Browsing by discipline "Geologia"

Työn tarkoituksena oli tutkia geologisten taustatekijöiden, kuten pohjavesi-pintavesi vuorovaikutuksen sekä maaperän vaikutuksia piilevien yhteisökoostumukseen. Pohjaveden purkautumisvyöhykkeissä silikaattipitoisuudet ovat usein korkeat. Koska piilevät käyttävät silikaattia kuorensa rakennusaineena, on oletettavaa, että puroon purkautuva pohjavesi vaikuttaa piilevälajistoon. Tutkimuksen aineisto kerättiin heinä-elokuussa 2017 ja tutkimuskohteina oli 51 latvapuroa Etelä-, Itä- ja Kaakkois-Suomessa. Aineistona käytettiin piilevien lajistokoostumusta, purojen hydrogeokemiallista koostumusta, lämpötilahavaintoja sekä pohjasedimentin luonnetta. Lisäksi tutkimuksessa hyödynnettiin olemassa olevaa paikkatietoaineistoa sekä maaperästä että pohjavesialueista. Näytteistä määritettiin veden kemiallinen koostumus sekä sedimentin raekokokojakauma. Pohja-pintavesi vuorovaikutusten selvityksissä käytettiin hyväksi fysikaalisia ja kemiallisia menetelmiä, kuten veden hapen ja vedyn stabiilien isotooppien koostumusta, silikaattipitoisuuksia sekä lämpötilamittauksia. Tutkimuksessa pyrittiin paikantamaan ne purot, joissa pohjavesi-pintavesi vuorovaikutusta tapahtuu. Piilevien yhteisökoostumukseen vaikuttavia tekijöitä analysoitiin redundanssianalyysin, pääkomponenttianalyysin, hajonnan osituksen sekä similariteettianalyysin avulla. Saatujen tulosten perusteella voitiin nimetä yhteensä 19 pohjavesivaikutteista puroa. Pohjavesivaikutteisten purojen geokemiallinen koostumus erosi selvästi ei-pohjavesivaikutteisista puroista. Redundanssianalyysin mukaan tärkeimpiä piilevien yhteisökoostumukseen vaikuttavia tekijöitä olivat sähkönjohtokyky, pH, savi- ja silttipitoinen maaperä, fosfori ja veden väri. Lajiston koostumukseen vaikuttivat hajonnan osituksen mukaan eniten kaikki vedenlaatumuuttujat, kun puolestaan pelkkien pohjavesimuuttujien vaikutus oli pienempi. Similariteettianalyysin mukaan pohjavesivaikutteisten purojen yhteisökoostumukset erosivat merkitsevästi ei-pohjavesivaikutteisista puroista. Tulosten perusteella voidaan päätellä, että pohjavesivuorovaikutusta ilmentävillä muuttujilla ei ole suurta vaikutusta piileväyhteisöjen koostumukseen. Siitä huolimatta pohjavesivaikutteisten ja ei-pohjavesivaikutteisten purojen lajistoissa oli havaittavissa eroja.

