Facies Architecture and Provenance of the Highly Progradational, Fluvial Dominated Deltaic Depositional System of the Cretaceous Nanushuk Formation on the North Slope of Alaska

• Main Author: Naone, Sarah N.
• Format: Text
• Language: unknown
• Published: BYU ScholarsArchive 2022
• Subjects: Nanushuk Formation; facies prediction; reservoir quality; delta; 3-D modeling; Physical Sciences and Mathematics; Brooks Range; north slope; Alaska
• Online Access: https://scholarsarchive.byu.edu/etd/9746; https://scholarsarchive.byu.edu/context/etd/article/10755/viewcontent/1222444122883420210101_etd.pdf

The Cretaceous Nanushuk Formation of northern Alaska records extremely rapid shoreline progradation across the Colville Basin during the Albian-Cenomanian epochs. Additionally, it records a period of tectonic realignment in the region, as the main sediment source began to transition from the Chukotkan orogeny to the west to a more local sediment source of the proximal Brooks Range to the south. Through detailed outcrop characterization and 3-D modeling of three exposed outcrops along the axial trend of the Colville Basin on the North Slope and the Upper section of the Nanushuk, this study clarifies the relative timing of the early Brookian orogenic uplift. Outcrop characterization also allows for a detailed description of spatial and temporal distribution of deltaic facies associations within the Nanushuk Formation. Previously these outcrops were hypothesized to represent dominantly shoreface depositional processes, but field studies indicate the Nanushuk Formation has a complex facies architecture consistent with deltaic environments. This work has important significance for geometry predictions for hydrocarbon exploration and development targeting the Nanushuk sands as a reservoir unit. This new interpretation of both dominant sedimentary process and provenance has implications for 1) reservoir architecture and connectivity, and 2) textural and compositional maturity of Nanushuk sandstones, an emerging hydrocarbon play along the North Slope of Alaska. A detailed mineralogical analysis of 50 samples, coming from the three key outcrops and two additional outcrops from previous studies, using TESCAN Integrated Mineral Analyzer (TIMA), an automated system that utilizes Scanning Electron Microscopy (SEM), shows increased amounts of chromite and biotite associated with key outcrops proximal to the Brooks Range. Chromite mass weight percent ranges from 0.00 % to 0.15 % across five outcrops, with Tuktu Bluff, which is proximal to the Brookian orogenic front having weight percentages that range from 0.01 % to 0.15 % ...