Coal seams occur in the Lower Gething Formation (320 to 345 metres thick) of the Bullhead Group which consists of sandstones, siltstones, mudstones and minor conglomerate. Nine coal zones occur predominantly in the middle third of the Lower Gething Formation. These are from oldest to youngest, the Lake Cadomin, Bumpy, Meadow, Unnamed Zone, Grizzly, Pump and B Lower and Upper. Of these the B varies from 0.8 to 2.54 metres thick and has resource potential in the north and south, while an associated C zone 2.65 to 3.13 metres thick, is also important in the south. The Pump, 2.89 metres thick and the Grizzly averaging 1.69 to 4.85 metres thick are the only other significant seams to the north of Rocky Creek. The B zones are regionally extensive, while the Pump, Grizzly and Cadomin in the east decrease in thickness to the east.

Coal also occurs in the Juro-Cretaceous Beattie Peaks Formation and the Bickford Formation (Minnes Group). In the latter, several thin (up to 1 metre) seams occur in addition to two seams in the Mount Merrick area which are each approximately 2 metres thick. They dip 40 to 60 degrees southwest and cannot be traced into less disturbed areas.

The Mount Merrick (MINFILE 093P 11), Jilg (MINFILE 093P 010) and Rocky Creek (Triangle) prospects were all part of the British Petroleum Exploration's Sukunka North project area in 1979 (Coal Assessment Report 671). The property was reconfigured slightly in 1981 by British Petroleum Selco, including the addition of the Terrace Hill block (which partly overlaps with the Triangle block), and renamed it the Rocky Creek property. BP Selco conducted exploration programs in 1981, 1984 and 1985.

Coal seams occur in the Juro-Cretaceous Minnes Group and Lower Cretaceous Gething Formation (Bullhead Group) consisting of sandstone, siltstone, mudstone and carbonaceous shale. Minnes Group coal occurs in the Bickford Formation and consists of two seams, the Merrick and Rusty, each on average 2 metres thick within 30 metres of the Cadomin Formation (Bullhead Group) base. The seams are laterally extensive over considerable distances in the Merrick block, but deteriorate and thin out across the depositional strike within the Jilg/Triangle regions; and in the Beattie Peaks Formation (Minnes Group). The latter are generally thin and uneconomic, with the exception of the Hill seam which is over 2.5 metres thick and occurs within an isolated high terrain.

The Gething Formation coal occurs in two coal zones, each 3 to 4 metres thick. Gething Formation strata is present quite extensively in the Sukunka North block, however within the Jilg, Triangle and Merrick blocks the Gething Formation sediments are confined to small tight folds and only the lowermost strata, containing at most 2 seams 0.5 to 1.5 metres thick in the Merrick block, are preserved.

The structure consists of northwest trending folds and thrust faults. The Triangle block contains a central broad syncline with a series of tight folds to the southwest and numerous southwest dipping thrust faults both in the southwest and northeast.

The structure consists of a series of northwest trending tight, isoclinal folds of the Merrick syncline in the southwest, and more gentle folds including the Rocky Creek synclinorium in the northeast. The folded strata are faulted by at least four major thrust faults.