The topography of the Earth's surface is the result of the interaction of tectonics, erosion and climate. Thus, topography should contain a record of these processes that can be extracted by topographic analysis. The question considered in this study is whether the spatial variations in erosion that have sculpted the modern topography are representative of the long-term erosion rates in mountainous regions. We compare long-term erosion rates derived from low-temperature thermochronometry to erosional proxies calculated from topographic and climatic data analysis. The study has been performed on a global scale including six orogens: The Himalaya, Andes, Taiwan, Olympic Mountains, Southern Alps in New Zealand and European Alps. The data was analyzed using a new swath profile analysis tool for ArcGIS called ArcSwath to determine the correlations between the long-term erosion rates and modern elevations, slope angles, relief in 2.5-km- and 5-km-diameter circles, erosion potential, normalized channel steepness index ksn, and annual rainfall. ArcSwath uses a Python script that has been incorporated into an ArcMap 10.2 add-in tool, extracting swath profiles in about ten seconds compared to earlier workflows that could take more than an hour. Swath profile analysis is a relatively common method for geomorphological research. A swath profile is a rectangular extraction of a digital model to a cross-section, where statistical parameters (minimum, mean and maximum) are presented along the profile length. In previous studies swath profiles have been used to identify relationships between topography and major structures, to compare various climatic, erosional and topographic data across a given orogen and along strike, and to recognize fluvially and glacially eroded forms. An unambiguous correlation between the topographic or climatic metrics and long-term erosion rates was not found. Fitting of linear regression lines to the topographic/climatic metric data and the long-term erosion rates shows that 86 of 288 plots (30%) have 'good' R2 values (> 0.35) and 135 of 288 (47%) have an 'acceptable' R2 value (> 0.2). The 'acceptable' and 'good' values have been selected on the basis of visual fit to the regression line. The majority of the plots with a 'good' correlation value have positive correlations, while 11/86 plots have negative slopes for the regression lines. Interestingly, two topographic profile shapes were clear in swath profiles: Concave-up (e.g., the central-western Himalaya and the northern Bolivian Andes) and concave-down or straight (e.g., the eastern Himalayas and the southern Bolivian Andes). On the orogen scale, the concave-up shape is often related to relatively high precipitation and erosion rates on the slopes of steep topography. The concave-down/straight profiles seem to occur in association of low rainfall and/or erosion rates. Though we cannot say with confidence, the lack of a clear correlation between long-term erosion rates and climate or topography may be due to the difference in their respective timescales as climate can vary over shorter timescales than 10^5-10^7 years. In that case, variations between fluvial and glacial erosion may have overprinted the erosional effects of one another.

Bedrock fracturing is considerably extensive and distinct in Finland, and the fractures that are open, conductive and interconnected usually control the groundwater flow paths in fractured bedrock. This highlights the importance of knowing the locations and hydraulic connections of water conducting fracture zones particularly in mining areas, because they can transport adverse substances outside the mining area. In this study, it is focused on examining possible hydraulic connections of bedrock groundwater by using the stable isotopes of oxygen (δ18O) and hydrogen (δ2H). The study was carried out in the Talvivaara mining area in Northeastern Finland alongside a project from the Geological Survey of Finland (GTK). After November 2012, when a leakage of acidic, metal-containing waste water occurred in the gypsum ponds, there was an urgent need to study the groundwater transport routes in the bedrock fractures. The aim was to find hydraulic connections between surface water and groundwater, and to study the flow of the groundwater in the fracture zones based on the different isotopic characteristics of waters from different sources and isotopic similarities. Most of the materials used in this study were obtained from the results of the project from the GTK. These materials included geophysical interpretations of the locations and water content of the main fracture zones and the results from the geochemical analyzes. Together with the interpretations of groundwater flow direction based on hydraulic heads these materials formed a frame for this study. The isotope composition of 39 water samples from bedrock wells, shallow wells and surface water was analyzed using cavity ring-down spectroscopy (CRDS) method. The surface waters were clearly distinguished based on their evident evaporation signal, but no significant such a signal was observed in the bedrock and shallow groundwaters. However, similarities between groundwater from different depths of same well were found, in addition to similarities between different wells along same fracture zones. Although the isotopes did not indicate surface water contamination, groundwater contamination with smaller amounts of water is possible, in which case the changes in isotope composition are not yet significant, while certain elements have elevated concentrations. A NE-SW oriented fracture zone passing in the center of the study area was concluded to have the most important role in collecting and transporting groundwater outside the mining area. More detailed interpretations would require regular sampling for a longer period of time to better distinguish naturally and artificially induced changes both in the isotopic but also geochemical compositions. Also the usage of packer tests possibly together with pumping tests would be useful in obtaining more comprehensive image of the groundwater flow in the fracture zones and their hydraulic connections.

