LIMNOLOGY AND THE EOCENE LAKES OF THE ROCKY MOUNTAIN REGION
Principles of limnology (science of lakes) and their application to the development of the oil-shale-containing lakes of the Green River formation are given. Because of changes in the density of water over a relatively short temperature range, bodies of water tend to become heterogeneous and thermally stratified into layers called epilimnion and hypolimnion. The latter rests on the bottom of the lake and becomes deficient in oxygen but with an abundance of carbon dioxide and hydrogen sulfide. At the end of Upper Cretaceous time, the Rocky Mountain ranges were upfolded and the intermontane basins formed. Inside these basins, streams eroded new mountains and filled the basins with various mineral deposits. A predominance of mineral carbonates is explained by the fact that the streams draining into the lakes crossed upturned limestones or limy formations. Vast quantities of organic material were deposited in this formation by various methods in amounts from trace to more than 80 percent by volume. The organic material was preserved under stagnant conditions at the bottom of the lake, where oxygen was scarce or absent and hydrogen sulfide was abundant. A stratified condition existed during most of the period of oil-shale formation and preserved the organic material frommore » complete oxidation.« less