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1.	van Mourik, Caroline A., 1969- (author) The Greenhouse - Icehouse Transition : a dinoflagellate perspective 2006 Doctoral thesis (other academic/artistic)abstract Through the analysis of the stratigraphic and spatial distribution of organic walled dinoflagellate cysts (dinocysts) from climatologically and oceanographically key sites, this project aims to contribute to a better understanding of the Eocene-Oligocene (E/O) environmental changes and their timing. A central issue is to identify the global environmental changes which are responsible for the Eocene cooling and its underlying mechanisms with the focus on the Oligocene isotope-1 (Oi-1) event, thought to mark the onset of major Antarctic glaciation.Two low-latitude sites were selected, Blake Nose (western North Atlantic) and Massignano (central Italy). For the first time a coherent taxonomy and biostratigraphy of dinocysts was established for the late Eocene at these latitudes. A high resolution correlation was established between the Massignano E/O Stratotype Section and the stratigraphically more extended ‘Massicore’. The composite section was used to analyse sea surface temperature (SST) change across the greenhouse-icehouse transition by means of dinocyst distribution.At Massignano, the Oi-1 event was recognised both qualitatively and quantitatively. In the power spectrum of the SSTdino the ~100 and ~400 kyr eccentricity cycles may be distinguished and correlated with La04. When orbitally tuned, the E/O GSSP dates ~100 kyr older than the Oi-1 event. The boundary’s age could either be ~33.75 or ~34.1 Ma, both differ significantly from the ~33.9 Ma age in the GTS 2004.Furthermore, when the data from the low-latitude sites were combined with extensive datasets from the Proto North Atlantic and adjacent regions, a suite of species sensitive to changes in SST was recognised. Their first and last occurrences reflect seven distinct phases of decreasing SSTs during the Middle Eocene to earliest Oligocene.These results clearly indicate that atmospheric cooling together with higher frequency orbital forcing played a key role in the transition from the Greenhouse to the Icehouse world.
2.	Muschitiello, Francesco, 1985- (author) Deglacial impact of the Scandinavian Ice Sheet on the North Atlantic climate system 2016 Doctoral thesis (other academic/artistic)abstract The long warming transition from the Last Ice Age into the present Interglacial period, the last deglaciation, holds the key to our understanding of future abrupt climate change. In the last decades, a great effort has been put into deciphering the linkage between freshwater fluxes from melting ice sheets and rapid shifts in global ocean-atmospheric circulation that characterized this puzzling climate period. In particular, the regional expressions of climate change in response to freshwater forcing are still largely unresolved.This projects aims at evaluating the environmental, hydro-climatic and oceanographic response in the Eastern North Atlantic domain to freshwater fluxes from the Scandinavian Ice Sheet during the last deglaciation (~19,000-11,000 years ago). The results presented in this thesis involve an overview of the regional representations of climate change across rapid climatic transitions and provide the groundwork to better understand spatial and temporal propagations of past atmospheric and ocean perturbations.Specifically, this thesis comprises i) a comparison of pollenstratigraphic records from densely 14C dated lake sediment sequences, which provides insight into the regional sensitivity of North European vegetation to freshwater forcing in the Nordic Seas around the onset of the Younger Dryas stadial (~12,900 years ago); ii) a reconstruction of North European hydro-climate, which, together with transient climate simulations, shed light on the mechanisms and regionality of climate shortly prior to the transition into the Younger Dryas stadial; iii) studies of a ~1250-year long glacial varve chronology, which provides an accurate timing for the sudden drainage of proglacial freshwater stored in the former ice-dammed Baltic Ice Lake into the North Atlantic Ocean; iv) a 5000-year long terrestrial-marine reconstruction of Eastern North Atlantic hydro-climate and oceanographic changes that clarifies the hitherto elusive relationship between freshwater forcing and the transient behaviour of the North Atlantic overturning circulation system. The results presented in this thesis provide new important temporal constraints on the events that punctuated the last deglaciation in Northern Europe, and give a clearer understanding of the ocean – atmosphere – ice-sheet feedbacks that were at work in the North Atlantic. This increases our understanding of how the Earth climate system functions in more extreme situations.
3.	Achimo, Mussa, 1965- (author) Sedimentology and geochemistry of the recent sediments in Maputo Bay, Mozambique 2002 Doctoral thesis (other academic/artistic)
4.	Aigars, Juris (author) The role of sediments in the biogeochemical cycles of nutrients in the Gulf of Riga 2001 Doctoral thesis (other academic/artistic)abstract The sediment biogeochemistry of C, N, P and biologic silica (BSi) plays an important role in cycling of these elements in aquatic ecosystems. In shallow coastal and estuarine systems, water-sediment nutrient dynamics can influence biological processes (e.g., primary production) in overlying waters.The objectives of this study are:characterize C, N, P and BSi geochemistry of the surface sediments in the Gulf of Riga,estimate the spatial distribution, including net flux and sink, for organic C, N and P in the Gulf of Riga,examine if there are any appropriate bulk, regional and/or vertical relationships between the nutrients,examine if nutrient biogeochemistry in surface sediments vary as a response to naturally occurring processes i.e., intensity of sedimentation and bioturbation, oxygen deficiency, variation of temperatureSpatial and vertical distribution reveals that organic C and N ratio is almost independent of sediment characteristics and location, and exhibit a stable value down the sediment core. Over 90 % of carbon and nitrogen in sediments is organic. In contrast, organic P constitutes less than 50 % of the total phosphorus pool. The organic C:N:P ratio in sediments indicate that N and P are decomposed preferentially to C, whereas P is decomposed preferentially to N. The stable C:N ratio in sediments indicates that preferential N decomposition occurs in water column and/or immediately upon settling at sediment surface. Distribution pattern of BSi suggests that accumulation rate of sediments controls BSi concentration. Although nutrient loading from drainage area increased drastically over the past 100 years, vertical profiles of C, N and BSi show no variation in element concentrations except in the top few centimeters. A corresponding increase of benthic biomass most likely results in low elemental accumulation in these sediments.Although Gulf of Riga is one of the most productive areas in the Baltic Sea, seasonal alterations of C and N levels were limited. However, during spring and autumn algae blooms total C and N concentrations increased in the study area. Limited data suggests that burrowing amphipods directly impact the C and N concentrations in the top 2-3 cm of sediments. The vertical distribution of P is more dependent on oxygen concentration, which is largely controlled by bioturbation and sedimentation rates. Moreover, the results suggest that bioturbation is largely responsible for temporal accumulation of inorganic P in surface sediments.The low unidirectional fluxes of dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP) in early spring is consistent with low water temperature and poor nutritional quality of experimentally added material. The high water temperature and better nutritional quality of material added in summer, comparatively to winter, resulted in large DIN and DIP fluxes. Moreover, flux experiments under low oxygen conditions and pulse input of large quantities of settling seston suggest that sediment surface might experience lack of oxygen despite availability of oxygen in the overlying water column.
5.	Al-Hanbali, Hakam, 1963- (author) The geochemistry of two selected areas of the deep sea, the TAG hydrothermal mound, Mid-Atlantic Ridge and the Lomonosov Ridge, central Arctic Ocean 2000 Doctoral thesis (other academic/artistic)
6.	Alm, Elisabet, 1948- (author) Sveconorwegian metallogenesis in Sweden 2000 Doctoral thesis (other academic/artistic)abstract Two main ore types are found in the Sveconorwegian Orogen in southwestern Sweden (Southwest Scandinavian Domain). One of them comprises stratabound Cu mineralizations in the Dal group, located west of lake Vänern. The other comprises quartz veins with varying precious and base metal contents, distributed over 250 km between lake Mjøsa (southeastern Norway) and lake Vänern. In this thesis, both ore types are discussed, although the main emphasis is on Au-bearing quartz veins, particularly those in the Harnäs area near lake Vänern.The Dal group is a 2000 m thick sequence of clastic sediments and intercalated mafic volcanic rocks, metamorphosed under greenschist facies conditions. It records deposition mainly in a shallow marine basin, formed during a rift stage preceding the Sveconorwegian orogeny (c. 1.15-0.9 Ga). The volcanic rocks have been subject to various degrees of sodic and/or potassic alteration. Geochemical and Sm-Nd isotopic evidence indicate a continental setting of volcanism. Cu mineralizations (chalcopyrite and bornite) occur at two stratigraphic levels. An ore-genetic model involving synsedimentary (or syndiagenetic) deposition of sulphides from metal-bearing fluids is favoured.Among Au-bearing quartz veins in the Mjøsa-Vänern ore district, four paragenetic types have been distinguished: Cu-dominated veins with chalcopyrite and/or bornite; Pb-Cu-bearing veins with pyrite, galena and chalcopyrite; Zn-Pb-dominated veins with sphalerite, galena, pyrite and chalcopyrite; Mn-bearing vein(s) with galena, chalcopyrite and hausmannite. In addition, e.g. native gold, argyrodite, hessite, tellurobismuthite and altaite are recognized. The ore lead isotopic composition is complex and metals appear to be derived from a variety of source rocks.The orthogneisses, which constitute the host rocks to the Harnäs veins and the Brustad Au quartz veins (Eidsvoll, near lake Mjøsa), have been investigated with respect to geochemistry, U-Pb zircon age and feldspar lead isotopic composition. The obtained intrusion age of the Brustad augen gneiss is 1674 ± 10 Ma and this rock is considered to belong to the Transscandinavian Igneous Belt. The Harnäs gneiss yielded a protolith age of 1595 +24/-17 Ma and is considered to be a member of the Åmål granitoid suite. Both orthogneisses have undergone ductile deformation during the Sveconorwegian orogeny. A complete isotopic resetting of the feldspar lead through dynamic recrystallization in conjunction with this deformation, at c. 1.0 Ga, has been demonstrated.The steeply dipping Harnäs veins are hosted in a local left-lateral shear zone, which transects the fabric in the surrounding orthogneisses. The moderate wall rock alteration was mainly sericitic. Fluid inclusions show that the ore-bearing vein system at Harnäs developed essentially in three stages: a quartz stage, a pyrite-gold stage and finally a galena stage. The early ore fluid was CO2-bearing, of low salinity and with a temperature of c. 200 oC, while in the galena stage it was purely aqueous, with a slightly higher salinity and a slightly lower temperature. Oxygen and sulphur isotope results imply a predominantly metamorphic origin for the ore fluid and suggest that the fluid constituents were derived from the regional orthogneisses. Ore lead isotopic compositions indicate metal derivation from these orthogneisses shortly after the Sveconorwegian deformation and resetting of feldspar lead. Subordinate Au-anomalous quartz veins in the Harnäs area as well as the Brustad Au quartz veins show characteristics similar to the Harnäs veins. Despite recognized variations, e.g. in mineralogy, a common origin is envisaged for most veins in the Mjøsa-Vänern ore district. They are characterized as late Proterozoic orogenic type Au deposits, with modern analogues e.g. in the western Alps.
