Browsing by Subject "Geology"

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  • Jousi, Netta (Helsingfors universitet, 2017)
    137Cs is an artificial isotope generated by fission reactions, whose deposition times are well known both globally and locally. The 137Cs dating method measures the 137Cs activity in sediment layers from different depths, and by utilizing knowledge of the deposition moment dating accuracy can be up to one year. The prerequisites of the dating method are not only the knowledge of precise moments of deposition, but also calm sedimentation and understanding of the sediment disturbances. The best destinations for using the 137Cs dating method are deep basin sediments, where bioturbation is very low and sedimentation is calm. This study looked at the accuracy and reliability of the 137Cs dating of the bottom sediment from five different lakes. There were clear annual varves in four out of five lakes, so the sediment was not mixed and mechanical movements of 137Cs had not occurred. The most significant fall-off affecting Finland in 1986 was the Chernobyl nuclear accident and when analyzing sediment samples in 1986, it could even be traced back to a single varve. Another significant 137Cs fall-off has been the nuclear tests of the 1950s to 1960s. The 137Cs peak of these events was almost invisible compared to the 137Cs activity of 1986. Regardless of the limnological features of the lake, 1986 had also migrated downward in the analysis results. The more porous sediment was, the stronger the spread had occurred. According to the results of this study the 137Cs dating method is still usable, especially in Finland at the time of the Chernobyl nuclear accident of 1986. From 1950 to 1960, the time of nuclear testing, this method is far more uncertain in Finland, although the marker horizon is more globally distinguishable. However, downward migration of 137Cs was clearly evident even in a calm sedimentation environment, which is a major hindrance to the method. Chemical follow-up studies would be useful to clarify the causes of migration.
  • Lindqvist, Teemu (Helsingfors universitet, 2014)
    This work aims at delineating the geometry and geotechnical properties of major fracture zones within the Kevitsa open pit excavation in northern Finland. The results are intended to be used as input parameters for a comprehensive slope stability study scheduled for 2014 by Engineering Consulting Group WSP Finland Ltd. The present work has both a regional and local-scale focus. The regional study focuses on identifying major linear trends from topographic and aeromagnetic maps, whereas the local scale study focuses on building 3D fracture zone models by merging lineaments interpreted from detailed digital elevation model and fracture data mapped from open pit mapping, 3D photogrammetry models and borehole videos. The orientation constraints derived from the fracture data are merged with RQD- and RG-logs to build the 3D fracture zone models. The regional topographic lineaments (RTL) comprise two main orientations with NNW-SSE and SSW-NNE trends. The regional aeromagnetic lineaments (RAL) indicate NW-SE and SW-NE orientations. The local topographic lineaments (LTL) indicate NNW-SSE, SSW-NNE, WSW-ENE and NW-SE orientations. Ground surface fracture data mapped from 3D photogrammetry models comprise steeply ENE- and steeply SE-dipping fracture sets. Fracture data derived from borehole videos show steeply ENE-, steeply SE-, sub-horizontally SW- and gently NNE-dipping fracture sets. Furthermore, the open pit mapping observations reveal the presence of gently WNW- and steeply ENE-dipping brittle zones of rock. The main 3D photogrammetry and borehole video fracture sets define wedge shaped blocks of rock at the slopes of the Kevitsa open pit excavation. The studied brittle fractures and fracture zones most probably originate from the general NW-SE oriented compressive stress field in the Finnish bedrock. However, most of the observed fracture sets are not oriented parallel to the compression. Instead, the fracture sets form conjugate shear fracture pairs that are attributed to a transpressive stress field comprising the NW-SE oriented normal stress combined with a smaller NE-SW oriented shear component. 3D fracture zone models arising from this work include a 50 m fracture zone model (50M), a statistical population model (SPM) and a merged fracture zone model (MFM). The 50M model illustrates the geometry of the fracture zones within the uppermost 50 meters of the Kevitsa open pit area. The SPM model extracts the dominant orientations from the fracture observations mapped from borehole videos by generalizing the observations and forming statistical clusters that represent these dominant orientations. The clusters are visualized with 3D surfaces that indicate the orientation of the cluster. The MFM model combines geometries derived from the SPM model with the RQD and RG-diamond drillcore logs to build the final 3D fracture zone models. The 3D models are delivered with the M.Sc. thesis as digital end-products.
  • Koivulehto, Liisa (Helsingfors universitet, 2016)
    Äänekosken Energia Oy is planning an artificial groundwater recharge plant in Äänekoski Central Finland. Consulting company Ramboll is in charge of the water intake project that is situated at an important groundwater recharge area, Kulopalokangas. The aim of this study is to collect data from previous studies in the area, create a three-dimensional geological model of the study area's bedrock surface and sediments as well as discuss their effect on groundwater flow. Further objective is to test modelling software Leapfrog Geo and its suitability in this type of study. The study area is characterized by an esker formation that was deposited during the deglaciation of the Weichselian glaciation. This esker originates from a end moraine formation in Central Finland that formed at the rim of the continental ice sheet about 11 000 years ago. The bedrock is relatively homogenous and there are no faults. The bedrock is considerably exposed in the area and the sediment package consists of coarse sand and gravel units in the central part of the study area, whereas finer material is located at the rims and on the outside of the esker. Geological and geophysical investigations have been conducted previously within the water intake project. The data used in this study was gathered from seismic refraction surveys, drilling data and groundwater table measurements. The input data was in point data and drill hole format, and the surfaces and volumes of soil units were created subsequently. Cross sections were created to illustrate inner structures of the sediments throughout the area. The results are presented as a digital elevation map of bedrock, a groundwater map, images and cross sections of the model. They show the distribution of soil units. In addition, they provide information of the areas for artificial recharge as well as factors effecting the groundwater flow. The bedrock surface forms a NW-SE oriented depression valley that is filled with soil units. A two-meter thick unit of till is located above the bedrock and the innermost coarse gravel unit of the esker shows an elongated dome-like structure. The topmost unit is fine sand or silt at the western side of the esker, whereas the eastern side top unit is mostly composed of sand and coarse sand. Results of this study correspond with the previous studies. The three-dimensional soil model is used as a basis for a numerical groundwater flow model in the next stage of the project. The model is a simplified representation of the area and the results are absolute only at the vicinity of the observation points. The three-dimensional geological model offers more accuracy and information about subsurface geological conditions and furthermore helps to communicate between different stakeholders.
