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.