Current estimates put the combined bitumen in these deposits at 1.7 trillion barrels, and somegeologists believe more field work will jack that number up a fair bit further.
Basically, to assess mineral content the geologists drill some holes and assay the ore for potash exploring percentage of mineral content as well as the thickness of the pay zone.
Some tools were sandwiched in ash from the eruption of the Toba super-volcano in Indonesia that geologists can date very accurately to 74, 000 years ago.