  • Kähkönen, Mervi (Helsingin yliopisto, 2017)
    Fracturing of the ore and wall rock in Pyhäsalmi mine was analysed from 3D-photographs, using Structural Suite –add-on to Surpac. Observations of geological structures were also made. The suitability of 3D-photographing method to observe rock mass movement was also tested. 33 fracture zones, which differ from the main joint direction, were observed from the pictures. In particularly, fracture zones that trend from southwest to northeast and pierce the ore body from the middle, were prominent. There was also a zone of rock inclusions, almost at the same direction and same location, as the southwest to northeast trending fracture zones are. Presumably, from southwest to northeast trending fracture zones have been noticed earlier on the basis of the seismic events. Gently dipping fracture zones were also noted, in which dip direction was mostly towards north or south. In wall rock, there were pegmatite veins, singular joints and possibly small-scale faults, which were gently dipping toward north or south. Apparently clearly visible rock mass movement did likely not occur during the monitoring period. It is not possible to observe small-scale movement with 3D-photographs, but large scale movement can possibly be observed from the pictures. Avainsanat – Nyckelord – Keywords Pyhäsalmi, mine, 3D-photogrammetry, 3D-photograph, 3D, fracture, fracturing, rock, rock mechanic, rock mass movement Säilytyspaikka – Förvaringställe – Where deposited Muita tietoja
  • Savolainen, Talvikki (Helsingfors universitet, 2013)
    A mining facility is planned to Hannukainen, Kolari, where iron, copper and gold will be enriched. The brown-field of Rautuvaara in the Niesajoki valley is one of the options for the tailings disposal area in the environmental assessment plan. It has been used by the Rautuvaara and Saattopora mines to dispose tailings from 1962 to 1995. The target of the study was to define groundwater table and directions, hydrostratigraphical features and water qualities as well as research groundwater – surface water interactions in order to evaluate the present state and possibility for future use as a tailings disposal area. The hydraulic gradient was delineated with ArcGIS to be towards the center part of the valley and a watershed was identified in the middle part of the northern settling pond. The hydraulic pattern was simple. Mostly, the valley is covered by till, with some alternating sand, gravel and silt units. No good aquitards were identified with permeabilities calculated from grain-size analysis and slug tests. However, the hydraulic conductivity was determined to be poor or moderate (from 10^-2 to 10^-7 m s^-1) in the till units, they dominated in the area. The surrounding surface and groundwaters followed the baseline in the area for the most and were determined to be natural waters (calciumhydrogencarbonate) with Aquachem software. Contaminated (acid mine drainage) surface and groundwaters (sulphate-magnesium) were quite restricted in area, they were identified in surface waters and groundwater observation wells close by the abandoned tailings area. Some of these groundwater observation wells were evaluated to contain surface water by their oxygen and hydrogen ionic compositions, where others of the evaporated observations wells situated near a bog area. Groundwater seepage from the west coast was also concluded, which could have had a part in the AMD generation process. On the other hand, some of the wells contained enriched waters, in form of elevated trace element concentrations, however they were still Ca-HCO3 waters. This was the case for two artesian monitoring wells on the tailings area. It was concluded that the existing peat layer underneath the tailings is impermeable and leads to the assumption that mostly the contamination is restricted in area because of a separate tailings water body. The tailings waters had only very limited connection to the confined aquifer underneath. The thickness of the peat layer should be examined as well as the hydrostratigraphy of the aquifer, to prevent any future leaking risks to the groundwaters.
  • Rytkönen, Jussi (Helsingin yliopisto, 2018)
    Critical metals are defined as rare specialty metals (e.g. Be, Sc, Co, Ga, Ge, Nb, REEs, In, Ta) that are critical for the facilitation of the Strategic Energy Technology Plan set by the European Union. These rare metals are typically associated with highly evolved granitic ores. Trioctahedral micas are often one of the main, if not sole, hydrous ferromagnesian phases in these granite-related rare metal deposits. Since many critical metals are readily incorporated in the mica crystal structure, micas are often used as petrogenetic indicators in assessing granite melt evolution. This study is a preliminary investigation in the critical metal distribution of trioctahedral micas in Fennoscandian S-I-A type granites. Ten granite samples (6 A-type, 2 S-type, and 2 I-type samples) were selected for examination that represent three distinct areas within the Fennoscandian shield: the Paleoproterozoic Wiborg rapakivi batholith (A-type) in southeastern Finland, the Paleoproterozoic Västervik metasedimentary formation (S-type) in southeastern Sweden, and the Neoarchean Hattu schist belt (S- and I-type) in eastern Finland. Whole-rock major and trace element chemistry was determined via WD-XRF, mineral major element chemistry via WDS-EPMA, and mineral trace element chemistry via LA-ICP-MS. The A-type granites are predominantly ferroan, alkali-calcic, and metaluminous, whereas the S- and I-type granites are predominantly magnesian, calc-alkalic, and peraluminous. Trioctahedral micas in the A-type granites are characteristically annitic, whereas S- and I-type granites trend progressively towards more phlogopitic compositions. Trace element data indicates that most critical and rare metal abundances (Li, Be, B, Sc, Ga, Ge, Zr, Nb, In, Sn, Ta) tend to increase with progressing fractionation, but largely independent from granite type. Moreover, the absolute differences in abundances are often small, but distinct. However, owing to their more primitive character, I-type granites are typically less fractionated than A- and S-type granites, and thus contain lower amounts of critical and rare metals. Furthermore, it is indicated that the fractionation of the following elements may be correlated: Be & Al, Be & Sc, and In & Sc. Moreover, it is indicated that amphibole and muscovite minerals may incorporate Be, Sc, Zr, and In more readily than trioctahedral micas.
