Introduction to this special section: Gravity and potential fields

Abstract

Tien Grauch and her coauthors describe an integrated study of high-resolution aeromagnetics, ground gravity, airborne gravity gradiometry, TEM, and 2D seismic data for imaging not only basement faulting and relief, but also shallow faulting within the sedimentary section. Rather than invoking magnetic mineralization along fault zones (or other geochemical explanations) as an explanation for the observed sedimentary magnetic anomalies, they show that the anomalies can be completely explained by tectonic juxtaposition of strata of differing magnetic properties across the fault zones. They document, through 2D forward magnetic modeling, a faulted geologic column of juxtaposed magnetite-enriched clastics with magnetite-depleted clastics. These laterally varying magnetite-bearing horizons stack to produce super-positioned magnetic anomalies of relatively low amplitude and short wavelength which are superimposed on the longer wavelength, higher-amplitude magnetic anom-alies sourced by basement composition heterogeneities and structural relief.