Stratigraphic Analysis of Cretaceous Strata Flanking the Southern Nechako Basin ( Parts of NTS 092 M , O ; 093 B ) , British Columbia : Constraining Basin Architecture and Reservoir Potential

The Nechako Ba sin (Fig 1) is part of the In te rior Pla teau phys io graphic re gion of Brit ish Co lum bia and has been var i ously de fined in terms of ex tent and age (Ferri and Rid dell, 2006). Ac cu rate as sess ment of the pe tro leum po ten tial of the Nechako Ba sin hinges on a com pre hen sive un der stand ing of the ba sin ar chi tec ture de vel oped within Cre ta ceous strata, which rep re sent the most pro spec tive tar gets in the subsurface. Mod el ling the subsurface dis tri bu tion of these Cre ta ceous strata re quires de tailed strati graphic anal y sis of co eval, lat er ally ad ja cent strata ex posed along the ba sin mar gins. The age and gen eral lithological char ac ter of strata in the subsurface of the Nechako Ba sin are broadly known from in dus try drillholes and ex am i na tion of iso lated out crops of Cre ta ceous strata ex posed be neath ex ten sive Neo gene vol ca nic cover (re viewed in Ferri and Rid dell [2006], also see Fig 1 for the lo ca tion of many of these drillholes). How ever, re gional fa cies pat terns and ba sin ar chi tec ture are poorly un der stood, and even the strati graphic af fin i ties of subsurface strata are un clear. For ex am ple, Hunt (1992) iden ti fies some subsurface strata as pos si ble Jack ass Moun tain Group, a gen er ally ma rine suc ces sion which is ex posed along the south ern mar gins of the Nechako Ba sin, whereas Hannigan et al. (1994) as signs these rocks to the Skeena ‘As sem blage’ (more com monly termed the Skeena Group), a gen er ally nonmarine suc ces sion which is ex posed along the north ern mar gins of the Nechako Ba sin. This con fu sion il lus trates the poorly known na ture of the subsurface strata in this re gion. For a more thor ough dis cus sion of stratigraphic problems, see Ferri and Riddell (2006).