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OUTCROP-BASED LITHOFACIES AND DEPOSITIONAL SETTING OF ARSENIC-BEARING PERMIAN RED BEDS IN THE CENTRAL OKLAHOMA AQUIFER (COA), CLEVELAND COUNTY, OKLAHOMA
Citation:
Kenney, K., S. T. Paxton, S. J. Smith, S. Christenson, AND R W. Puls*. OUTCROP-BASED LITHOFACIES AND DEPOSITIONAL SETTING OF ARSENIC-BEARING PERMIAN RED BEDS IN THE CENTRAL OKLAHOMA AQUIFER (COA), CLEVELAND COUNTY, OKLAHOMA. Presented at American Assn. of Petroleum Geologists Annual Mtg, Dallas, TX, April 18 - 21, 2004.
Impact/Purpose:
To inform the public.
Description:
In January 2001, the Environmental Protection Agency established safe drinking water standards for arsenic at a maximum concentration of 10 mg/L. Results from the National Water-Quality Assessment Program (USGS), however, document the occurrence of arsenic concentrations in drinking water well above the allowable standard. Based on the work of Schlottman et al. (1998), concentrations of arsenic tend to occur in thin sandstone layers that are isolated between thick layers of mudstone. In contrast, arsenic concentrations are lower in thicker sandstone-prone intervals that tie into areas of active surface recharge. As a means to evaluate various approaches to arsenic remediation, we are developing a lithofacies and stratigraphic framework for the Permian (Leonardian) Garber Sandstone. Detailed study of outcrops in Cleveland County and surrounding area has yielded nine lithofacies. The very fine- to fine-grained and moderately well-sorted sandstone lithofacies include 1) massive sandstone, 2) ripple laminated sandstone, 3) sandstones with horizontal to low angle planar laminations, and 4) tabular and trough cross bedded sandstone, some with mud rip-up clasts. Other lithofacies include 5) carbonate clast conglomerate, 6) mud clast conglomerate, 7) iron stone, 8) shale/laminated siltstones, and 9) blocky mudstones. These lithofacies and their associations provide the foundation for construction of lithofacies maps, vertical stratigraphic profiles, and paleoenvironmental reconstructions. A fluvial depositional setting for the Garber Sandstone is supported by the presence of lenticular-shaped sandstone bodies, erosional truncation of underlying units to produce channel forms, fining upward vertical grain-size profiles, and rapid lateral changes in the proportion of sandstone and shale. These findings are being used to constrain the habitat of arsenic in the aquifer system and as input to regional fluid flow modeling.