Surface Gamma-Ray Profiling Technique Applied to Cretaceous Ferron Sandstone, East-Central Utah

Dan Howe

The preparation of total count gamma-ray profiles using a hand-held scintillometer is a powerful supplement to standard measured vertical sections. Gamma readings taken at 1-ft intervals produce a composite profile which bears a striking resemblance to borehole well logs. Rock unit boundaries, marker beds, and subtle changes in rock composition can be detected with the profiling technique. Overall pattern shape and the distribution of gamma-ray measurements on histograms are useful in the recognition of depositional environments.

Exposures of the Turonian Ferron Sandstone Member, located near the towns of Ferron and Emery in east-central Utah, were measured using the gamma-ray profiling technique. Various deltaic and barrier island subenvironments are shown to have characteristic profiles and histograms. Gamma-ray profiles of stream mouth bars, point bars, crevasse splays, barrier spits, tidal deltas, and washovers are presented. Vertical sequences are recognized, and correlations to adjacent measured sections have been established.

The surface profiles also correlate favorably with nearby subsurface well logs, including those within the Ferron gas field. The integration of surface and subsurface data sets by the correlation of gamma-ray signatures results in a stronger, more sophisticated stratigraphic framework than either data set can yield independently.

AAPG Search and Discovery Article #91022©1989 AAPG Annual Convention, April 23-26, 1989, San Antonio, Texas.