United States Meteorite Impact Craters

Rock Elm crater, Wisconsin

The partially exposed Rock Elm crater, located in Wisconsin, is listed in the Earth Impact Database as a 6 km struture that is preserved in sedimentary rock and dates from the Ordivician period or more recent. According to an article in the March 2004 issue of Geotimes, the structure was first recorded as a disturbance during geologic mapping work in 1942.

Evidence of Impact Origin

The impact origin of each location listed on this website has been supported by unambiguous diagnostic evidence of hypervelocity impact that has been reported in a scientific (usually peer reviewed) context. Without such evidence, a geological structure is not a confirmed impact crater. This section, which is included for each crater on this website, is not an exhaustive list of such published evidence, but is meant to demonstrate that appropriate work has been done for each listing.

Bevan M. French, William S. Cordua and J.B. Plescia, The Rock Elm meteorite impact structure, Wisconsin: Geology and shock-metamorphic effects in quartz Geological Society of America Bulletin, January/February, 2004, v. 116, no. 1-2, p. 200-218.

Taken individually, the lines of evidence for an impact origin for the Rock Elm structure are somewhat ambiguous. Considered together, however, the morphological and petrologic evidence is compelling. This is summarized in the above article. Notably, no clear PDFs or shatter cones have been recovered at this site (so far as I have been able to find in publications).

Nature of diagnostic evidence:

multiple orientations of PFs with feather features and apparent incipient planar deformation features in quartz grains.
high pressure mineral, reidite

Other significant evidence: breccia, feather features on PFs in quartz, planar fractures (in 1 to 4 orientations, Cavosie et al., 2013), characteristic structural morphology (Cordua, 1987).

Bibliography and References:

(If links to articles don't work, don't give up. Try pasting the link shown into a search engine or searching for the article authors, title, or other reference information. If your research leads you to additional scientific references related to this crater, please help improve this resource by sending a note with the new citation(s) to: )

Arana-Morales, A. and Cavosie, A. J. (2014) A study of shocked quartz in breccia from the Rock Elm impact structure (abstract #2185). Abstracts of the 45th Lunar and Planetary Science Conference,

Cavosie, A. J., Erickson, T. M., and Timms, N. (2014) Reidite and shock-twinned zircon in polymict breccia from the Ordovician Rock Elm impact structure, USA (abstract). Geological Society of America Annual Meeting, Abstracts with Programs, volume 46, number 6.

Cavosie, A. J., Erickson, T. M., and Timms, N. E. (2015) Nanoscale records of ancient shock deformation: Reidite (ZrSiO4) in sandstone at the Ordovician Rock Elm impact crater, Geology, volume 43, number 4, p. 315–318. doi: 10.1130/G36489.1

Cavosie, A. J., Roig, C. I., McDougal, D. J., Ushikubo, T., Spicuzza, M. J., Fournelle, J., Valley, J. W., Cordua, W. S., Mattson, C. (2013) The Sedimentary Record of a Small, Deeply Eroded Impact Structure: A Search for Detrital Shocked Minerals and Extraterrestrial Chromites in Sediments Eroded from the Ordovician Rock Elm Impact Structure (USA) (abstract #2028), Abstracts of the 44th Lunar and Planetary Science Conference,

Cordua, W. S. (1983) An Ordovician cryptoexplosion structure from near Rock Elm, Pierce County, Wisconsin (abstract), in Bornhorst, T. J., and Diehl, J. F., 29th annual institute on Lake Superior geology, Proceedings: Annual Institute on Lake Superior Geology, v. 29, p. 8-9.

no link found

Cordua, W. S. (1985) The Rock Elm Structure, Pierce County, Wisconsin, a possible cryptoexplosion structure, Geology, volume 13, number 5, pp. 372-374. doi: 10.1130/0091-7613(1985)13<372:RESPCW>2.0.CO;2

Cordua, W. S. (1985) Comment and Reply on “Rock Elm structure, Pierce County, Wisconsin: A possible cryptoexplosion structure”: Reply.Geology, volume 13, number 12, p. 891-892, doi:10.1130/0091-7613(1985)13<891:CARORB>2.0.CO;2

Cordua, W. S. (1987) "The Rock Elm Disturbance, Pierce County, Wisconsin" (field trip guide), in Field Trip Guidebook for the Upper Mississippi Valley Minnesota, Iowa, and Wisconsin, Balaban, N. H. (editor), Minnesota Geological Survey Guidebook Series #15, p. 123-152.

