Halfway River map-area, British Columbia, lies between 56 and 57 degrees north and 122 and 124 degrees west; it includes part of the Interior Plains and all of the Rocky Mountains and Foothills along Peace River valley. Most of the area is mountainous, has been
glaciated, and is underlain by a succession of sedimentary strata, about 25, OOO feet thick, and of Precambrian to Late Cretaceous age. For descriptive purposes the map-area has been divided into Rocky Mountains, Foothills, and Interior Plains divisions. The region has been deformed by thrust
faulting and by folding as a result of compressive stresses. Thrust faulting is considered to be the more important and the initial type of structural deformation within the Rocky Mountains. Folding is thought to have started after or contemporaneously with the initial thrusts and to have persisted
after movement on the faults had ceased. Most of the thrust faults are west dipping and some are folded. In the Foothills and Plains divisions folding may be the more important type of deformation. Paleozoic strata underlie the Rocky Mountain division within the map-area. Few formational names exist
for the lower Paleozoic rocks in this area and, because of east-west and probably north-south facies changes; new names have not been given at this time. A brief lithological description of each formation or larger unit together with its distribution and probable age is given. Several unconformities
occur within the Paleozoic succession. Mesozoic strata underlie the Foothills and Plains divisions of the map-area. Within these rocks existing formational names have been used and the lithology, paleontology, and distribution of each formation is described. Unconformities are present at the top of
the Fernie Formation and within the Lower Cretaceous sequence. Natural gas, the most important economic mineral, is produced in the northeastern part of the map-area. Large reserves of good coal are known in the Lower Cretaceous Gething Formation, but no mining is being done at this time. The site
finally selected for the high dam now being constructed for the British Columbia Hydro and Power Authority is located a short distance downstream from the head of Peace River Canyon. Stratigraphy and structure were important considerations in the choice of the site.
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