  • Martikainen, Kaisa (Helsingfors universitet, 2016)
    Tutkimuskohteena on Salon kaupungissa sijaitseva Aijalan vanha kaivos, joka on ollut tunnettu sulfidimalmeistaan jo 1600-luvulta lähtien. Kaivos oli toiminnassa vuosina 1949-1958. Kaivoksella on käsitelty myös läheisen Metsämontun Zn-Pb-malmeja (v.1951-1958, v.1964-1974) sekä Telkkälän Ni-Cumalmeja (v.1969-1970), joiden jätteet sijoitettiin samalle rikastushiekka-alueelle Aijalan jätteiden kanssa. Aijalan kaivoksen rikastushiekka-alue kuormittaa tällä hetkellä ympäristöä hallitsemattomasti hyvin voimakkaasti metallipitoisilla vesillä (mm. Fe, Zn, Cu, Pb) Aikolanlahteen sekä Kiskonjokeen, joka luokitellaan Natura-alueeksi. Rikastushiekka-aluetta ei ole jälkihoidettu kunnolla, minkä johdosta alueella muodostuvat sekä alueen läpi virtaavat pinta- ja pohjavedet happamoituvat voimakkaasti. Kuormittumista on tutkittu useaan otteeseen, mutta kunnostustoimiin alueella ei ole ryhdytty. Tarkoituksena oli saada tietoa rikastushiekka-alueelta tulevasta metallikuormituksesta alueen vesiin, ja mikä kuormitus tulee mahdollisesti olemaan tulevaisuudessa. Aiempien tutkimusten perusteella alueelle suunniteltiin vesinäytteenotto. Aijalan alueelle luotiin myös ArcGis-ohjelmalla pintavesien virtausmalli, jonka pohjalta tulkittiin alueen osavaluma-alueet. Merkittävin havainto oli, että Koskossuolta tulee suuri pintavalunta rikastushiekka-alueelle. Kiskonjokeen rikastushiekka-alueelta laskevan puron ja sen sivuhaarojen kautta tulee valuntaa noin 790 000 m3 vuodessa ja Aikolanlahteen noin 170 000 m3 vuodessa. Kiskonjokea kuormittavista metalleista lyijy ja kupari muodostavat suurimman riskin. Kuparikuormitus Kiskonjokeen on noin 35 kg vuodessa ja lyijykuormitus noin 1 kg vuodessa. Kuormittavien metallien pitoisuudet Kiskonjokeen laskevassa purossa ovat laskeneet viimeisen 30 vuoden aikana, mikä todennäköisesti johtuu valuntamäärien lisääntymisestä alueella. Aikolanlahteen ei kohdistu merkittävää metallikuormitusta. Tärkein havainto oli, että länsimalmin kaivoskuilusta todennäköisesti pääsee purkautumaan hyvin metallipitoista pohjavettä maanpinnalle. Metallikuormitus alueella tulee jatkumaan alueella satoja vuosia. Vaikka kuormitus ei ole merkittävän suuri, tulisi alueelle laatia päivitetty kunnostussuunnitelma. Rikastushiekka-alue tulisi peittää ja suolta tulevan luontaisen valunnan pääsy rikastushiekka-alueelle tulisi estää. Myös länsimalmin kaivoskuiluista tapahtuvaa pohjaveden purkautumista tulisi tutkia enemmän.
  • Järvinen, Ville (Helsingfors universitet, 2015)
    Five granulite xenoliths entrained in the ~600 Ma Lahtojoki kimberlite pipe in eastern Finland represent the lower crust below the suture zone between the Archaean Karelian craton and the Paleoproterozoic Svecofennian terranes. They provide direct information on the petrology of the lower cratonic crust, and the processes that controlled its evolution. Studied xenoliths comprise a dry intermediate garnet granulite, three mafic garnet granulites with amphibole contents ranging from 3–50 vol–%, and a peraluminous micaceous garnet gneiss. Granulites have granoblastic fabrics with mineral assemblage Grt – Cpx – Plg ± Amb ± Qtz ± Ilm ± Rt ± Bt, with pink garnet and green clinopyroxene. Gneiss is coarse grained with a heavily deformed and strained fabric with mineral assemblage Qzt – Bt – Grt – Sil. Mineral chemistry based TWEEQU–thermobarometry indicates equilibration of mafic granulites at ca. 800 °C and 9.5–10.5 kbar and intermediate granulite at ca 800 °C and 17.5 kbar. The pressure estimates correspond to crustal depths of 38–55 km. Equilibration temperature for garnet gneiss is ca. 700 °C – TWEEQU based pressure estimate was not possible, but based on Grt–Sil stability equilibration pressure can be constrained to ca. 4–8.5 kbar. Mineral zonation indicates slight post peak cooling and decompression of some samples. Whole-rock geochemical composition (major and trace elements) implies derivation of dry (<10 vol–% Amb) mafic granulite from a Ni-Cr fractionated basaltic melt. Enrichment in LREE and other trace elements suggests a low to moderate degree of melting of a primitive mantle source. The sample could represent a mafic underplate crystallized in situ. Amphibole and enrichment in K and Rb could indicate a later metasomatic enrichment event. The intermediate granulite is anomalous in composition compared to other Kaavi-Kuopio lower crustal xenoliths. REE composition, depletion in K, Rb, Zr, Hf, Nb, Ta, and strong enrichment in Sr and a prominent positive Eu anomaly imply that the sample represents a restitic residue after partial melting, possibly of a plagioclase cumulate protolith. The results add on to earlier xenolith studies performed in eastern Finland. Restite formation indicates that partial melting of lower crust occurred under Kaavi-Kuopio. LILE enrichment and abundant hydrous phases in many samples suggests metasomatic events, possibly coincident with the partial melting events.
