The Facies Front of the Devonian Slave Point-Elk Point Sequence in Northeastern British Columbia and the Northwest Territories

Abstract

Abstract The facies front of the Slave Point – Elk Point sequence is the narrow zoneof contact between the carbonate Slave Point, Sulphur Point and Pine Pointformations and the equivalent shales of the Horn River formation. The faciesfront trends approximately north-northeast in British Columbia andeast-northeast in the Northwest Territories. The shales lie to the northwest ofthe front and the carbonates to the southeast. The facies front of the Slave Point Elk Point sequence is in the order of 1000 miles in length. It extends over a maximum known stratigraphic interval ofabout 1,300 feet. In parts of the Northwest Territories, the interval overwhich the facies front is developed is considerably less due to the influence of a positive tectonic feature known as the Tathlina High. In most areas, the Slave Point and Sulphur Point formations pass to shalequite abruptly and tend to behave as a unit in this respect. The zone in whichthe Pine Point formation passes to shale is much broader than that in which the two overlying formations pass to shale. Three main tectonic divisions of the facies front are recognized. It is probable that the major morphological features of the front result from structural control. Drilling has shown that, in many areas, the dolomitized Slave Point formation at the facies front contains abundant reserves of natural gas. There are sufficient grounds for believing that the underlying formations at the front also contain significant hydrocarbon reserves. Introduction In the eastern part of northeastern British Columbia and in northern Alberta, the Slave Point Elk Point sequence consists of a series of evaporites and carbonates, mainly Givetian in age. When traced to the northwest, the evaporites are lost from the sequence and the Slave Point – Elk Point rocksconsist of a series of limestones and dolomites with occasional interbedded shales. Beyond a relatively narrow zone of profound lithologic change whichtrends east-northeast across the southern part of the Northwest Territories and north-northeast across northeastern British Columbia, the upper three-quarters of the Slave Point – Elk Point sequence is represented by a series of shales.