COMPARING THE LITHOFACIES, CHEMOFACIES AND MICROFACIES ANALYSES OF THE HARE INDIAN FORMATION, NORTHWEST TERRITORIES, CANADA

This study compares the advantages and efficacies of various facies classification schemes for the Hare Indian Formation, which is the basal mudrock formation of the Devonian Horn River Group in the Northwest Territories. Fine-grained successions often require a different approach than coarser-grained successions as traditional lithological facies analysis may not always be effective. This is because the features that workers normally use to classify lithofacies, such as physical sedimentary structures and biogenic sedimentary structures may be limited in their occurrence, too small or subtle to see at the core scale, and the rock composition may appear relatively homogenous. Owing to these difficulties, additional methods like petrographic microfacies facies or chemofacies are commonly used to supplement lithofacies. Building on previous lithofacies schemes presented for the Hare Indian Formation, this study uses lithological facies, chemofacies (primarily built from a portable x-ray fluorescence dataset), and thin-section based microfacies to present an integrated analysis of three oil-exploration cores from southwest of Norman Wells, NWT. Using agglomerative hierarchical clustering, five lithofacies and five chemofacies are identified and compared to our microfacies scheme. Notably, the correspondence between the facies schemes was difficult to establish. Lithofacies, which are influenced in part by colour, locally correspond with chemofacies, but as a rule, chemofacies provide a superior record of composition and thus mineralogy and redox conditions. Likewise, microfacies could reveal sedimentary process and the presence or absence of bioturbation, suggesting they may proxy factors such as oxygenation and even have a passive relationship to rock composition (i.e. sedimentary process can be associated to characteristic grain size, etc.).