The evolution of herbivore mammal teeth has been the subject of palaeoecological research for decades. Hypsodonty, high-crowned teeth, has been linked to global climate cooling and drying during the Cenozoic Era. As grasslands conquered forested areas, terrestrial herbivores had to adapt to different environments and resource changes. Many browsers adapted to more grazing habits. Low vegetation included more exogenous grit, such as dust and sand, which in the result of soil ingestion causes dental wear, as does the phytoliths found inside the coarse grasses. As a result of natural selection, the dental crowns of many herbivorous mammal teeth began to grow, resisting dietary wear. Environments with high levels of volcanism and erosion the airborne ash that settles on plant surfaces and is released from sediments, is also likely to wear down herbivore teeth. One such area is Patagonia in South America. There, the teeth of many species have evolved to become hypsodont under the pressure of environmental stress. In this Master´s thesis, an experimental study was conducted using a mechanical masticator to investigate microscopic tooth wear caused by volcanic ash. Based on the results, it was considered whether the ash causes the hardest part of the tooth, the enamel, to be worn and if so, what kind of wear pattern it produces. The relevance of volcanic ash for the evolution of hypsodonty was also discussed. The experimental study was conducted with a mechanical masticator fitted with modern horse teeth that chewed in four different diet formulas, one tooth pair at a time. The first diet contained, in addition to water, nothing but volcanic ash, the second was a lucerne pellet mixture corresponding to browse and the third and fourth contained the plant pellet in addition to different amounts of volcanic ash. After chewing stage, the microscopic wear patterns of the tooth occlusion surfaces were analyzed. According to the results, the ash causes a pit dominated wear and the browse scratch dominated wear. The diet formulas with both, ash and plant pellet mixture, caused the most wear. Based on this Master´s thesis, it can be concluded that the volcanic ash causes tooth wear and may have influenced the evolution of hypsodonty.

The occurrence of high-aluminum orthopyroxene megacrysts (HAOMs) has been used to argue for polybaric crystallization of Proterozoic anorthosites. In this study, the petrography, geochemistry, and petrologic significance of HAOMs discovered from the 1.64 Ga Ahvenisto rapakivi granite – massif type anorthosite complex were studied. Fieldwork in the northwestern flank of the Ahvenisto complex revealed new outcrops with two different types of HAOM embedded in leucogabbroic rocks. Type 1 HAOM are autonomous, euhedral to subhedral, and up to 15 cm in diameter. Type 2 HAOMs occur in pegmatitic pockets with megacrystic (up to 30 cm long) laths of plagioclase. Especially the type 1 HAOMs are surrounded by complex rim structures comprised of plagioclase, low-Al orthopyroxene, iddingsite (after olivine), and sulphides. A quantitative electron microprobe wavelength dispersive spectroscopy analysis (EMPA-WDS) of orthopyroxene, plagioclase, and olivine was conducted on nine samples. Also, a bulk-analysis (WD-XRF) was performed on a set of twelve whole-rock and mineral samples. The precision and applicability of these methods in the HAOM research is briefly discussed. The geochemical data was used to evaluate the crystallization pressures of orthopyroxene in the system with an 'Al-in-orthopyroxene' geobarometer. A relatively clear three-stage compositional evolution is observed. The Al content decreases significantly from the core regions of the HAOM (4.4–7.6 wt. % Al2O3), through the rims (1.3–3.6 wt. %), into the host rock (0.5–1.5 wt. %). Enstatite compositions overlap but are generally higher in the cores (En~60–70) and rims (En~50–70) of the HAOMs than in the host rock (En~45–60) orthopyroxenes. The highest recorded Al abundances in the HAOM cores correspond to crystallization pressures of up to ~1.1 GPa and depths of ~34 km. The HAOM rims have crystallized in lower pressures (maximum of ~0.5 GPa/20 km). The highest pressure-estimates within barometer calibration for the host rock orthopyroxene were ~0.2 GPa (<10 km). The observations made in this study suggest that the inner parts of the HAOMs have crystallized in high-pressure conditions at lower crustal levels. The reaction coronas between the HAOM and the host rock were most likely formed during initial igneous cooling and in the presence of some melt, followed by subsequent hydration of the system. The occurrence of magmatic olivine within the rim may reflect the effects of pressure decrease in the ternary Fo-An-Si system, which stabilized olivine over orthopyroxene in the late stages of crystallization. Groundmass orthopyroxene composition is concurrent with late low-pressure crystallization at intrusion depth. This information is concordant with the latest research from the Ahvenisto area, which suggest that the anorthosistic rocks have a mantle origin.

