Impact events and associated processes can significantly reshape the natural environment of the Earth and other bodies in the Solar system. The Siljan impact crater in the middle of Sweden was created in late Devonian and it is the biggest known morphostructure of this kind in Europe. The presented paper aims at the relief evolution of the Siljan impact crater area. Landforms of the region are studied, including relicts of the impact event, and main stages of relief evolution from the Paleozoic to the present are determined. Special attention is focused to discussion about the range and types of erosional and denudational processes in relation to the level of preservation of morphological and geological indices about the Devonian impact. Ascertained knowledge about relicts of the Siljan impact event are compared with selected impact craters on the Earth, the Moon and Mars.

In the Swedish peasant society, the church was an important venue. In areas were the church in the parish was located nearby a lake, the easiest way to reach the church was by boat. This was the case in several parishes around the lake Siljan in the province Dalarna, which is the focal point of this study. The villages were large, and the villagers would organise themselves in large boats, so called church-boats. Due to technological innovations, as one important aspect, there were no longer any need for the church-boats at the time of the turn of the 20th century. Some decades into the new century the old boats were once again taken into use and new boats of the same type were taken into production. In 1936 an organized racing competition with church-boats was initiated, and this still lives on today. This study examines the contemporary customs surrounding church-boats on Siljan in the character of competition as well as journeys to the church. The main part of the material is collected through ethnological fieldwork, conducted through interviews and observation/participant-observation, supplemented with a wide range of other material such as internet sources as well as textual and visual material. Aspects that are highlighted is the different characters of the custom, how the custom today is expressed in relation to the past, how local identity is expressed through the custom and what role its performers see for the custom today and for the future. One aspect that is highlighted is the stagnated interest in the usage of the church-boats but narratives with a positive tone are given room as well. A crucial proposition of the study is how the custom in its era as revitalized cultural heritage is filled with new values. Its historical purpose is no longer of relevance and today the usage of the church-boats comes with other purposes such as a cultural historical interest, tourism and sport. It is also shown how changes and preservation both serves as necessary components for the further existence of the cultural heritage. Crucial theoretical frameworks that is used, apart from cultural heritage and revitalization, are performance and nostalgia.

This thesis utilizes several geophysical methods to study the Siljan Ring impact structure, focusing on the western part of the structure. This thesis, and the three papers upon which it is based, reports on attempts to delineate the Paleozoic rocks at depth within the annular ring graben and characterize their structure. In addition, the nature of the basement, which underlies these sedimentary rocks is investigated. Papers I and III focus on analysis of the down-hole logging and borehole core data. As well as the acquisition, processing and interpretation of 2D high-resolution reflection seismic data from the Mora area. The borehole log responses were compared with the core lithology from the Mora 001 borehole and information from two other cores (Mora VM 2 and Mora MV 3) in order to interpret the logs. The logs reveal significant changes in the lithology between boreholes, indicating a very high level of structural complexity, which is attributed to impact tectonics. In addition, the log data revealed a high sonic velocity contrast between the Silurian and Ordovician successions and a higher apparent temperature gradient than in the northern part of the structure. The interpretation of the high-resolution 2D seismic data suggest that the Mora area has been significantly affected by the impact. Several potential faults were identified in the area and interpreted to be post depositional and related to the impact. In paper II, a 2D seismic profile from the Orsa area (12 km) located in the northwestern part of the Siljan Ring was re-processed. To compliment this seismic line, first break traveltime tomography results, vintage seismic OPAB profiles, new and pre-existing gravity data, aeromagnetic data and the bedrock geological map were used to present a geological model along the Orsa profile. Reprocessing of the seismic data resulted in improved stacked and migrated sections and better imaging of the top of the crystalline basement than the original processing. Integrated interpretation of the seismic profiles suggests that the area has been significantly affected by faulting and that the depth to the basement varies greatly along the different profiles.

