LAKE BASIN MODELS THROUGH TIME

The study of ancient lakes began in the late 19th century with the work of Gilbert on Pleistocene Lake Bonneville and Russell on Pleistocene Lake Lahontan. The study of modern lakes began about the same time with Forel at Lake Geneva and Birge at Lake Mendota, Wisconsion. Though research in modern lakes continue uninterrupted until today, limnogeological investigations began anew in the 20th century when Bradley published work on the Eocene Green River Fm. in 1924. By the time of Bradley’s overview on "Paleolimnology" in 1963, research on eleven lakes in the US was in the "fact-finding stage". Picard and High accumulated data on 242 lacustrine "stratigraphic units" in the US in 1972. Their conclusion, after analyzing lithology, geochemistry (including isotopes), sedimentary structures, fossils, hydrology, and geomorphology, was that there were no diagnostic criteria with which to identify ancient lacustrine deposits. In the 1970s to 1980s, geochemical indicators such as boron, biomarkers, and a range of stable isotopes were used to expand interpretation of lake paleoenvironments, along with modern sedimentologic and environmental analyses. These tools let to the development of a three-fold lake model in 1990 by Schlische and Olsen for the Newark Supergroup basins based on lithologies and tectonics and in 1991 by Glenn and Kelts for all lakes based on lake levels and sedimentation rates derived from geochemical analyses. Global petroleum exploration on fossil and modern lakes lead Bohacs and Carroll in 1999 to refine the three-fold lake model by linking geochemistry with tectonics, defining the fluvial-lacustrine, fluctuating profundal, and evaporitic lake-basin-type facies associations. Progress in better resolution of stratigraphic sequences within lake basins (and hopefully among lake basins) rests with magnetostratigraphy, more precise age dating using minerals in sedimentary rocks, and other geochemical tools.