Canwest News Service: Nearly a quarter of the world’s undiscovered petroleum resources lie in the Arctic, confirms a U.S. study that should only intensify pressure on countries such as Canada to stake their claims to the Far North. The U.S. Geological Survey has previously offered a rough estimate of the Arctic’s vast oil and gas resources. On Wednesday, the state-funded agency released a study that refines its estimates for the entire Arctic region. According to the new assessment, the Arctic holds …