7.	Andersson, Carin, 1967- (author) Pliocene foraminiferal biostratigraphy and paleoceanography of the Ontong Java Plateau, western equatorial Pacific Ocean 1995 Doctoral thesis (other academic/artistic)
8.	Andersson, Daniel, 1966- (author) Geochemical trends and provenance of the Tanqua submarine fan-complex southwestern Karoo Basin, South Africa 2003 Doctoral thesis (other academic/artistic)
9.	Andersson, Eva, 1967- (author) Hydrothermal alteration of organic matter at spreading centers 1998 Doctoral thesis (other academic/artistic)abstract Alteration of organic matter, mainly amino acids, at sub-seafloor hydrothermal conditions has been investigated by performing laboratory experiments and by studying deep-sea sediments from hydrothermally active areas on the northern Juan de Fuca Ridge, northeast Pacific Ocean.Quaternary sediments from Middle Valley and the eastern flank of the Juan de Fuca Ridge recovered during the Ocean Drilling Program Legs 139 and 168 have been analyzed for total hydrolyzable amino acid concentrations, individual amino acid abundances and stereochemistry in order to evaluate the effects of hydrothermal stress on the decomposition of sedimentary amino acids. In near surface sediments, amino acids account for up to 3.3% of the total organic carbon content and up to 12% of the total nitrogen content. The non-protein amino acid b-alanine and g-aminobutyric acid become increasingly abundant with depth in low temperature holes (Leg 168) as a result of enzymatic decarboxylation of aspartic acid and glutamic acid, respectively. The decomposition of amino acid in high temperature holes (Leg 139) is enhanced with depth and the amino acid patterns indicates that most amino acids are incorporated into geopolymers and that condensation results in increased stability of some amino acids.The effects of low temperature hydrothermal activity on microbially mediated organic matter diagenesis were studied by comparing depth concentration profiles of interstitial sulfate and methane of Holes 1023A, 1024B, 1025B and 1028A, ODP Leg 168. Diffusional exchange between sulfate-rich basement fluids and pore-waters increases the interstitial sulfate concentrations with depth below local sulfate minima caused by bacterial sulfate reduction. The effects of diffusional processes on pore-water chemistry in the sediment column is reflected by the inhibition of methane production and is largely dependent on sediment thickness.The decomposition of alanine, leucine, aspartic acid and serine in aqueous solutions was studied at 200oC and 50 bar with the purpose of evaluating the effect dissolved oxygen on decomposition rates. The redox buffering mineral assemblage pyrite-pyrrhotite-magnetite was used to constrain the oxygen fugacity to geologically realistic values. Comparisons between results obtained from buffered and nonbuffered runs show that the decomposition is faster for most amino acids but serine in nonbuffered experiments.
10.	Andersson, Per, 1960- (author) Hydrogeochemistry of iron, manganese and sulphur- and strontium isotopes in a coniferous catchment, central Sweden 1991 Doctoral thesis (other academic/artistic)
11.	Andrén, Elinor, 1966- (author) Holocene environmental changes recorded by diatom stratigraphy in the southern Baltic Sea 1999 Doctoral thesis (other academic/artistic)abstract Sediment cores from the southern Baltic Sea and the Oder River estuary are analysed for their siliceous microfossil assemblages and organic carbon content. Long piston cores from the Bornholm and Gotland Basins provide data on the long-term Holocene history of the Baltic proper and serve as a natural background when evaluating the most recent environmental changes recorded in the short gravity cores. Corrected and calibrated 14C dates for the Holocene part, together with 210Pb and 137Cs dates for the sediments deposited during the last century, are used as a basis for constructing chronologies and age models. The main results are:The brackish phase of the Yoldia Sea stage in the Bornholm Basin is recorded by a diatom assemblage of periphytic taxa indicating a shallower water depth than today and more marine conditions than are recorded by the planktonic assemblage found in the Gotland Basin.The transition between the Yoldia Sea and the Ancylus Lake stages is distinguished in the offshore facies and recorded in the sediments in the form of a small increase in organic carbon coinciding with a peak in the diatom abundance and increased diatom diversity.The onset of the Initial Litorina Sea stage, recorded about 10,100 calendar years BP (c. 8900 14C years BP) in the Bornholm Basin, indicates a complex transition with different phases of brackish-water inflow.Six periods with major marine water inflow into the Baltic basin are recorded during the Holocene. Once an open connection was established with the North Sea, climatic influence seems to have been the most important factor controlling such inflow events.Comparison between the organic carbon content, the absolute abundance of siliceous microfossils and a regional climate proxy, the Greenland (GRIP) ice core (18O record, shows a tentative link between primary production in the Baltic proper and climate. A high temperature on Greenland corresponds to high organic carbon content and increased diatom abundance in the Baltic proper.Climate change is recorded in both the siliceous microfossil assemblages and the organic carbon content. A sediment sequence indicating high productivity c. 950-800 calendar years BP (AD 1000-1150) correlates with the Medieval warm period. An alteration in the diatom assemblage interpreted as being due to a deterioration in the climate correlates with the start of the Little Ice Age about 850-700 calendar years BP (AD 1100-1250).The effects of eutrophication are recorded AD 1850-1860 in the southwestern Baltic proper, AD 1900 in the Oder estuary and AD 1950-1960 in the Gotland Basin. These effects were probably caused by increased discharge of nutrients deriving from fertilisers, as the responding diatom species partly indicate a cold climate rather than a warm one, as would have been expected if this had been only a response to the warmer climate documented during the last 100 years or so.
12.	Bjerkeus, Monica, 1956- (author) Sediment structures in the Phanerozoic bedrock of the Baltic Proper 1999 Doctoral thesis (other academic/artistic)
13.	Björkvald, Louise, 1973- (author) Landscape hydrogeochemistry of Fe, Mn, S and trace elements (As, Co, Pb) in a boreal stream network 2008 Doctoral thesis (other academic/artistic)abstract The transport of elements by streams from headwater regions to the sea is influenced by landscape characteristics. This thesis focuses on the influence of landscape characteristics (e.g. proportion of wetland/forest coverage) on temporal and spatial variations of Fe, Mn, S and trace elements (As, Co, Pb) in streams located in northern Sweden, a boreal region characterized by coniferous forests and peat wetlands.Water samples from a network of 15 streams revealed a different hydrogeochemistry in forested catchments compared to wetland catchments. The temporal variation was dominated by spring flood, when concentrations of Fe, Mn and trace elements increased in forested headwaters. However, in streams of wetland catchments concentrations decreased, but Pb concentrations were higher in comparison to other streams. Both Fe and Pb showed positive correlations with wetland area, while Co correlated with forest coverage. The anthropogenic contribution of As and Pb appear to be larger than the supply from natural sources.During spring flood SO42- decreased in most streams, although concentrations increased in streams of wetland catchments. Concentrations of SO42- were higher in streams of forested catchments than in wetland dominated streams, the former being net exporters of S and the latter net accumulators. Isotope values of stream water SO42- (δ34SSO4) were close to that of precipitation during spring flood, indicating that the major source of S is from deposition. The results show that, although emissions of anthropogenic S have been reduced, there is still a strong influence of past and current S deposition on runoff in this region.In conclusion, wetlands are key areas for the hydrogeochemistry in this boreal landscape. The findings emphasize the importance of understanding stream water chemistry and element cycling from a landscape perspective. This may be important for predicting how boreal regions respond to environmental disturbances such as climate change.
14.	Blaj, Teodora, 1979- (author) Late Eocene through Oligocene calcareous nannofossils from the paleo-equatorial Pacific Ocean – taxonomy, preservation history, biochronology and evolution 2009 Doctoral thesis (other academic/artistic)abstract This study aims to unravel the ecological and evolutionary dynamics within the calcareous nannofossil communities at the Eocene/Oligocene (E/O) transition and during the Oligocene time when Cenozoic 'icehouse' conditions were established. The main question this study aims to answer is whether the changes in the nannofossil assemblages were controlled by intrinsic evolutionary trends or if the changes were controlled by environmental factors such as changes in temperature and nutrient availability in the surface water. These questions are addressed with detailed analyses of the taxonomy, biostratigraphy and fluctuations in abundance and diversity of calcareous nannofossil assemblages from a continuous latest Eocene through Oligocene sediment section from the ODP Site 1218 (8°53.38´N, 135°22.00´W), paleo-equatorial Pacific Ocean. An improved nannofossil taxonomy and biostratigraphy has been established. At the E/O transition, changes in the nannofossil preservation mimics changes in calcium carbonate content. A detailed investigation of late Eocene and Oligocene sediments yields age estimates for ten nannofossil bioevents. Morphometric studies of the Reticulofenestra umbilicus-R. hillae show that these cannot be subdivided into two different morphospecies. Based on different morphometry and stratigraphic ranges, the Oligocene Sphenolithus lineage appears to be the result of a combined anagenetic and cladogenetic evolution. A new nannolith species is described: Triquetrorhabdulus longus. High-resolution nannofossil data indicate changes in the composition, abundance and diversity of the mid-Oligocene assemblages. Intervals of high diversity index coincide with Oi-glaciation events. However, visual examination of the variations in abundance of nannofossil taxa do not appear to correlate with changes in either oxygen or carbon isotopes. This presumably indicates that a dynamic equilibrium did not exist between these Oligocene nannoplankton assemblages and changes in surface water temperature or productivity conditions.
15.	Blomqvist, Sven, 1952- (author) Geochemistry of coastal Baltic sediments : processes and sampling procedures 1992 Doctoral thesis (other academic/artistic)abstract Quantitative and experimental studies on Recent sedimentary processes, with particular reference to element dynamics and mass transport, were conducted in a coastal area of the north-western Baltic proper. A five-year geochemical study reports sediment trap catches, and estimates the flux dynamics of resuspended sediments and primary settling matter. Considerable variations within and between years, seasons and nearby stations were revealed for gross sedimentation rate, and for the ratio between primary settling matter and resuspended sediment. This pattern also applied to carbon. Resuspended matter was found to be a large item in the annual budget for all years and stations. In fact, the resuspended portion commonly exceeded 50 %, and periods without resuspension seem rarely or never to occur in the investigated area. Dominance of primary settling matter was recorded mainly in spring. These findings illustrate problems that may be caused by the use of coastal marine data onsettling flux uncorrected for the resuspended portion. These conclusions are based on analyses of petrogenic elements, and their use as markers, to derive quantitative estimates of the origin of the intercepted matter. A second geochemical paper also deals with petrogenic elements, and illustrates the importance of considering natural geochemical variation in sediments when assessing changes in metal loading. Conclusions drawn in these two papers may have implications for much geochemical, ecological and environmental research in coastal areas. The credibility of these geochemical conclusions depend critically on the use of reliable and dependable sedimentological field sampling techniques. The methods used were selected after extensive evaluations of available methods and instruments. These evaluations include an insitu experiment on the dependence of the orifice area of the collecting tubes on sediment trapping, and studies on soft bottom sediment sampling, and the biases caused by coreshortening, redistribution, resuspension and loss of enclosed sediments. Newly designed instruments for acquisition of sediments and a new sediment trap system are described. The methodological evaluations also involve two review papers, one on the sediment trap technique and one on quantitative sampling of soft-bottom sediments.
