LOCATION OF WATER-WELL SITES IN A BURIED FLUVIAL CHANNEL IN THE JURASSIC MORRISON FORMATION, MCKINLEY COUNTY,
NEW MEXICO, U.S.A.
William M. Turner, Ph.D.
AGW scientists completed a major project for the Sohio Uranium
Company on its L-Bar uranium property using its proprietary Thermonic geophysical
methods. The location of the property is shown in Figure 1.
The objectives of the project were to:
Locate optimal well sites for a well field to supply a
uranium mill; and,
Determine if Thermonics is a useful uranium-exploration
The project area lies in the New Mexico uranium belt on the
southern edge of the San Juan Basin about 50 miles (80 km) west of Albuquerque, New
Uranium is concentrated in organic material entrained in
sandstone of the Jackpile Channel-Sand Member of the Morrison Formation of Jurassic
age. The channel sands are overlain by 600 to 1,500 feet (180 to 450 m) of
Cretaceous marine sandstone and shale. The Jackpile Channel Sand is the primary
channel sand underlying the L-Bar property. The Jackpile Channel Sand ranges in
thickness from feather edges to about 85 feet (26 m) in the center of the channel.
Tributaries to the main Jackpile Channel were expected by Sohio but could not be located
AGW scientists measured temperature in both the saturated and
unsaturated parts of more than 90 40-foot (121 m) deep uranium-exploration bore
holes. We made temperature measurements in lines of bore holes perpendicular to the
axis of the ore body in other areas. We also measured water-level measurements in each
We processed the temperature data using our proprietary methods
to remove effects of downward solar-heat propagation and variable thermal properties of
the rocks. We plotted corrected heat-flow data from a depth of 95 feet (30
m). We contoured the data using AGW's proprietary "valley mapping
function" because of the inability of commercial contouring software to
consider subsurface temperature distributions caused by moving ground water.
We successfully traced the axis of the Jackpile Sand Channel and
identified and traced several tributaries. The main channel sand was about 400 feet
(122 m) wide. Later mining found the tributary channel to be about 25 feet (8 m)
- Uranium mineralization follows the Jackpile Channel Sand and
- The axial zone of the Jackpile channel sand is the zone of greatest aquifer
transmissivity, maximum mass rate of ground-water flow, and the best site for water
We conclude that:
- Data from 50 feet beneath the land surface provides the same
information as data from greater depths.
- Despite the use of drilling mud and a mud cake in the bore holes,
fluid levels return to their pre-drilling level within a few days of drilling.
- Control of mine water is easiest with wells located in the channel..
- Thermonics can trace uranium-bearing paleo-stream channels and is a useful uranium
exploration method for these types of deposits.
- Thermonics can trace buried stream channels and is a valuable ground-water exploration
and well-site location method.