Stratigraphic and Structural Framework of Ellesmerian and Older Sequences in Sadlerochit and Shublik Mountains, Arctic National Wildlife Refuge (ANWR), Northeastern Alaska

Mark S. Robinson, John Decker, J. G. Clough, J. T. Dillon, Wesley K. Wallace, K. Crowder, K. Watts

Detailed geological mapping (1:25,000 scale) and stratigraphic reconstructions in the Sadlerochit and Shublik Mountains of northeastern Alaska, immediately south of the ANWR coastal plain, indicate a compressive structural province dominated by major thrust-ramp-related anticlinal uplifts.

The Katakturuk Dolomite, a Proterozoic sequence, has been subdivided into 15 lithostratigraphic units that can be traced the entire length of both the Sadlerochit and Shublik Mountains. Overlying the Katakturuk Dolomite in these ranges is the Middle Devonian to Cambrian or older Nanook Limestone. In the Early Mississippian a major erosional event produced the pre-Mississippian unconformity upon which a Mississippian through Triassic sequence was deposited: (A) Kayak Shale; (B) Lisburne Group carbonates; and (C) Sadlerochit Group clastic rocks. In the northern Sadlerochit Mountains, basal units of the Mississippian Alapah Limestone lie on the pre-Mississippian unconformity with no intervening Kayak Shale. The basal Alapah contains lithologies derived from the rock units on which it res s, indicating that the contact between the Alapah and the underlying units is depositional.

A regional decollement, localized along the pre-Mississippian unconformity in the Kayak Shale, is not a significant detachment surface north of the Shublik Mountains because the Kayak Shale is depositionally discontinuous and thin in the Sadlerochit Mountains.

AAPG Search and Discovery Article #91030©1988 AAPG Annual Convention, Houston, Texas, 20-23 March 1988.