16.	Bodén, Per, 1958- (author) Biostratigraphic implications of Neogene diatom abundances in the Norwegian Sea, the North Atlantic and the western North Pacific 1992 Doctoral thesis (other academic/artistic)abstract This thesis consists of three separate articles and are mainly concerned with the taxonomy of species from the genus Thalassiosira and quantitative diatom biostratigraphy in three oceanic regions of the northern hemisphere. The study material consists of Ocean Drilling Program (ODP) Holes 642B, 642C and 644A at about 67°N in the Norwegian Sea, Deep Sea Drilling Project (DSDP) Hole 552A at 56 N in the North Atlantic, and DSDP Site 578 at 34°N in the northwest Pacific. The stratigraphic sequences examined range in age from early Miocene to late Pliocene (18.0 to 1.8 Ma) in the Norwegian Sea, late Miocene to early Pliocene (5.7 to 4.4 Ma) in the North Atlantic, and late Miocene to early Pliocene (6.4 to 4.0 Ma) in the North Pacific.The first article presents an empirically derived evaluation of the accuracy and reproducibility in Moore’s (1973) random settling method. This method is here adopted to quantitative diatom analysis. The results of the evaluation of Moore’s method provide estimates of errors to be expected at different abundance levels. These results made it possible to rank the reliability of diatom data produced throughout the thesis.The second and third articles investigate a total of 53 diatom events. These articles also contain evaluations of the stratigraphic precision by which these 53 events can be determined on the basis of the observed absolute abundance patterns. Some of the 53 events discussed represent previously established datums. The quantitative data presented in this thesis allow establishment of several new biostratigraphic datums, from all three investigated regions. Of the 36 events investigated for the Norwegian Sea, 22 have been given chronological estimates through direct correlation to the established paleomagnetic polarity history. All 5 events for the North Atlantic and all 12 events for the North Pacific are also given age estimates through correlation to existing magnetostratigraphies. Five new Thalassiosira species are described, T. baldaufii, T. labimarginata, T. lindstroemii, T. tetraoestrupii and T. voeringensis. These species are all considered as stratigraphically useful.Two Neogene hiatuses are identified in the outer Vdring Plateau sequence (ODP Site 642). The older falls in the late Miocene having a duration of approximately 3.5 m.y., representing the time interval between approximately 10 and 6.5 Ma. The younger hiatus represents the time interval between approximately 3.1 and 2.5 Ma in the late Pliocene.
17.	Bohlin, Hanna, 1974- (author) The influence by point sources on carbon, nitrogen and metals in two sedimentary environments 2005 Doctoral thesis (other academic/artistic)abstract Sediments in two aquatic environments have been investigated. Both are anthropogenically affected and polluted. The focus has been on stable carbon and nitrogen isotopes, C/N ratios, and heavy metals. The first site is Höggarnsfjärden Bay in the inner parts of the Stockholm Archipelago, Sweden, where a garbage dump releases treated leach water. The effect on carbon and nitrogen in the sediment close to the discharge is large, but 1200 m downstream the effect is diluted by the background discharge of the town of Stockholm and the Lake Mälaren, which drains into the archipelago. The main source of the studied metals is not the garbage dump itself. The sediment close to the discharge shows high enrichment factors due to high sedimentation rate and adsorption, and low decomposition of organic matter. The metal enrichment factors of downstream sites are not higher than the upstream sites. The second site is Lake Verkasjön close to the north part of Lake Vättern, in the county of Örebro, Sweden. River Salaån flows through Lake Verkasjön on the way through a former mining area to Lake Vättern. Upstream of Lake Verkasjön an ore dressing plant site was used in 1877-1881 for extraction of zinc. During that period the sediment of Lake Verkasjön received high loadings of sulphidic tailings. Normal sedimentation after the event has lead to that the polluted sediment is found as a distinct layer at 18-22 cm. The layer is characterized by elevated metal concentrations, decreased organic matter content and increased stable carbon composition. The sediment that has accumulated above 18 cm works as a physicochemical barrier that seals the waste from the overlying sediment. At the time of the event the signal of aquatic production in the sediment changed; the sediment above the layer has an increased proportion of aquatically produced material, implying changed land use in the catchment area.
18.	Borgendahl, Johanna, 1972- (author) Environmental and climatic changes in the Baltic Sea and the eastern Mediterranean Sea : as recorded by pigments and isotopes in sediments 2006 Doctoral thesis (other academic/artistic)abstract This thesis is a study of Holocene sapropels from two semi-enclosed seas; the Baltic Sea and the Mediterranean Sea. Sapropels are sedimentary layers with organic C > 2%. The Baltic Sea and the Mediterranean Sea have a limited water exchange, and despite differences in water depth and salinity, mechanisms for fluxes and preservation of Corg are principally the same. Primary focus is on biomarkers for increased primary productivity and anoxic/euxinic bottom water. Pigments (primarily from cyanobacteria), δ15N, δ13C, N and Corg have been used for studying increased primary productivity. Presence of the pigment isorenieratene from green sulphur bacteria indicates photic zone anoxia. Zn, Mn and δ34S have also been used to identify different scenarios during sapropel formation.Pigments start to appear at the beginning of both the Baltic Sea sapropel and S1, the Holocene sapropel in the Mediterranean Sea. Cyanobacterial pigments generally increase early in the sapropel, due to fast adaptation to more P-rich conditions. Cyanobacteria are favored by low N/P-ratios and P was probably in excess during the formation of S1 and the Baltic Sea sapropel sediments. Lowering of δ15N and concurrent increase in N in both the Baltic Sea and S1 sapropels is probably caused by cyanobacterial N2-fixation. This most likely increased the N/P-ratio and enhanced overall primary productivity. Both increased primary productivity and enhanced preservation of organic carbon are important mechanisms for sapropel formation. The appearance of isorenieratene in the protosapropel is most likely the result of an environment where even moderate increases in primary productivity could create anoxic conditions. This favours an estuarine water circulation scenario with anoxic bottom waters. δ34S of sulphate and sulphide confirm this scenario, which can be explained by the coexistence of sulphate reducing and sulphur disproportionating bacteria together with phototrophic purple and green sulphur bacteria.
19.	Broman, Curt, 1956- (author) Origin of massive sulfide ores in the Skellefte district, as indicated by fluid inclusions 1992 Doctoral thesis (other academic/artistic)abstract The Proterozoic SkeUefte massive sulfide ore district is confined to a 200 km long belt of a submarine metavolcanic and metasedimentary rock sequence in northern Sweden. It is located between an area of terrestrial metavolcanics in the north and gneisses, migmatites and granites in the south. Intrusions of granitoid complexes occur in several places, some of them are cogenetic with the volcanics and some post-date the emplacement of the supacrustals. The regional metamorphism has reached greenschist facies conditions. The district has characteristics typical of a subduction-related volcanic arc formation, which is reflected by the geology, the chemistry of rocks and the appearance of massive sulfide deposits. In the district approximately 100 sulfide mineralizations have been discovered, about 9 are currently mined with a total annual output of roughly 2 million tons of base metal ore. These deposit exhibit many ore features which are common in the Kuroko-type massive sulfide deposits.Microthermometric measurements of aqueous two-phase fluid inclusions in sphalerite, quartz and calcite from the massive sulfide ores indicate that they were deposited from Ca-Na-Cl solutions with a salinity of 1-6 eq. wt. % NaCl under nonboiling conditions at seawater depths between 1 and 2.5 km. The inclusions reveal trapping temperatures of 160-370 °C, similar to the temperatures obtained for the sulfide forming hydrothermal fluids which emerge from the sea floor vents at the East Pacific Rise.The massive ores are underlain by chalcopyrite-rich stockwork mineralizations. The aqueous inclusions hosted by them display temperatures and salinities equal to those in the massive ores, but were C02- and CH4-bearing as well. The characteristics of these inclusions suggest a heterogeneous system with gas-bubbles in a liquid phase. The lack of gases in the inclusions from the massive parts may indicate that the escaping gas have reacted with bottom water and formed the carbonate horizons which are associated with the massive ores.The ores have been affected in various degrees by subsequent metamorphic processes involving fluids of different compositions. Fluid inclusions in healed microfractures and quartz veins indicate that the metamorphic fluids during the peak of the regional metamorphic alteration were dominated by C02-rich compositions. The pressures deduced from the molar volumes of these inclusions can be used to construct a metamorphic isograd which follows the contour of the southern late-orogenic granite, creating a northern and a southern subarea with pressures below and above 3 kbar respectively.Retrograde conditions are recorded by N2-bearing hydrocarbon-rich fluids trapped in microfractures under low metamorphic pressures. No regional gradient was indicated by the N2/CH4 ratio and therefore implying that the amounts were controlled by local mineral reactions. However, the distribution trend of higher molecular weight hydrocarbons in these inclusions suggest a steeper cooling path in the western part of the district.At the final stage of the metamorphism, aqueous solutions with temperatures below 150 “C percolated through the rocks, these were highly saline brines in the western district and solutions with low to medium salinities in the eastern part.
20.	Bäckstrand, Kristina, 1979- (author) Carbon gas biogeochemistry of a northern peatland - in a dynamic permafrost landscape 2008 Doctoral thesis (other academic/artistic)abstract This thesis is about biogeochemical processes of a northern peatland and their importance as a link between the climate and the terrestrial system. Increased temperatures on a global level, and particularly in the Arctic, have led to melting permafrost and changes in hydrology. In turn, this affect the natural exchange of radiatively important trace gases between land and atmosphere that may reinforce climate change. The aim of this thesis is to increase the understanding about the exchange of carbon dioxide (CO2), methane (CH4) and non-methane volatile organic compounds (NMVOCs) occurring in northern peatlands, to decrease uncertainty about their future carbon (C) balance. In order to pursue this aim, we designed a study that allowed measuring the C exchange at a subarctic peatland, accounting for spatial and temporal analysis at several levels. The field site was the Stordalen mire, northern Sweden. Exchange rates of CO2, and total hydrocarbons (THCs; CH4 and NMVOCs) were measured using an automatic chamber system for up to six years, at three different types of vegetation communities and permafrost regimes. The gas exchange was found to relate to different environmental and biological variables at different vegetation communities and at different temporal scales. Differences in flux rates and controls between sites could be explained with biological and environmental variables in a better way than the seasonal and interannual variability within a site.Snow season flux measurements were determined to be of high importance regarding the annual C budget. By excluding the snow season, the potential C source strength of a peatland is likely to be underestimated. The importance of combining the THCs with the CO2 to estimate the annual C balance was demonstrated as THC could be sufficient to shift the mire from a sink to a source of C to the atmosphere. Again, the C source strength may be significantly underestimated if only focusing on CO2 fluxes in wet peatland environments.
