Abstract: Exploration in Rugged Terrain in Overthrust Belt

T. R. Lafehr, D. J. Guion, A. T. Herring

Exploration in the rugged terrain of the Overthrust belt of the western United States is made difficult by severe topographic conditions and complex geology. However, it can be highly rewarding, as proved by several recent significant discoveries. Seismic data generally are acquired along widely spaced trails and roads and are distorted by near-surface velocity variations and structurally deceiving diffraction patterns. Detailed-profile gravity data acquired along the same trails moderately help seismic interpretation by identifying direction of throw on fault systems and by confirming deeper structural highs. We believe, however, that the two independent data sets mutually reinforce each other and that the seismic data can effectively "calibrate" the gravity data for the more importa t next step, which is acquisition of gravity data on a more or less regular grid by helicopter. Elevations and horizontal coordinates are determined by an inertial navigation system. These areal data show anomalies and patterns not identified by the profile data, effectively extend the seismic-gravity profile interpretation into the regions of no seismic control, and help significantly with the location of drilling sites.

AAPG Search and Discovery Article #90963©1978 AAPG/SEG/SEPM Pacific Section Meeting, Sacramento, California