  • Söderström, Sara (Helsingfors universitet, 2015)
    Itämeren Ancylusjärveen kerrostuneissa sedimenteissä esiintyy rautamonosulfidiraitoja. Raitojen alkuperä on ollut tutkimuksen kohteena jo pitkään, sillä muodostuakseen rautamonosulfidi tarvitsee sulfaattia, jota on makeassa vedessä yleisesti hyvin vähän. Tällä hetkellä onkin kiistanalaista, missä vaiheessa nämä raidat ovat syntyneet. Syntytavasta on esitetty kaksi eri teoriaa, joista ensimmäisen mukaan raidat olisivat syntyneet vasta murtovesivaiheessa, jolloin sulfaattirikki olisi bakteerien toiminnan seurauksena muuttunut rikkivedyksi ja diffundoitunut alla olevaan rautapitoiseen järvisedimenttiin. Tämä olisi johtanut rautamonosulfidin muodostumiseen suunnilleen samalle syvyydelle järvisedimentissä laajalla alueella. Toisen teorian mukaan jokin, esimerkiksi suolapulssi, olisi käynnistänyt rikkiä metabolisoivien mikrobimattojen voimakkaan kasvun jo Itämeren järvivaiheen aikana. Orgaaninen aines olisi ylläpitänyt mikrobitoimintaa hautautuneissa matoissa, johtaen lopulta niiden korvautumiseen rautamonosulfidilla. Tämä syntytapa olisi johtanut Fe-monosulfidin laikuittaiseen esiintymiseen järvisedimentissä. Tämä tutkimus perustuu kolmeen läntiseltä Suomenlahdelta kairattuun sedimenttinäytesarjaan. Sarjoja tutkittiin sekä visuaalisesti että näytesarjoista otettujen röntgenkuvien avulla. Näytesarjat korreloitiin toisiinsa hehkutushäviö- ja suskeptibiliteettikäyrien avulla, jonka jälkeen Fe-monosulfidiraitojen jatkuvuutta näytesarjasta toiseen seurattiin. Näytteistä tehtiin myös pintahieet, joiden avulla tutkittiin rautasulfidimineraalien mineralogiaa sekä kiteytymisjärjestystä. Petrografisten tutkimusten perusteella rautamonosulfidiraidoissa esiintyy pääasiassa framboidista pyriittiä sekä euhedrisia pyriittikiteitä. Framboidinen pyriitti tarvitsee muodostuakseen rauta(II)sulfidista ja rikkivedystä voimakkaasti ylikylläisen liuoksen sekä avoimen huokostilan. Tästä johtuen on todennäköistä, että framboidinen pyriitti on kiteytynyt lähellä sedimentin pintaa, eli Itämeren järvivaiheen aikana ennen sedimentin tiivistymistä. Euhedrinen pyriitti puolestaan muodostui myöhemmässä vaiheessa diffuusion seurauksena. Myös näytesarjojen korrelointitulokset viittaavat tähän syntytapaan, sillä ainoastaan yksi rautamonosulfidiraita näyttäisi jatkuvan kaikissa kolmessa näytesarjassa.
  • Jalas, Marika Emmy Margareta (Helsingfors universitet, 2016)
    Over the last 30 years, the geology and paleohydrology has been examined at Olkiluoto as to predict how they may change in the future and affect the final placement of nuclear waste. Some knowledge about the hydrology can be seen directly from present groundwater and the fracture calcite reflect older environments from where they were precipitated. Calcite is the most used fracture mineral within paleohydrogeochemical studies since it easily precipitates during different conditions, including colder climate. The calcite at Olkiluoto has also earlier been examined and dating and grouping of the calcite has been carried out. The aim of the study was to further analyze the trace element composition in fracture calcite samples from earlier studies, in order to understand the influences of groundwater in calcite. The REE concentrations and their anomalies were of special interest. 31 calcite samples from a depth of about 12–660 m under the surface, from 20 different drill cores were analyzed. The calcite had been precipitated at pegmatitc granite, mica gneiss, migmatitic mica gneiss, quartz gneiss and veined gneiss. The calcite was analyzed with ICP-AES (Agilent MP4100), ICP-MS (Agilent 7500ce/cx) and LA-ICP-MS (Coherent GeoLasPro MV and Agilent 7900s). The ICP-AES method was found unsuited for trace element analyses of calcite. The trace element concentrations showed large variations. The later calcite had larger concentrations and more variation towards the surface than deeper in the ground. REE concentrations decreased over depth which can reflect the Ca in the groundwater that increases with depth. LREE showed higher concentrations than HREE since soluble HREE tend to stay in the groundwater during calcite precipitation as LREE migrates to the calcite. Larger LREE concentrations may have occurred from hydrothermal conditions. Usually the calcite had negative Eu anomaly but also positive occurred. Reducing conditions create negative Eu anomalies when Eu3+ takes divalent form. The positive Eu anomalies may also have occurred during hydrothermal conditions or may reflect plagioclase in the bedrock. No direct influence between bedrock and calcite trace element composition could however be determined. The calcite usually lacked Ce anomaly except for a couple near the surface which may be caused by oxidizing conditions where Ce3+ changes to soluble Ce4+. The negative Ce anomalies in calcite from meteoric water, may have inherited the anomaly from earlier seawater. A few La anomalies were observed. Negative La anomaly may occur if La has been taken by other minerals. Usually the calcite lacked Y anomaly except for the oldest calcite that had positive Y anomaly. Acidic conditions tend to cause Fe oxyhydroxation and reduce REE in comparison to Y which may have produced positive Y anomalies. Reducing conditions may also have caused the higher Mn and Fe concentrations in calcite while oxidizing conditions may have created the higher U concentrations. Bacterial activity and clay accumulations during calcite precipitation may have affected Mn concentrations and sulfide precipitation may have affected Fe. The U concentrations in groundwater tend to decrease with depth and at high salinity which may have affected the U concentration in calcite. Variations in Mg concentrations may have been caused by Mg ion exchange. High Sr concentrations may reflect hydrothermal conditions while low Sr concentrations may reflect low temperatures or precipitation of other minerals.