In 2011 AA Sakatti Mining Oy published a promising ore discovery in Sodankylä, Finnish Lapland. The need for more knowledge led to the start of Sakatti geoenvironments -project in collaboration with the University of Helsinki. As a part of this project, the Holocene paleohydrology of Viiankiaapa mire was reconstructed. Viiankiaapa mire is located on the eastern side of Kitinen River and has developed in close connection to it. It is a large aapamire complex consisting of multiple smaller minerotrophic mire sites and bogs. Viiankiaapa conservation area was first established in 1988. A large portion of Viiankiaapa is now part of the Natura 2000 conservation network. To study the development and paleohydrology of Viiankiaapa mire, a 4.3 meter peat core (VA310315, 7497803 N/0490511 E) was collected using a Russian peat sampler. From the peat core, six specimens from increasing depth levels were sampled for age determinations to establish reliable chronology. Dating was conducted at LUOMUS Laboratory of chronology at the University of Helsinki, using 14C AMS dating method. Peat stratigraphy was studied on site and humification determined using von Post method. Physical properties of the peat (LOI550 and water content) were determined in 2 cm resolution. The colour of the ash was determined using Munsell soil color chart. Same resolution was used in geochemical analyses of 17 individual elements (C, N, S, P, K, Ca, Mg, Na, Fe, Al, Cu, Ni, Zn, Ti, Mn, Pb, Si). C, N, and S contents were determined using gas chromatography, while all the other elements were analyzed using ICP-MS. From the element contents, multiple ratios were calculated in order to study the Holocene deposition pattern of individual elements. Element/Ti profiles show an increase in mineral material input in c. 8 000 – 6 000 cal. BP, c. 4 800 – 3 000 cal. BP, and 2 500 – 1 900 cal. BP, suggesting enhanced flooding of Kitinen and increased humidity. Early Holocene (11 700 – 8 200 cal. BP) is indicated as a period of higher detritic material input. Waterlogged conditions, however, have most likely not been continuous during early Holocene. This is suggested by the occurrence of dark red color of iron oxide (FeO) in the ash. The occurrence of iron sulphides (possibly pyrite, FeS2) in the ash of the bottom section of the core suggests that waterlogged conditions were reached during Mid -Holocene. The 8.2k event is showcased in the profiles of multiple elements, including the main nutrients (C, N, P). These elements show significant increase after the cold event. Ca/Mg, Ca/K, and Mg/K ratios were used to estimate the trophic state of the mire and the sources of the mineral material. Also the accumulation of Pb was studied more closely. All of these factors suggest that atmospheric input and groundwater alone could not have transported the entire volume of the mineral material, and therefore river Kitinen may be considered as the main water and nutrient source until the damming of the river in 1984 and 1995.

In 2011, Anglo American Sakatti Mining Oy published an ore discovery in Sodankylä, Finnish Lapland. The rich Ni-Cu-PGE orebody, named Sakatti ore, is partially underlying Viiankiaapa-mire’s Natura 2000 protection area. This sets additional challenges for the utilization of the resource without compromising the fragile nature of the area. To estimate the impacts of possible future mining operations, the complex hydrochemical and hydrogeochemical conditions at Viiankiaapa must be well understood. Most water samples from the research area show a chemical composition close to the natural Finnish groundwater composition Ca–HCO3. However, in four groundwater observation wells, located south from Kiimakuusikko, Na–HCO3 type waters were detected. These sites were GA300 (8.26 ppm of Na), GA202 (17.34 ppm of Na), GA202 deep (15.23 ppm of Na) and GA201 (7.92 ppm of Na). Source for the anomaly is likely lithological due to lack of chloride in the samples. One possible source could be weathering of albite to kaolinite. Albite is hosted in the breccia unit, located close to the site. Albite-kaolinite weathering could release Na+ ions into the surrounding soil solution, which would provide a source for the high sodium concentrations. Kitinen river shows slightly higher Al, Li and Cu contents compared to other waters from the research area. This could possibly be used to distinguish river water from groundwater at sites where river water infiltrates the groundwater system. On the other side, Na, K and DSi have higher concentrations in groundwaters compared to surface waters. This could make them useful groundwater indicators. Sakattioja and the other smaller streams draining the mire, are characterized by very high isotope values, low amounts of DSi and low EC. These characteristics likely reflect the hydrogeochemistry of the water on the surface of the mire. The hydrogeochemical similarity of these streams is also highlighted by the hierarchical cluster analysis, where the samples from these sites form a clear cluster of their own. Stable isotope results are mixed and difficult to interpret. The most striking features are the low values observed at the mire near Kiimakuusikko and the high values observed in Sakattioja. Many groundwater samples show signs of evaporated source water component or re-infiltration of surface waters. This could be due to water from the mire infiltrating the groundwater system and then re-emerging in the observation wells and springs close to Kitinen. Overall, based on the results, the hydrogeochemistry at the research area can be considered to be very complex. The samples represent multiple different water compositions residing in poorly connected groundwater and surface water systems. This makes interpreting the results particularly difficult and is also reflected in the statistical analyzes which produce somewhat mixed results.