21.	Carman, Rolf, 1956- (author) Biogeochemical constraints on phosphorus exchange and related diagenetic processes in Baltic Sea sediments 1990 Doctoral thesis (other academic/artistic)
22.	Claesson, Lillemor, 1976- (author) Fluid-rock interaction in two seismically active areas : The Tjörnes Fracture Zone, northern Iceland and the Shillong Plateau, northeastern India 2007 Doctoral thesis (other academic/artistic)abstract Hydrogeochemical monitoring can improve our understanding of fluid-rock interaction, and may detect anomalies that are precursory to- or caused by- earthquakes. In this study, hydrogeochemical monitoring was carried out in two distinct tectonic settings, to study coupling between hydrogeochemical changes and seismic activity. The Tjörnes Fracture Zone, north Iceland (HU-01), and the Shillong Plateau, northeastern India (Silver Drop), are two seismically active areas with differing geology. Hydrogeochemical monitoring included regular groundwater sampling with subsequent major and trace element analysis and supporting stable isotope analysis at HU-01 only. Transition metal concentrations anomalies were detected at HU-01 prior to a MW 5.8 earthquake. Concentration increases of many major elements were detected after this earthquake. Hydrogeochemical recovery took place during the subsequent two years. The preseismic anomalies are interpreted as the result of increased fluid-rock interaction due to preseismic fracturing whereas the postseismic changes are attributed to source switching and/or mixing of fluids enabled by fault unsealing. The two-year recovery is probably related to the gradual sealing off of a fluid source. Pre- and post-seismic hydrogeochemical shifts (e.g. Na/Si, Ba/Sr) were detected at Silver Drop coinciding with two MW > 5 earthquakes. These shifts are likely due to changes in the type of feldspar weathering. A basalt dissolution experiment was carried out in order to understand the preseismic changes at HU-01. Rates and dissolution mechanisms interpreted from this experiment confirm that the metal anomalies at HU-01 could be induced by transient exposure of weakly altered basalt to groundwater interaction caused by microfracturing. Finally, from this study it can be concluded that a seismic event need not cause a hydrogeochemical shift, but a hydrogeochemical shift was always associated with a seismic event.
23.	Colleoni, Florence, 1983- (author) On the Late Saalian glaciation : A climate modeling study 2009 Doctoral thesis (other academic/artistic)abstract This thesis focuses on the glaciation of the Late Saalian period (160 -140 ka) over Eurasia. The Quaternary Environment of the Eurasian North (QUEEN) project determined that during this period, the Eurasian ice sheet was substantially larger than during the entire Weichselian cycle and especially that of the Last Glacial Maximum (21 ka, LGM). The Late Saalian astronomical forcing was different than during the LGM while greenhouse gas concentrations were similar. To understand how this ice sheet could have grown so large over Eurasia during the Late Saalian, we use an Atmospherical General Circulation Model (AGCM) coupled to an oceanic mixed layer and a vegetation model to explore the influence of regional parameters, sea surface temperatures (SST) and orbital parameters on the surface mass balance (SMB) of the Late Saalian Eurasian ice sheet. At140 ka, proglacial lakes, vegetation and simulated Late Saalian SST cool the Eurasian climate, which reduce the ablation along the southern ice sheet margins. Dust deposition on snow has the opposite effect. The presence of a Canada Basin ice-shelf during MIS6 in the Arctic Ocean, does not affect the mass balance of the ice sheet. According to geological evidence, the Late Saalian Eurasian ice sheet reached its maximum extent before 160 ka. Northern Hemisphere high latitude summer insolation shows a large insolation peak near 150 ka. The simulated climate prior to 140 ka is milder and ablation is larger along the southern margins of the Eurasian ice sheet although the mean annual SMB is positive. The Late Saalian Eurasian ice sheet may have been large enough to generate its own cooling, thus maintaining itself over Eurasia.
24.	Dahlqvist, Ralf, 1973- (author) Speciation and fractionation of Ca and the REE in fresh and marine waters 2004 Doctoral thesis (other academic/artistic)abstract This study is concerned with speciation and fractionation of the rare earth elements (REE) and calcium (Ca) in aqueous solutions. The aim is to investigate the chemical states and physical sizes in which these elements can be present. The REE (including neodymium) and Ca have contrasting geochemical behavior in aqueous solutions. Ca is a major dissolved element, while the REE are trace components and highly reactive with aquatic particles.The major interests of the five papers included in this thesis are the following:· Papers I and V deal with the behavior of neodymium (Nd) and its isotopes in the Kalix River and some marine waters.· The diffusive gradients in thin-films (DGT) method is developed for measuring Ca and Mg in Paper II.· Paper III presents a speciation and fractionation study of Ca in the Kalix and Amazonian rivers.· The rare earth elements and their carrier phases are investigated in the Kalix river in Paper IV.For most elements a detailed study of speciation and fractionation can not be performed using only one method. This is due to the overall heterogeneity of the material, considering both size and chemical composition, which is present in aquatic solutions. During this project the aquatic geochemistry of the REE and Ca has been studied using mainly three methods; cross-flow filtration (CFF), field-flow fractionation (FFF) and diffusive gradients in thin-films (DGT). Field work has to a large part been conducted in the Kalix River, in northern Sweden, which is one of the last pristine river systems in Europe. Some field work has also been conducted in the Baltic Sea and the Arctic Ocean. Results from Amazonian rivers are also presented.These are the main conclusions from this work:The DGT technique works equally well for measuring Ca and Mg in natural waters as previously reported for trace metal.A significant colloidal phase for Ca could be detected in the Kalix River and in different Amazonian rivers. This was concluded independently using both CFF and FFF.Variations in REE signatures in the Kalix River suggests two different pathways for the REE during weathering and release form soil profiles and transport in the river.No significant variation in Nd-isotopic composition could be detected in the Kalix River although concentrations varied by a factor of ~10. This suggests that there is one major source for Nd in the river although different pathways for the REE may exist.A study of Nd in the Kalix River, the Baltic Sea and the Arctic Ocean showed that the isotopic compositions in the diffusible fractions were similar to water samples. However, the relative amount of diffusible Nd increased with salinity, probably reflecting the lower concentration of colloidal and particulate material in marine waters.
25.	Das, Supriyo, 1978- (author) Biogeochemical evidences of human intervention in a shallow lake, Zeekoevlei, South Africa 2007 Doctoral thesis (other academic/artistic)abstract This thesis describes a multi-parameter biogeochemical investigation in a shallow hyper-eutrophic freshwater coastal lake, Zeekoevlei, in South Africa. The predominance of autochthonous algal-derived organic matter in lake sediments is indicated by low C/N, high H/C ratios and δ13Corganic values. Seepage from a nearby waste water treatment plant, rapid urbanization, raw sewage input and heavily fertilized farming in the catchments have caused enhanced productivity and is reflected by the changes in TOC concentrations, δ15N values, terrestrial to aquatic (n-alkane) ratio (TAR) and low carbon preference index (CPI) values. Eutrophic conditions were initiated in the lake with the start of recreational activities in early 1900s. Construction of dams and pondweed eradication in mid-1900s caused the transformation of the lake towards a hyper-eutrophic water body. Moreover, the aquatic macrophyte n-alkane proxy (Paq) values indicate the slow takeover by floating macrophytes after the eradication of submerged pondweeds in 1951. Low δ15N values and appearance of zeaxanthin indicate initiation of cyanobacterial bloom in the lake following pondweed eradication. Furthermore, the lake experienced intense cyanobacterial bloom after 1983 dredging. Although, cyanobacterial domination has decreased in recent years, hyper-eutrophic condition persists in the lake.Chemical weathering process supplies major fraction of trace metals, whereas fertilizers, agricultural wastes, sewage effluents and road runoff constitute the anthropogenic fraction. Low industrialization in the catchments causes low metal pollution in waters. In addition, high pH and metal scavenging by planktons result low dissolved trace metal concentrations. Adsorption by CaCO3 and planktonic assimilation control trace metal and phosphorus (P) sedimentation. Lake sediments have low P retention capacity and P is released from surface sediments by wind-induced resuspension.
26.	Engström, Anna, 1975- (author) Deformation and fluid-flow in magma-poor margins : A study of the Tasna Ocean-Continent transition, SE Switzerland 2006 Doctoral thesis (other academic/artistic)abstract In this study, interaction between fluids and deformation during the final stages of magma-poor rifting was investigated. The Tasna Ocean-Continent transition, located in the Swiss Alps, was studied and a large data set was obtained from profiles oriented perpendicular to two detachment faults. One of these juxtaposed serpentinized mantle against continental crust and the other exhumed both mantle and continental crust to the seafloor. Deformation associated with detachment faulting showed many common features but also some phenomena which were unique to each fault, confirming their sequential activity and differing roles in the exhumation process. Oxygen isotopes indicated the presence of both pervasive and channeled fluid phases, either accompanying or post-dating serpentinization. Deformation in the fault zone occurred in previously serpentinized mantle indicating that serpentinization pre-dated final exhumation. Most strain localization and displacement occurred in fault cores which are narrow zones beneath the detachments. These are underlain by wide zones characterized by more distributed strain. Transitional fabrics as well as reactivated and/or overprinted deformation structures indicated that the final phase of rifting is complex. Fault cores acted as fluid conduits or barriers. Thus, the most deformed zones may become the least permeable. Hence the coupling between deformation and fluid flow is complex in a study area subjected to several phases of deformation and fluid flow. Finally the importance of serpentinization in the evolution of magma-poor rifting was investigated. It was found that serpentinization is the consequence rather than the reason for strain localization at magma-poor margins. However, serpentinization may be an important process which can accelerate exhumation rates in the very latest stages of magma-poor rifting. The pre-existing deformation history of the crust may also be of importance for the development and location of margins.
27.	Estmark Kalinowski, Birgitta (author) Dissolution Kinetics and Alteration Products of Micas and Epidote in Acidic Solutions at Room Temperature 1997 Doctoral thesis (other academic/artistic)abstract The reaction kinetics of the weathering of several phyllosilicates and one sorosilicate were stud ied experimentally. The alteration products were characterised by various methods in clud ing XRD, HRTEM, SEM, FTIR, NMR and Mössbauer spectroscopy. Weathering of silicates is of particular concern to our knowledge of several areas in low temperature geochemistry, such as el e ment cy cling, ground water chemistry and soil formation. The importance of these processes ex tends to the long-term nutrient supply to forest ecosystems and control of soil and water acidity, es pe cial ly in Scandinavia.Several soil models designed to predict the impact of acid rain on the soil chemistry rely on kinetic data of mineral weathering. The reaction kinetics for minerals are used in such models to predict chang es in soil chem is try. This enables calculation of the effect of acid rain (i. e. critical load) in a 100-year per spec tive. For some minerals relatively little knowledge is available for the reaction kinetics. There fore the dissolution kinetics of muscovite, biotite, phlogopite, vermiculite and epi dote were studied over the pH range 1 to 6.5 at room temperature using flow-through reactors.Silica release rates based on specific surface area are about the same for as divers silicates as epidote (sorosilicate), K-feldspar (tectosilicate) and phlogopite (phyllosilicate). At pH 3 log R = -15.41, -15.5 and -15.46 respectively for these min er als. However, the framework of Si and Al is likely to determine with what ease cations positioned in between the conformation of Si and Al tetrahedra are re leased. For example, K in micas have transportation channels due to the layer struc ture and ought there fore to be released easier than in K-feldspar. In most cases Si is the most slowly released element in silicates, but in epidote, Si and Ca are the fastest released elements from the structure, while Al and Fe are retained. Leaching of inter framework cations creates strain and charge im bal ance in the silicate structure, causing Si to be more readily released in base cation containing silicates than in quartz. Released Si may repolymerise directly at the surface of silicates or interlayers. Amor phous silica gel has been detected, as a weathering product between packages of 2:1 layers in bi otite, using AEM. Iron(hydr)oxides have been found as the end-product of biotite weathering. Re sid u al layer calculations based on the solution composition show that Al and Fe form an enriched layer with a thickness of 1-2 nm at the surface of epidote.Biotite and phlogopite probably alter to trioctahedral vermiculite from the edges and inwards. Mössbauer spectroscopy shows that weathering of biotite as well as ver micu lite is accompanied by oxidation. Al-hydroxy polymers are introduced in the in ter lay er during weathering of phlogopite and vermiculite, which is supported by both XRD and 27Al MAS-NMR analyses. Additions of KCl and AlCl3 to the reactant solutions show that release rates, exfoliation and oxidation processes decrease with increased concentrations for both biotite and phlogopite. Leaching of interlayer cat i ons seems thus to initiate oxidation of ferrous iron.
