased seasonality during the mid Eemian and a cooling late Eemian with increased seasonality. The high latitude Sokli Eemian palaeolake record lengthens the latitudinal extent of Eemian terrestrial records across Europe, adding to the understanding of climatic gradients and drivers over Europe.

  • 32. Pérez-Rodríguez, Marta
    et al.
    Silva-Sánchez, Noemí
    Kylander, Malin E.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Bindler, Richard
    Mighall, Tim M.
    Edward Schofield, J.
    Edwards, Kevin J.
    Martinez Cortizas, Antonio
    Industrial-era lead and mercury contamination in southern Greenland implicates North American sources2018In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 613, p. 919-930Article in journal (Refereed)
    Abstract [en]

    To study the long-range transport of atmospheric pollutants from lower latitude industrial areas to the Arctic, we analysed a peat core spanning the last similar to 700 cal. yr (similar to 1300-2000 CE) from southern Greenland, an area sensitive to atmospheric pollution from North American and Eurasian sources. A previous investigation conducted in the same location recorded atmospheric lead (Pb) pollution after similar to 1845, with peak values recorded in the 1970s, and concluded that a North American source was most likely. To confirm the origin of the lead, we present new Pb isotope data from Sandhavn, together with a high-resolution record for mercury (Hg) deposition. Results demonstrate that the mercury accumulation rate has steadily increased since the beginning of the 19th century, with maximum values of 9.3 mu g m(-2) yr(-1) recorded similar to 1940. Lead isotopic ratios show two mixing lines: one which represents inputs from local and regional geogenic sources, and another that comprises regional geogenic and pollution sources. Detrending the Pb isotopic ratio record (thereby extracting the effect of the geogenic mixing) has enabled us to reconstruct a detailed chronology of metal pollution. The first sustained decrease in Pb isotope signals is recorded as beginning similar to 1740-1780 with the lowest values (indicating the highest pollution signature) dated to similar to 1960-1970. The 206Pb/207Pb ratio of excess Pb (measuring 1.222, and reflecting pollution generated Pb), when compared with the Pb isotopic composition of the Sandhavn peat record since the 19th century and the timing of Pb enrichments, clearly points to the dominance of pollution sources fromNorth America, although it did not prove possible to further differentiate the emissions sources geographically.

  • 33. Rauch, Sebastien
    et al.
    Peucker-Ehrenbrink, Bernhard
    Kylander, Malin E.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Weiss, Dominik J.
    Martinez-Cortizas, Antonio
    Heslop, David
    Olid, Carolina
    Mighall, Tim M.
    Hemond, Harold F.
    Anthropogenic Forcings on the Surficial Osmium Cycle2010In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 44, no 3, p. 881-887Article in journal (Refereed)
    Abstract [en]

    Osmium is among the least abundant elements in the Earth's continental crust. Recent anthropogenic Os contamination of the environment from mining and smelting activities, automotive catalytic converter use, and hospital discharges has been documented. Here we present evidence for anthropogenic overprinting of the natural Os cycle using a ca. 7000-year record of atmospheric Os deposition and isotopic composition from an ombrotrophic peat bog in NW Spain. Preanthropogenic Os accumulation in this area is 0.10 +/- 0.04 ng m(-2) y(-1). The oldest strata showing human influence correspond to early metal mining and processing on the Iberian Peninsula (ca. 4700-2500 cal. BP). Elevated Os accumulation rates are found thereafter with a local maximum of 1.1 ng m(-2) y(-1) during the Roman occupation of the Iberian Peninsula (ca. 1930 cal. BP)and a further increase starting in 1750 AD with Os accumulation reaching 30 ng m(-2) y(-1) in the most recent samples. Osmium isotopic composition (Os-187/Os-188) indicates that recent elevated Os accumulation results from increased input of unradiogenic Os from industrial and automotive sources as well as from enhanced deposition of radiogenic Os through increased fossil fuel combustion and soil erosion. We posit that the rapid increase in catalyst-equipped vehicles, increased fossil fuel combustion, and changes in land-use make the changes observed in NW Spain globally relevant.

