| 1. |
- Andersson-Sköld, Yvonne, et al.
(författare)
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Quick clay - A case study of chemical perspective in Southwest Sweden
- 2005
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Ingår i: Engineering Geology. - : Elsevier BV. - 0013-7952. ; 82:2, s. 107-118
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Tidskriftsartikel (refereegranskat)abstract
- Quick clay, a soil that changes from normal firm ground to a liquid mass when it is disturbed, has been involved in most of the large and serious clay slides in Sweden, Norway and Canada. The location, time of occurrence and size of quick clay slides are difficult to predict and large slides may cause great devastation. Some geochemical studies of Swedish quick clay were done in the 1960s and early 1970s, but no systematic studies of the interrelationships of pore water chemistry, mineralogy, geotechnical properties and other parameters on quick clays in Sweden have been published. Such studies are of national and general interest because of the many combinations of rock flour source areas and sedimentation conditions that occurred across central Sweden and into the Baltic Sea area during deglaciation. In this study, geotechnical properties related to the in situ chemistry at one quick clay site were extensively studied, and spot sampling was conducted at two other locations in Southwest Sweden. In this area the clay minerals mainly are non-expanding phyllosilicate minerals (illite) and primary minerals (quartz, feldspar), which is consistent with previous studies of quick clay mineralogy. Extensive leaching has occurred at all three locations. At the extensively studied site, Surte, the lowest salinity was found at the greatest depth, inferring that the leaching by fresh water was accomplished by water movement upward and laterally through the sediment from the underlying bedrock. This is consistent with the local setting where bedrock hills rise sharply to over 100 in above the marine sediment surface. An artesian pressure would also be anticipated at this location. There is a correlation (negative) between sensitivity and salinity but there is an indication that the maximum salinity or electrical conductivity consistent with the quick clay behaviour is higher than reported elsewhere. However, for high sensitivities the salinity is about the same as reported elsewhere. In the deepest part of the borehole, there is a higher content of Fe and Al in the pore water, indicating reduced state. Further work is needed to confirm the difference in salinity and to investigate the possible interplay of salinity and potential dispersing agents such as the role of anoxic conditions, in this region. Further work is especially needed in the locations where the sediment accumulation occurred under lower salinity conditions. At all three locations, high remoulded shear strength and low sensitivity have been seen near the surface together with a decrease in pore water cation concentrations. (c) 2005 Elsevier B.V. All rights reserved.
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| 2. |
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| 3. |
- Kairytè, Milda, et al.
(författare)
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Provenance of silt and clay within sandy deposits of the Lithuanian coastal zone (Baltic Sea)
- 2005
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Ingår i: Marine Geology. - : Elsevier BV. - 0025-3227. ; 218:1-4, s. 97-112
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Tidskriftsartikel (refereegranskat)abstract
- Mineralogical analysis of the silt and clay fraction of sandy deposits of 37 surface samples and grain-size data are used to interpret sediment sources acting in the SE Baltic Sea along the Lithuanian coast. Mineralogical composition was determined using X-ray diffraction (XRD) methods. Grain-size distribution was obtained by standard dry sieving and pipette techniques. For identification of sources we combined known compositional information of possible sources with logical models for mineral combinations related to regional geological provinces and processes, supported by results of correlation and factor (principal component) analyses between minerals, grain-size parameters and bathymetric features of the area. The main sources supplying sediment into the area are: 1) the Sambian Peninsula to the south, 2) the Nemunas River, whose discharge passes through the Curonian Lagoon, and 3) Late Pleistocene till erosion on the sea floor in the north and at the Olando Kepure shore cliffs. The general pattern of spatial distribution related to the identified sources for the fine-grained sediment fraction is interpreted as a shore-parallel transport of suspended matter, flowing northwards in the southeastern part of the Baltic Sea. (c) 2005 Elsevier B.V. All rights reserved.
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| 4. |
- Kairytè, Milda, et al.
