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Terrestrial cosmogenic nuclide dating applied in glacial stratigraphy and transportation studies on a greenfield exploration project in Kaarestunturi, Finnish Lapland

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Title: Terrestrial cosmogenic nuclide dating applied in glacial stratigraphy and transportation studies on a greenfield exploration project in Kaarestunturi, Finnish Lapland
Author(s): Peltonen, Veikko
Contributor: University of Helsinki, Faculty of Science, Geotieteiden ja maantieteen osasto
Discipline: Geologia
Language: English
Acceptance year: 2020
Abstract:
This study reviews the glacial history and the glacial transportation history in Kaarestunturi, Sodankylä in the Finnish Central Lapland interlobate region. The study is conducted on the Aamurusko prospect, where gold bearing quartz vein boulders have been discovered. The local glacial transportation history is studied in order to deduct the likely origin of the boulders. The local portion of the study involves rock and soil sample assays, glacial sedimentological studies, trenching and more unconventional Glacier Dynamic (GD) mapping and Terrestrial Cosmogenic Nuclide (TCN) dating. The local interpretation is set in a regional glacial history framework that is based on wide scaled GD mapping and existing literature. Kaarestunturi is incorporated in multiple regional glacial studies, but no local glacial studies have been conducted in the area. GD mapping indicates that the area has not hosted pronounced ice streams during recent stadials, however, it has experienced different types of glacial transportation. Till fabric analysis shows that the Kaarestunturi and adjacent Kiimajänkä have been subjected to both pronounced and indecisive ice flow directions. The most strongly orientated till fabrics portray repeated flow from NE for the lower till units and a flow from NW for surficial till. The NW flow is also indicated by fans interpreted from soil and rock sample assays. Field studies indicate that the Kaarestunturi fell likely interfered with local glacial flow, making some of the orientations local and till units topographically controlled. However, the till fabric analyses were too distal to confirm the impact the steering had on till deposition. The apparent ages of the four TCN samples are in the range of 27.9 ± 0.9–87.6 ± 2.4 ka BP. The TCN dating based glacial history model indicate that the dated boulders were affected by 2–3 glacial transportation events. The exposure ages together with sedimentological studies argue that at least the dated boulders are allochthonous. Based on this study TCN dating can offer new insight for ore exploration projects in glaciated terrain. Although the sampling has many prerequisites, being able to date exposure time of both boulders and bedrock makes it a versatile technique. However, it is apparent that the potential of the method is elevated in regions with a sound framework of glacial history knowledge. In complicated glaciated regions, more accurate information on erosion rates and reburial may be beneficial. It can be gained by analyzing multiple elements, as oppose to using 10Be only.
Keyword(s): Weichselian glaciation glacial transportation till stratigraphy glacial sedimentology glacial dynamics cosmogenic nuclides terrestrial nuclide dating 10Be dating exploration Central Lapland Kaarestunturi Aamurusko


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