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The Ordovician meteor event was a dramatic increase in the rate at which
L chondrite
The L type ordinary chondrites are the second most common group of meteorites, accounting for approximately 35% of all those catalogued, and 40% of the ordinary chondrites. The ordinary chondrites are thought to have originated from three parent a ...
meteorites fell to Earth during the
Middle Ordovician
The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start of the Silurian Period Mya.
The ...
period, about 467.5±0.28 million years ago.
This is indicated by abundant fossil L chondrite meteorites in a quarry in Sweden and enhanced concentrations of ordinary chondritic
chromite
Chromite is a crystalline mineral composed primarily of iron(II) oxide and chromium(III) oxide compounds. It can be represented by the chemical formula of FeCr2O4. It is an oxide mineral belonging to the spinel group. The element magnesium can s ...
grains in sedimentary rocks from this time.
This temporary increase in the impact rate was most likely caused by the destruction of the L chondrite parent body 468 ± 0.3 million years ago having scattered fragments into Earth-crossing orbits, a chronology which is also supported by shock ages in numerous L chondrite meteorites that fall to Earth today.
It has been speculated that this influx contributed to, or possibly even instigated, the
Great Ordovician Biodiversification Event
The Great Ordovician Biodiversification Event (GOBE), was an evolutionary radiation of animal life throughout the Ordovician period, 40 million years after the Cambrian explosion, whereby the distinctive Cambrian fauna fizzled out to be replaced wi ...
, although this has been questioned.
[An extraterrestrial trigger for the mid-Ordovician ice age: Dust from the breakup of the L-chondrite parent body](_blank)
Birger Schmitz
Birger is a Scandinavian name from Old Norse, ''bjarga'', meaning "to help, to save, to protect". It is widely used in Norway as Birger but also as Børge. The Swedish variant of ''Birger'' would soon evolve into ''Börje'', however, the prior form ...
et al, AAAS Science Advances
''Science Advances'' is a peer-reviewed multidisciplinary open-access scientific journal established in early 2015 and published by the American Association for the Advancement of Science. The journal's scope includes all areas of science, incl ...
, 18 Sep 2019: Vol. 5, no. 9, eaax4184; DOI: 10.1126/sciadv.aax4184, accessed 2019-10-09
Possible craters
See also
*
Österplana 065
Österplana 065 (Öst 65) is an Ordovician fossil meteorite found in the Thorsberg quarry in Sweden on June 26, 2011, and scientifically described in 2016. Measuring 8×6.5×2 cm, it impacted the Earth 470 million years ago, during the Ordovician ...
*
Late Ordovician
The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start of the Silurian Period Mya.
The ...
impact craters
**
Lockne crater
Lockne is a meteorite crater, located approximately south of the city of Östersund in northern Sweden. It has been suggested that it is a doublet with the nearby smaller Målingen Crater, apart.Raul Rincon (2014BBC News: "Ancient Earth hammere ...
**
Målingen crater
Målingen was confirmed as an impact crater in 2014. It is located near the city of Östersund in northern Sweden. It is "probable" that it formed simultaneously with the nearby Lockne crater.Raul Rincon (2014)BBC News: "Ancient Earth hammered by ...
**
Pilot crater
Pilot crater is an impact crater in the Northwest Territories, Canada, just north of the Alberta border and near Fort Smith . It is in diameter and the age is estimated to be 445 ± 2 million years (Upper Ordovician).
The crater contains ...
**
Tvären Tvären is a circular bay close to Studsvik, Sweden.
Within the bay is an ancient buried impact crater about 2 km in diameter. It was first identified using reflection seismology. The crater is estimated to be about 455 million years old (L ...
References
{{Impact cratering on Earth
Meteor
A meteoroid () is a small rocky or metallic body in outer space.
Meteoroids are defined as objects significantly smaller than asteroids, ranging in size from grains to objects up to a meter wide. Objects smaller than this are classified as micr ...
Meteor
A meteoroid () is a small rocky or metallic body in outer space.
Meteoroids are defined as objects significantly smaller than asteroids, ranging in size from grains to objects up to a meter wide. Objects smaller than this are classified as micr ...
Meteor
A meteoroid () is a small rocky or metallic body in outer space.
Meteoroids are defined as objects significantly smaller than asteroids, ranging in size from grains to objects up to a meter wide. Objects smaller than this are classified as micr ...
Meteor
A meteoroid () is a small rocky or metallic body in outer space.
Meteoroids are defined as objects significantly smaller than asteroids, ranging in size from grains to objects up to a meter wide. Objects smaller than this are classified as micr ...
Meteor
A meteoroid () is a small rocky or metallic body in outer space.
Meteoroids are defined as objects significantly smaller than asteroids, ranging in size from grains to objects up to a meter wide. Objects smaller than this are classified as micr ...
Meteor
A meteoroid () is a small rocky or metallic body in outer space.
Meteoroids are defined as objects significantly smaller than asteroids, ranging in size from grains to objects up to a meter wide. Objects smaller than this are classified as micr ...
Impact craters of Canada
Impact craters of Sweden
Impact craters of the United States