(författare)
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Quantitative provenance of silt and clay within sandy deposits of the Lithuanian coastal zone (Baltic Sea)
- 2009
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Ingår i: Marine Geology. - : Elsevier BV. - 0025-3227. ; 257:1-4, s. 87-93
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Tidskriftsartikel (refereegranskat)abstract
- A quantitative provenance approach is developed and in this study applied for the silt and clay fractions of sandy deposits along the Sea coast. Mineralogical composition of 37 surface samples was determined by X-ray diffraction (XRD). Grain-size distributions were obtained by standard dry sieving and pipette techniques. The characterization of mineralogical provenance is based upon known compositional information of possible sources, logical models for mineral combinations related to regional geological provinces and processes, and geographical features of the documented mineral distribution in the area of investigation. These interpretations are further supported by results of correlation and principal component analyses of mineral varieties, grain-size parameters and bathymetric features of the area. Partitioning of source contributions specific for each site of deposition is derived by solving simultaneous equations. Then, the quantified mineral composition at the initial source is reconstructed in the SE Baltic Sea along the Lithuanian coast, which serves as a test bed for the new method to quantify sediment sources The main sources supplying sediment to the area are: 1) Sambian Peninsula to the south (erosion of Pleistocene till and “Blue Earth” Paleogene sediments), supplying 33% of fine-grained sediment on average, 2) Nemunas River, the discharge of which passes through Curonian Lagoon and supplies an average 17% of the coastal fine sediments, and 3) Pleistocene till, eroded on the sea floor in the north and at the Olando Kepurė shore cliff and contributing an average of 50% of the sediment. This mathematically fairly simple site-to-site quantification approach applied here on the environmentally important fine-fraction could also be used with any other parameters characterizing identified sources. Our study is focused upon the stable, mineralogical components of the “sediment archive”, which offer a time-integrated, net-effect reflection of the combined processes of an entire environmental system, and recorded for each individual site of accumulation.
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| 5. |
- Larsson, Olof, 1962, et al.
(författare)
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Seismic stratigraphy of Late Quaternary deposits in the eastern Skagerrak
- 2008
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Ingår i: Marine and Petroleum Geology. - 0264-8172. ; 25:10, s. 1023-1039
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Tidskriftsartikel (refereegranskat)abstract
- High resolution seismic profiles from the Swedish west coast have been used in this study. The Quaternary deposits have been divided into six seismic sequences, containing together thirteen different seismic facies. Documentation of these sequences and facies, their stratigraphic and geographic variability is the first step in a basin-fill analysis aiming at interpreting the depositional environments and the major controlling processes. The deposits are interpreted to consist of one deglaciation cycle. The sequences are; I) bedrock, II) coarse glacial deposits, III) Weichselian glaciomarine ice-proximal deposits, IV) Weichselian glaciomarine ice-distal deposits, V) channel fill deposits, VI) Holocene marine deposits. The major part of the sediment package is the Weichselian glaciomarine ice-proximal deposits, deposited during the ice recession period, close to or adjacent to the retreating ice. Typical for these deposits are conformably, well stratified deposits with high amplitude. The second large part is the Holocene marine deposits, these are mainly found in the southern part. They have typically a near transparent seismic configuration with only weak parallel stratification. These two major sequences are separated by a regional unconformity, creating a hiatus of at least 6000 year.
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| 6. |
- Larsson, Olof, 1962, et al.
(författare)
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The transition from glacimarine to marine conditions during the last deglacieation in the eastern Skagerrak
- 2007
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Ingår i: Marine Geology. - 0025-3227. ; 241, s. 45-61
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Tidskriftsartikel (refereegranskat)abstract
- The paleoceanographic and paleoenvironmental evolution is described in the eastern Skagerrak. Separable stratigraphic units in seismic profiles and twelve piston cores document a changing balance between erosion and accumulation since the latest deglaciation. sediment supply and water depth but also whether the water mass is stratified or not are the important parameters in the processes controlling the depositional environment. The cores can be divided into two main units: a lower, well consolidated and clay-rich glacimarine mud with low organic content, and a silty, sandy, marine mud with relatively high organic content. The boundary between these two main units consists of an erosional surface, overlain by a coarse-grained lag. The deposition of the lower glacimarine mud started directly after deglaciation, at about 18.0 kyr BP. A major change in the sedimentation conditions at about 9.0 kyr BP led to a change from depositional to erosional conditions. The erosion has presumably removed a great part of the earlier deposits, creating the erosional surface which is present in the entire study area. Several dated samples above and below the erosional surface indicate a hiatus of about 10 kyr. In the south, the conditions changed again at about 5.0 cal kyr BP, allowing accumulation of the marine mud, while in the northern part erosive conditions continue to prevail. In the northern part, the marine mud is only deposited in limited areas, preferably sheltered areas along the coast.
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| 7. |
- Maurebrecher, P. M., et al.
