Kenney, Kathleen M.¹, Stanley T. Paxton¹, Robert W. Puls², Jamie L. Schlottmann³ 
(1) Oklahoma State University, Stillwater, OK 
(2) USEPA, Ada, OK 
(3) Consultant, Edmond, OK

ABSTRACT: Outcrop-Based Lithofacies and Depositional Setting of Arsenic-Bearing Permian Red Beds in the Central Oklahoma Aquifer (COA), Cleveland County, Oklahoma

In January 2001, the Environmental Protection Agency established the new safe drinking water standard for arsenic at a maximum concentration of 10 mg/L. Water-quality assessments for parts of the COA, however, document arsenic concentrations above this standard. Based on the work of Schlottmann et al. (1998), concentrations of arsenic tend to occur in sandstone layers that are isolated between thick layers of mudstone. As a means to evaluate various approaches to arsenic remediation during well construction, we are developing a lithofacies and stratigraphic conceptual model for the Permian (Leonardian) Garber Sandstone. Detailed study of outcrops in Cleveland County and surrounding area has resulted in identification of nine lithofacies. The sandstone lithofacies include 1) massive, 2) ripple-laminated, 3) sandstone 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/siltstones, and 9) blocky mudstones. These lithofacies and lithofacies 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, fining upward 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 flow modeling. (This is an abstract of a proposed presentation and does not necessarily reflect EPA policy.)

AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.