The Secus Mountain coal occurrences are located between Muinok Mountain to the west and Secus Mountain to the east, approximately 94 kilometres south-southeast of Tumbler Ridge.

The region is underlain by an assemblage of sedimentary rocks consisting mainly of continental margin and shelf facies rocks. This assemblage was deposited on and to the west of the Ancestral North American craton. These sedimentary rocks, for the most part typical continental shelf slope and basin facies, range in age from Hadrynian to Upper Cretaceous. Structurally these rocks are part of the Foreland thrust and fold belt of the North American Cordillera.

The coal measures of the region occur mainly in Cretaceous sediments deposited unconformably on older slope and basin strata. These sediments were subjected to fold and thrust tectonics, which also affected the older rocks.

The Lower Cretaceous Gates Formation (Fort St. John Group) is the major coal-bearing unit of the area and consists of siltstone, shale, sandstone, conglomerate and several cycles of coal deposition. Within the Secus Mountain area, the Gates Formation is approximately 390 metres thick and composed of alternating sequences of conglomerates, sandstones, siltstones, mudstones and coal seams. Individual conglomerate units, though massive and often prominent, are thinner and have better-developed bedding than the underlying Lower Cretaceous Gething and Cadomin formation (Bullhead Group) conglomerates. The Middle Gates Formation consists of a series of fining-upward sequences that culminate in coal development, and hosts all of the economic coal seams of the Gates Formation.

The structural setting of the South Secus Block is a broad syncline cut off on the west by the Front Range thrust of the Rocky Mountains. This major fault has thrust Paleozoic carbonates over the Mesozoic coal-bearing strata of the foothills. To the east of the synclinal axis, the east limb of the syncline is the west limb of the Wapiti anticline. Stereographic analysis of surface outcrop bedding attitudes performed in 1980 indicates the syncline has a shallow plunge trending at 339 degrees (Coal Assessment Report 633).

The prominent Torrens sandstone (greater than 50 metres thick) is located at the base of the Gates Formation. The upper part of the Torrens is hard, grey sandstone; the underlying, thicker unit contains softer, brown sandstones that weather distinctively. The first coal zone (greater than 20 metres) encompasses the strata between the Torrens sandstone and a conglomerate unit. The conglomerate (greater than 25 metres) is a massive coarse-grained unit lying stratigraphically above the coal zone and forms a convenient top to the recessive coal zone. In the South Secus area, the coal zone contains 4 to 9 metres of coal in two main seams.

Only one Gething Formation coal seam is noted in the Secus Mountain area. Stratigraphically, the coal, approximately 1.6 metres thick, is positioned approximately 20 metres below the top of the Gething Formation.

The objective of a 1983 drillhole was to intersect and core the upper to middle section of the coal-bearing Gates Formation. In 1981, three holes drilled in the South Secus area (two by Petro-Canada and one by Crows Nest Resources Ltd.) intersected the lower Gates, containing eight metres of coal in four seams in 107 metres of section. Based on a 1976 Petro-Canada drillhole (BBD 76-1), which intersected a 7 metre and a 1.5 metre coal seam in the Middle Gates, and on the stratigraphic consistency within the Gates, as shown by the three 1981 holes, it is believed that the Middle Gates may contain significant amounts of coal in the South Secus area. The 1983 drillhole was spotted 350 metres southwest of 1981 drillhole SC 81-1. Based on the 1981 interpretation, it was expected that the 1983 drillhole would intersect the Middle Gates and the top of the Torrens sandstone within the 300-metre depth capacity of the drill (Coal Assessment Report 633).

Drillhole SC83-1 intersected the Torrens sandstone at 179.9 metres, and 155.4 metres of the Lower Gates was cored. Four seams greater than 1.0 metre thick were intersected, totalling 9 metres of coal in 110 metres of section. This hole intersected the same section of the Gates as 1981 drillhole SC81-1. The target section, believed to contain a 7-metre seam, was missed. The results of the drilling indicate that the axis of the syncline occurs between drillholes SC81-1 and SC83-1. As a result, the lower section of the Gates is closer to the surface than expected (Coal Assessment Report 633).

Coal quality analyses of the core from SC83-1 and SC81-1 indicate that the coal rank is high-volatile A bituminous (Coal Assessment Report 633).

Work History

During 1978 through 1981, Crows Nest Resources Limited, on behalf of owner Shell Canada Resources Ltd., conducted an exploration program consisting of two helicopter-supported diamond drill holes, totalling 451 metres, geological mapping and trenching. In 1983, Crows Nest Resources Ltd. drilled one NQ diamond drill hole on the South Secus Block to a total depth of 187.8 metres.