Viiankiaapa mire, located in the municipality of Sodankylä, has drawn public attention after mining company, AA Sakatti Mining Oy published their discovery in 2011. The discovered Ni-Cu-PGE ore deposit, Sakatti, is located mainly under the Natura 2000 protected Viiankiaapa. Viiankiaapa is Natura 2000 protected due to the several natural habitat types and plant species one of these, H. vernicosus is known to thrive at the areas of groundwater influence. The Sakatti deposit is in exploration phase but it is possible that mining will start in future. Knowing the hydrogeology of the area is crucial for preventing possible negative changes if the mining starts. In this study the objectives were to study 1) the influence of groundwater at the western margin of Viiankiaapa, 2) the influence of Sakatti ore deposit to the hydrogeochemistry of the area, 3) the influence of hydrology and hydrogeochemistry to the endangered H. vernicosus species. The sampling was done in September and October 2016, March and April 2017 and continued in summer 2017. Samples were collected from surface water of the mire, groundwater, spring water as well as from different depth of peat pore water using mini-piezometer. EC, pH, temperature, stable isotopes, DSi, main ions, trace elements and dissolved organic carbon (DOC) were analyzed. The groundwater influence was visible at the area of Lake Viiankijärvi and Särkikoskenmaa fluvial sediment deposit. Depth profiles of stable isotopes and main ions indicated groundwater flow in deep peat layer and mixing with surface water as the groundwater flow upwards through the peat layer. At the Sakatti ore deposit area the isotopic composition of surface water samples represented mainly season’s precipitation with few exceptions. Possible groundwater discharge was visible at the area between Sakatti main deposit and River Kitinen as well as near Pahanlaaksonmaa. The isotopic chemistry of spring water samples at the bend of River Kitinen had values of mixed groundwater and surface water. It is likely that the mire water infiltrates through the peat layer and fluvial sediments and discharges to the springs and River Kitinen. The bedrock of the area is known to be weathered, which could explain surface water like isotope values in springs and in some of the bedrock groundwater observation wells. Positive correlation was found between H. vernicosus ecosystems and the depth of peat. A ribbon-shaped zone of habitats and 2 – 4 m thick peat layer crosses the mire. The correlation with groundwater discharge was not clear. Ca and Mg concentrations were smaller but pH and alkalinity were higher at the areas of H. vernicosus ecosystems. However the Ca and Mg concentrations resembled areal spring water chemistry, which could indicate groundwater influence. Areas without the ecosystems are located mainly near the Sakatti ore deposit. The influence of the deposit in hydrogeochemistry was locally visible as elevated electric conductivity, main ion and trace element concentrations of the surface water and peat pore water. This most likely explains why the areas without the ecosystems had higher element concentrations.