Quality and error assessment is an essential part of spatial analysis which with the increasingamount of applications resulting from today’s extensive access to spatial data, such as satelliteimagery and computer power is extra important to address. This study evaluates the impact ofinput errors associated with satellite sensor noise for a spatial method aimed at characterisingaspects of landscapes associated with the historical village structure, called the HybridCharacterisation Model (HCM), that was developed as a tool to monitor sub goals of theSwedish Environmental Goal “A varied agricultural landscape”. The method and errorsimulation method employed for generating random errors in the input data, is implemented andautomated as a Python script enabling easy iteration of the procedure. The HCM is evaluatedqualitatively (by visual analysis) and quantitatively comparing kappa index values between theoutputs affected by error. Comparing the result of the qualitative and quantitative evaluationshows that the kappa index is an applicable measurement of quality for the HCM. Thequalitative analysis compares impact of error for two different scales, the village scale and thelandscape scale, and shows that the HCM is performing well on the landscape scale for up to30% error and on the village scale for up to 10% and shows that the impact of error differsdepending on the shape of the analysed feature. The Python script produced in this study couldbe further developed and modified to evaluate the HCM for other aspects of input error, such asclassification errors, although for such studies to be motivated the potential errors associatedwith the model and its parameters must first be further evaluated.

No description available.

No description available.

The Siljan Ring in Dalarna, Sweden is the site of the largest meteor impact crater in Europe and has long been a topic of discussion regarding methane production. However, the source of this methane and the timing of production in relation to the impact remain unclear. An outcrop of red Ordovician limestone preserved on the edge of a downfaulted zone encircling the crater’s central plateau is crosscut by fractures surrounded by pale-coloured reduction haloes within which precipitates can be observed. These haloes suggest interaction with a reducing agent mobilised within a fluid flow, of which methane would be a prime candidate. A field study was subsequently undertaken to establish the reaction whereby these haloes were formed, as well as the timing of their formation relative to the Siljan impact based upon petrological, geochemical, and structural data obtained in the field. Results from this study show that a methane-bearing hydrothermal fluid mobilised within the fractures has preserved the original mineralogy of the limestone within the reaction haloes whilst the country rock beyond was being oxidised. Pyrite is shown to be preserved within the pale reaction haloes, whilst its oxidation within the country rock is shown to be the source of the limestone’s distinct red colouring. Fracture and bedding orientation at the study site suggest the hydrothermal event to have been simultaneous with the meteor impact, with the fractures forming part of a wider complex network of impact features. Whilst mobilisation associated with the meteor impact is a likely cause of methane release, the exact source of the methane active at the study site is unclear.

I Österdalälven har mängden Siljansöring (Salmo trutta) minskat avsevärt på grund av kraftverk som stoppar fiskens vandringsvägar. För att lyckas med att stärka beståndet krävs en fördjupad kunskap kring fiskens beteendemönster, bland annat rörelser i samband med uppströms lekvandring. Denna studie är ett försök att ge en överblick av den lekmogna Siljansöringens uppströmsvandring i Österdalälven och se om det föreligger några skillnader mellan odlad/vild öring respektive hanar/honor. Genom akustisk telemetri har 18 Siljanöringars rörelser längs en begränsad älvsträcka registrerats under 56 dagar. Analys har gjorts för hitta variationer både rumsligt och tidsmässigt samt mellan odlade/vilda Siljansöringar respektive honor/hanar, likväl som skillnader avseende rörelser, tim- och dygnsaktivitet och benägenhet att söka sig uppströms till det definitiva vandringshindret Spjutmo kraftverk. Siljansöringarna rörde sig mer under dagen jämfört med natt vilket skulle kunna kopplas till påverkan från elproduktion och vattenströmmar som skapas vid Spjutmo kraftverks turbinutlopp och/eller att dagsljuset är en fördel då de använder sig av synintryck för att kunna navigera. Skillnader (dock ej statistiskt säkerställda) kunde urskiljas mellan odlade och vilda fiskar och hanar/honor, såsom exempelvis att vild fisk simmade längre sträckor än odlad. Studier som denna är viktiga för att kunna få en helhetsbild kring livsvillkor och beteendemönster för Siljansöring och därigenom lyckas med framtida förvaltnings- och åtgärdsarbeten. / The number of Siljan trout (Salmo trutta) in the River Österdalälven has declined due to hydropower development. To restore the river information about the behavioural patterns of the trout, such as upstream migration, are needed. The aim of this study is to describe the upstream movements of tagged Siljan trout as well as to identify differences between hatchery-reared and wild trout and between males and females. During 56 days, 18 individuals tagged with acoustic telemetry transmitters were registered in a section of the River Österdalälven. The data were analysed to identify variation in time and space as well as differences between origin (hatchery-reared vs wild trout) and sex. Analyses were also performed on hourly and diel movement patterns and if the fish swam upstream to the first migration barrier, the power station in Spjutmo. Variation in diurnal activity was identified, with higher activity during daytime compared to night, which might be related to power production in relation to currents flowing from turbine outlets and/or the importance of daylight for effective navigation. There were no significant differences identified between hatchery-reared and wild trout, respectively, nor were there any sex-related differences. Information obtained from this study is important to understand the situation for Siljan trout, to help in future management and restoration of this valuable stock of trout.

