The Last Chance Canyon area of southwestern Eddy County, New Mexico exhibits relations between the Permian strata that are of regional geologic significance. Recent mapping suggests that some interpretations of the age relations of the San Andres limestone and overlying units should be modified. Intertonguing between the upper part of the San Andres and the sandstone tongue of the Cherry Canyon formation (middle Guadalupe series) is well displayed in Last Chance Canyon. These two units unconformably overlie rocks of latest Leonard and (or) earliest Guadalupe age that are correlated with the lower part of the San Andres of areas on the north and west. In the Big Dog Canyon scarp a few miles west, the rocks of Cherry Canyon age are apparently separated from rocks of latest Leonard and (or) earliest Guadalupe age by more than 579 feet of carbonate rocks which are considered equivalent in age to the Brushy Canyon formation (early Guadalupe age) of the Delaware Basin. The sequence within the San Andres limestone in Big Dog Canyon may therefore represent nearly continuous deposition from latest Leonard and (or) earliest Guadalupe time into Cherry Canyon time.

The San Andres limestone is overlain by the Grayburg formation which is equivalent to the Grayburg formation of subsurface usage. The Grayburg formation and overlying Queen formation are laterally equivalent to the Goat Seep limestone and thus of middle Guadalupe age.

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