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3,5 billion years of history

A cache by Haaskalintu Send Message to Owner Message this owner
Hidden : 12/5/2007
Difficulty:
1 out of 5
Terrain:
3 out of 5

Size: Size: not chosen (not chosen)

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Geocache Description:

[ENG]: The Siurua tonalite gneiss is the oldest known bedrock occurrence within the European Union.

[FIN]: Pudasjärven Siuruankankaalta löytyy koko EU:n alueen vanhin kivilaji, harmaa tonaliittigneissi, jonka ikä on n. 3.5 miljardia vuotta
(vertailun vuoksi voi todeta, että Maapallon iäiksi arvioidaan nykyisin 4.5 miljardia vuotta)

[ENG]: The outcrop in the Siuruankangas locality consists of three rock types that have an age difference of of nearly 800 million years.
The oldest rock type in the locality, the core of Europe, is gray, fine to medium-grained tonalite the age of which is circa 3.5 billion years (see Mutanen and Huhma, 2003). The gray, gneissose tonalite is cross-cut by medium to coarse-grained granitic leucosome dikes and veins, which are off-white to pink in colour. The age of the granites is circa 2.7 billion years. The third rock type in the area is greenish-black amphibolite that occurs as angular fragments within the granite. The age of the amphibolite is also circa 2.7 billion years, but as it is crosscut by the granite, it has to be slightly older than the granite. Amphibolites can be found mainly in the central parts of the outcrop.
Age reference: Mutanen, T. and Huhma, H., 2003. Bull. Geol. Soc. Finland 75 (1–2), 51–68.

As a geocacher your task is this:

Try to find all three rock types in the Siuruankangas locality, take some photos (optional) and include them into your logging. Please include yourself and your GPSr in one of the photographs to confirm that you actually have been there.


[FIN]: Paljastuman (elikkäs sen kallion :)) vanhaa tonaliittia leikkaavat n. 2.7 miljardin vuoden ikäiset, karkearakeiset graniittijuonet (vaaleanpunaisia) ja graniittien kanssa oletettavasti suht samanikäiset amfiboliitit (mustia). Paikalla ramppaa niin paljon geologiväkeä, että sinne on muodostunut viime vuosina ihan käypä polku tieltä, joka on parinsadan metrin päässä.

Geokätköilijänä tehtävänäsi on tämä:

Etsi kallioalueelta (1) se 3.5 miljardia vuotta vanha, harmaa gneissi ja (2) sitä leikkaavat, n. 2.7 miljardin vuoden ikäiset graniitit (vaaleanpunaisia luikuroita) ja amfiboliitit (mustia, kulmikkaita kappaleita).

Ota löydöksistäsi valokuvia, sisällytä ainakin yhteen myös oma naama ja gepsi ja liitä kuvat loggaukseesi.

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