THE LINK BETWEEN REMOTELY SENSED LINEAMENTS AND FRACTURE-CONTROLLED FLUID MOVEMENT IN DRIFT AND BEDROCK

Linear elements in the topography, surface drainage, natural vegetation and soils are visible as individual and composite lineaments in airphotos and satellite images of glaciated landscapes in Western Canada. Clusters of subparallel lineaments aligned roughly end-to-end define long lineament zones. Dominant lineament trends commonly follow NW-SE and NE-SW orientations. Subdominant trends are also present in many areas.

In studies conducted over the past 50 years, surficial lineaments have been correlated with diverse subsurface data sets, at regional and local scales, to investigate their origin and geological significance. Correlated data include regional isopach and structure contour maps, aeromagnetic and gravity maps, seismic data, subsurface fractures in drift and bedrock, groundwater yield, artesian groundwater discharge, soil gas microseepage patterns and production trends in oil reservoirs.

These studies demonstrate that many remotely sensed lineaments are surficial manifestations of regional systematic fractures. Periodic reactivation of basement faults and fault block boundaries, salt dissolution, differential compaction, crustal compression, regional uplift, and earth tides are among the many mechanisms thought to be responsible for propagation of deep-seated structural features over geologic time. Glacial loading and unloading, neotectonic adjustments, preferential surface erosion and fracture-controlled gas venting and fluid discharge are some ways by which dominant lineament trends are imprinted in glaciated landscapes.

Because of the close connection between lineaments and subsurface structures, integration of remotely sensed lineaments with multidisciplinary data sets aids identification of fracture-enhanced permeability zones in oil and gas reservoirs and interpretation of soil gas geochemical surveys. These methods are also used for groundwater exploration, and to assess potential pathways for seepage of CO₂ from storage reservoirs and water inflow into underground mines.

Data from studies in Western Canada provide examples of lineaments mapped from satellite and airphoto images, and illustrate their link to fracture-controlled movement of water, gas and oil in the subsurface.