  • 34.
    Shala, Shyhrete
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Helmens, Karin F.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Jansson, Krister N.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Kylander, Malin E.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Risberg, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Löwemark, Ludvig
    Palaeoenvironmental record of glacial lake evolution during the early Holocene at Sokli, NE Finland2014In: Boreas, ISSN 0300-9483, E-ISSN 1502-3885, Vol. 43, no 2, p. 362-376Article in journal (Refereed)
    Abstract [en]

    The development of a glacial lake impounded along the retreating, northeastern ice margin of the Fennoscandian Ice Sheet during the last deglaciation and environmental conditions directly following the early Holocene deglaciation have been studied in NE Finland. This so-called Sokli Ice Lake has been reconstructed previously using topographic and geomorphologic evidence. In this paper a multiproxy approach is employed to study a 3-m-thick sediment succession consisting of laminated silts grading into gyttja cored in Lake Loitsana, a remnant of the Sokli Ice Lake. Variations in the sediment and siliceous microfossil records indicate distinct changes in water depth and lake size in the Loitsana basin as the Sokli Ice Lake was drained through various spillways opening up along the retreating ice front. Geochemical data (XRF core-scanning) show changes in the influence of regional catchment geochemistry (Precambrian crystalline rocks) in the glacial lake drainage area versus local catchment geochemistry (Sokli Carbonatite Massif) within the Lake Loitsana drainage area during the lake evolution. Principal component analysis on the geochemical data further suggests that grain-size is an additional factor responsible for the variability of the sediment geochemistry record. The trophic state of the lake changed drastically as a result of morphometric eutrophication once the glacial lake developed into Lake Loitsana. The AMS radiocarbon dating on tree birch seeds found in the glaciolacustrine sediment indicates that Lake Loitsana was deglaciated sometime prior to 10 700 cal. a BP showing that tree Betula was present on the deglaciated land surrounding the glacial lake. Although glacial lakes covered large areas of northern Finland during the last deglaciation, only few glaciolacustrine sediment successions have been studied in any detail. Our study shows the potential of these sediments for multiproxy analysis and contributes to the reconstruction of environmental conditions in NE Finland directly following deglaciation in the early Holocene.

  • 35.
    Steinthorsdottir, Margret
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Wohlfarth, Barbara
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Kylander, Malin E.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Blaauw, Maarten
    Reimer, Paula J.
    Stomatal proxy record of CO2 concentrations from the last termination suggests an important role for CO2 at climate change transitions2013In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 68, p. 43-58Article in journal (Refereed)
    Abstract [en]

    A new stomatal proxy-based record of CO2 concentrations ([CO2]), based on Betula nana (dwarf birch) leaves from the Hasseldala Port sedimentary sequence in south-eastern Sweden, is presented. The record is of high chronological resolution and spans most of Greenland Interstadial 1 (GI-1a to 1c, Allerod pollen zone), Greenland Stadial 1 (GS-1, Younger Dryas pollen zone) and the very beginning of the Holocene (Preboreal pollen zone). The record clearly demonstrates that i) [CO2] were significantly higher than usually reported for the Last Termination and ii) the overall pattern of CO2 evolution through the studied time period is fairly dynamic, with significant abrupt fluctuations in [CO2] when the climate moved from interstadial to stadial state and vice versa. A new loss-on-ignition chemical record (used here as a proxy for temperature) lends independent support to the Hasseldala Port [CO2] record. The large-amplitude fluctuations around the climate change transitions may indicate unstable climates and that tipping-point situations were involved in Last Termination climate evolution. The scenario presented here is in contrast to [CO2] records reconstructed from air bubbles trapped in ice, which indicate lower concentrations and a gradual, linear increase of [CO2] through time. The prevalent explanation for the main climate forcer during the Last Termination being ocean circulation patterns needs to re-examined, and a larger role for atmospheric [CO2] considered.

  • 36.
    Swärd, Henrik
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    O'Regan, Matt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Ampel, Linda
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Ananyev, Roman
    Chernykh, Denis
    Flodén, Tom
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Greenwood, Sarah L.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Kylander, Malin E.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Mörth, Carl Magnus
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Preto, Pedro
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Regional deglaciation and postglacial lake development as reflected in a 74m sedimentary record from Lake Vättern, southern Sweden2016In: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 138, no 2, p. 336-354Article in journal (Refereed)
    Abstract [en]

    The withdrawal of the Late Weichselian ice sheet and rapid isostatic uplift in southern Scandinavia led to the entrainment of large volumes of melt water within the proglacial Baltic Ice Lake (BIL). The eventual western outpost of BIL, Lake Vattern, has been a focal point for studying the dynamic retreat history of the Late Weichselian ice sheet in south central Sweden. This part of the deglacial history is described from an abundance of terrestrial studies, but, to date, no complimentary long sediment cores from Lake Vattern have been available. Here, we present the results from a unique, 74m borehole in southern Lake Vattern that recovered a Late Pleistocene to Holocene sedimentary sequence. Physical and chemical analyses of the sediment and pore water, together with geophysical mapping, reveal glacial as well as postglacial imprints implying an oscillating ice sheet margin, evidence for neotectonic activity and one or more marine incursions into the lake during deglaciation. We attribute the glaciotectonic deformation of the sediments at 54m below the lake floor to an ice readvance that likely occurred at the same time or before the advance that formed the Levene moraine (approximate to 13.8-13.4cal.kaBP). After this event, potential readvances were likely restricted to a more northerly position in the basin. We identify the final drainage of the BIL, but find evidence for an earlier marine incursion into the Vattern basin (approximate to 13.0cal.kaBP), indicating water exchange between the North Atlantic and the Baltic Ice Lake during the late Allerod.