Cordua, W. S. (2008) The Rock Elm Impact Structure: Recent Findings and Relevance to the Local Non-Geologic Community (abstract). Abstracts presented at the 33rd International Geological Congress.

Cordua, W.S., Evans, T.J. (2007) Geology of the Rock Elm Complex, Pierce County, Wisconsin (map, 1:12,000 scale). Wisconsin Geological and Natural History Survey Open-File Report 2007-02.

Crane, K. W. (or Crain, K. W. ?) (1986) A preliminary study of the Washington Road sandstone of the Rock Elm structure: Unpublished Master's thesis, University of Wisconsin-River Falls.

referenced in Cordua, 1987 - no link found

Evans, T. J., Cordua, W. S., and LePain, D. L. (2007) Preliminary geology of the buried bedrock surface, Pierce County, Wisconsin (map). Wisconsin Geological and Natural History Survey, Open File Report 2007–08, 1:100,000 scale.

French, B. M. and Cordua, W. S. (1999) Intense fracturing of quartz at the Rock Elm (Wisconsin) "cryptoexplosion" structure: evidence for meteorite impact (abstract #1123), Abstracts of the 30th Annual Lunar and Planetary Science Conference.

French, B. M., Cordua, W. S., and Plescia, J. B. (2004) The Rock Elm meteorite impact structure, Wisconsin: Geology and shock-metamorphic effects in quartz, Geological Society of America Bulletin, volume 116, number 1-2, pp. 200-218. doi: 10.1130/B25207.1

Ladd, J., (1985) Geologic map of the Rock Elm area. Tucson, unpublished map made for the Minerals Division of the Superior Oil Company, 2 sheets.

referenced in Cordua, 1987, no link found.

Plescia, J. B. (2002) Gravity Survey of the Rock Elm, Wisconsin Structure (abstract #1573). Abstracts of the 33rd Lunar and Planetary Science Conference.

Read, W., 1985, Comment and Reply on “Rock Elm structure, Pierce County, Wisconsin: A possible cryptoexplosion structure”: Comment. Geology, volume 13, issue 12, p. 891, doi:10.1130/0091-7613(1985)13<891:CARORA>2.0.CO;2

Roig, C. I. and Cavosie, A. J., (2013) A search for detrital shocked zircons from the Rock Elm impact structure in Wisconsin, USA (abstract). Abstracts of the Southeastern Section 62nd Annual Meeting of the Geological Society of America, Abstracts with Programs, volume 45, number 2, p.61.

Roig, C. I., Cavosie, A. J., McDougal, D. J., Cordua, W. S., and Mattson, C. (2013) Detrital shocked quartz in modern sediments eroded from the Rock Elm impact structure, Wisconsin, USA (abstract #2685). Abstracts of the 44th Lunar and Planetary Science Conference.

Rossman, N. R. and Anderson, J. L. B. (2008) The Rock Elm Impact Structure: Morphometry of the Southern Fault Block from Seismic Refraction Surveys (abstract #1112). Abstracts of the 39th Lunar and Planetary Science Conference.

Ruenger, C. E. (1986) An aeromagnetic study of the Rock Elm Structure, Pierce County, Wisconsin. University of Wisconsin-Oshkosh.

no link found

Ruenger, C. (1986) An aeromagnetic study of the Rock Elm structure, Pierce County, Wisconsin (abstract), Institute on Lake Superior Geology, 32nd Annual Meeting, Wisconsin Rapids, Wisconsin, Proceedings and Abstracts, p. 70.

no link found - referenced in Cordua, 1987

Viridis, M. and Cavosie, A. J. (2015) The origin of detrital shocked quartz grains from the central uplift of the Rock Elm impact structure, Wisconsin, USA (abstract). Abstracts of the 2015 GSA Annual Meeting, Geological Society of America Abstracts with Programs. Vol. 47, No. 7, p.436.