Rock Elm - Hypervelocity Impact Crater

Alternate Names
Local Language
Coordinates 44° 42' 42" N; 92° 14' 3" W
Notes
  1. SW part of state in town of Rock Elm, Pierce County.
Country United States of America
Region Wisconsin
Date Confirmed 2004
Notes
  1. Confirmed based on PDF's and multiple orientations of PF's observed in quartz grains from sandstone (French et al., 2004).
Buried? No
Drilled? No
Target Type Sedimentary
Notes
  1. Rock Elm shale and Washington Road sandstone are local facies of the St. Peter Sandstone within the crater (Cordua, 1987). Shallow marine.
Sub-Type Sandstone, Shale
Apparent Crater Diameter (km) 6.5 km
Age (Ma) 458 - 485
Notes :
  1. 458-485 Ma based on stratigraphic age constraints (Cordua, 1985) (French et al., 2004). Middle Ordovician is a minimum age based on palaeontological studies and by estimating sedimentation rates for the region (French et al., 2004).

Method :
  1. Stratigraphy
Impactor Type Unknown

Advanced Data Fields

Notes

Erosion
7
Final Rim Diameter
Unknown
Apparent Rim Diameter
6.5 km
  1. 6.5 km (French et al., 2004). Characteristic structural morphology (Cordua, 1987).
Rim Reliability Index
1
  1. Central uplift is ~1 x 2 km; oldest rocks in centre raised 250–300 m above their normal stratigraphic position (French et al., 2004).
Crater Morphology
Complex
Central Uplift Diameter
1-2km
Central Uplift Height
Unknown
Uplift Reliability Index
3
Structural Uplift
300 m
Thickness of Seds
Target Age
Palaeozoic
Marine
No
Impactor Type
Other Shock Metamorphism
Reidite, shock-twinned zircon, and FRIGN zircon
  1. Reidite and shock-twinned zircon found in polymict sandstone breccia. (Cavosie et al., 2015)
Shatter Cones
No
  1. None observed. Absence of observed shatter cones may be due poor/lack of outcrops and may not be distinctive in coarse grained sandstone (French et al., 2004).
Planar Fractures
Yes
  1. Multiple orientations of PFs with feather features and apparent incipient planar deformation features in quartz grains; occur in sets of 2-3 per quartz grain (French et al., 2004) (Cavosie et al., 2013).
Planar Deformation Features
Yes
  1. PDF in quartz with shock pressure estimated between ~5 to <10 GPa; occur in sets of 2-3 per quartz grain (French et al., 2004).
Diaplectic Glass
No
Coesite
No
Stisovite
No
Crater Fill
LB
  1. A drill core taken in 1987 north of the central uplift intersected 60 m of a breccia with a sandy matrix and large clasts of of Early Paleozoic sedimentary rocks (French et al., 2004). Breccia observed in central dome only as float fragments (Cordua, 1987).
Proximal Ejecta
Distal Ejecta
Dykes
Volume of Melt
Depth of Melting

References

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

M L Barnes, G L Osborn, L S Chan, A B Dickas, B A Brown (1992) An integrated gravity and magnetic survey of the Rock Elm structure, western Wisconsin, Proceedings and Abstracts - Institute on Lake Superior Geology. Meeting 38, Part 1, p. 6-7, Institute on Lake Superior Geology, Eau Claire, WI, url

B M French, W S Cordua (1999) Intense fracturing of quartz at the Rock Elm (Wisconsin) "cryptoexplosion" structure: Evidence for meteorite impact, Abstracts of Papers Submitted to the Lunar and Planetary Science Conference 30, p. abstr. no. 1123, Lunar and Planetary Science Conference, Houston, TX, url

C W Peters, M D Middleton, W S Cordua (2002) The paleontology of the Rock Elm disturbance: Pierce county, Wisconsin, Abstracts with Programs - Geological Society of America 34(2), p. 95, Geological Society of America (GSA), Boulder, CO, url

