Relative timing and significance of folding in the western Skeena Fold Belt, northwestern Bowser Basin, British Columbia : interpretation of structural and seismic reflection data

• Main Author: Bone, Katherine E.
• Language: English
• Published: 2009
• Online Access: http://hdl.handle.net/2429/12033

The northwestern Bowser Basin overlies Mesozoic units of Stikine Terrane and encompasses deformation of the western Skeena Fold Belt. The region includes a portion of Lithoprobe SNORCLE Line 2A seismic reflection transect. The research has allowed detailed observation of the surface geology to be combined with high quality subsurface information. Folds within the western Skeena Fold Belt are separated into three groups, based on fold trend. Northeast-trending folds are located in select areas through the region and exhibit transected cleavage that is northwest-striking. North- and northwest-trending folds comprise separate fold groups in the area. North-trending folds are observed in the central area of the region and are spatially associated with north- or northwest-striking cleavage. In the majority of cases northwest-trending folds are spatially associated with relatively axial-planar cleavage. The transected nature of folds in this region is interpreted to be the result of a temporal sequence of rotating fold orientation, with initial northeast-trending folds overprinted by north- then northwest-trending folds. This temporal sequence supports the work of Evenchick [2001] within the western Skeena Fold Belt. Seismic reflection data for the area were post-stack migrated to produce a data set highlighting near surface structures. Near surface velocity variations were examined using forward modelling and 2-D tomographic inversion of first-break arrival data. The near surface velocities were used to produce a laterally varying velocity sequence for post-stack migration. Reflection data for the upper eight seconds contains the boundary between the Bowser Basin and Stikine Terrane. The Bowser Basin is observed to have a variable thickness, with the thickest sections caused by the structural stacking of units. The data set also indicates that below the Bowser Basin Stikine Terrane is involved in Skeena Fold Belt deformation, with faulting and overthrusting of Stikine Terrane on Bowser Basin units observable.