Integrated Gravity and Magnetic Interpretations Yield New
Insights to Basin and Range Structures
George L. Lisle, Lisle Gravity Inc, 621 17th #2600, Denver, CO
80293, phone: 303 592 4373, fax: 303 592 4374,
[email protected]
New interpretation techniques using detailed gravity and
aeromagnetic surveys show faults, lineaments, contacts and regional structural
patterns in Eastern Nevada. Oil companies have
used gravity surveys as a primary exploration tool in Nevada, partly because seismic data quality is
often poor. Within Tertiary basins, the gravity data reflects structures cored
with Paleozoic carbonates, and detailed gravity surveys show the fault blocks
that form Grant Canyon,
Trap Springs and Blackburn fields. The
detailed gravity shows complex fault patterns. Gravity surveys are typically
acquired only in the valleys, and most exploration efforts have not focused on
regional gravity trends. Magnetics can be used to map
the subsurface distribution of volcanic rocks over eastern Nevada, but previous magnetic images and
interpretations did not correlate well with gravity. The magnetic susceptibly
differences are much grater in the volcanics than
within the sedimentary section. The aeromagnetic surveys cover both the valleys
and ranges, helping to constrain the gravity interpretations in areas of no
coverage. The results of these new interpretations show correlation between the
gravity and magnetics, revealing new structural
information and regional styles. Between the two data sets, faults and contacts
may be coincident, or show a longer fault, or show a fault's terminus. Three
regional structural styles become apparent: Pine-Huntington-Diamond
Valleys; Little Smoky-Butte-Long
Valleys; Big Sand-Railroad-White River
Valleys.