Glasford - Hypervelocity Impact Crater

Alternate Names
Local Language
Coordinates 40° 36' 8" N; 89° 47' 6" W
Notes
  1. 16 km WSW of Peoria, Illinois.
Country United States of America
Region Illinois
Date Confirmed 1986
Notes
  1. Confirmed by shatter cone fragments, breccias, and strain lamellae/planar microfractures/percussion features in quartz grains (McHone et al., 1986).
Buried? Yes
Notes
  1. Buried by 350 m of Palaeozoic rocks (Ordovician to Carboniferous) and Quaternary sediments (Monson et al., 2019) and references therein.
Drilled? Yes
Notes
  1. Drilled for coal exploration and gas storage. Cowser well No. 1 reached 8/9 m at center of structure and yielded excellent core recovery.
Target Type Sedimentary
Notes
  1. (Monson et al., 2019) infer that this event occured on a marine environment, based on sedimentology of crater-fill deposits. Shales, sandstones and dolomites of Cambrian to Ordovician age.
Sub-Type Dolomite, Sandstone, Shale
Apparent Crater Diameter (km) 4 km
Age (Ma) 453 - 457
Notes :
  1. 453-457 Ma based on stratigraphic age constraints (Monson et al., 2019). The impact affected Upper Ordovician strata but not Silurian (Buschbach and Ryan, 1963). Previous age constraints: Early Cincinnatian (i.e., Late Ordovician; (Buschbach and Ryan, 1963) ~470 to 485 Ma (i.e., Early Ordovician; (Schmieder et al., 2015) <430 Ma (i.e., Silurian or younger; (Hodge, 1994)

Method :
  1. Stratigraphy
Impactor Type Unknown

Advanced Data Fields

Notes

Erosion
5
  1. Crater-fill deposits described by (Monson et al., 2019).
Final Rim Diameter
Unknown
Apparent Rim Diameter
4 km
  1. This estimate was obtained from a gravity survey from (Buschbach and Ryan, 1963) (McHone et al., 1986) (Monson et al., 2019).
Rim Reliability Index
2
  1. A central dome-shape uplift with 500 m of breccia in the core of the structure; Eau Claire Formation elevated some 240–300 m above their usual stratigraphic level (Buschbach and Ryan, 1963).
Crater Morphology
Complex
Central Uplift Diameter
0.9km
Central Uplift Height
Unknown
Uplift Reliability Index
4
Structural Uplift
300 m
Thickness of Seds
Target Age
Palaeozoic
Marine
Yes
Impactor Type
Other Shock Metamorphism
No
Shatter Cones
Yes
  1. Shatter cones (rare but well-developed) occur in fractured blocks of massive brittle dolomite and also as dolomite clasts within breccia veins (McHone et al., 1986). (Monson et al., 2019) reports <2cm shatter cones identified in the Cowser #1 core.
Planar Fractures
No
Planar Deformation Features
No
  1. No PDF reported. (Monson et al., 2019) shows possible PDFs but suggests a follow up on this.
Diaplectic Glass
No
Coesite
No
Stisovite
No
Crater Fill
LB
  1. The crater-fill deposits are grouped into the Kingston Mines Unit. Overlying parautochthonous basement breccias, a layer of allochthonous polymict, lithic and matrix-supported breccias is observed and interpreted to be a resurge deposit. On top of this lithic breccia, the Sandy Dolomite Interval (SDI) is observed: sandy dolomites with clasts that represent mass-flows (lower part) and sandstones, sandy dolomites and dolomitic sandstones that represent density currents (upper part), consistent with debris flows. Possible PFs and PDFs are observed in the SDI. The Dolomite-Limestone Interval (DLI) overlies the SDI, is composed of silty dolomites and represents suspension depositional processes, and the Dolomictic Shale Interval (DSI) overlies the DLI and represents the return to regular sedimentation conditions (Monson et al., 2019).
Proximal Ejecta
Distal Ejecta
Dykes
Volume of Melt
Depth of Melting

References

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T C Buschbach, R Ryan (1963) Glasford (Illinois) cryptoexplosion structure, Special Paper - Geological Society of America, p. 126, Geological Society of America (GSA), Boulder, CO

T C Buschbach, R Ryan (1963) Ordovician explosion structure at Glasford, Illinois, Bulletin of the American Association of Petroleum Geologists 47(12), p. 2011-2015, American Association of Petroleum Geologists, Tulsa, OK, pdf, doi:http://dx.doi.org/10.1306/BC743B8D-16BE-11D7-8645000102C1865D

J F McHone, M L Sargent, W J Nelson (1987) Shatter cones in Illinois: Evidence for meteoritic impacts at Glasford and Des Plaines, NASA Technical Memorandum 89810, p. 438, National Aeronautics and Space Administration (NASA), Washington, DC, url

M L Sargent, J F Jr McHone (1988) Glasford meteorite-impact structure exhibits positive gravity anomaly and post-impact uplift, Eos, Transactions, American Geophysical Union 69(44), p. 1292, American Geophysical Union, Washington, DC

G Cheng, S Marshak, C C Monson, D E Sweet, B Segvic, C C Lundstrom (2018) Mesoscopic and microscopic deformation in the Glasford meteorite impact structure, Illinois: Impact fracking in carbonate bedrock, Geological Society of America Annual Meeting, url, doi:10.1130/abs/2018AM-320099

C C Monson, D E Sweet, B Segvic, G Zanoni, K Balling, J M Wittmer, G R Ganis, G Cheng (2019) The Late Ordovician (Sandbian) Glasford structure: A marine‐target impact crater with a possible connection to the Ordovician meteorite event, Meteoritics & Planetary Science 54(12), url, doi:10.1111/maps.13401