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Location map. This map shows boundaries
of 1999 and 2000 aeromagnetic surveys. The surveys were flown by
different Canadian contractors but with essentially identical survey specifications. |
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Simplified geology map. Dark dashed
lines indicate limits of aeromagnetic surveys. Volcanic rocks comprise
the most important magnetic lithology, exposed mostly in the Yucca Mountain
area and within the Death Valley volcanic complex. |
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Merged aeromagnetic data. Note high-amplitude,
short-wavelength anomalies over volcanic exposures, which contrast with
subdued anomalies over Mesquite Flat, Furnace Creek Wash, Ash Meadows,
and Pahrump Valley. The large anomaly over the Black Mountains is
probably caused by the Willow Springs diorite and indicates its subsurface
extent. It may extend beneath the floor of Death Valley to connect
with similar rocks in the Panamint Range. |
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Residual magnetic anomalies.
Here the aeromagnetic data have been processed in order to emphasize shallow
magnetic sources. The margins of volcanic terranes are clearly demarcated.
Also note various strands of the Furnace Creek fault. |
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High-definition magnetic anomalies.
Residual anomalies of the previous slide have been filtered to emphasize
near-surface sources that strike northwest-southeast. Multiple strands
of the Furnace Creek fault are evident, one extending entirely across Mesquite
Flat to the Cottonwood Mountains. A north-south pattern of anomalies
connects the volcanic terrane of Yucca Mountain with the Death Valley volcanic
complex through the Amargosa trough. |
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Intepreted magnetic lineations.
Magnetic lineations, interpreted from the previous maps (and others), reflect
faults, ancient fluvial channels, and erosional or depositional margins
of volcanic deposits. The State Line and Furnace Creek fault zones
are evident. |
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Isostatic residual gravity. |
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Magnetic lineations and Cenozoic
basins. This map reflects the last 15 m.y. of tectonic evolution.
Rainbow colors represent Cenozoic basins determined from an inversion of
gravity data, whereas lines are interpreted magnetic lineations.
Magnetic lineations manifest near-surface deformation of Quaternary deposits,
whereas the basins highlight very deep deformation of pre-Tertiary basement.
The fact that they correlate spatially suggests a kinematic link . |
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Regional picture. Dashed lines
represent fundamental crustal structures, namely major strike-slip fault
zones (Furnace Creek, State Line, and Highway 95 faults) and pull-apart
zones (e.g., Amargosa trough, northern Amargosa Valley, Ash Meadows, and
Pahrump Valley) that transfer strain between the faults. |
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Zoom-in on Furnace Creek.
A major strand of the Furnace Creek fault passes between Nevares and Salt
Springs. Note the narrow lineation that connects Salt, Texas, and
Travertine springs. It presumably is caused by a near-surface fault
that focuses the discharge of water at the springs. This fault may
extend to Lemonade Spring, a total distance of 25 km. |
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Zoom-in on Devils Hole.
Springs at Ash Meadows lie along near-surface faults expressed in the aeromagnetic
data. These faults in turn lie along the eastern margin of the Amargosa
trough, well defined in gravity data. |
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Zoom-in on Pahrump Valley.
The three southern springs lie along the northeastern margin of a horst
that divides two deep sub-basins beneath Pahrump Valley. The horst
marks the State Line fault and apparently acts as a barrier to the flow
of water from the Spring Mountains. The northern spring lies along
a magnetic anomaly that traces the deepest parts of the Pahrump Valley
sub-basin. Perhaps the magnetic anomaly reflects near surface fluvial
channels, part of the sub-basin's longpterm depocenter. |
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What is the link between magnetic anomalies
and water discharge? Perhaps faults that influence the flow of
water have offset underlying magnetic units. Or perhaps ground water
concentrates magnetic minerals along the fault plane, through precipitation
of iron oxides/sulfides or deposition of detrital magnetite. |
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