Hydrostructural Maps of the Death Valley Regional Flow System, Nevada and California

These maps (maps A and B) were prepared in support of a regional
three-dimensional ground-water model currently being constructed by the U.S.
Geological Survey (USGS) for the DVRFS. The maps identify regional geologic
structures whose possible hydrologic significance merits their inclusion in the
HFM for the DVRFS.

The locations of principal faults and structural zones that may influence
ground-water flow were compiled in support of a three-dimensional ground-water
model for the Death Valley regional flow system (DVRFS), which covers 80,000
square km in southwestern Nevada and southeastern California. Faults include
Neogene extensional and strike-slip faults and pre-Tertiary thrust faults.
Emphasis was given to characteristics of faults and deformed zones that may
have a high potential for influencing hydraulic conductivity. These include:
(1) faulting that results in the juxtaposition of stratigraphic units with
contrasting hydrologic properties, which may cause ground-water discharge and
other perturbations in the flow system; (2) special physical characteristics of
the fault zones, such as brecciation and fracturing, that may cause specific
parts of the zone to act either as conduits or as barriers to fluid flow; (3)
the presence of a variety of lithologies whose physical and deformational
characteristics may serve to impede or enhance flow in fault zones; (4)
orientation of a fault with respect to the present-day stress field, possibly
influencing hydraulic conductivity along the fault zone; and (5) faults that
have been active in late Pleistocene or Holocene time and areas of contemporary
seismicity, which may be associated with enhanced permeabilities.

The faults shown on maps A (Structural Framework, Neogene Basins, and
Potentiometric Surface) and B (Structural Framework, Earthquake Epicenters, and
Potential Zones of Enhanced Hydraulic Conductivity) are largely from Workman
and others (in press), and fit one or more of the following criteria: (1)
faults that are more than 10 km in map length; (2) faults with more than 500 m
of displacement; and (3) faults in sets that define a significant structural
fabric that characterizes a particular domain of the DVRFS. The following fault
types are shown: Neogene normal, Neogene strike-slip, Neogene low-angle
normal, pre-Tertiary thrust, and structural boundaries of Miocene calderas. We
have highlighted faults that have late Pleistocene to Holocene displacement
(Piety, 1996). Areas of thick Neogene basin-fill deposits (thicknesses 1-2 km,
2-3 km, and >3 km) are shown on map A, based on gravity anomalies and
depth-to-basement modeling by Blakely and others (1999). We have interpreted
the positions of faults in the subsurface, generally following the
interpretations of Blakely and others (1999). Where geophysical constraints
are not present, the faults beneath late Tertiary and Quaternary cover have
been extended based on geologic reasoning. Nearly all of these concealed faults
are shown with continuous solid lines on maps A and B, in order to provide
continuous structures for incorporation into the hydrogeologic framework model
(HFM). Map A also shows the potentiometric surface, regional springs (25-35
degrees Celsius, D'Agnese and others, 1997), and cold springs (Turner and
others, 1996).

A composite base map is included based upon published 83-m DEM data from USGS
1:250,000-scale quadrangles, as well as road lines and political boundaries
from published USGS 1:100,000-scale DLG data. The 1:100,000-scale data were
generalized to 1:250,000 scale for inclusion with the 1:250,000-scale database.

Additional coverages include a ground-water model area coverage, and text
labels for structural features. Files necessary for printing the map are also
included such as text fonts, linesets, shadesets, projection files, and AML
files. These files are all explained in the included README.txt file.