Evaluation of a Structurally Disturbed Portion of Wilcox Lignite Trend: ABSTRACT

Abstract

End_Page 525------------------------------Northwestern Resources Co.'s Jewett Project is located approximately 100 mi (160 km) south of Dallas. It is within the Wilcox Group and is bounded on the west by the Navasota River and the east by Interstate Highway 45. The geology is generally typical of the upper Calvert Bluff Formation, with the exception of the project's west end. This area is abruptly separated from the rest of the project by a series of normal faults with displacements of up to 200 ft (66 m). The area is characterized by steeply dipping beds (15 to 20°), discontinuous lignite seams, anomalous lignite thickness (up to 35 ft, 11 m), stacked seams, and low-quality lignite. Core information reveals areas where pebble to cobble-sized angular lignite fragments are contained in a silty to sandy matrix. On a more local scale, lignite elevations, and parting and lignite thicknesses have been observed to range as much as 15 to 20 ft (4.5 to 6 m) between pilot hole and core hole. Core sampling has revealed bedding planes oriented at 40° or horizontal in overburden material at one site and horizontal bedding in a 28-ft (8.5-m) lignite seam at another site. Various exploration and evaluation methods have been used in an attempt to decipher this geologically complex area. Electric logs, geologic mapping, and cross sections show some of the anomalous features. The paper presents the area in a regional framework with consideration given to the Elkhorn graben system to the northeast and the Marquez dome to the immediate south. Evaluation of the depositional environment and subsequent geologic history has assisted in determining the potential for mining in this area. End_of_Article - Last_Page 526------------