Ames Hole
Oklahoma: Impact-Formed Petroleum Reservoirs
John F. McHone
Ames Hole
is a 16 km wide circular subsurface structure centered at 36°15^primenorth,
98°12^primewest in Major County, northern Oklahoma. An impact origin is
confirmed by the presence of shock metamorphosed mineral grains and impact melt
rocks recovered from drill cores and by a negative Bouger gravity anomaly over
its center. Buried about three km deep, the structure is composed of shattered,
central zone of uplifted Precambrian granite and Cambrian-Ordovician Arbuckle
dolomite surrounded by two concentric rims of fractured and brecciated Arbuckle
dolomite. The crater is filled with, and covered by, marine sediments of the
middle Ordovician Oil Greek shale. The crater was formed during Ordovician time
in a shallow sea on the northern shelf of the Anadarko Basin Restricted water
circulation and anoxic conditions within the deep crater promoted precipitation
of plankton-rich sediments. This Oil Greek shale became both the source and the
sealing rocks for hydrocarbons which migrated into underlying porous target
rocks fractured during the impact event. About one hundred wells within the area
underlain by the Ames
Hole
astroblem presently produce nearly half of Oklahoma's
oil and gas.
AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California