Hyvinkäänkylä pumping station extracts groundwater from a local esker aquifer and supplies drinking water within the Hyvinkää municipality. There have been problems with the aquifer’s water quality, when surface water from the Vantaa river has mixed with groundwater during flooding season. As a result of the mixing, the pumping at the station must be periodically stopped. For more effective groundwater acquisition, management and protection it is critical to gain better understanding of the structure of the aquifer better. In addition, more knowledge of the groundwater-surface water interaction is needed and information on the possible routes of groundwater flow, particularly those which most affect the groundwater supply coming to the pumping station. The purpose of this study is to gather the previous research on the area and to create a 3D hydrogeological structural model using the Leapfrog Geo program. The model in this study visualizes the hydrogeological structures and serves as input for a groundwater flow model. The data in this study can be categorized into three groups: the structure of the bedrock and sediments, the level of the groundwater and the groundwater discharge. The structure of the bedrock and sediments was surveyed by geophysical methods, using previous data as well as some additional data gathered by field measurements. Data on the groundwater level measurements were obtained from both the Finnish Environment Institute and the Hyvinkää Water station. Additional data were collected using field measurements. To measure the amount of groundwater discharge, data were collected using flow measurements in the Vantaa River and the results compared with previous research. The geological and geophysical data were compiled and georeferenced first in ArcGis and then transferred into Leapfrog, which was used to build the 3D hydrogeological structural model. On the basis of the geological units of the drill data, five hydrogeological units were formed: coarse glaciofluvial material, fine glaciofluvial material, fine grained material, till and other. The hydraulic conductivity of the drill core sediment samples were calculated, and then used to estimate the hydraulic conductivity within and between the different sediment layers. Since one purpose for the 3D structural model was to serve as a base for the flow model, it was simplified into a 2-layer model. The study area was divided into smaller subareas, which were visualized with cross sections that were sliced from the 3D model. The measured groundwater levels were interpolated to demonstrate the groundwater flow direction in the study area. The groundwater monitoring levels were examined over a five year period and compared with weather and groundwater pumping data. The flow measurements obtained from the Vantaa River were compared to previous research to estimate the amount of groundwater discharge into the Vantaa River. The contribution of this study is five new significant observations about the structure of the aquifer: 1) the north and south part of the aquifer are connected to each other 2) the three-dimensional shape of the esker is different from its geomorphologic shape 3) most of the groundwater flowing to the pumping station is from the south side of the river 4) the amount of groundwater flowing to the pumping station is very high compared to the surface area of the aquifer 5) thick glaciofluvial layers underneath the Hirvisuo bog allow groundwater flow from the first Salpausselkä to the esker.

Tropical Africa has been under intense land cover change during the last decades. Human activities have had an impact on natural ecosystems and this has accelerated changes in them. Soil can be considered as an ecosystem and changes in natural soil formation can lead to soil loss and erosion. Taita Hills located in south-east Kenya are no exception. Almost all recoverable land is used for agriculture in these subtropical hills despite the great altitude differences and steepness of the hill slopes. Wundanyi catchment at the altitude 1400 - 2100m above sea level was studied in order to identify certain physical parameters of the soil in the hills and to define if these could be explained by changes in the physical environment like alteration in altitude, slope angle and land uses. A total of 68 study points were selected within the catchment in order to represent different physical environments. At each study point, the slope angle was measured, an approximately one meter deep soil cut was dug into the hill slope of which the soil profile was drawn and the subsamples were taken for the grain size analysis and bulk density determination. At 21 study points, the soil was not sampled due to a thick humus layer. The soil hydraulic conductivity was determined experimentally at three study points with an infiltration ring and theoretically for the rest of the study points by estimation, using other physical soil properties obtained from grain size analysis. The soil at the Wundanyi catchment was found to be massive, chemically weathered fine residual soil originating from the weathered gneissic bedrock. It was discovered that generally the soil is quite homogeneous within the catchment area and the physical parameters of the soil are similar despite the different land cover classes. The most common soil type at the catchment is fine sand. The deepness of the organic layer varied greatly, the mean being 0.7 meters. The thickest organic layers were found in indigenous forests and in places that had not been used for agricultural purposes. Soil hydraulic conductivity at the studied area is low. The degree of correlation between soil grain size distribution and varying physical environments was found low. However, there seems to be moderate correlation between the elevation and the proportion of clay and the aspect and the proportion of clay. Topographic environment mainly defines the land use and land cover within the studied area. Only the steepest slopes and areas that are not accessible have avoided the excessive exploitation of the soil. The vegetation protects the mineral soil and, therefore, the removal of natural vegetation exposes the soil to impacts of climatic conditions. The exposition of the soil together with fine soil texture can reduce the infiltration making the soil compacted. This increases the surface runoff, which can increase the sediment transportation and can lead to environmental problems such as erosion, gullying, silting of rivers and transportation of nutrients to rivers. Signs of these environmental problems can already be seen at the Taita Hills, proving that soil exploitation is not sustainable.