J B Plescia (2002) Gravity survey of the Rock Elm, Wisconsin structure, Abstracts of Papers Submitted to the Lunar and Planetary Science Conference 33, p. Abstract 1573, Lunar and Planetary Science Conference, Houston, TX, url

N R Rossman, J L B Anderson (2008) The Rock Elm impact structure: Morphometry of the southern fault block from seismic refraction surveys, Abstracts of Papers Submitted to the Lunar and Planetary Science Conference 39, p. Abstract 1112, Lunar and Planetary Science Conference, Houston, TX, url

W S Cordua (2008) The Rock Elm impact structure, Wisconsin: Recent findings and relevance to the local non-geologic community, International Geological Congress, Abstracts = Congres Geologique International, Resumes 33, p. Abstract 1284963, [International Geological Congress], [location varies], url

J R Dierauer, J L B Anderson (2009) Geophysical exploration of the southern fault block of the Rock Elm impact crater in Pierce County, WI, Abstracts with Programs - Geological Society of America 41(4), p. 51, Geological Society of America (GSA), Boulder, CO, url

R McKay, H Liu, B J Witzke, B M French, D E G Briggs (2011) Preservation of the Middle Ordovician Winneshiek Shale in a probable impact crater, Abstracts with Programs - Geological Society of America 43(5), p. 189, Geological Society of America (GSA), Boulder, CO, url

J L B Anderson, W L Beatty, C L Kairies Beatty, H A S Dolliver (2011) Interdisciplinary investigation of crater-related deposits in the upper Midwest using GigaPan technologies, Abstracts with Programs - Geological Society of America 43(5), p. 623, Geological Society of America (GSA), Boulder, CO, url

A M Stickle, P H Schultz (2011) Investigating pressure magnitudes at depth for oblique impacts into layered targets: Applications to impacts into sedimentary targets, Meteoritics & Planetary Science 46, SUPPL., p. 1, Meteoritical Society, Fayetteville, AR, url, doi:http://dx.doi.org/10.1111/j.1945-5100.2011.01241.x

C I Roig, A J Cavosie, D J McDougal, W S Cordua, C Mattson (2013) Detrital shocked quartz in modern sediments eroded from the Rock Elm impact structure, Wisconsin, USA, Abstracts of Papers Submitted to the Lunar and Planetary Science Conference 44, p. Abstract 2685, Lunar and Planetary Science Conference, Houston, TX, pdf

C I Roig, A J Cavosie (2013) A search for detrital shocked zircons from the Rock Elm impact structure in Wisconsin, USA, Abstracts with Programs - Geological Society of America 45(2), p. 61, Geological Society of America (GSA), Boulder, CO, url

A J Cavosie, C I Roig, D J McDougal, T Ushikubo, M J Spicuzza, J Fournelle, J W Valley, W S Cordua, C Mattson (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), Abstracts of Papers Submitted to the Lunar and Planetary Science Conference 44, p. Abstract 2028, Lunar and Planetary Science Conference, Houston, TX, pdf

C M Slowinski, M M Navis, C L Kairies Beatty, W L Beatty, J L B Anderson, H A S Dolliver (2013) Rock Elm Crater, Pierce County, WI: Stratigraphy of a recently exposed central peak outcrop and characterization of soils, Abstracts of Papers Submitted to the Lunar and Planetary Science Conference 44, p. Abstract 2700, Lunar and Planetary Science Conference, Houston, TX, pdf

A J Cavosie, T M Erickson, N Timms (2014) Reidite and shock-twinned zircon in polymict breccia from the Ordovician Rock Elm impact structure, USA, Abstracts with Programs - Geological Society of America 46(6), p. 706, Geological Society of America (GSA), Boulder, CO, url

A Arana-Morales, A J Cavosie (2014) A study of shocked quartz in breccia from the Rock Elm impact structure, Abstracts of Papers Submitted to the Lunar and Planetary Science Conference 45, p. Abstract 2185, Lunar and Planetary Science Conference, Houston, TX, pdf

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