Hydrogeochemical processes involved in salt‐dissolution zones, texas panhandle, U.S.A.

Abstract

Permian evaporite deposits have been extensively dissolved beneath the perimeter of the Southern High Plains in the Texas Panhandle. Hydrologic and geochemical data were collected from six test wells to determine hydrogeochemical processes involved and the source and flow paths of ground water moving in salt‐dissolution zones. Geochemical similarities and hydraulic‐head relationships indicate that ground water dissolving halite and anhydrite moves downward from aquifers in post‐Permian formations and follows flow paths influenced by topography. Holocene salt‐dissolution rates probably are lower than Tertiary and Pleistocene rates owing to regional changes in physiography and climate that probably decreased the amount of recharge to salt‐dissolution zones. Present as well as palaeohydrologic ground‐water velocities and salt‐dissolution rates are probably less beneath the Southern High Plains than in adjacent, peripheral salt‐dissolution zones because of lower hydraulic conductivities and lower hydraulic‐head gradients. Salinities in peripheral salt‐dissolution zones are low (67 000 to 95 000 mg L−1) despite high solubility of halite, reflecting relatively open circulation of ground water. In interior salt‐dissolution zones beneath the Southern High Plains, ground‐water circulation is low and water composition tends to reach halite saturation.

Modeling regional salinization of the Ogallala aquifer, Southern High Plains, TX, USA

“…The identified flow paths and flow velocities suggest that the upwarddischarging Whitehorse Group waters beneath the Carson-Gray Counties plume could have been recharged during the Pleistocene or earlier times. This observation is consistent with previous interpretations by Dutton (1989Dutton ( , 1995 The other two regions of upward discharge identified in the Whitehorse Group occur toward the southwest (left) side of the paleovalley and near the northeast (right) boundary of the model close to the Canadian River (Fig. 8).…”

“…The Dockum Group thins northeastward and pinches out approximately 40 km southwest of the western edges of the saline plumes. Present-day recharge to the Dockum aquifer is primarily through downward leakage from the Ogallala aquifer (Dutton, 1989;Dutton, 1995). The flow in the lower Dockum Group in the study area is toward the east-northeast and the water quality is marked by a mixed cation and mixed anion hydrochemical facies with TDS generally Ͻ2000 mg l Ϫ1 (Dutton and Simpkins, 1986;Dutton and Simpkins, 1989).…”

“…2). These zones seem to have developed as a result of shallow, gravity-driven circulation of meteoric water (Dutton, 1989). Hydraulic conductivity ranges from 0.5 m day Ϫ1 in salt-dissolution zones to less than 10 Ϫ5 m day Ϫ1 for the deeper parts of the confining unit (Dutton, 1989) and TDS varies from 5000 mg l Ϫ1 to Ͼ300,000 mg l…”

“…Values were taken from Senger and Fogg (1987) and later modified where newer data were available. For salt-dissolution zones, the permeability values range from 10 Ϫ13 to 10 Ϫ17 m 2 (Dutton, 1989). An average salt-dissolution zone permeability was taken for the Whitehorse Group on the basis of mapping of salt-dissolution zones by Gustavson (1986).…”

Characteristics of streams and aquifers and processes affecting the salinity of water in the upper Colorado River basin, Texas

“…Total organic carbon analyses were made using techniques described by Wershaw and others (1987). Water samples collected by the BEG were preserved and analyzed using methods described by Dutton (1989) and generally were consistent with USGS procedures. Analytical methods for proprietary data obtained from the Petroleum Information Corp. (written commun., 1990) are not documented in this report.…”