Subsurface Analysis and Correlation of Cambrian Formations Beneath the Colville Hills, Northern Mainland, Northwest Territories

Abstract

The Lower and Middle Cambrian succession in the Colville Hills region, Northwest Territories consists of the Mount Clark, Mount Cap and Saline River Formations, which were deposited in an epicontinental basin. Significant research had been conducted over the last hundred years to better understand the stratigraphy of the region. To further these efforts, a high-resolution facies analysis that included ichnology, in addition to updated lithostratigraphic and sequence stratigraphic frameworks were required. To achieve this object, sedimentological and ichnological data was acquired from 10 drill cores, in conjunction with wireline data and geological reports from 45 wells that were used for correlations within an area approximately 300,000 km2. Twenty distinct facies were observed and categorized into 4 facies associations: FA1 storm-influenced shoreface, FA2 fairweather shoreface, FA3 offshore and FA4 carbonate ramp. FA1 tended to preserved primary sedimentary structures with absent to minimal bioturbation suggesting ichnologically stressed environments during deposition, while FA2 recorded abundant bioturbation and relatively high ichno-diversity. A lithostratigraphic and sequence stratigraphic framework of the Lower and Middle Cambrian succession was then constructed, consisting of the Mount Clark and lower Mount Cap Formations. At the base of the Cambrian is a regional-scale sequence boundary, the sub-Cambrian unconformity. Up-section, three maximum transgressive surfaces and three maximum regressive surfaces were identified, resulting in three T-R cycles.