Chemostratigraphy and facies analysis of the Hare Indian Formation in the Mackenzie Mountains and Central Mackenzie Valley, Northwest Territories, Canada

Abstract

The Hare Indian Formation, a Givetian aged organic rich mudstone, is the basal formation of the Horn River Group in the Northwest Territories, Canada. It is subdivided into two members: the basal Bluefish Member and the upper Bell Creek Member. Recent interest in unconventional resource plays sparked interest in the Hare Indian Formation and the overlying Canol Formation as targets for exploration. The Kee Scarp Reef near Norman Wells has produced oil sourced from the Canol Formation since the 1920s. There are aspects of the depositional model, paleoredox conditions and sequence stratigraphy of the Hare Indian Formation that are not well understood. Here, a detailed examination of the sedimentology and sequence stratigraphy of the Hare Indian Formation is made. High-resolution portable X-ray fluorescence (pXRF) data is collected from four cores in the Central Mackenzie Valley and three outcrop locations in the Mackenzie Mountains. The pXRF data is used as geochemical proxies using elements like Al, Ti, K, Si, Ca, Mg, Mo and V to interpret terrigenous input and paleoredox conditions in order to construct a chemostratigraphic framework for the Hare Indian Formation. The results suggest a maximum flooding surface in the Bluefish Member and a maximum regressive surface at the top of the Bell Creek Member. Relative sea level transgression occurred during the onset of the deposition of the Bluefish Member, followed by relative sea level regression throughout the remaining deposition of the Hare Indian Formation. Redox sensitive trace metals support intermittent euxinia throughout deposition. The pXRF data is also used to interpret five distinct chemofacies based on three cores using agglomerative hierarchical clustering (AHC) to compare to more traditional lithofacies and microfacies models using the same cores. Different facies types correspond locally, though different classification schemes have particular uses. Chemofacies are particularly useful in producing a high-resolution understanding of the geochemical ratios present in a succession, tracing the relative amounts of clay or silica. Microfacies show sedimentary processes and biogenic activity. The best use of facies models in fine-grained successions are often in conjunction with one another.