113
A)
Vertical scale greatly exaggerated
Explanation
Stream alluvium
Upper basin fill (confining unit)
Lower basin fill (fine grained)
Lower basin fill (coarse grained)
Pre-Basin & Range sediments
Bedrock
5 to 16 miles
Fault
B)
Unit
Lower basin fill
Pre-Basin and
Range Sediments
Bedrock of the
mountains
Mudstone and
evaporite deposits
(8-26 km)
DESCRIPTION OF PRINCIPAL HYDROGEOLOGIC UNITS
Lithology
Stream sediments Unconsolidated alluvial deposits along major
streams and washes; boulders and gravel to
lacustrine clay; typically well sorted sandy gravel
Upper basin fill
2000 feet
(610 m)
Looking North
Unconsolidated to moderately consolidated
alluvial deposits. Grades from coarse- to
fine-grained toward basin centers; includes
basin center silts and clays, also lake
and basalt flows in a few basins
Weakly to highly consolidated gravel, sand, silt,
and clay with interbedded to massive evaporites
and volcanic rocks in some areas
Weakly to highly consolidated fanglomerate and
alluvial deposits found on the perimeter of most
basins. In some places grades into the fine-grained
facies near major basin faults; underlies the finegrained facies in extensive areas of many basins
Basin-center fine-grained facies, weakly to
moderately consolidated silt and clay, generally
55 to 80% fine sediments, few evaporites
Basin-center fine-grained facies, moderately
consolidated silt and clay, greater than 80%
Fine-grained sediments, gypsiferous in many
Places, with interbedded or massive
evaporites and volcanics in a few basins
Moderately to highly consolidated fanglomerate
and alluvial deposits and interbedded volcanics
that are structurally disturbed. Range in
composition from silt, clay, limestone to gravel and
conglomerates, includes some interbedded volcanics
Range in
Thickness
(in feet)
0 - <300
(0 - <91 m)
<100-1000
(<30 - 305 m)
0-1000
(0 - 305 m)
Range in
hydrologic
properties
Only locally
saturated
Hydraulic
conductivity
30-1000 ft/day
Specific yield
15-25 percent
Hydraulic
conductivity
1-100 ft/day
Specific yield
3-25 percent
Hydraulic
conductivity
1-50 ft/day
Storage coefficient
10 -1 to 10-5
1000-5000
(305-1524 m)
<1000
(<305 m)
<1000-15000
(<305-4572 m)
Hydraulic
Conductivity
1-13 ft/day
Storage coefficient
10-1 to 6 x 10-5
Igneous, metamorphic and sedimentary
rocks
FIGURE 19. Generalized cross section (A) and descriptions (B) of the principal
hydrogeologic units of the southeast basins of Arizona and New Mexico. Modified from
Figures 7 and 21 of Anderson et al. (1992)