Carbonate facies and sequence stratigraphy of the carboniferous Lisburne group, Upper Nanushuk River Region, Central Brooks Range, Alaska

Abstract

This study documents the stratigraphy, facies, facies associations, depositional environment, sequence stratigraphy, and conodont biostratigraphy of the upper Nanushuk River section of the Lisburne Group. 1621 meters of Kayak Shale and Lisburne Group rocks were measured and studied for facies analysis. Sixteen lithofacies and eleven microfacies were identified composing six facies assemblages. Facies analysis, stacking patterns, and associations suggest that the Nansushuk River section represents a homoclinal carbonate ramp recording an intertidal (Kayak Shale) and open marine to basin transitional sequence. Facies associations, stacking patterns and marine flooding surfaces helped to delineate major sequence boundaries and maximum flooding surfaces. Six 3rd order stratigraphic sequences have been identified in the Nanushuk River section. The section ranges in age from Osagean to lower Morrowan based on conodont biostratigraphy. The reservoir rock potential of the Nanushuk River section resides primarily in the dolomite of the Wachsmuth Limestone. The remainder of the section is considered 'tight' from a microfacies standpoint. Regionally, this study is important for paleogeographic reconstruction of the Lisburne Group across northern Alaska and adds to the general geologic knowledge of the Lisburne Group by obtaining stratigraphic data from a relatively isolated area in the Brooks Range.