28.	Frogner, Paul, 1964- (author) Dissolution mechanisms of albite and hornblende and of calcite in sandstone 1998 Doctoral thesis (other academic/artistic)
29.	Gebeyehu, Mekbib, 1952- (author) Geochemistry, Pb, C-O isotope data and genesis of some lower proterozoic massive sulfide deposits in the Bergslagen ore province, south central Sweden. 1992 Doctoral thesis (other academic/artistic)
30.	Gleisner, Magdalena, 1972- (author) Quantification of mineral weathering rates in sulfidic mine tailings under water-saturated conditions 2005 Doctoral thesis (other academic/artistic)abstract Tailings are a fine-grained waste product produced during the metal recovery process. Tailings consist mostly of different silicates but also sulfides (e.g. pyrite), since 100 % metal recovery is not possible. Freshly processed tailings are deposited in large impoundments. If the mine tailings in the impoundments are exposed to water and oxygen, the sulfides will oxidize and release acidity and metals such as Fe, Cu, Zn, and Pb. The sulfide mineral oxidation reactions are catalyzed by sulfur and iron oxidizing bacteria (principally Acidithiobacillus ferrooxidans) that oxidize ferrous iron to ferric iron, which then oxidizes pyrite. When the leachate produced by this process discharges from the impoundment, it is called acid mine drainage, which may lead to the pollution of adjacent streams and lakes.The intention with this thesis is to investigate and quantify mineral weathering processes and element release rates occurring in water-saturated and soil-covered sulfidic mine tailings. The study was performed in different batch and column experiments in room temperature and in the laboratory. The batch experiments were conducted for ca. three months and investigated: a) microbial and abiotic sulfide oxidation in freshly processed tailings under oxic conditions at pH 2-3 and pH 8, b) microbial oxidation of pure pyrite grains at pH 2-3 under different oxygen concentrations ranging from anoxic to oxic conditions. The column experiments, consisting of unoxidized tailings in water-saturated columns, were conducted for up to three years. In these experiments, an oxygen-saturated solution was continually pumped into the column inlet, and investigated: a) differences in oxidation rates between tailings of two different grain sizes, b) factors affecting element discharge rates, acid neutralization, and sulfide oxidation, c) the effect of ions released in a soil cover on release rates in the tailings.Sulfide oxidation processes within the batch experiments were limited by surface kinetics. The microbial oxidation of pure pyrite at atmospheric conditions produced the most rapid rate, while the microbial oxidation of pure pyrite at anoxic conditions was slower by 1.8 orders of magnitude. Microbial and abiotic oxidation of pyrite in freshly-processed tailings resulted in pyrite oxidation rates that were intermediate between these two extremes. The results from the microbial experiments with pure pyrite indicated a positive correlation between the concentration of dissolved oxygen, ferric iron and bacterial cells (at a total cell concentration > 106 cells/mL and a dissolved oxygen concentration ≥ 13.2 µM), which implies an interdependence of these factors. The results from these batch experiments support the indirect mechanism for microbial oxidation by the ferric oxidation pathway. Pyrite oxidation rates estimated from the batch experiments may be comparable with oxidation rates in the unsaturated zone and at the groundwater table in a tailings impoundment.Acid neutralization reactions in the column experiments resulted in the release of base cations to the column leachate. Calcite was the most important neutralizing mineral despite that it was only present in minor amounts in the tailings. It was confirmed that acidity forced the calcite dissolution. Element release rates in the column experiments were controlled by the availability of dissolved oxygen, which was a function of the water flow rate into the column. These column experiments also showed that the results are comparable with results from field studies, justifying the use of column experiments to study processes within tailings impoundments.
31.	Gyllencreutz, Richard, 1974- (author) Holocene and Latest Glacial Paleoceanography in the North-Eastern Skagerrak 2005 Doctoral thesis (other academic/artistic)abstract Detailed information on past oceanographic and climatic changes is crucial for our understanding of natural climate variability and for the assessment of future climate variations. Sediments strongly influenced by the North Atlantic Current accumulate at high rates in the northeastern Skagerrak, forming a potential highresolution archive for information on past climatic and oceanographic processes and events. Through a highresolution, multi-proxy study of the 32 meter long core MD99-2286 from the north-eastern Skagerrak, and interpretation of chirp sonar profiles from the coring area, this thesis provides new and detailed insights about the paleoceanographic development of the eastern North Sea region since the deglaciation.The chronostratigraphic control of core MD99-2286 relies on 27 radiocarbon dates. Ages are presented in calibrated thousand years before present (abbreviated “kyr”). Core MD99-2286 was correlated to chirp sonar profiles using measured physical properties. This correlation demonstrates that a strong regional acoustic reflector, previously assumed to represent the Pleistocene/Holocene boundary, was formed as a result of rapid ice retreat during the latest Pleistocene. Based on the distribution of ice rafted debris in the core, ice berg calving in the Skagerrak ended at 10.7 kyr. Detailed grain-size analyses of the core were interpreted using a novel 3D-visualization technique. Between 11.3 and 10.3 kyr, clay-rich distal glacial marine sediments were deposited in the northeastern Skagerrak, derived from Baltic melt-water outflow across south-central Sweden through the Otteid-Stenselva strait. As a result of differential isostatic uplift, the route of the major outflow and the associated sediment deposition moved southwards along the Swedish west coast. After 10.3 kyr, sediment deposition in the north-eastern Skagerrak gradually adopted to a fully interglacial normal marine sedimentation dominated by Atlantic inflow and the North Jutland Current.The establishment of the modern circulation system in the eastern North Sea is marked by abrupt coarsening of the sediments in core MD99-2286 at 8.5 kyr. This was a result of increased Atlantic inflow, opening of the English Channel and the Danish straits, and formation of the South Jutland Current. Mineral magnetic properties of the core show a distinct relationship reflecting general sediment source variability. After 8.5 kyr, sediments in the northeastern Skagerrak were derived predominantly from the Atlantic Ocean and the North Sea, with varying contributions from the South Jutland Current, the Baltic Current, and the currents along the coasts of western Sweden and southern Norway. Between 6.3 and 3.8 kyr, the eastern North Sea was further developed towards the modern situation by an increase of the South Jutland Current flow. The Skagerrak bottom currents were probably forced by strong Atlantic water inflow between 0.9 and 0.5 kyr, and after that by increased wind stress. The influence of regional climate on the eastern North Sea circulation has increased since the middle of the Holocene.
32.	Hjorth, Tomas, 1972- (author) Metal speciation and historical trends in lake sediments 2003 Doctoral thesis (other academic/artistic)
33.	Hode, Tomas, 1973- (author) The Search for Life on Mars - Preparation for Sample Return 2005 Doctoral thesis (other academic/artistic)abstract The purpose of the thesis work has been to develop methods and concepts to aid in the search, detection and assessment of ancient microfossils here on Earth as a guide to the search for ancient life on Mars. The intention has been to identify and characterize environments on Earth that may be considered analogous to Martian environments and in which fossil preservation is expected to be good, and to develop and apply methods to characterize the isotopic and chemical composition of possible traces of life in order to assess their biogenicity and biological affinities.An investigation of the Siljan impact structure, Sweden, demonstrated that niches for thermophilic organisms were created in the associated hydrothermal system. The temperature regimes were favorable for thermophilic life in the outer parts of the structure during the early and main stages of the hydrothermal system, but that these niches moved toward the center of the crater during the final cooling stages. It was demonstrated that the hydrothermal system contains traces of a thermophilic microbial community, represented by fossilized extracellular polymeric substances (EPS). Given the presence of water on Mars, similar impact-induced hydrothermal systems were probably generated on Mars as well. These regions, like those at Siljan, may have supported hyperthermophilic microbial communities on the red planet, emphasizing the relevance of searching for impact-induced hydrothermal deposits for evidence of microbial life on Mars.A method for the determination of stable carbon isotopes with high lateral resolution of TEM (transmission electron microscopy) samples has been developed. The method is based on alpha-particle Rutherford backscattering (RBS), it is non-destructive, and therefore suitable for analysis of extraterrestrial and other rare or irreplaceable material. Also, a novel concept to extract fluid inclusions without ablating the sample has been proposed, and a proof-of-concept has been demonstrated. The purpose is to analyze organic biomarkers trapped in fluid inclusions without risking contamination, and also to extract and analyze single fluid inclusions. The minimized contamination risk and the potential to extract single fluid inclusions could make the method a useful tool in the search for organic biomarkers in early-Earth material, and eventually, in samples returned from Mars.
34.	Hode Vuorinen, Jaana, 1974- (author) The Alnö alkaline and carbonatitic complex, east central Sweden - a petrogenetic study 2005 Doctoral thesis (other academic/artistic)abstract The Alnö complex on the central Swedish east coast is composed of a main composite intrusion (the main intrusion) and four smaller satellite intrusions (Söråker, Sälskär, Långharsholmen and Båräng) distributed around the main intrusion on Alnö Island and on the mainland north of the island. The major rock types exposed within the complex are melilitolite, pyroxenite, ijolite series (melteigite-ijolite-urtite), nepheline syenite, carbonatite and alnöite dykes. Melilitolite is only exposed within the Söråker intrusion. The intrusive sequence is melilitolite → pyroxenite → ijolite series → nepheline syenite → carbonatite → alnöite.Mineralogical, whole rock geochemical and radiogenic isotope (Nd-Sr-Pb) studies of exposed rocks from the Alnö alkaline complex, east central Sweden, were performed in order to investigate the genetic relationships between the diverse rock-types, and to evaluate the contributions from mantle and crustal components in the genesis of the complex. Most analysed samples fall within the depleted quadrant in a eNd-eSr diagram, similar to carbonatites and alkaline silicate rocks from other complexes, indicating derivation of parental magma(s) from a source that had experienced time-integrated depletion in LIL elements. Contamination by local crust is indicated by Sr and Pb isotope data, but is geographically restricted to samples collected from the outer parts of the main intrusion and from satellite intrusions. This localized contamination is attributed to selective hydrothermal element leaching of surrounding bedrock during fenitization. Nd- and Sr-isotope data separates the carbonatites into two groups (group I and II), each related to a specific set of silicate rock types. The overlap of group II carbonatites with ijolite and nepheline syenite could indicate a common origin through liquid immiscibility but this hypothesis cannot be confirmed by trace element data because initial concentrations are obscured by fractionation processes. Interestingly, results from AFC-modelling suggest that production of ijolite residual magma requires addition of a small volume (2.4 %) of carbonatite component to the parental magma, whereas formation of nepheline syenite residuals requires removal of an almost equal amount of carbonatite (1.5 %) to yield a statistically significant result. AFC-modelling further suggests that the various silicate rock types exposed within the complex are related to the same parental olivine-melilitite magma through crystal fractionation of olivine, melilite, clinopyroxene, nepheline, Ti-andradite and minor phases. These results agree with compositional trends exhibited by clinopyroxene and Ti-andradite from the silicate rocks of the main intrusion, which suggests co-genesis of pyroxenite, ijolite series rocks and nepheline syenite. Production of ijolite-like residual liquids can be achieved by <40% fractionation whereas production of nepheline syenite residuals requires >80% fractionation.An investigation of the origin of silicate minerals in carbonatites suggest that most silicate minerals observed in the carbonatites on Alnö Island are derived from surrounding wall-rock and/or produced through corrosive interaction between carbonatite liquid and assimilated phases. This leads to ambiguities when addressing the possible genetic link between carbonatites and associated silicate rocks as occurrences of identical “liquidus” phases in inferred immiscible liquids may not actually be such.
