Utility of Magnetotelluric Data in Unravelling the Stratigraphic - Structural

The Ca na dian Cor dil lera, where the Juan de Fuca oce anic plate is cur rently be ing subducted be neath the North Amer i can con ti nent, is com prised of oce anic and is land arc ter ranes accreted to the west ern edge of an ces tral North Amer ica since the Neoproterozoic (Gabrielse and Yorath, 1991; Mon ger et al., 1972; Mon ger and Price, 1979; Mon ger et al., 1982). The Me so zoic Nechako Ba sin, lo cated within the Intermontane Belt of the Ca na dian Cor dil lera, in cludes over lap ping sed i men tary se quences de pos ited in re sponse to this terrane amal gam ation. Re gional transcurrent fault ing and as so ci ated east-west ex ten sion, be gin ning in the Late Cre ta ceous, was ac com pa nied by the ex tru sion of ba saltic lava in Eocene and Mio cene times that forms a vari ably thick sheet, av er ag ing 100 m in thick ness and pos si bly ex tend ing up to 1 km thick in iso lated places, cov er ing much of the ba sin. The main geo log i cal el e ments within the south ern Nechako area in clude Mio cene flood ba salt, Ter tiary vol ca nic and sed i men tary rocks, Cre ta ceous sed i men tary rocks and Ju ras sic sed i men tary rocks (Fig 1). Un der stand ing the dis tri bu tion and struc ture of these sed i men tary rocks at depth is vi tal for as sess ing pos si ble re sources. An as sess ment of the hy dro car bon po ten tial based on ex ist ing geo log i cal in for ma tion and well data, per formed by the Geo log i cal Sur vey of Can ada in 1994, sug gested that the Nechako Ba sin may con tain as much as a tril lion cu bic metres of gas and a bil lion cu bic metres of oil (Hannigan et al., 1994). The thick vol ca nic cover lim its the transmission of reflection seismic waves and has made it difficult to determine the physical boundaries of the basin, impeding exploration.