(författare)
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'Geophysiotechnics' in the harbour of Gothenburg: a most beautiful geophysical profile
- 2009
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Ingår i: Ingeokring Newsletter (Royal Geological and Mining Society of the The Netherlands). - 1384-1351. ; 2009, s. 41-43
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- A high-resolution seismic profile was obtained using a Chirp sub-bottom profiler. Following deglaciation, rapid sedimenetation of glaciomarine sediments is interpreted to alternative with periods of erosion during times of low-sea level and changed coastal current patterns. A paleo-landslide is recoreded along one such channel. During the Holocene, more horizontal layering developed and sedimentation decreased markedly.
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| 8. |
- Mil-homens, Mario, et al.
(författare)
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Heavy metal assessment for surface sediments from three areas of the Portuguese continental shelf
- 2006
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Ingår i: Continental Shelf Research. - : Elsevier BV. - 0278-4343. ; 26:10, s. 1184-1205
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Tidskriftsartikel (refereegranskat)abstract
- Twenty-nine surface samples from the Portuguese shelf, recovered offshore from the mouths of the Ave, Douro, Lis and Mira rivers, were analysed using ICP-OES for selected major and trace elements, after total dissolution. Organic carbon, carbonate content and grain size were also determined. Five evaluation tools have been applied in order to compare the three study areas and to evaluate sediment geochemistry and other sediment compositional variability in the acquired samples: (1) empirical methods based on comparison with standard reference criteria, e.g. the NOAA sediment quality guidelines, (2) normalisation ratios using a grain-size proxy element, (3) "Gradient Method", plotting contaminant vs. organic matter or Al, (4) definition of a regional geochemical baseline from a compiled database, and (5) enrichment factors. The evaluation of element and component associations indicates differences related both to the onshore drainage areas and to the environmental shelf setting. Despite the considerable variability in total metal contents indicated by our results, the sediment metal composition is largely of natural origin. Metal enrichments observed in the Mira area are associated with the drainage of mineralised areas rich in Cu, Pb, Zn, Fe and Mn. The near absence of human impact on shelf sediments, despite the vicinity to urban areas with high industrialisation levels, such as the Ave-Douro and Lis areas, is attributed to effective trapping in the estuaries and coastal zones, as well dilution with less contaminated sediments shelf sediments and removal with fine fractions due to grain-size sorting. The character of the contaminated sediments transported to these shelf areas is further influenced by grain-size sorting as well as by dilution with less contaminated marine sediments. The results obtained individually by the different methods complement each other and allow more specific interpretations. (c) 2006 Elsevier Ltd. All rights reserved.
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| 9. |
- Mil-homens, Mario, et al.
(författare)
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Historical trends in Hg, Pb and Zn sedimentation in the central shelf area of Portugal
- 2008
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Ingår i: Journal of Iberian Geology. - 1698-6180. ; 34:2, s. 287-298
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Tidskriftsartikel (refereegranskat)abstract
- Temporal records of excess 210Pb, and the determination of major (Al and Ca) and trace elements (Zn, Cr, Ni, Pb, Cu and Hg) in two sediment box-cores collected in the central area of the Portuguese shelf at North of the Nazaré canyon (offshore from the Lis River), allow identifying the deposition of various chemical elements normally associated with anthropogenic activities. In order to compensate for the natural sediment variability, heavy metal contents were normalised to Al. Temporal variations of Hg, Pb and Zn (Al-normalised) show an increasing trend since the beginning of the 1920s recording the development of industrial activities. Enrichment factors (EF) were calculated to estimate the level of contamination in these sediments. Mercury is the element with the highest average EF values (EF = 3), followed by Pb (EF = 1.5) and Zn (EF = 1.2). The results indicate that since 1991 64% of total Hg, 44% of total Pb and 24% of total Zn are derived from anthropogenic sources. The average anthropogenic fluxes of Hg, Pb and Zn (0.008, 3, 6 g cm-2yr-1, respectively) for the last 40 years in a ca. 400 km2 area of deposition represent a total accumulation of approximately 30, 12000 and 24400 kg per year of Hg, Pb and Zn, respectively. These results indicate that despite the high-energy conditions and the generally sandy nature of the Portuguese shelf sediments, it is possible to identify significant anthropogenic enrichments in some sediment accumulation areas. These contaminants are not necessarily related to immediate sources but may instead indicate atmospheric and or marine transport from more distant sources.
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| 10. |
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