| 1. |
- Carugati, Gabriele, 1980, et al.
(författare)
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Experimental assessment of a large sample cell for laser ablation-ICP-MS, and its application to sediment core micro-analysis
- 2010
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Ingår i: Mikrochimica Acta. - : Springer Science and Business Media LLC. - 1436-5073 .- 0026-3672. ; 170:1-2, s. 39-45
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 2. |
- Chawchai, Sakonvan, et al.
(författare)
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Lake Kumphawapi - an archive of Holocene palaeoenvironmental and palaeoclimatic changes in northeast Thailand
- 2013
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Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 68, s. 59-75
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 3. |
- Gallagher, K, et al.
(författare)
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Inference of abrupt changes in noisy geochemical records using transdimensional changepoint models
- 2011
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Ingår i: Earth and Planetary Science Letters. - : Elsevier BV. - 0012-821X .- 1385-013X. ; 311:1-2, s. 182-194
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 4. |
- Hansson, Sophia V., et al.
(författare)
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Evaluating paleoproxies for peat decomposition and their relationship to peat geochemistry
- 2013
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Ingår i: The Holocene. - : SAGE Publications. - 0959-6836 .- 1477-0911. ; 23:12, s. 1666-1671
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 5. |
- Johnson, Mark D., et al.
(författare)
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Varved glaciomarine clay in central Sweden before and after the Baltic Ice Lake drainage : a further clue to the drainage events at Mt Billingen
- 2013
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Ingår i: GFF. - : Informa UK Limited. - 1103-5897 .- 2000-0863. ; 135:3-4, s. 293-307
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 6. |
- Johnson, Mark D., 1954, et al.
(författare)
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Varved glaciomarine clay in central Sweden before and the Baltic Ice Lake drainage: a further clue to the drainage event at Mt. Bilingen
- 2013
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Ingår i: GFF. - : Informa UK Limited. - 1103-5897 .- 2000-0863. ; 135:3-4, s. 293-307
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Tidskriftsartikel (refereegranskat)abstract
- 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 La°ngen basin west of Mt Billingen support the idea of glacier ice in the La°ngen basin during the drainage and a retreat and advance of the ice sheet during Allero¨d and Younger Dryas, including the possibility of an earlier, Allero¨d drainage.
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| 7. |
- Kylander, Malin, 1977-, et al.
(författare)
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A novel geochemical approach to paleorecords of dust deposition and effective humidity: 8500 years of peat accumulation at Store Mosse (the "Great Bog") , Sweden )
- 2013
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Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 69, s. 69-82
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 8. |
- Kylander, Malin, 1977-, et al.
(författare)
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High‐Resolution XRF Core Scanning Analysis of Les Echets (France) Sedimentary Sequence: New Insights from Chemical Proxies
- 2011
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Ingår i: Journal of Quaternary Science. - : Wiley. - 1099-1417 .- 0267-8179. ; 26:1, s. 109-117
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 9. |
- Kylander, Malin M, et al.
(författare)
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Geochemical responses to paleoclimatic changes in southern Sweden since the late glacial : the Hasseldala Port lake sediment record
- 2013
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Ingår i: Journal of Paleolimnology. - : Springer Science and Business Media LLC. - 0921-2728 .- 1573-0417. ; 50:1, s. 57-70
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 10. |
- Kylander, Malin M, et al.
(författare)
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Recommendations for using XRF core scanning as a tool in tephrochronology
- 2012
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Ingår i: The Holocene. - : Sage. - 0959-6836 .- 1477-0911. ; 22:3, s. 371-375
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 11. |
- Kylander, Malin, 1977-, et al.
(författare)
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Natural lead isotope variations in the atmosphere
- 2010
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Ingår i: Earth and Planetary Science Letters. - : Elsevier BV. - 0012-821X .- 1385-013X. ; 290:1-2, s. 44-53
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 12. |
- Kylander, Malin, 1977-, et al.
(författare)
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The Itrax and organic rich sediments: Tephrochronologyand humification
- 2010
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 13. |
- Kylander, Malin, et al.
(författare)
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Using Peatlands as Archives of Dust Deposition : A Preliminary Record from Southern Sweden
- 2010
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Ingår i: European Geosciences Union. ; , s. 2677-
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 14. |
- Lind Mettävainio, Ewa, 1968-, et al.