Many populations of salmonids are threatened by fragmentation and degradation of spawning habitats. Common remedial measures are habitat restoration and stocking of hatchery fish to support degraded wild populations. Many populations of brown trout in Sweden have been extirpated. The restoration plan for the endangered brown trout in Lake Siljan started decades ago and involves releases of hatchery produced trout. A decline of the spawning run of hatchery fish has been observed. In this study, wild and hatchery fish were tagged and monitored using hydroacustic telemetry during May-October, 2018. Movement patterns were studied to detect potential differences between wild and hatchery fish during lake and spawning migration. The results showed a difference of preferred territories between the groups. The wild trout stayed in the northern part of the lake and the hatchery trout were more evenly distributed over the lake, but with a preference for the southern part of the lake. During spawning migration a larger proportion of the wild trout (44 %) moved to potential spawning habitats as compared to hatchery trout (16 %). The wild fish migrated more or less direct to the potential spawning grounds in River Österdal as compared to the hatchery fish, which showed an erratic behavior and preferred to migrate to the tributaries in Lake Siljan. Differences in movement patterns and preferred habitats in the lake can be caused by differences in behavior between the groups. This should motivate more studies of behavior of wild and hatchery trout. The time for spawning and potential spawning habitats are also important to study for future management and restoration of the wild population of brown trout in Lake Siljan. / Många salmonider är idag hotade av habitatfragmentering och brist på lekplatser. För att främja kvarvarande bestånd är vanliga åtgärder habitatrestaurering och utsättning av odlad fisk. Många bestånd av sjövandrande öring i Sverige är idag försvunna. I sjön Siljan har man under årtionden satt ut odlad fisk då den vilda stammen av siljansöringen är starkt hotad. En minskning av återvändande uppströmsvandrande odlad lekfisk har uppmärksammats. Vild och odlad öring märktes med sändare och data samlades in med akustisk telemetri under maj till oktober, 2018. Eventuella skillnader i rörelsemönster mellan fisk av olika ursprung har studerats under tillväxtperiod och lekmigration. Resultatet visade att det finns skillnader i var fiskarna uppehåller sig i sjön beroende på ursprung. Den vilda öringen föredrog den norra delen av Siljan, den odlade var mer spridd i hela sjön men föredrog den södra delen av sjön. Under tid för lekmigration rörde sig en större andel av den vilda fisken (44 %) mot potentiella lekhabitat jämfört med den odlade (16 %). Den vilda fisken var mer fokuserad i sin vandring mot Österdalälven än den odlade som uppvisade ett erratiskt beteende och som i större utsträckning besökte biflöden som mynnar i Siljan. Skillnader i rörelsemönster och placering i sjön kan bero på beteendeskillnader och interaktioner mellan grupperna. Detta borde öka intresset för att studera detta vidare hos den vilda och odlade öringen. Önskvärt är också att öka kunskapen om lekperiod och potentiella lekhabitat för att kunna upprätta ett effektivt åtgärdsprogram som ger ökade möjligheter för en återhämtning av den vilda populationen.