Implications of Geologic Structure and Regional Sedimentation Patterns for Rifting Geometry of Arctic Basin: ABSTRACT

Abstract

The smooth, passive continental margin north of Alaska is geometrically more complex than its simple physiography suggests. Multichannel seismic reflection profiles across the continental shelf reveal three sectors of contrasting structure and stratigraphy. The Barrow sector of central northern Alaska is characterized by a prominent arch in lower Paleozoic metasedimentary basement rocks overlain by a southward-thickening wedge of Mississippian to Lower Cretaceous (Neocomian) shelf sediments and a northward-thickening prism of Lower Cretaceous (Albian) to Tertiary clastic sediments. The Chukchi and Barter Island sectors, lying respectively west and east of the Barrow sector, comprise Mesozoic and Tertiary basins so deep that acoustic basement was not reached. We suggest th t this geometry (in which lower Paleozoic basement rocks extend much farther north in the central sector than they do in the east and west) is inherited from the configuration of the rift that opened the Arctic basin, probably beginning in Early Jurassic time. In this scheme, old, pre-rift highlands, originally continuous with the basement rocks of the central Barrow sector, were rotated northward away from Alaska along two sectors of the rift that lay well south of the present-day shelf edge. In these, the Chukchi and Barter Island sectors, the rift created room for the deep shelf basins observed there now. In the intervening Barrow sector, the rift opened along the present-day shelf edge, leaving a broad tongue of lower Paleozoic rocks, the site of upper Paleozoic and lower Mesozoic hi hlands, attached to Alaska. Presumably the sector boundaries were ridge-ridge transform faults during nascent rifting. The Chukchi-Barrow sector boundary is well defined by the trend of the Northwind Escarpment and the abrupt termination of the Barrow arch against the North Chukchi basin. The Barrow-Barter Island boundary is more obscure and is inferred from the provenance and distribution of Mesozoic sediments in northeastern Alaska and Yukon Territory. End_of_Article - Last_Page 714------------