  • Mechenich, Michael (Helsingfors universitet, 2017)
    Ecometric analysis allows one to identify relationships between traits measured in organisms and conditions measured in the organisms' local environment. In developing an ecometric model, one selects phenotypic features of organisms which potentially are adaptations to local environment, aggregates measures of these features by organismal community, and quantitatively relates these to measures of the environment via statistical modeling, such that organismal traits may be used to predict environmental conditions. Once established, these models may be applied to fossil assemblages, to reconstruct local paleoenvironment using traits preserved in the fossil record. In this ecometrics case study, we addressed a number of related research questions: what bioclimatic and threshold measures of temperature and/or precipitation are most closely correlated with large, herbivorous mammal communities' mean hypsodonty (HYP) in sub-Saharan Africa? Do these correlations differ at differing spatial scales; specifically, do mammal communities in Kenya's national parks and reserves together relate differently to local environment than do communities in the Afrotropics ecoregions? Finally, what do results obtained by ecometric analysis suggest concerning organismal evolution and dispersal in sub-Saharan Africa? In pursuing answers to these questions, we also pursued the case study's primary objective: we developed and implemented a set of best practices for ecometric analysis, based on an assessment of the sensitivity of ecometric models to model-building decisions, and to uncertainty in source datasets. Ecometric analyses frequently make use of raster datasets - continuous coverages of temperature, precipitation, productivity, and other environmental properties - in characterizing local environment at study localities. Thus we primarily asked: are ecometric results dependent on raster resolution or resampling algorithm? Results of these sensitivity analyses are encouraging. Using the recommended mean resampling algorithm, change in linear regression equations with raster resolution is predictable, and not significant until very low resolutions, in which the average raster cell area is an order of magnitude or more greater than the average locality area. Moreover, using the recommended area-weighted averaging in calculating environmental observations at localities ameliorates this predicable trend in derived regressions. In working 'behind the scenes' addressing these methodological questions, we enable more informed interpretation of ecometric results, and allow future researchers to proceed to the real business of ecometrics with a vetted set of analytical methods. Moreover, in promoting better understanding of ecometric results, we promote better understanding of the complex relationships between organisms and environment, essential to understanding the biosphere's past and present, and to protecting it in the future.
  • Sova, Susanna (Helsingfors universitet, 2015)
    The evolution of biominerals, including teeth, has been an important step in the evolutionary diversification of organisms. For an organism, biominerals allow various advantages, such as ion storage, protection, food capture and processing, and locomotion. In mammals, tooth enamel is the hardest and most mineralized part of the body. Although tooth development is better known than that of many other organs, the maturation of enamel is still not completely understood. Enamel formation is a slow process biologically. In humans, the mineralization of the enamel in the first permanent molars starts at the time of birth, and the process continues even after the eruption of the teeth at the age of six years. Any disturbances during the enamel formation or other damage later in life will become permanent, as enamel does not reform. The aim of this work is to document the maturation of domestic pig molars, and use mineralogical and physics research methods to study enamel growth. The domestic pig (Sus scrofa domesticus) is a plant-dominated herbivore with large, bunodont molars. The relatively fast development of pig teeth together with their large size makes pig teeth a suitable model for comparisons of different methods. One of the methodological interests was to test if mineral grains can be used in computational microtomography for relative calibration of the absorption models. Three minerals (fluorapatite, quartz and siderite) were chosen by their physical and chemical features. The calibrated absorption models were compared with the results of more traditional methods, such as thin sections and hardness tests. X-ray diffraction and scanning electron microscopy were also used for structural studies. The results show that the microtomography is a valuable starting point for the traditional destructive methods used in the study of biomineralization, but does not substitute for the other methods. The mineral calibration was an efficient method for the microtomography-absorption models. Additionally, the calibration minerals allowed detection of microtomography artifacts better than using teeth only.
