Engineering, Economic, and Environmental Assessment of Lower Wilcox Lignite

Paul C. Albertson

A lower Wilcox lignite body was delineated in Caddo Parish, Louisiana (Sec. 28, T15N, R11W) during the foundation investigation for Red River Lock and Dam No. 5 by the U.S. Army Corps of Engineers. The thickness (up to 6.0 ft) and areal extent of the deposit within the project limits were defined, using closely spaced borings and geophysical logs. Geologic cross sections, lignite and overburden isopach maps, and lignite surface maps were constructed from the field data. Selected samples were analyzed by the Center for Coal and Coal Products Research at University of Southern Mississippi. The average results are: 9,680 btu/lb, 22% ash, 40% fixed carbon, 24% moisture, and 34% volatiles, according to ASTM standards. Paleobotanic analysis of fossil leaf and fruit imprints rev aled broad-leaf dicots, and linear reedlike monocots. Paleobotanic and stratigraphic evidence suggests a fluvial-deltaic interface. The lignite seam is overlain by a transgressive sequence of sandy glauconitic claystone.

The size of the reserve in the project area is estimated to be 350,000 tons with a stripping ratio between 15/1 and 35/1. The recovery of the deposit is not considered to be economically feasible at this time, owing to limited quantity, overburden thickness, and the dewatering of the alluvial aquifer.

AAPG Search and Discovery Article #91042©1987 GCAGS and GC-SEPM Section Meeting, San Antonio, Texas, October 28-31, 1987.