Coal Rank Distribution within the Bluesky - Gething

The top of the Gething Formation is one of the more important formational picks routinely performed by the oil and gas industry during their exploratory and development drilling as this horizon is very c:on-tinuous through northeastern British Columbia and much of northern Alberta. The name Bluesky is given to the rock unit which occupies this stratigraphic level, namely a sandstone-conglomerate unit of marine origin which separates the continental coal measures of the Gething Formation from thc overlying marine shales of the Moosebar Formation (see Fig. 32). The Bluesky is commonly glauconitic .and has a variable thickness (0 to 50 metres1 over relatively short distances and most likely represents shoreline deposition of the rapidly transgressing Clearwater Sea from the north. The Bluesky-Gething is an important petroleum producer in the Fort St. John area. Coalification is mainly a result of temperature to which the host sedimentary rocks are exposed. In turn, this temperature is determined by the geothermal gradient and the depth of subsidence. Coal rank is the1.e-fore a very sensitive indicator of these temperatures. A coal rank map of a specific stratigraphic horizon is particularly useful in portraying regional variations in geothermal heat-flow, tectonism, and post-deposi-tional basin history. Any coal rank variation due to differences in the stratigraphic level of the coal occurrences is eliminated because only one stratigraphic horizon is sampled. This effectively screl?ns out the back