HIGH-RESOLUTION GRAVITY STUDY REVEALS THE STRUCTURAL STYLE AND FORWARD LIMIT OF A TECTONIC WEDGE, CENTRAL BROOKS RANGE FOOTHILLS, ALASKA

A GPS-located gravity transect with 50 m station spacing through a complex region of the Brooks Range foothills, northern Alaska, provides a test for multiple geologic structural hypotheses. A two-dimensional forward gravity model, constrained by available geologic, petrophysical, and geophysical information, supports a structural cross section that includes a northward-extending subsurface wedge of higher-density rocks than those exposed at the surface. Between two previously published, end-member structural theories, our results support multistory duplexes as opposed to large-offset overthrust faulting. Closely spaced precision gravity measurements, when adequately constrained by additional data, provide important complementary information to seismic investigations in this difficult-to-image structural setting.