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The Mid-Ordovician Osmussaar Breccia in Estonia linked to the disruption of the L-chondrite parent body in the asteroid belt

Carl Alwmark, Birger Schmitz and Kalle Kirsimae
The Mid-Ordovician Osmussaar Breccia in Estonia linked to the disruption of the L-chondrite parent body in the asteroid belt
Geological Society of America Bulletin (July 2010) 122 (7-8): 1039-1046

Abstract

The Middle Ordovician (466 Ma) Osmussaar breccia, situated along the northwestern coast of Estonia, is rich in angular chromite grains of extraterrestrial origin (>13 grains kg (super -1) ) and shocked quartz. The angularity of the chromite grains implies that they have not been transported or reworked to any large extent, connoting that the brecciation is the result of a contemporary impactor, either as a direct consequence of the impact or as a result of an earthquake triggered by the impact, and thus is not, as previously suggested, redeposited material from the nearby approximately 70 m.y. older Neugrund impact structure. The chemical composition of the chromite indicates that the impactor was an ordinary chondrite of L-type, which concurs well with the hypothesis that the influx of large bodies to Earth increased during this period due to the breakup of the L-chondrite parent body. This in turn gives support to the recent suggestion that abundant coeval megabreccias worldwide are impact triggered. The presence of extraterrestrial chromite also strengthens the theory that physical pieces of a large celestial body can survive upon impact with Earth.


ISSN: 0016-7606
EISSN: 1943-2674
Coden: BUGMAF
Serial Title: Geological Society of America Bulletin
Serial Volume: 122
Serial Issue: 7-8
Title: The Mid-Ordovician Osmussaar Breccia in Estonia linked to the disruption of the L-chondrite parent body in the asteroid belt
Affiliation: University of Lund, Department of Geology, Lund, Sweden
Pages: 1039-1046
Published: 201007
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 31
Accession Number: 2010-050184
Categories: StratigraphySedimentary petrology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: With GSA Data Repository Item 2010017
Illustration Description: illus. incl. strat. cols., 2 tables, geol. sketch map
N59°15'00" - N59°15'00", E23°19'60" - E23°19'60"
Secondary Affiliation: University of Tartu, EST, Estonia
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201027
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