  • Rantala, Marttiina (Helsingfors universitet, 2013)
    Multiple anthropogenic stressors on lake ecosystems demand effective measures towards improved protection and management of water bodies. The Water Framework Directive defines a common goal for sound water management and obliges EU member countries to monitor and protect the ecological status and water quality of all relevant surface waters. However, major problems hindering the attempts for effective water management are the lack of long-term observational data on reference status and an inadequate understanding of the responses of lake ecosystems to environmental pressures. With this regard, paleolimnological techniques are invaluable as they provide means to seek for past analogies of lake-environment interactions. Long-term development in the water quality and ecological status of Lake Storträsk, located in southern Finland, was assessed using a variety of paleolimnological proxies. The aim was to determine the reference status of this dystrophic lake, and to attain holistic understanding of late Holocene environmental changes and their influences on the lake's status. The principal hypothesis of the study was that late Holocene climate changes, catchment development and contemporary human activities have affected the status of the lake leaving records in the abiotic and biotic features of the sediment deposits. A 43-cm sediment core was obtained from the lake basin and studied for its physicochemical and biological attributes. The core was dated with radiometric methods, and a time frame of ca. 4500 years was established for the sediment sequence. Loss-on-ignition and magnetic susceptibility were measured and the elemental content of the sediment was assessed by ICP-MS- and CNS-analyses. Fossil diatom assemblages were studied to reconstruct long-term development in lake-water pH. Ordination techniques and diversity indices were applied to identify temporal patterns and relationships in the bioassemblages, and Spearman's correlation coefficients were calculated to assess statistical relationships between the studied abiotic and biotic parameters. The results reveal that, whereas long-term climate changes have had the most profound impact on the water quality and ecology of Lake Storträsk, the status of the lake has also been altered by early catchment disturbances and historical human activities as well as more intensive anthropogenic disturbances after the establishment of intensive agriculture in the area. The base of the sediment core reflects the transition from the warm and dry Holocene Thermal Maximum to the cooling and increasingly humid late Holocene. After the initial phase, a more stable development took place, disrupted by possible signs of forest fires and early clearance periods in the area. From the late Middle Ages onwards, human activities within the vicinity of the lake became more intensive leaving highly distinct marks in the sediment, but were receded towards the present. Regardless of the current location of Lake Storträsk in a conservation area, and the apparent inability of the barren catchment to support any intensive agricultural practices, it is clear that human influences on the lake have been significant. The results of this study highlight the importance of long-term perspective in the assessment of lake reference conditions since lake ontogeny is often far from linear. Furthermore, this study emphasizes the importance of combining information from multiple paleolimnological proxies as they provide a more robust and holistic basis for understanding lake-environment dynamics particularly in humic boreal lakes which often respond to environmental change in distinct ways.
  • Martikainen, Noora (Helsingin yliopisto, 2017)
    In the Neoprotezoic Era (1.0Ga – 540Ma) the earth’s climate changed by multiple large glaciations and supercontinent formations and break-ups. Climate changes can be seen from the carbon isotope record, where the steep negative excursions indicate glaciation. The Neoproterozoic Era is known for the Snowball Earth events, when the earth has been covered by snow even in the equator. At the same time, there was Rodinia supercontinent break-up and continent regroup, which led to Mozambique Ocean to form and close during the East African orogen 650 – 620 Ma ago. The Taita Hills is located in South Kenya and lies in the Mozambique Belt. Taita Hills is divided into the Kurase and Kasigau groups. The Kurase group is considered to be metasediments from a continental shelf and the Kasigau group from the continental margin. The Kurase group contains multiple sedimentary carbonate rock layers, which are surveyed by Horkel et al. (1979) and offers a base for this study. The sedimentary carbonate rock samples were analysed with MP-AES for the elemental concentrations of Ca, Mg, Fe, Sr and Mn and for the δ13C and δ18O composition of carbonate. Three of the samples were calcites (Mg/Ca ratio 0.00 – 0.04) and 45 were dolomites (Mg/Ca 0.38 – 0.61). The δ13C values varies from -1.55 to 6.96‰ and the δ18O composition were between -10.2 and -0.66‰. The Mn/Sr ratio indicates that the samples have retained primary δ13C composition. The δ13C composition differs remarkably between the calcite and the dolomite samples, which might indicate that the calcite carbonates have a secondary composition even if the Mn/Sr ratio is low. The positive δ13C values represents the interglacial time. The δ13C compositions of the global δ13C record indicate that the Taita Hills region sedimentary carbonate rocks were precipitated before or after the Sturtian Snowball Earth event.
  • Paasi, Teea (Helsingfors universitet, 2016)
    The Pleistocene (2588-11,2 ka) is known as the time of the ice age. The ice age ended at the beginning of the warm and more humid Holocene. Large carnivorous predators, which survived the transition, have adapted to the current new environments. The goal of this thesis was to compare the osteological changes in the large carnivores from the Pleistocene to present. The data consists Finnish Recent and Central European fossil carnivore carnassial teeth, the calcaneum and the femoral head. Body mass estimates and carnivory indexes were taken from the carnassial tooth, the calcaneal indices were used to determine environmental openness and femoral head measurements indicated locomotory category. The femoral head changes have not been tested on carnivores, so the applicability to carnivores was also tested. The wolf (Canis lupus), the wolverine (Gulo gulo) and the bear (Ursus arctos) are smaller Recently than in the Pleistocene. Wolf's diet has changed to more omnivorous, and changes in the calcaneum indicate more closed habitats. There are no significant intraspecific differences in Finnish carnivore populations between latitudes. The femoral head indices confirm the benefits of certain osteological traits in terrestrial animals (the wolf, the wolverine, the bear) compared to the traits of a more scansorial ambush predator, the lynx (Lynx lynx). The decline in the body masses from Pleistocene to Recent has been known previously. The changes in the body masses in Finland have not been made. The lack of intraspecific differences reflects constant environmental conditions throughout Finland. The differences between fossil and Recent wolf bring new insight on the matter. The more closed environments in Finland are reflected in the wolf, and differences in locomotion between species can be detected from the material.
