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DEPOSITION

Of the great amount of sediment removed from the Rocky Mountain
area little remains on the continent. Much of it may have been carried
north to the Arctic Sea, along some old Tertiary drainage route. The lignite
and clay of Coal River record swamps and advanced weathering of sedi-
ments, and deposition on alluvial plains on the site of the Liard Plain. This
may have been when the mountains were reduced to a low level after the
first uplift; doubtless one or more uplifts have followed.

Remnants of Tertiary gravels, like the Cypress Hills and Wood Moun-
tain gravels ot southern Saskatchewan, may yet be preserved in the Plains
of northeastern British Columbia, but as yet they have not been discovered.