Structural framework of the Sadleroohit and Shublik Mountains and Adjacent Arctic Coastal Plain - Abstract

Abstract Interpretation of the bedrock geology of the eastern Sadlerochit and Shublik Mountains and selected reflection seismic profiles from the Arctic Coastal Plain illustrate the structural framework of the 1002 area. Structural detachment and development of thrust sheets is elemental to the framework of the Sadlerochit and Shublik Mountains and the ANWR coastal plain. The structural framework of the Sadlerochit and Shublik Mountains and adjacent coastal plain comprises at least 6 thrust sheets. In ascending order the thrust sheets are: unnamed sheet(s) overlying unnamed detachment(s) in pre-Mississippian rocks, the Sunset thrust sheet, the Marsh Creek thrust sheet, the West Fork thrust sheet, the Nularvik thrust sheet, and the Katakturuk thrust sheet. Thrust faults branch upward from (a) basal sole thrust fault(s) in pre-Mississippian rocks forming large anticlines. The structural grain in the pre-Mississippian rocks affects the orientation of these faults and folds in pre-Mississippian rocks. The Sunset thrust sheet overlies a detachment that occurs along the pre-Mississippian unconformity. The Sunset thrust sheet overlies inclined and at least locally imbricated pre-Mississippian rocks. The Sunset thrust sheet, comprises unimbricated and relatively little-deformed Mississippian to Jurassic strata. The Marsh Creek thrust sheet comprises Jurassic and Cretaceous Kingak Shale, Kemik Sandstone, and pebble shale unit. The Marsh Creek thrust fault underlies the Marsh Creek thrust sheet and cuts the Lower Cretaceous unconformity (LCU) and emplaces Jurassic strata north of the truncation of Jurassic Kingak Shale under the LCU. The West Fork and Nularvik thrust sheets comprise Tertiary(?) and Cretaceous strata including the pebble shale unit, Hue Shale, and Canning Formation. The Kataturuk thrust sheet consists of Paleocene turbidites in the Canning Formation and younger strata, and overlies duplexes involving the Hue Shale and that part of the Canning Formation underlying the Paleocene turbidites. The Katakturuk thrust sheet includes triangle zones and generally small subsidiary thrust faults that branch upward from the basal thrust fault. North-northwest directed thrusting probably began under the coastal plain during Eocene time and continues to the present. Although timing of individual thrust faults is unknown and emplacement relations between the 6 thrust sheets is complex, the general sequence of thrusting at a particular locality appears to be structurally highest sheets involving youngest strata first followed by structurally lower sheets involving older strata.