  • Silventoinen, Saara (Helsingin yliopisto, 2020)
    Chromite (Fe2+, Mg)(Cr, Al)2O4 contains in addition to the main elements a variety of minor and trace elements. It often occurs as an accessory mineral in cumulate rich olivine rocks. The melt composition is recorded into crystallised chromite. Due to these characteristics, the composition of chromite can be used as a proxy for the petrogenesis of the magma, providing vital information on how the sulphur saturation occurred, and, in particular, to record the conditions of the cooling cumulates. The Sakatti Cu-Ni-PGE orthomagmatic deposit is located in northern Finland in the CLGB. The deposit is hosted by an olivine cumulate body (the main body), where both disseminated and massive sulphides occur. In addition to the main body, the smaller satellite bodies, the NE and the SW bodies also host mineralisation. The upper barren olivine peridotite body occurs on top of the main body. Thin sections were selected from each of the olivine peridotite bodies (the main, the upper, the NE and the SW body). The chromites can be divided into two groups; unzoned chromites from the main body and the NE body, and zoned chromites from the upper body and the SW body. The chromite grains occur either as intercumulus positions relative to olivine grains or enclosed by unaltered olivine and pyroxene cumulus grains. The elemental compositions, including SiO2, TiO2, Al2O3, Fe2O3, FeO, V2O3, MnO, MgO, ZnO and NiO, of the chromites were analysed using EPMA. The trace element, Ru, was analysed using the LA-ICP-MS. The Sakatti chromites are characterised by variable content of Mg# (0.18 -0.56), moderately high Cr# (0.56 -0.92) and Fe3+# (0.11 -0.50). In addition to Mg# and Cr#, the Al2O3 and TiO2 compositions and textural features, the Sakatti chromites resemble more of those chromites which saturate from komatiitic magmas than chromites which are associated with picritic or basaltic melts. A subset from those chromites that are spatially associated with massive sulphides display high ZnO (> 0.5 wt.%), low Ni (as low as 225 ppm) and higher TiO2 (up to 3.22 wt.%). The source behind the elevated Zn-levels could be the assimilation of sulphide bearing sediments to the magma. The Ti enrichment could be explained by the magma being contaminated by iron-rich gabbro during its evolutional history. Nickel contents of the Sakatti chromites range from 225 ppm to 1731 ppm. The majority of the analysed chromite grains are Ni-depleted due to the separation of a sulphide liquid during the magmatic evolution of the Sakatti geological environment. Portion of the Sakatti chromites are Fe3+-rich, which is interpreted to reflect their crystallisation from a melt that have potentially assimilated a sulphur-rich evaporitic rocks, anhydrite. Fe3+-rich chromites together with high Zn, high Ti and low Ni contents represent primary magmatic features in the Sakatti olivine cumulate hosted chromite. Ru content in the Sakatti chromites are low (<2 pbb) and therefore, the low Ru values are an indication of mineralised geological environment.
  • Aalto, Aleksi Jeremias (Helsingfors universitet, 2017)
    Geologic knowledge is often inferred from heterogeneous and sparse datasets. Thus, integrating disparate data is one of the essential phases in geologic research. Integrating geologic and geophysical observations and models is typically performed using proprietary modeling software. The methods for integrating data often utilise concepts based on the relational model for data. The relational model provides the theoretical basis for designing data management systems where the consistency of data is ensured. In this study, the relational model was used for geologic and geophysical data by designing a data model for integrating reflection seismic data from the Finnish Reflection Experiment together with chosen geophysical and geologic data. The data model was implemented in a relational database management system and the data is handled in a manner that ensures the internal and referential consistency of the data. A web GIS application was designed and implemented to visualise the Finnish Reflection Experiment data together with other relevant datasets. The application utilises a service-oriented architecture, where external services providing data or features are utilised to enhance the capabilities of the application. The external services are accessed using widely standardised web technologies and thus it is easy to extend or alter the datasets used in the application. The web GIS application makes it possible to visualise Finnish Reflection Experiment data together with other data using any device with a web browser. The web GIS application has been published as a part of the OpenFIRE service, running in the AVAA portal of the Open Science and Research Initiative. In the OpenFIRE service, additional download service has been designed for the application in collaboration with the AVAA team of the Open Science and Resarch Initiative. In the service, the web GIS application can be used to browse Finnish Reflection Experiment data in a proper context together with other datasets. By modeling data it was possible to improve the quality of the national geologic data repository from which data was used in the web GIS application. The data management processes of the national data repository are recommended to be reviewed using the data management theory methods discussed in this study. Considering that there are currently various ongoing data and research infrastructure programmes without many prototypes in production, the methods discussed and utilised in this study could be considered as examples of design and implementation of a domain-specific data visualisation service and data management practices, especially in the fields of bedrock geology and solid Earth geophysics.
  • Seitsamo-Ryynänen, Minja (Helsingfors universitet, 2016)
    The northern peatlands are significant sources of methane into the atmosphere. As methane (CH4) is a powerful greenhouse gas, understanding the mechanics of peatland CH4 production/consumption and the controls on CH4 emissions are vital in order to calculate global CH4 budgets. The isotopic composition of CH4 can be used as a tool to identify pathways of methanogenesis, CH4 oxidation and transport. The aim was to learn how microtopography effects CH4 emission and its δ13C values at a boreal mire complex Siikaneva, located in southern Finland. The study sites were an ombrotrophic bog and a minerotrophic fen. The hypothesis of the study was that microtopography is an integrating controlling factor of CH4 emissions and that isotopic composition of the emitted CH4 would reflect the processes beneath the peat surface. Also, it was expected that at the fen there would be more acetate fermentation which would show in the isotope results. Gas samples of emitted CH4 were drawn from hummocks, lawns and hollows using a closed chamber method to analyse CH4 flux and δ13CCH4. Pore water samples for DIC analysis were collected at the depth of 0.5 m to analyse δ13CDIC. In addition, water table levels and peat temperatures were measured at each sampled plot. All samples were collected once a month from May to August to identify changes during the growing period in 2015. The results revealed that the emissions of CH4 were the lowest from the hummocks at both sites, but the differences between fluxes from the hollows and lawns were less affected by microtopography. Water table levels and peat temperatures seem not to be the controlling factors for CH4 emissions. The isotopic composition of emitted CH4 was also mostly unaffected by microtopography. Only the hummocks at the bog had distinctively higher carbon isotope values compared to the other microsites. Unlike the CH4 flux results, the δ13CCH4 results depicted a seasonal trend during the growing period with all the microsites showing the most negative values in July. Combined to the results of the DIC analyses, it appears that the fen is characterized by more acetate fermentation, though the production pathway could not be identified unambiguously. The isotopic composition of emitted CH4 proved to be a suitable, but not sufficient application to differentiate CH4 production pathways, oxidation and transport. To better understand the processes beneath the peat surface and the effects of microtopography, CH4 flux and isotope data should be combined to multi-isotopic (CH4 and DIC) pore water samples drawn from multiple depths to demonstrate the vertical changes in the isotope composition at different layers of peat.
