>Worldwide distribution of confirmed impact craters. Craters mentioned in the text appear as black dots. (Data from Planetary and Space Science Centre, reference 13.)
Hydrocarbons in Impact Structures Dozens of buried impact craters have produced oil and gas.15
One of the best-studied is the Ames
structure, in Oklahoma. Some geologists argue that this structure could be the result of igneous activity or subsurface solution.16
However, others
contend that the evidence for impact origin is incontrovertible. The Ames feature was initially thought to be a
graben, or downdropped fault block, because drilling in the early 1970s indicated unusually thick sections of Ordovician to Pennsylvanian rocks called the Hunton Formation. In 1990 and 1991, exploratory boreholes established the pres- ence of hydrocarbons at depths of approximately 9,000 ft [2,700 m] in closed, isolated highs encir- cling the low feature (right). A number of these
12. Reimold WU, Koeberl C, Hough RM, McDonald I, Bevan A, Amare K and French BM: “Woodleigh Impact Structure, Australia: Shock Petrography and Geochemical Studies,” Meteoritics & Planetary Science 38, no. 7 (2003): 1109–1130.
13. Planetary and Space Science Centre, Earth Impact Database, 2006,
http://www.unb.ca/passc/ ImpactDatabase/ (accessed August 13, 2009).
14. Grieve, reference 8. 15. Buthman, reference 1.
16. Coughlon JP and Denney PP: “The Ames Structure and Other North American Cryptoexplosion Features: Evidence for Endogenic Emplacement,” in Johnson KS and Campbell JA (eds): Ames Structure in Northwest Oklahoma and Similar Features: Origin and Petroleum Production (1995 Symposium). Norman, Oklahoma: Oklahoma Geological Survey, Circular 100 (1997): 133–152.
Bridges LWD: “Ames Depression, Oklahoma: Domal Collapse and Later Subsurface Solution,” in Johnson KS and Campbell JA (eds): Ames Structure in Northwest Oklahoma and Similar Features: Origin and Petroleum Production (1995 Symposium). Norman, Oklahoma: Oklahoma Geological Survey, Circular 100 (1997): 153–168.
Oilfield Review Autumn 09 Impact Fig. 8
Ames impact structure
Oklahoma
ORAUT09-Impact Fig. 8
N
> Ames impact structure. This crater, in Oklahoma, was first recognized as a circular anomaly based on drilling. A contour map of the Sylvan Shale (bottom), overlying the crater, reveals the ringed structure, which is currently about 9,000 ft below the surface. Vertical lines show well locations.
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