35.	Högdahl, Karin, 1962- (author) Late-orogenic, ductile shear zones and protolith ages in the Svecofennian domain, central Sweden 2000 Doctoral thesis (other academic/artistic)abstract The timing of deformation along ductile shear zones in the Svecofennian Domain in central Sweden has generally been constrained by their relationship to magmatic and metamorphic events of known age. A better resolution for the timing of the deformation can be obtained by direct, radiometric dating of minerals which are constituents of the shear fabric.In this study, several, high-T shear zones related to two large-scale, shear zone systems in central Sweden, the Hassela Shear Zone (HSZ) and the Storsjön-Edsbyn Deformation Zone (SEDZ) have been dated using the U-Pb isotopic system in titanite. The microstructures in these zones indicate that the titanite is part of the deformational fabric. The U-Pb titanite results define a narrow time interval between c. 1815 Ma and 1800 Ma as a period of ductile shearing. In combination with previous and new kinematic data - this dominated by dextral horizontal components - indicates that ductile shearing was related to approximately N-S contraction during the late stage of the Svecokarelian orogeny. Temporally and kinematically these results are in accordance with shear zone activity in southeastern Sweden and southern Finland.The character of the shear zones is dependant on the nature of the protolith rocks and the temperature during deformation. In the northwest, where the HSZ and the SEDZ partly join, coarse C/S-mylonites are typical for deformation zones developed in 1.86-1.85 Ga K-feldspar megacryst bearing granites. Deformation zones in older rocks are usually plane-parallel and commonly consist of juxtaposed lithologies. The kinematic characteristics of these, essentially coeval, zones vary. Strain partitioning during transpressive conditions is indicated by the high proportion of orthogonal pure shear recorded in the most prominent zone (the Forsaån zone) and the oblique dextral, and dextral strike-slip kinematics of neighbouring shear zones.Some of the shear zones in this area appear to have been reactivated, or affected by a hydrothermal or magmatic event at c. 1.75 Ga, as indicated by U-Pb titanite and apatite data. One of these zones has further localised warm, saline fluids in Phanerozoic time. These fluids have affected the outer parts of titanite crystals, formed composite zircon grains and almost completely reset the U-Pb system in metamict zircon. These minerals yield a lower intercept age of c. 0.4 Ga in a U-Pb diagram, suggesting that the fluid flow was driven by the Caledonian orogeny at temperatures as low as 150-200oC.The shear zones are mainly separated by generally undeformed K-feldspar megacryst bearing granites. These granites were previously interpreted to be part of the c. 1.80 Ga Revsund suite. However, the unexpectedly high emplacement ages of 1.86-1.85 Ga obtained here for this type of granites requires a reassessment of that assumption. Their, to a large extent, undeformed character may also indicate that the regional tectonometamorphism occurred earlier in this area than further to the south.
36.	Ivarsson, Magnus, 1975- (author) Fossilized microorganisms in volcanic rocks from sub-seafloor environments 2008 Doctoral thesis (other academic/artistic)abstract Fossilized microorganisms are focused in this thesis. Such organisms have been observed in drilled basalt samples from the Emperor Seamounts in the Pacific Ocean collected during ODP (Ocean Drilling Program) Leg 197. The fossilized microorganisms occur in veins where they are attached to the vein walls of altered basalt, volcanic glass or zeolites and entombed in secondary mineral phases like calcite, aragonite and gypsum. The fossilized microorganisms consist of various morphological types: sheaths, segmented filaments, twisted filaments, amorphous filaments and branched filaments. Fossilized cells are also found in association with the filaments as well as microbially produced tunnel structures.The work has mainly been divided in two parts: (1) proving biogenicity of the microfossils and (2) studying the paleoenvironment that prevailed while the microorganisms lived, as well as the interaction between the microorganisms and their environment. The first part has been focused on various instruments and methods with the aim of gathering as much data as possible regarding the biogenicity of the microfossils. The methods that have been used are ESEM/EDS, ToF-SIMS, Raman spectroscopy, laser ablation ICP-MS and staining with the pigment PI (propidium iodide) in combination with fluorescence light. The use of these methods have resulted in various data that, when combined, display a strong case for the biogenicity of the microfossils.The second part has been focused on the minerals in which the microfossils are preserved as well as mineral phases closely associated with the microfossils. Studying fluid inclusions present in the same minerals that the microfossils are found in has made it possible to reconstruct the conditions that prevailed at the moment of preservation regarding fluid composition, fluid temperatures and water depth. With laser ablation ICP-MS it has been possible to study micro-scale variations in iron isotopes within the microfossils and to indicate iron fractionation that has taken place during the involvement in iron oxidation reactions and precipitation of iron oxides. Association with various minerals and alteration products has shown that the microorganisms have been able to inhabit various mineral surfaces and micro-environments as the alteration of the ocean crust has proceeded and the conditions for a biosphere have changed. The work extends the present knowledge about the deep-sub-seafloor biosphere and shows that it probably inhabits much larger volumes of the ocean crusts around the world than was previously known. The work introduces new geological niches and new micro-structures to search for and to study in the ongoing search for traces of life in geological environments. This has implications for the exploration of the ocean crusts and sub-surface environments on Earth as well as future exploration for a fossil record on other planetary bodies like Mars.
37.	Jakobsson, Martin, 1966- (author) Mapping the Arctic Ocean : bathymetry and pleistocene paleoceanography 2000 Doctoral thesis (other academic/artistic)
38.	Jonsson, Erik, 1967- (author) Fissure-hosted mineral formation and metallogenesis in the Långban Fe-Mn-(Ba-As-Pb-Sb...) deposit, Bergslagen, Sweden 2004 Doctoral thesis (other academic/artistic)abstract The Långban deposit in the Bergslagen ore province is one of the most mineral-rich and complex localities on Earth. Yet, despite more than 100 years of research, much about its origin and evolution has remained unknown. In this study, new data from studies of field geology, mineral assemblages, fluid inclusions, and stable as well as radiogenic isotopes enable interpretations of the origins and evolution of this deposit in more detail. The initial stage of mineral formation took place in association with ca. 1.89 Ga (Svecofennian) felsic volcanism. C and O isotope data suggest that the stratabound Fe-Mn oxide ores were formed from volcanic-hydrothermal processes, indicating protore precipitation from a seawater-derived fluid modified through interaction with magmatic rocks. These most likely comprised the then unconsolidated pile of mainly felsic volcanic material. Possibly, the relative abundance of stratabound mineralisations in this area could be an effect of the nearby, ca. 1.89-1.88 Ga Horrsjö subvolcanic complex, which is likely to have created extensive and long-lived hydrothermal activity coeval with the formation of the local volcanic and carbonate rocks. Pb isotope systematics in minerals from different paragenetic stages implicate volcanogenic Bergslagen-type ore Pb as the dominant source of Pb in the deposit, with a minor input of a more radiogenic component that may have been derived from epiclastic sediments. S isotope data exhibit a very large range, which is interpreted as being largely the result of post-Svecofennian remobilisation of magmatic sulphur that had originally been precipitated as syn-volcanic sulphides. This remobilisation was initiated during Svecokarelian regional amphibolite facies metamorphism. Calcites hosted by skarn only exhibit isotope compositions (C, O) indicative of decarbonation and calc-silicate formation during regional metamorphism, and no evidence for overprinting by granite-derived fluids. Thus, C, O, and Pb isotope data refute previous hypotheses about influence from post-Svecokarelian granites during the evolution of the deposit. Typical vein assemblages formed during regional metamorphism and the subsequent retrograde evolution. A suggested small increase in T during the late or post-Svecokarelian stage may have been related to the TIB magmatism. The unique fissure-controlled Ba-As-Mn-Pb…mineralisation formed in a brittle-tectonic setting. O, S and Pb isotope data together with mineralogical and fluid inclusion evidence suggest that these exotic assemblages formed in a shallow crustal setting (P~atmospheric, T~180°C to room-temperature) from surface water (possibly seawater) modified through water-rock interaction. Metals were transported by a moderately saline Ca-Na-Cl-dominated aqueous fluid that had probably leached these metals from the pre-existing mineralisation at some depth. Although Cl was present, e.g. as early Pb oxychlorides, in locally significant amounts prior to fissure mineralisation, it was probably introduced extensively in the active fluid of the fissure stage. The leached components were reprecipitated in the fissure system during repeated fracturing, where sporadic open-system conditions led to fluid boiling and massive precipitation of baryte-bearing assemblages. It is suggested that the large mineralogical diversity within the fissure system mainly reflects variations in fissure substrate, combined with variable lateral position in respect to the boiling zone. The former governed paragenetic variation through reactions between wallrocks and fluid. That a majority of necessary components for the formation of fissure assemblages was sequestered from the local host rocks and pre-existing mineralisation is not least suggested by the complete absence of mineralised fissures outside the mining area. The most reasonable candidates for the tectonothermal regime leading to fissure mineralisation in the Långban deposit are; 1) the post-1.78 Ga evolution of the TIB; 2) late-Proterozoic extension and basic magmatism; 3) the ca. 1.0 Ga Sveconorwegian orogeny. A concluding stage of calcite precipitation from low-temperature meteoric waters enriched in organic carbon probably took place during the Phanerozoic.
39.	Jönsson, Anders, 1969- (author) An evaluation of the distributions of polychlorinated biphenyls and organic matter in coastal sediments 2004 Doctoral thesis (other academic/artistic)abstract The objective of this thesis is to improve the understanding of what processes and mechanism affects the distribution of polychlorinated biphenyls (PCBs) and organic carbon in coastal sediments. Because of the strong association of hydrophobic organic contaminants (HOCs) such as PCBs with organic matter in the aquatic environment, these two entities are naturally linked. The coastal environment is the most complex and dynamic part of the ocean when it comes to both cycling of organic matter and HOCs. This environment is characterised by the largest fluxes and most diverse sources of both entities. A wide array of methods was used to study these processes throughout this thesis. In the field sites in the Stockholm archipelago of the Baltic proper, bottom sediments and settling particulate matter were retrieved using sediment coring devices and sediment traps from morphometrically and seismically well-characterized locations. In the laboratory, the samples have been analysed for PCBs, stable carbon isotope ratios, carbon-nitrogen atom ratios as well as standard sediment properties. From the fieldwork in the Stockholm Archipelago and the following laboratory work it was concluded that the inner Stockholm archipelago has a low (≈ 4%) trapping efficiency for freshwater-derived organic carbon. The corollary is a large potential for long-range waterborne transport of OC and OC-associated nutrients and hydrophobic organic pollutants from urban Stockholm to more pristine offshore Baltic Sea ecosystems.Theoretical work has been carried out using Geographical Information Systems (GIS) and statistical methods on a database of 4214 individual sediment samples, each with reported individual PCB congener concentrations. From this work it was concluded that the continental shelf sediments are key global inventories and ultimate sinks of PCBs. Depending on congener, 10-80% of the cumulative historical emissions to the environment are accounted for in continental shelf sediments. Further it was concluded that the many infamous and highly contaminated surface sediments of urban harbours and estuaries of contaminated rivers cannot be of importance as a secondary source to sustain the concentrations observed in remote sediments. Of the global shelf PCB inventory < 1% are in sediments near population centres while ≥ 90% is in remote areas (> 10 km from any dwellings). The remote sub-basin of the North Atlantic Ocean contains approximately half of the global shelf sediment inventory for most of the PCBs studied.
