Exjobbsförslag från företag

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Förslaget inkom 2008-05-30

Total size, shape and surface texture analysis of till with different boulder size and frequencey

The project is associated with a larger project, financed by Formas. The aim is to study the physical composition of the till and see if and how there is a couple to bedrock properties. The project studies till from all different aspects. Two test areas associated with rock quarries have been studied in detail, one at Olunda near Uppsala, and one at Bäckseda near Vetlanda. Several geophysical tests have been made over a test area of till at each site. This includes georadar, resistivity, magnetic susceptibility, VLF and seismic. The total size distribution and lithological composition of the clasts has been studied at each site, from either sections or sample pits. The size distribution and the composition of the clasts are determined.
The surface boulder frequency of till varies drastically from place to place. Some tills nearly lack boulders at the surface while others have numerous and very large boulders at the surface. The aim of the master’s thesis project is to determine the total size, shape and surface texture of different tills that have large variation in surface boulder frequency. A further aim is to couple this to till genesis. Why does the boulder size and frequency vary? Is it primarily coupled to the quality of the local bedrock or due to glacial processes?
The project will study the total size, shape and surface texture as well as the petrography of the clasts in different tills using a new method. Approximately 8 sample sites will be chosen based on till boulder distribution. The number, size and lithology of boulders at the surface will be determined in a test area of about 100 m2. One ton of till is sieved in the field using the following sieves: 1, 1,4, 2, 6, 20 cm. For the two course fractions, 2-6 and 6- 20 cm, all the particles are weighed and the lithology of the particles determined. Then the particles are imaged (in the field) in two positions, lying and standing, in order to determine the 3-D size and shape distribution of the particles using image analysis. The two finer fractions are transported back to the lab for lithological analysis.
One aspect of the study is to determine the lithology of the particles in the different fractions and to determine which percent are from local versus distal bedrock sources. To do this sampling of the different local bedrock is required.
The student must have good geological background primarily of Quaternary geology but also be able to identify different types of rocks.


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