A Gravity Survey of the Chukchi Sea Region, and Its Bearing on Westward Extension of Structures in Northern Alaska

Gravity data are used to support the conclusion that the Brooks Range structure is continuous across the Chukchi Sea with the Chukchi-Anadyr fold belt. A morphological reconstruction of this section of the mobile belt that is consistent with known geologic and structural similarities, recorded sub-bottom seismic profiles and observed gravity follows: Moderate Tertiary folding produced a dry-land intercontinental connection that persisted until about a million years ago when erosion finally reduced the low mountain barrier to a near peneplain. Subsequently, the sea shelf has been modified by numerous changes in sea level and deposition of a thin, often patchy veneer of sediments. Scanty gravity data suggest that the Brooks Range structure is not continuous with the Franklin geosyncline to the east.

The Chukchi Shelf is now in isostatic equilibrium. A Bouguer gravity low over Herald Island and Herald Reef suggests that they are formed by a single large granitic pluton. Small gravity highs off Lisburne Peninsula and south of Wrangel Island may be caused by basic or intermediate extrusives of Cretaceous to early Cenozoic age. The Tigara uplift produces a relative gravity high across the end of the Lisburne Peninsula.