IMPACT CRATER EXPLORATIONS
by: Charles O'Dale
ELBOW IMPACT STRUCTURE
Possible link to the Late Devonian Extinction
The Elbow impact structure in south-central Saskatchewan, is just north of the village of Riverhurst and south of the town of Elbow (north of Diefenbaker lake). It is 8 kilometers (5.0 mi) in diameter and the impact occurred between 370 to 420 million years ago during the Devonian Period.
The red dot represents the approximate area of the Elbow impact 395 million years ago in the Devonian Period.
Ground zero of the Elbow impact structure is imaged under the wing of GO ZooM
. The superimposed circle illustrates the position of the 8 km diameter buried crater. Lake Diefenbaker is in the background.
The Elbow structure was discovered during a search for oil. It consists of a symmetrical dome in Mesozoic rocks beneath which reposes a cylindrical mass of broken Paleozoic rock. There is evidence of some broken rock having been displaced stratigraphically upward by violent movement, possibly explosive in nature. The structure is marked by a positive gravity anomaly which reflects the upward displacement of the disturbed mass and the dome formed in Mesozoic strata.
The position of the Elbow impact structure is illustrated by the superimposed circle in the background. The Gardiner Dam, under the wing of GO ZooM
, is the largest embankment dam in Canada and one of the largest embankment dams in the world. Lake Diefenbaker is upstream. The dam rises 64 metres (209 feet) in height, is almost 5 km (3.1 mi) long and has a width of 1.5 km (0.93 mi) at its base with a volume of 65,000,000 cubic meters.
The structure apparently experienced two periods of activity. The first was post-Mississippian in age and explosive in nature; the other, probably Tertiary in age and non-violent, resulted in the uplift of the Mesozoic and Tertiary strata to form a dome. The nature of the second movement is unknown but it is believed to be related to the Laramide orogeny (DeMille 1960).
The Elbow complex structure is centered at 106°45’ W and 49°51’N in west Saskatchewan. The rim-to-rim diameter is approximately 8 km with a central uplift surrounded by an annular depression on the seismic profiles [Grieve et al., 1998; Sawatzky, 1977]. These structural anomalies were first noticed by DeMille  from the seismic images, and the impact origin was not emphasized until 1998 when the PDFs were detected in the well cuttings. However, only limited materials are currently available to discuss the impact origin of the structure. (Wei Xie, 2014 )
Demille, G., The Elbow structure of south-central Saskatchewan. Journal of the Alberta Society of Petroleum Geologists, v 8, n 5, p 154-162. 1960.
Grieve, R. A. F., Kreis, K., Therriault,A.M.and P.B.Robertson., Impact structures in the Williston Basin. Meteoritics and Planetary Science, v 33, n 4, p A63-A64. 1998.
Grieve R.A.F., Impact structures in Canada, Geological Association of Canada, 2006.
Sawatzky, H. (1976), Two Probable Late Cretaceous Astroblemes in Western Canada-Eagle Butte, Alberta and Dumas, Saskatchewan, Geophysics, 41(6), 1261-1271.
Sawatzky, H. (1977), Buried impact craters in the Williston Basin and adjacent area, paper presented at Impact and Explosion Cratering: Planetary and Terrestrial Implications.
Xie W. Seismic Characterization of A Possible Buried Impact Structure near Bow City in Southern Alberta Department of Physics University of Alberta 2014
Earth Impact Database
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