Turgay Trough - geological region in Western Siberia and Northern Kazakhstan, part of which in the Cretaceous era, about a hundred million years ago, was the Turgai strait between the Mediterranean Sea and the Arctic Ocean. Later it formed layers of brown coal, which is mined today in a career, “Priozerny" near the village of Kushmurun Kostanai region.

http://turgay.kz/7.html    Turgay plateau