40.	Kano, Akihiro (author) Deposition, palaeoecology and diagenesis of the Silurian reef-like limestones on Gotland 1990 Doctoral thesis (other academic/artistic)abstract Several Silurian (Wenlockian-Ludlovian) reef-like limestones on Gotland wereselected for studies of depositional, palaeoecological, and diagenetic conditions. Thereef-like limestones were deposited on a warm, shallow and open marine shelf. Theywere often exposed above the sea level in their depositional time as indicated byoccurrences of karstic features and vadose cement. The constituents of the reef-likelimestones were quantitatively analysed. The most important reef-building organismswere stromatoporoids for all the investigated limestones. However, the limestones in theupper part of the Gotland sequence (Sundre and Hemse Beds) show stronger dominationby stromatoporoids and higher stromatoporoid density on the rock surfaces than thelimestones in the lower sequence (Slite and Högklint Beds). The stromatoporoids ofGotland were subdivided into three ecomorphotypes: ambitopic, enveloping, andintermediate species. Ambitopic species were capable of growing extensively on loosebottom, whereas enveloping species preferred to encrust hard substrate. Intermediatespecies developed both ambitopic and enveloping characteristics. The most importantidentifiable sediment producers in the Gotland reef-like limestones were echinoderms,with the exception of one of the Högklint Beds in which calcareous algae were dominant.The investigated reef-like limestones vary as to stages of maturity. Only one of theinvestigated limestones (Holmhällar 1; Sundre Beds) can be strictly regarded as a reeflimestone. The limestone shows obvious zones consisting of boundstones and crinoidaldebris. The boundstones were formed by large laminar stromatoporoids rigidly bound toeach other. The other investigated limestones exhibit no or poorly developedframeworks. Important conditions for the development of the Gotland reefs were theformation of stable bottom associated with karstic processes, low sedimentation stress,and domination by stromatoporoids as a condition for faunal capacity in constructingframeworks. This last condition may have been dependent on the stages of globalevolution of the Palaeozoic reef community.
41.	Machiwa, John (author) Fate of organic carbon in a tropical mangrove ecosystem 1999 Doctoral thesis (other academic/artistic)abstract The aim of this thesis was to study the budget and fluxes of organic carbon in a tropical mangrove forest. Maruhubi forest is located in the Island of Zanzibar, East Africa. Aspects of structure and functions of the ecosystem are investigated. Litterfall, litter standing stock and the effect of macrofauna and the tidal regime on litter turn-over, are key factors in the present study.The inventory of the forest in terms macrofauna and flora was taken. Avicennia marina forms an almost pure stand at the terrestrial edge of the forest, nevertheless, the species is ubiquitous in the area. Sonerratia alba grows exclusively at the marine fringe and the shoreline areas that are frequently inundated. Grapsid crabs, mainly Neosarmatium meinerti occupy the terrestrial edge mangrove area which has a hard mud substrate. Ocypodid crabs, mainly Uca spp occur seaward in the marine fringe and shoreline zones with a sand/muddy bottom. The mollusc Cerithidea decollata is entirely abundant in the terrestrial mangrove fringe sub-area. The marine fringe and shoreline sub-areas are colonised by several species of snails.Lateral fluxes of macrodetritus, suspended particulate matter and dissolved organic carbon showed a significant export of mangrove litter to the adjacent marine area during spring tides. However, in the terrestrial fringe litter was not effectively transported by the tide. Net organic carbon export for the entire forest was 79 x 106 g C y-1, dissolved organic carbon accounted for 78% of the total export.Distribution of sedimentary organic carbon in this mangrove forest which is partly contaminated with raw sewage, shows that a high proportion of carbon in the landward extending zone is organic. Relative content of inorganic carbon increases seaward with carbonate shells of gastropods, oysters and coral sand dominating. Vertical profiles of organic carbon showed a general surface enrichment and subsurface depletion. Interstitial water in the terrestrial mangrove fringe with sewage was acidic (pH 4 - 5) and strongly reducing (Eh approx. -300 mV). pH in the terrestrial fringe sub-area without sewage was close to neutral values (pH > 6). There was no significant difference between the rates of organic matter mineralization in the forest zones. Relative values, however, indicate mineralization was slowest in sewage contaminated areas followed by areas with high litter loading on the sediment floor. The rate was high in the frequently inundated mangrove areas.An empirical model of the fate of organic carbon in Maruhubi forest was constructed. Results from the model supports the field observation that outwelling of dissolved organic carbon was the dominant component of the mangrove forest which influences litter dynamics. Grapsid crabs are important for litter turn-over in the intermittently flooded zones of the forest. Further, stable isotope data confirmed that crabs in the terrestrial fringe zone fed almost exclusively on mangrove litter (d13C = 27.97±0.25). In addition to that, the sedimentary organic matter (d13C = 22.50±3.54) was also to a large extent, of mangrove origin.
42.	Mansfeld, Joakim, 1963- (author) Crustal evolution in the southeastern part of the Fennoscandian Shield 1995 Doctoral thesis (other academic/artistic)
43.	Mattsson, Hannes B., 1975- (author) Volcanism at the tip of a propagating rift : the Heimaey volcanic centre, south Iceland 2004 Doctoral thesis (other academic/artistic)abstract Primary magmas are generated by 4-6% partial melting near the garnet-spinel stability fields beneath Heimaey (i.e. 80-65 km depth). The magmas fractionate 31% olivine and clinopyroxene en-route to ponding at the base of the crust (and forming a parental Vestmannaeyjar magma). Abundant normally zoned phenocrysts of olivine and plagioclase, in combination with curvilinear trends in major element variation diagrams and heterogeneous isotope ratios (similar to MORB) suggests that the rock suite evolved by fractional crystallization and that crustal contamination and/or magma-mixing was insignificant. Although Heimaey rocks are devoid of clinopyroxene as a phenocryst phase, decreasing ratios of CaO/Al2O3 and Sc/Y with increasing degree of fractionation suggest that clinopyroxene was present as a fractionating phase. The most evolved lava on Heimaey (Eldfell) can be successfully related to the most primitive (Stórhöfði) through 73% fractional crystallization of an olivine + clinopyroxene + plagioclase + titanomagnetite assemblage. Individual magma batches were emplaced into different levels of the crust where they evolved separately from each other prior to eruption. The lack of equilibrium phenocryst assemblages in the Heimaey rocks suggests that the residence times in crustal magma chambers were short. Upon eruption, the pathways used by the rising magma are probably zones of weaknesses associated with extensional stress exerted by the propagating Eastern Volcanic Zone (as indicated by the preferentially aligned eruptive fissures). When magmas erupt in a shallow marine environment, tuff-cones are formed as a result of explosive interactions between magma and water/sediment mixtures. Tuffs comprise about 65% of total erupted volume on Heimaey. The tuff cones deposits consists of normally graded planar air-fall deposits and undulating cross-bedded base-surge deposits, with an increase in frequency of base-surge deposits closer to the vent regions. The distribution of crustal xenoliths in the Sæfell tuff-cone suggests that there is a downward migration of explosion foci in tuff cone forming eruptions, and that a diatreme (at least 820 meters deep) formed during the eruption. This is also supported by the steep dip (35-45°) measured for ring-fractures at the crater-rim of the tuff cone, which creates sharp unconformities between early and late stage tuff-deposits. A zone of graded tuff-breccias (5-20 m thick) marks the transition from phreatomagmatic to subaerial activity. The subaerial stage is characterized by effusive lava emplacement and the formation of scoria cones and lava ponds inside the tuff-cones. The most common type of lava flows found on Heimaey are inflated pahoehoe (e.g. the Helgafell lava field). Based on measurements of lava inflation features (i.e. the thickness of the upper-vesicular crust of flow-lobes) in the Helgafell lava field an eruption duration was estimated for that eruption (11-12 months). This estimate seems reasonable as it yields an averaged volumetric effusion rate of 0.05-0.06 km3/month, which is similar to the 1963-1967 Surtsey eruption (0.02 km3/month) and the 1973 Eldfell eruption (0.04 km3/month) considering that the estimate does not account for early spatter-fed flows. The oldest units on Heimaey (i.e. the six units comprising the Norðurklettar formation) formed over a short time span following the deglaciation of southern Iceland 10-9.3 ka ago. The Stórhöfði eruption occurred sometime between 9-6 ka, Sæfell and Helgafell to approximately 6 ka, and finally the Eldfell eruption, which occurred in 1973. Heimaey is believed to represent the early stage of forming a central volcano in the Vestmannaeyjar system, mainly because (1) the average erupted volumes for a single eruption are twice (0.33 km3 DRE) that previously reported as an average for Vestmannaeyjar, (2) there have been close to 1 eruption/km2 on Heimaey, compared to 0.1 eruption/km2 as average for the Vestmannaeyjar system, and (3) the occurrence of more evolved lavas, such as the hawaiites of Dalfjallshryggur and Eldfell, suggesting that a crustal magma chamber is developing under the island.
