generally assume that the Alberta, Canada, oil sand deposit
formed when dinosaurs prowled Earth during the late Cretaceous.
But new isotopic measurements reveal that these previous
estimates may be off by tens of millions of years. The Western
Canada Sedimentary Basin is a large source of recoverable oil,
and researchers have recently redated the deposit to some 60
million years older than previously thought. Photo courtesy of
Syncrude Canada Ltd. About the size of Ireland, the Western
Canada Sedimentary Basin is the largest oil sand deposit in the
world. But the age and source of that oil has remained unknown.
One idea has held that the oil formed and moved to fill the
basin 60 million years ago during the Laramide orogeny a series
of mountain-building events that greatly affected the Rocky
Mountains in western Canada. But according to David Selby and
Robert Creaser in the May 27 Science, measurements of rhenium
and osmium ratios in the oil date the deposit to about 112
million years old. The thing that is s