IMPACT CRATER EXPLORATIONS
by: Charles O'Dale
LAC LA MOINERIE IMPACT CRATER
Lac La Moinerie, a highly eroded complex meteorite crater, is visible just to the left of center in the above landsat image (Courtesy NASA/LPI). The structure was visited by D.P. Gold (Pennsylvania State University), who discovered impact breccia float on the northern shoreline (Grieve 2006). The central islands in the lake are thought to be the remains of the crater’s central peak. There is a gravity low coincident with the basin area of the crater but is distorted considerably by the presence of a strong regional gradient. The amplitude of this gravity low, estimated to be about 5 mgal, is a value consistent with other impact sites of similar size. Granophyre breccia has been recovered from the crater area (Gold et al., 1978).
|We approached Lac La Moinerie from the south after our exploration of the Mistastin Crater. Fuel constraints would only allow us a relatively short time for observation. The sequence of this series of images was taken counter-clockwise from the south, from the east and from the north east of the crater respectively. Eons of erosion has taken its toll on this crater as all that appears to remain of the original structure is a circular water filled hole in the bedrock. It would be very difficult to recognize the structure as an impact site without pre-knowledge of the studies done here.|
Side NoteClear Lakes Meteorite Craters. Note the esker visible on the right (west) part of the circular lake. This “might” indicate a shallow part of the lake caused by a rim structure.
Bottomley, R. J., York, D. and Grieve,R.A.F., 40Argon-39Argon dating of impact craters. Proceedings Lunar and Planetary Science Conference 20th, pp. 421-431. 1990.
Gold, D. P., Tanner, J.G. and Halliday,D.W., The Lac La Moinerie crater: A probable impact site in New Quebec (abstract). Geological Society of America, v. 10, p. 44. 1978.
Grieve, R.A.F., Impact Structures in Canada. Geological Association of Canada, 2006.