  • Sakaguchi, Ilona (Helsingfors universitet, 2017)
    The topic of this thesis is the emplacement conditions and wallrock reactions of pegmatitic granitoids dikes in Kopparnäs, Southwestern Finland. Two locations from Kopparnäs peninsula, where pegmatitic granitoid dikes intrude into mafic host rocks, were chosen for a detailed petrological study. In the first study location, the granitoid dikes intrude into a noritic host rock and in the second study location the dikes intrude into a migmatitic host rock. Analysis on previous studies, field observations and aerial pictures taken with a drone revealed that two generations of granitoid dikes were emplaced in quick succession during the formation of the Southern Finland Granitoid Zone at around 1.83 Ga. The first generation of dikes intruded into E-W trending shear zones. The second generation of dikes intruded into N-S trending shear zones that were formed under SE-NW transpression. Quantitative estimates of pressure and temperature conditions could not be made. The structural evidence points to an intrusion of hot magma into a cold host rock. This information combined with PT-information from previous studies implies a high temperature and low pressure environment. A study of the rock microstucture was done with optical and cathodoluminescence microscopes in order to describe melt-wall rock reactions. Mineral identification and a study of major element composition were done with the electron probe microanalyzer (EMPA). Trace element measurements were made on the laser ablation inductively coupled mass spectrometer (LA-ICP-MS) to find out what transpired chemically when the dikes were emplaced in the host rocks. There are clear sings of melt-wallrock interaction between the granitoid dikes and the mafic host rocks. It is possible that a drop in pressure caused expulsion of fluids from the dikes. Alteration was most extensive in first study location where amphibole devolatilization reactions in the host norite released fluids to the contact zone causing further alteration. The alteration zone around the contacts of the dikes and the migmatites is much narrower in the second study location, since no fluid was released from devolatilization reactions. Despite this, existence of myrmekite in the contact zone in the second location point to sodic-calcic auto-metasomatism. The alteration reactions had a big effect on the trace element compositions, creating some clear linear diffusion trends. Elements, such as zinc, gallium, niobium and tantalum were mobilized and diffused from the dikes to the host rocks. The most hydrothermally altered rocks in the first study location were enriched in easily soluble elements, such as barium and cesium, and depleted in rare earth elements.
  • Pakarinen, Antti (Helsingfors universitet, 2013)
    Tämän Pro Gradu –tutkielman tarkoituksena oli selvittää Euran Vaaniin pohjavesialueen rajojen muutostarve. Tutkimus oli osana laajempaa ympäristöministeriön ja maa –ja metsätalousministeriön hanketta, jonka tarkoituksena on luoda yhtenäinen ja selkeä ohjeistus hienoainespeitteisten akviferien pohjavesialueiden rajaamiselle. Kenttätyöt tehtiin kesällä 2011. Tutkimusmenetelminä olivat raekokoanalyysi kuiva- ja märkäseulonnalla ja hiukkasmittarilla, ionikromatografia, massaspektrometria, veden stabiilien isotooppien määritys ja rakennetulkinta. Tutkimusten perusteella Vaaniin pohjavesialueen nykyiset rajat eivät ole toimivia pohjaveden suojelun kannalta. Nykyisen pohjavesialueen ulkopuolisilta alueilta, joiden vedenjohtavuusarvot mahdollistavat pohjaveden muodostumisen, on hydraulinen yhteys harjuun. Vedenjohtavuusarvojen perusteella tutkimusalue voidaan jakaa kolmeen eri luokkaan, jotka ovat muodostumisalue (K > 10-6 ms-1), vettä osittain läpäisevä alue (10-7 < K < 10-6 ms-1) ja vettä läpäisemätön alue (K < 10-7 ms-1). Rakennetulkinnan perusteella hyvin vettä johtavat kerrokset ovat jatkuvia Vaaniin ja Euran keskustan välisellä osuudella. Harjun morfologia on vaihtelevaa eivätkä muutokset näy maanpinnalla aluilla, joilla harju on hienoainessedimenttien peittämä. Pohjaveden päävirtaussuunnat Kauttualta kohti Vaaniita ja jokilaakson reunoilta harjuun. Pohjaveden redox-oloissa tapahtuu muutos Mölsin alueen hapettavista oloista pelkistäviksi kohti Vaaniin vedenottamoa ja samanaikaisesti kemiallinen koostumus muuttuu jonkin verran. Veden stabiilien isotooppien perusteella pohjaveden osuus jokivedestä on noin 5 – 8 %. Vaaniin pohjavesialueen rajoja on tutkimusten perusteella syytä muuttaa. Ehdotetaan kahta muutosvaihtoehtoa. Ensimmäisessä pohjavesialueen rajoja siirretään itään ja länteen siten, että muodostumisalueeksi lukeutuvat moreenikumpareet ovat pohjavesialueella. Toisessa vaihtoehdossa pohjavesi- ja muodostumisalueiksi rajataan alueet, joiden vedenjohtavuusarvot mahdollistavat pohjaveden muodostumisen. Peitteisten akviferien pohjavesialueiden rajauksissa tulisi tutkimusten perusteella ottaa huomioon myös harjualueen ulkopuoliset alueet, joilta voi olla hydraulinen yhteys harjuun. Muodostumisalueen rajauksissa käytetään perusteena, että muodostumisalueeksi rajaan alue, jonka vedenjohtavuusarvo vastaa hienon hiekan vedenjohtavuutta tai on sitä suurempi. Tutkimusten perusteella määritelmää suositellaan muutettavaksi siten, että rajaksi otetaan vedenjohtavuusarvo 10-6 ms-1, koska se ei ota kantaa sedimentin laatuun.