PRELIMINARY CLAY-MINERAL INVESTIGATION OF SOME IMPACTITIES RECOVERED BY CORE DRILLING IN THE MANSON IMPACT STRUCTURE

by
M.C. Jones, G.R. McCormick, and R.R. Anderson

The Geological Society of America
Special Paper 302, 1996, p. 341-346
The Manson Impact Structure, Iowa: Anatomy of an impact crater
C. Koeberl and R.R. Anderson, eds.

ABSTRACT


Sixteen samples of Phanerozoic-clast breccia, Keweenawan shale-clast breccia, and impact melt breccia were obtained from eight different drill cores from the Manson impact structure. The Phanerozoic-clast breccia contains large clasts of Cretaceous marine shale and mudstone composed of kaolinite and illite in a matrix of kaolinite and illite with a trace of chlorite. The Keweenawan shale-clast breccia is dominated by clasts of Proterozoic black shale and mudstone composed of chlorite and illite in a matrix of smectite with lesser amounts of illite, chlorite, and kaolinite. The clasts in the impact melt breccia are composed of illite and a small amount of kaolinite. The clasts in the Phanerozoic-clast breccia may represent kaolin-rich Cretaceous clays (Parham, 1970) that have migrated westward from Minnesota. The clasts in the Keweenawan shale-clast breccia are most likely Keweenawan shales as reported from the Eischeid well by Pollastro and Finn (1990).


REFERENCES:

Parham, W.E., 1970, Clay mineralogy and geology of Minnesota's kaolin clays: Minnesota Geological Survey Special Publication Series SP-10, 142. p.

Pollastro, R.M., and Finn, T.M., 1990, Clay mineralogy and bulk rock composition of selected core and cutting samples from the Amoco Eischeid #1 well, Carroll County, Iowa - A reconnaissance study from X-ray powder diffraction analysis, in Anderson, R.R., ed., The Amoco M.G. Eischeid #1 Deep Petroleum Test, Carroll County, Iowa, preliminary investigations: Iowa Department of Natural Resources, Geological Survey Bureau, Special Report Series No. 2, p. 143-152.