  • 37.
    Swärd, Henrik
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    O'Regan, Matt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Björck, Svante
    Stockholm University, Faculty of Science, Department of Geological Sciences. Lund University, Sweden.
    Greenwood, Sarah L.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Kylander, Malin E.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Mörth, Carl-Magnus
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Pearce, Christof
    Stockholm University, Faculty of Science, Department of Geological Sciences. Aarhus University, Denmark.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    A chronology of environmental changes in the Lake Vättern basin from deglaciation to its final isolation2018In: Boreas, ISSN 0300-9483, E-ISSN 1502-3885, Vol. 47, no 2, p. 609-624Article in journal (Refereed)
    Abstract [en]

    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.

  • 38.
    Wohlfarth, Barbara
    et al.
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Kylander, Malin
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Ampel, Linda
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Veres, Daniel
    High Resolution ITRAX Analysis of Les Echets (France) Sedimentary Sequence: Linking Geochemical, Biological and Physical Proxies2008Conference paper (Other (popular science, discussion, etc.))
    Abstract [en]

    later part of Marine Isotope Stage (MIS) 3 and MIS 2 (40 and 16 ka BP). The sediments in the lower part of the studied sequence are composed of alternating organic rich and minerogenic layers, while the upper part consists predominantly of silt and clay. Organic geochemical, geophysical and biological environmental indicators (grain size, mineral magnetic parameters, TOC, TN, LOI, stable carbon isotopes, rock eval, biogenic silica, and diatom assemblages) show alternating phases of higher and low lake organic productivity which are interpreted as a response to DO climate variability. XRF is a well-established analytical tool that has recently taken a new direction with the introduction of core scanning systems. The ITRAX XRF core scanning system is non-destructive, acquires continuous data for a broad range of elements in situ as well as generates radiographic images. The Les Echets sequence was analysed using the ITRAX at 1 mm resolution. The radiographic images show significant changes that were not revealed by lithostratigraphic descriptions. Distinct, dense layers are associated with changes in elemental intensities which would have been missed using traditional sub-sampling techniques. The high resolution elemental profiles show associations

  • 39.
    Wohlfarth, Barbara
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Muschitiello, Francesco
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Greenwood, Sarah L.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Andersson, August
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Kylander, Malin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Smittenberg, Rienk H.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Steinthorsdottir, Margret
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Watson, Jenny
    Whitehouse, Nicola J.
    Hasseldala-a key site for Last Termination climate events in northern Europe2017In: Boreas, ISSN 0300-9483, E-ISSN 1502-3885, Vol. 46, no 2, p. 143-161Article in journal (Refereed)
    Abstract [en]

    The Last Termination (19 000-11 000 a BP) with its rapid and distinct climate shifts provides a perfect laboratory to study the nature and regional impact of climate variability. The sedimentary succession from the ancient lake at Hasseldala Port in southern Sweden with its distinct Lateglacial/early Holocene stratigraphy (> 14.1-9.5 cal. ka BP) is one of the few chronologically well-constrained, multi- proxy sites in Europe that capture a variety of local and regional climatic and environmental signals. Here we present Hasseldala's multi-proxy records (lithology, geochemistry, pollen, diatoms, chironomids, biomarkers, hydrogen isotopes) in a refined age model and place the observed changes in lake status, catchment vegetation, summer temperatures and hydroclimate in a wider regional context. Reconstructed mean July temperatures increased between c. 14.1 and c. 13.1 cal. ka BP and subsequently declined. This latter cooling coincided with drier hydroclimatic conditions that were probably associated with a freshening of the Nordic Seas and started a few hundred years before the onset of Greenland Stadial 1 (c. 12.9 cal. ka BP). Our proxies suggest a further shift towards colder and drier conditions as late as c. 12.7 cal. ka BP, which was followed by the establishment of a stadial climate regime (c. 12.5-11.8 cal. ka BP). The onset of warmer and wetter conditions preceded the Holocene warming over Greenland by c. 200 years. Hasseldala's proxies thus highlight the complexity of environmental and hydrological responses across abrupt climate transitions in northern Europe.

1 - 39 of 39
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