(författare)
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New Early Holocene tephra horizons from the Faroe Islands
- 2010
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Ingår i: International Field Conference and Workshop on Tephrochronology, Volcanism and Human Activity.. ; , s. 60-
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The early Holocene climate in the North Atlantic region was rather unstable and three cold events superimposed upon a general warming took place during the earliest part of the Holocene: the Preboreal oscillation (11.3-11.1 ka BP), the Erdalen event (10.3-10.2 ka BP) and the 9.3 ka BP event (e.g. Dahl et al., 2002; Rasmussen et al. 2007). There is relatively little known about early Holocene tephrochronology in comparison to the Last Glacial/Interglacial transition and the mid to late Holocene, although there is no reason to believe that Icelandic eruptions were less frequent during the early Holocene. The main focus of the present study is improve the dating and geochemical identification of early Holocene tephras on the Faroe Islands, using wiggle-match or Bayesian techniques for age-depth modelling and EMPA analyses for geochemical fingerprinting of tephras. Identification of tephras is also aided by XRF core scanning. While this method is still in its infancy, some promising results have been reported recently regarding the identification of cryptotephra in marine and lacustrine sediments. The Faroe Islands is an ideal area to test the method, since tephras ranging from basaltic to rhyolitic are abundant but usually not visible to the naked eye (Wastegård, 2002). We have investigated new cores taken in 2009 from previously studied sites and new sites with high sediment accumulation rates during the early Holocene. Results from the first analyzed peat and lake sediment cores from the Faroe Islands show that several previously unreported tephra horizons occur below the visible Saksunarvatn tephra dated to c. 10 300 cal. yr BP (Rasmussen et al. 2007). Two layers are rhyolitic, one dacitic and one basaltic. The XRF core-scanner data has been especially useful for identifying basaltic cryptotephra horizons.
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| 15. |
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| 16. |
- Löwemark, Ludvig, et al.
(författare)
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Normalizing XRF-scanner data : A cautionary note on the interpretation of high-resolution records from organic-rich lakes
- 2011
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Ingår i: Journal of Asian Earth Sciences. - : Elsevier BV. - 1367-9120 .- 1878-5786. ; 40:6, s. 1250-1256
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 17. |
- Margalef, O., et al.
(författare)
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Environmental processes in Rano Aroi (Easter Island) peat geochemistry forced by climate variability during the last 70 kyr
- 2014
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Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier BV. - 0031-0182 .- 1872-616X. ; 414, s. 438-450
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Tidskriftsartikel (refereegranskat)abstract
- We analyze the geochemistry of Rano Aroi mire record (Easter Island) using bulk peat composition (C, N, S) and stable isotopes (delta C-13, delta N-15, delta S-34) and major, minor and trace elemental compositions obtained by ICP-AES (Al, Ti, Zr, Sc, V, Y, Fe, Mn, Th, Ba, Ca, Mg and Sr). Peat geochemistry and the pollen record are used to reconstruct the environmental changes during the last 70 kyr BP. Principal component analysis on ICP-AES data revealed that three main components account for the chemical signatures of the peat. The first component, characterized by lithogenic elements (combined signal of V. Al, Sc, Y, Cr, Cd, Ti, Zr and Cu), evidences long-term changes in the basal fluxes of mineral material into the mire. This component, in combination with stable isotopes and pollen data suggests a link between soil erosion and vegetation cover changes in the Rano Aroi watershed. The second component is identified by the signal of Fe, Mn, Th, Ba, Zr and Ti, and is indicative of strong runoff events during enhanced precipitation periods. The third component (tied mainly to Ca, Sr and Mg) reflects a strong peat oxidation event that occurred during an arid period with more frequent droughts, sometime between 39 and 31 kyr BP. Correlation coefficients and a multiple regression model (PCR analysis) between peat organic chemistry and the principal components of ICP-AES analysis were calculated. Isotope chemistry of the peat organic matter further contributes to define Rano Aroi environmental history: delta C-13 data corroborates a vegetation shift documented by the palynological record from C-4 to C-3 between 55 and 45 cal kyr BP; the delta N-15 record identifies periods of changes in mire productivity and denitrification processes, while the delta S-34 peat signature indicates a marine origin of S and significant diagenetic cycling. The geochemical and environmental evolution of Rano Aroi mire is coherent with the regional climatic variability and suggests that climate was the main forcing in mire evolution during the last 70 kyr BP. The coupling of geochemical and biological proxies improves our ability to decipher depositional processes in tropical and subtropical peatlands and to use these sequences for paleoenvironmental and paleoclimate reconstructions.
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| 18. |
- Martinez Cortizas, Antonio, et al.
(författare)
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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)
- 2013
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Ingår i: Journal of Paleolimnology. - : Springer Science and Business Media LLC. - 0921-2728 .- 1573-0417. ; 50:1, s. 71-86
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 19. |
- Rauch, Sebastien, 1971, et al.
(författare)
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Anthropogenic Forcings on the Surficial Osmium Cycle
- 2010
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 44:3, s. 881-887
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 20. |
- Rauch, Sebastien, 1971, et al.
(författare)
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Trace metals in Stockholm sediments
- 2010
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Ingår i: Highway and Urban Environment; Rauch S, Morrison GM and Monzon A (Eds). - 9789048130429 ; , s. 267-273
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 21. |
- Shala, Shyhrete, et al.
(författare)
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Palaeoenvironmental record of glacial lake evolution during the early Holocene at Sokli, NE Finland
- 2014
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Ingår i: Boreas. - : Wiley. - 0300-9483 .- 1502-3885. ; 43:2, s. 362-376
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 22. |
- Steinthorsdottir, Margret, et al.
(författare)
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Stomatal proxy record of CO2 concentrations from the last termination suggests an important role for CO2 at climate change transitions
- 2013
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Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 68, s. 43-58
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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