Ritland Impact Crater
Friday, 14. August 2009, 16:44:02
In my post on the Gardnos Impact Crater in Norway, i wrote that of the three known Norwegian impact craters “the Ritland crater outside Stavanger is apparently not yet really recognised”. But now the last doubt seems removed.
The Ritland crater was discovered by the geologist Fridtjof Riis in the year 2000. Together with professor Henning Dypvik he has taken more than 200 rock samples, and in one of these they found shocked quartz this spring, which finally confirmed the hypothesis that the Ritland formation is the result of an impact.
The Ritland crater, which is 2 km wide and 350 m deep is situated in a mountainous area with excellent three dimensional exposures of the sedimentary rocks filling the structure and the deformed basement rocks along the crater rim. Within the crater, the crushed basement rocks are covered by sedimentary, post-impact breccias with fragments reaching up to 2-3 m. Lack of basement exposures in the central crater has made it difficult to find samples containing shocked minerals. In 2007, however, samples taken in a small area of exposed basement rocks in the crater interior revealed outcrops of a fine-grained rock with suevitic texture containing quartz grains with good planar structures of two directions - and shocked quartz is now confirmed.
Available geological observations indicate that the crater was formed on dry land. Dypvik is of the opinion that the crater must be about 600 million years old based on the strata in which it was formed and the age of fossils (of Middle Cambrian fauna) found in sediments (Cambrian shales and sandstones) deposited in the crater after its formation. The Caledonian orogeny (that occurred about 400 million years ago) buried the Ritland crater to a depth of more than 5 000 metres (5 km).
The third recognised Norwegian impact crater is the famous 40-km-diameter Mjølnir Crater, which is one of the best-preserved marine impact craters on Earth. I mentioned this crater in a post.
In Norwegian:
The Ritland crater was discovered by the geologist Fridtjof Riis in the year 2000. Together with professor Henning Dypvik he has taken more than 200 rock samples, and in one of these they found shocked quartz this spring, which finally confirmed the hypothesis that the Ritland formation is the result of an impact.The Ritland crater, which is 2 km wide and 350 m deep is situated in a mountainous area with excellent three dimensional exposures of the sedimentary rocks filling the structure and the deformed basement rocks along the crater rim. Within the crater, the crushed basement rocks are covered by sedimentary, post-impact breccias with fragments reaching up to 2-3 m. Lack of basement exposures in the central crater has made it difficult to find samples containing shocked minerals. In 2007, however, samples taken in a small area of exposed basement rocks in the crater interior revealed outcrops of a fine-grained rock with suevitic texture containing quartz grains with good planar structures of two directions - and shocked quartz is now confirmed.
Available geological observations indicate that the crater was formed on dry land. Dypvik is of the opinion that the crater must be about 600 million years old based on the strata in which it was formed and the age of fossils (of Middle Cambrian fauna) found in sediments (Cambrian shales and sandstones) deposited in the crater after its formation. The Caledonian orogeny (that occurred about 400 million years ago) buried the Ritland crater to a depth of more than 5 000 metres (5 km).
The third recognised Norwegian impact crater is the famous 40-km-diameter Mjølnir Crater, which is one of the best-preserved marine impact craters on Earth. I mentioned this crater in a post.
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http://www.cprm.gov.br/33IGC/1338980.html
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http://www.npd.no/English/Aktuelt/Nyheter/2008_12_14_En+geologisk+sjokkhistorie_NS.htm
In Norwegian:
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http://www.forskning.no/artikler/2009/juni/221868
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http://www.forskningsradet.no/no/Nyheter/Norsk+meteorittkrater+under+lupen/1240958498001?kilde=n
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http://www.ritlandcrater.org/Ritland.html
WIDGETIZE