44.	Mörth, Carl-Magnus, 1959- (author) Sulfur isotopes used as a tracer of acidification reversal, dispersion of acid mine drainage and sulfur dynamics in small and large catchments 1995 Doctoral thesis (other academic/artistic)
45.	Noormets, Riko, 1967- (author) Glacial deposits, sedimentary environments and ice sheet dynamics in the northern Baltic Sea and Lake Peipsi during the Late Weichselian 2001 Doctoral thesis (other academic/artistic)
46.	Ormö, Jens, 1968- (author) Impact cratering at sea 1998 Doctoral thesis (other academic/artistic)
47.	Paracha, Wasim, 1959- (author) Seismic stratigraphy and tectonics offshore Scania, south-western Baltic Sea 1998 Doctoral thesis (other academic/artistic)abstract Geophysical data and descriptions of deep wells, produced during hydrocarbon explorations in the south-western part of the Baltic Sea offshore Scania, have revealed new information on the geological development of the area. This investigation is concentrated to the offshore triangular segment between the northwest-southeast Permian Sorgenfrei-Tornquist Zone through Scania and the east-west Caledonian Front north of Rügen.The investigated area is traversed by complex tectonic structures of different genesis. In the southern part of the Swedish offshore area, the westnorthwest-eastsoutheast directed low angle thrust fault of the Caledonian Deformation Front, is expressed along the Rømø-Møn Fault Zone. Listric and wrench faults are present in the Swedish and Danish areas, which are caused by alternating extensional and compressional tectonic regimes during different periods.The Caledonian, Variscan and Kimmerian events are presented in three-dimensional maps, based on stratigraphically determined seismic marker layers. A total of 9 marker layers in the sedimentary bedrock are interpreted from multichannel seismic data. They are as far as possible in this structurally complex area, assigned to their chronostratigraphical levels on the basis of well logs. The basal Unit-1 on top of the Precambrian crystalline basement, includes a thin but rather complete Lower and Middle Cambrian series, starting with the Hardeberga quartzitic sandstone. Unit-2 includes the Upper Cambrian with its black Alum shale. Unit-3 is a thin pyritic Lower Ordovician unit with a seismically undifferentiated lithology. Unit-4 consists of Lower Silurian dark shales. The upper parts of the Silurian and the entire Devonian are eroded throughout the investigated area, as verified in the deep wells. Unit-5 consists of Lower Carboniferous which increases in thickness towards the eastern part of the investigated area. It is present north-west of the Fakse Bay - Møn Swell but is not found in the Falsterborev-1 well offshore Scania. Unit-6, the Permian, is found only within the Danish area with a reduced thickness northwards from the Fakse Bay-Møn-Swell. A thin, but presumably rather complete, Triassic series is present in both the Swedish and Danish areas, but only Keuper which forms Unit-7 could be fully evaluated from the present seismic profiles. This unit is followed by uniform almost horizontal Jurassic deposits which form Unit-8. The uppermost Unit-9 consists of a thin sandstone deposit from the Cenomanian of the Upper Cretaceous. Although it forms an excellent reservoir rock, a suitable cap-rock is not present.A deep seismic profile in the Danish offshore area demonstrates the Caledonian Deformation Front as a low angle Ordovician-Silurian transpressional thrust fault, causing different depositional events between the southern part of the Fennoscandian Border Zone and the northern part of the North German-Danish zone. The Lower Palaeozoic reveals the steep south to south-west dipping top of the Precambrian crystalline basement along the northeast-southwest directed Agricola-Svedala fault. The changing tectonic styles of the investigated area, its shear zones, compressional and tensional regimes, and fault movements have been observed in the Mesozoic as well as in the Palaeozoic sequences.The northwest-southeast trend of the Carlsberg fault has been confirmed in the offshore area. Seismic interpretation in the Danish area shows the southward dipping pre-Permian Ringkøbing-Fyn High, which in the Møn area is covered on Lower Carboniferous deposits. Syn-rifting during the Early Carboniferous Visean age created an unconformity in the Swedish area forming two large scale grabens, whereas depression in the Danish area led to the deposition of Mesozoic deposits starting with a thin Triassic Keuper formation in a number of grabens.
48.	Sellén, Emma, 1980- (author) Quaternary paleoceanography of the Arctic Ocean : A study of sediment stratigraphy and physical properties 2009 Doctoral thesis (other academic/artistic)abstract A Quaternary perspective on the paleoceanographic evolution of the central Arctic Ocean has been obtained in this PhD thesis by studying sediment cores from all of the Arctic’s major submarine ridges and plateaus. The included cores were mainly recovered during the Healy-Oden Trans-Arctic expedition in 2005 and the Lomonosov Ridge off Greenland expedition in 2007. One of the main thesis objectives is to establish whether different sediment depositional regimes prevailed in different parts of the central Arctic Ocean during the Quaternary and, if so, establish general sedimentation rates for these regimes. This was approached by dating key cores using the decay of the cosmogenic isotopes 10Be and 14C, and through stratigraphic core-to-core correlation using sediment physical properties. However, the Arctic Ocean sea ice complicated the use of 10Be for dating because a solid sea ice cover prevents the 10Be isotopes from reaching the seafloor, resulting in too old ages. Dating using 14C is also complicated due to uncertain marine reservoir age corrections in the central Arctic Ocean. The core-to-core correlations show five areas with different depositional regimes; the northern Mendeleev Ridge and Alpha Ridge, southern Mendeleev Ridge, Morris Jesup Rise, Lomonosov Ridge and Yermak Plateau, listed in the order of increasing sedimentation rates from ~0.5cm/ka to ~4.8 cm/ka. A detailed study of the relationship between sediment bulk density and grain sizes suggests a strong link between variations in clay abundance and bulk density. Grain size analysis of a Lomonosov Ridge core show that fine silt and clay dominates the interglacials, possibly due to increased suspension freezing of these size fractions into sea ice and/or nepheloid transport. Sediments younger than the marine isotope stage (MIS) 7 generally contain more coarse silt, attributed to a regime shift during the Quaternary with increased iceberg transport into the central Arctic Ocean from MIS 6 and onwards.
49.	Shaghude, Yohanna W (author) Shallow water carbonate basin of the Zanzibar channel, Tanzania 2001 Doctoral thesis (other academic/artistic)abstract The shallow water carbonate basin of the Zanzibar channel, Tanzania, has been investigated. This study discusses and describes the sea bottom topographic features, sediment composition, major characteristics of sediment distribution, provenance of sediments, and the depositional settings of the sediments . Zanzibar Channel consists of a Acentral deep@, a feature which is about 30-40 m in depth and approximately in the middle of the channel. The central deep is flanked to the east by an irregular topography, and to the west by a smooth topography. The morphological differences between the two sides of the channel are interpreted as partly caused by the differences in the tectonic development and partly due to differences in the deposition of land derived sediments on either side of the channel. The observed physiographic and tectonic difference between the western and eastern side of the channel have to a large extent controlled the major trends found in the sediment composition and distributions. The surface sediment composition is dominantly of biogenic origin except adjacent to the mainland coastline where the flux of siliciclastic (terrigenous) material from Rivers Ruvu and Wami occur along an approximately 5 km coastal band, and a thin lobe which projects from River Ruvu to the middle of the channel. The minor contribution of siliciclastic sediments originating from Zanzibar Island are generally limited to the intertidal areas west of the island. The lack of significant siliciclastic flux from Zanzibar Island and the shallow nature of the basin are considered to be the leading factors which have contributed to the development of the carbonate basin. The biogenic composition of the sediments in the channel is dominated by benthic foraminifera, followed by molluscs (pelecypods and gastropods) and corals.The mineralogy of the siliciclastic sediment is dominated by quartz, feldspar and hornblende. A possible source for the terrigenous sediments in the western part of the channel is the metamorphic rocks of the Mozambique belt. The siliciclastic sediments on the eastern side of the channel are most probably reworked materials from the Masingini ridge sandstones north of Zanzibar Town and former beach ridges, but the possible origin from the western side of the channel cannot totally be ruled out. Three bio-physiographic zones of the sediments in the basin have been discriminated: 1- the coastal zone, 2- the reef platforms/patch reefs zone and 3- the central channel zone. The Tidal Dominated Reef Platform Environment (TDPRE) east of the Zanzibar channel is further subdivided into two subdivisions; northern and southern. The current pattern in the TDPRE sediments is influenced by the ebb-flood tidal phases and the local variability of the topography in the area. Satellite remote sensing data has been used to investigate the nearshore bathymetry in some parts of the TDPRE sediments and the preliminary results of the study demonstrated that remote sensing approach may potentially be used for the nearshore bathymetric mapping of the Tanzanian coast, but the approach used by the present study needs to be further tested using other vegetation types. Remote sensing has also been used to investigate the coastal sediment dynamics in an accreting coast proximal to the river. The current growth rate of the Ruvu delta is potentially threatening the future existence of the Zanzibar channel carbonate basin, with its associated ecosystem. Future studies are therefore focusing on further investigation on the most important significant factors which have influenced the recent growth of the delta. The satellite remote sensing approach is being proposed for the future studies in other coastal sedimentary environments of Tanzania, as it might be the best and most cost effective option for obtaining the lacking geological data in the Tanzania integrated coastal zone management studies. The present study also recommends for further grab sampling in the central and western parts of the channel, as well as further analysis of the carbonate sediments. The suggested studies would shed further light on the hydraulic regime of the carbonate sediments and its bio-physiographic setting.
50.	Strandh, Heléne, 1968- (author) Mineral dissolution from molecular to field scale 1999 Doctoral thesis (other academic/artistic)abstract Mineral reactivity contributes to the global biogeochemical cycling of elements. CO2is consumed during the chemical weathering of many silicates and during formation of carbonates in the oceans. The balance of nutrients in soils and waters is coupled to the release of elements during weathering and the retention of elements during mineral precipitation. Dissolution of many minerals involves acid neutralization and the rate of most mineral reactions is dependent on the pH of the solution. The acid input to the atmosphere has increased drastically during the last century affecting our environment severely, with problems such as deterioration of the bronze-age rock carvings in the world heritage area Tanum, SW Sweden.This thesis compiles studies of quantum chemical calculations of the siloxane bond strength, laboratory dissolution experiments of quartz and brucite as well as field studies of the water chemistry of a rock surface in Tanum, SW Sweden.Quartz consists of only SiO2and provides the possibility to investigate specifically the siloxane bond, which is present in most silicates. Quartz dissolution is performed using plug-flow reactors during long-term experiments. This produced among the slowest rates reported in the literature, which suggests that long runtime is needed to approach natural dissolution rates. A rate minimum was obtained at pH 3-4, which was observed also after a short reaction time. Alkali metal cations increased the rate at pH>3, and KCl decreased the rate at pH<3, similar to results obtained for feldspar dissolution. The alkali metal effects and the pH dependence of the quartz dissolution emphasize the importance of surface species for the dissolution kinetics of silicate minerals, which may indicate the rate determining mechanisms in natural weathering environments.Quantum chemical methods are used to investigate the effects of different surface species on the siloxane bond strength. Direct adsorption of alkali metal cations reduces the bond strength for alkaline surface models and increases the bond strength for acid surface models, indicating that the surface species contribute to the rate of the quartz dissolution. Interaction with water molecules proved to be very important for the ion specific effects. For effects from protonation and deprotonation of the quartz surface, the hydration was essential. Further quantum chemical calculations showed that the pH dependence of the dissolution rate at high surface charge coverage could be due to acid-base repulsion within the surface layer.Brucite is a fast dissolving mineral that gives the possibility to investigate the rate dependence on the transport of ions. Rotating disc experiments are used to separate between surface reaction controls and molecular diffusion controls. Numerical modeling of the fluid equations is used to model a reaction zone near the brucite surface. The experiments and the model revealed that the solution pH determines the reaction mechanism in terms of surface reaction or diffusion reaction control. This is important information for the conclusion of the rate controlling mechanism of fast dissolving minerals on a rock surface.The water chemistry on the rock surface in Tanum gives information of rate controlling factors that can be used to reduce the chemical weathering rate. Extensive sampling of deposition, influenced by sea salt and acid rain, and runoff is performed on a rock surface in Tanum, SW Sweden. Two rock surfaces are investigated and compared; a roof protected, washed surface and a reference surface. The chemical weathering rate calculated as anorthite dissolution was 10 times slower than in literature data, due to a difference between the specific surface area and the reactive surface area in field. The chemical weathering rate of both surfaces was correlated with temperature and large differences in dissolution rate between the two ponds are due to differences in temperature and pH. Control of these parameters should give a surface that is preserved longer than an unprotected rock surface.

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