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Timing of Salt Dissolution
under Burial Conditions

Across the Permian Basin, dissolution has occurred several times in the past and continues today. Salt dissolution occurred during the Triassic, Cretaceous, and Cenozoic and continues in the present. The extent of salt dissolution during these times has been only locally determined because the effects of earlier and later dissolution are difficult to separate.

Much of the dissolution over the crest of the southern Central Basin Platform occurred before the Cretaceous, because these units are minimally deformed across and on the south edge of the uplift (Adams, 1940; Wessel, 1988a, b). In a detailed study of the Yates field, Wessel (1988a) showed that Cretaceous strata are warped downward and faulted along the Pecos River in the area of the Alibates-Salado-Tansill interval thinning and salt pinch out, showing that dissolution continued in this area after the Cretaceous. Although similar high-resolution data have not been collected and interpreted in the Howard-Glasscock area, slight dips on Cretaceous strata and complex Quaternary deposits (Eifler and others, 1974) suggest that deformation may have occurred before, as well as after, the Cretaceous.

A major regional episode of salt dissolution occurred during regional Cenozoic uplift when the entire area was uplifted from near sea level to its present elevation (Baker, 1977; Gustavson and others, 1980; Gustavson and others, 1982; Johnson, 1981; Boyd and Murphy, 1984; DeConto and Murphy, 1986; Goldstein and Collins, 1984; Gustavson, 1986; Johnson, 1989b). Like earlier dissolution episodes, Cenozoic dissolution was more pronounced over structural positive features than basins. In the Rolling Plains (Permian outcrop belt), Cenozoic dissolution has removed salt to depths of about 1,000 ft below land surface. Beneath the Southern High Plains (Midland Basin area), where the Permian units are overlain by Triassic, Cretaceous, and Cenozoic strata, dissolution has removed less salt than in the Permian outcrop. Cenozoic dissolution has also been documented along the Pecos Valley, overlying the Central Basin Platform structurally positive feature (Adams, 1940), and above the Capitan Reef trend in Winkler County (Bachman, 1984).

Depressions on the Southern High Plains surface that host large lakes have been interpreted as locations of focused salt dissolution (Reeves and Temple, 1986; Ateiga, 1990). The relationship between surface depression and salt dissolution and the timing and process involved are complex and poorly understood. Not all lakes overlie areas of salt dissolution, and the timing and rates of dissolution appear to be variable.

Dissolution continues today throughout the Permian Basin. Ground-water chemistry and saline-spring discharges provide evidence of current dissolution (Howard and Love, 1945; Rawson, 1982; Richter and Kreitler, 1986; Dutton, 1987; Richter and others, 1990; Paine and others, 1994; James and others, 1995). Collapse and subsidence features and rates can be identified using a variety of assumptions and dating techniques to determine the probable rate and process of salt dissolution (Swenson, 1974; Gustavson and others, 1980; Gustavson and Simpkins, 1989; Paine and others, 1994).

Case Study 1: Permian Facies Controls on the North Margin of the Midland Basin