Manson impact structure, Iowa: First geochemical results for drill core M-1

Koeberl, Christian; Anderson, Raymond R.; Hartung, Jack B.; Reimold, Wolf Uwe

The Manson Impact Structure is a large complex impact crater centered ca. S km north of the town of Manson, Iowa. It is the largest intact impact structure recognized in the United States (35 km in diameter). Its Ar-40/Ar-39 age is indistinguishable from that of the Cretaceous-Tertiary (K-T) boundary. The Manson structure may be one element of the events at the K-T boundary. The crater is completely covered by Quaternary glacial sedimentary deposits that are normally underlain by Cretaceous clastic sediments and flat-lying carbonate sediments of Phanerozoic age, as well as Proterozoic red clastic, metamorphic, volcanic, and plutonic rock sequences. The study of a reflection seismic profile, provided by Amoco, was critical in interpreting the structure. In the 35 km diameter zone that marks the extension of the crater the normal rock sequence is disturbed due to the impact, and at the center of the structure granitic basement rocks are present that have been uplifted from about 4 km depth. Our studies consist of detailed petrological and geochemical characterization of all cores, with emphasis on a detailed description of all rock types found in the core samples and their relationship to target rocks. Geochemical data on samples from the Manson M-1 core are presented.

Document ID

19940011849

Acquisition Source

Legacy CDMS

Document Type

Conference Paper

Authors

Date Acquired

September 6, 2013

Publication Date

January 1, 1993

Publication Information

Publication: Lunar and Planetary Inst., Twenty-Fourth Lunar and Planetary Science Conference. Part 2: G-M

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Accession Number

94N16322

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Public

Work of the US Gov. Public Use Permitted.

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