ABSTRACT

The Elbow structure in south-central Saskatchewan 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 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.

A similar feature, the Gilroy structure, lies about four miles south of Elbow. It is not indicated by a gravity anomaly. Both structures are considered to be cryptovolcanoes.