Preliminary results of the U.S. Geological Survey-Iowa Department of Natural Resources Geological Survey Bureau Manson Core Drilling Project

Raymond R. Anderson; Jack B. Hartung; Brian J. Witzke; Eugene Merle Shoemaker; David J. Roddy

doi:10.1130/SPE293-p237

Preliminary results of the U.S. Geological Survey-Iowa Department of Natural Resources Geological Survey Bureau Manson Core Drilling Project

Special Papers of the Geological Society of America

By: Raymond R. Anderson, Jack B. Hartung, Brian J. Witzke, Eugene Merle Shoemaker, and David J. Roddy

Edited by: B. O. Dressler, R. A. F. Grieve, and Virgil L. Sharpton

https://doi.org/10.1130/SPE293-p237

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Abstract

The U.S. Geological Survey and Iowa Department of Natural Resources Geological Survey Bureau completed, in 1992, a two-year core drilling program in the Manson Impact Structure, a 35-km-diameter, Cretaceous-Tertiary boundary-age feature located in north-central Iowa. A total of 12 cores sampled in excess of 1,200 m (4,000 ft) of crater rocks, supplementing the two previously drilled shallow cores from the structure. The cores penetrated the three major terranes in the Manson Impact Structure, the terrace terrane, crater moat, and central peak. Preliminary interpretations identified several important impact-related lithologies in these cores. The most widespread is sedimentary clast breccia, a postimpact polymictic breccia or mixtite that mantles at least part of all crater terranes. Two types of crystalline clast breccias were cored on the central peak, one with a melt matrix, the other with a matrix dominated by silt- to sand-sized grains. Large blocks of basement gneiss that formed the interior of the central peak were encountered in several cores. Within the terrace terrane, structurally preserved Cretaceous strata and an overturned ejecta flap of Proterozoic and Paleozoic sedimentary rocks were encountered. Only sedimentary clast breccia was encountered in the crater moat. The preliminary investigation of these cores has provided significant information on the geometry and history of the Manson Impact Structure, but it has also prompted many more questions.

Suggested Citation

Anderson, R., Hartung, J.B., Witzke, B.J., Shoemaker, E.M., Roddy, D.J., 1994, Preliminary results of the U.S. Geological Survey-Iowa Department of Natural Resources Geological Survey Bureau Manson Core Drilling Project, chap. of Large meteorite impacts and planetary evolution: Special Papers of the Geological Society of America, v. 293, p. 237-247, https://doi.org/10.1130/SPE293-p237.

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Additional publication details
Publication type	Book chapter
Publication Subtype	Book Chapter
Title	Preliminary results of the U.S. Geological Survey-Iowa Department of Natural Resources Geological Survey Bureau Manson Core Drilling Project
Series title	Special Papers of the Geological Society of America
DOI	10.1130/SPE293-p237
Volume	293
Publication Date	January 01, 1992
Year Published	1994
Language	English
Publisher	Geological Society of America
Description	11 p.
Larger Work Type	Book
Larger Work Subtype	Monograph
Larger Work Title	Large meteorite impacts and planetary evolution
First page	237
Last page	247
Country	United States
State	Iowa
Other Geospatial	Manson impact structure