Preliminary Map 51 presents the geology of the Jurassic-Cretaceous Kootenay Group exposures on the Greenhills Range of the Elk Valley coalfield west and south of Fording in southeastern British Columbia. Coal-bearing lands belonging to Fording Coal and B.C. Coal were covered. The Preliminary Map consists of three 1:10 000 scale geology maps on an orthophoto base; each contains a legend and schematic sections showing the distribution of coal seams in the coal-bearing rocks.
Data presented are based on examination of surface outcrops and road-cuts, with minor air-photograph interpretation.
In many cases, poor exposure has limited the amount of data and has restricted the ability to correlate seams.
Seam pinch-outs and wash-outs are common, however, and account for many of the discontinuities in seam traces.
Kootenay Formation is composed of, from oldest to youngest, the Morrissey Formation (basal sandstone), Mist Mountain Formation (former Coal-bearing Member), and Elk Formation. The last, which occurs only in the north half of the map-area, includes a significant number of resistant sandstone units, which are not indicated on the map. The presence of Elk coal, alginite-rich coal, was used to identify the Elk Formation, while the contact between Elk and Mist Mountain Formations was arbitrarily placed at a mappable sandstone horizon.
Coal deposits in the map-area are west of the trace of the west-dipping Erickson fault system. Other major structures include the Greenhills fault, probably a splay of the Erickson fault, the Greenhills syncline, and the Fording Mountain anticline, which parallels the Greenhills syncline throughout the entire length of the Greenhills Range.
The rank of the coal has been determined by measuring the mean maximum reflectance in oil (Ro max) of the maceral vitrinite. Values >1.12 per cent indicate medium-volatile bituminous coal, while those <1.12 per cent indicate high-volatile coal. The entire coal-bearing section on Greenhills Range (in the area mapped) is high-volatile in rank, with the exception of the lowest one or two seams in the southern part of the range, which are medium-volatile. This is in marked contrast with the adjacent portions of the Elk Valley coalfield, including the Fording Coal Greenhills pits, where rank values of the basal seams are in the range of 1.30 to 1.40 per cent. The fact that the map-area sits west of the Erickson fault probably accounts for this contrast, as normal faulting in southeastern British Columbia occurred some time after coalification. In corollary, Fording Coal Greenhills pits must be separated from the map-area by a normal fault, probably the northward extension (not indicated on the map) of the Erickson fault.