PALEOLAKES: WHERE THEY WERE AND WHERE THEY MIGHT HAVE BEEN

The study of paleolakes was a central research theme of Professor Elizabeth Gierlowski-Koredesch. To supplement her investigations and to continue her research in this area, a database has been compiled that records the location, age, sedimentology, and tectonic/physiographic setting of over 500 paleolakes. The lakes in this database range in age from Mesoproterozoic (Belt Group) to Miocene (Lake Meade) and are categorized by their tectonic/physiographic setting (e.g., continental rift, intermountane basin, internal drainage basin), the facies of the sediments that compose the lacustrine deposits ( e.g., clastic/carbonate, evaporites, varves, coals, etc.), and by the climatic zone in which the lakes formed (e.g., arid evaporitic, glacially influenced, etc.). In addition to the paleolakes culled from the geologic literature, a second group of lakes - "lakes that might have been”- were mapped using a predictive model based on estimates of paleotopography (PaleoDEMs) and paleoclimatic models (FOAM). In these cases, internal drainage basins likely to contain lakes were mapped using a topographic model (ArcGIS, Hydro tool) that predicted the location of ancient rivers and streams. If these internal drainage basins occurred within climatic zones where precipitation exceeded evaporation, i.e., areas of positive runoff, then the basins were classified as “potential lakes”. This dual approach of mapping lakes using geologic data and predicting the location of paleolakes allowed us to: 1) use the geological record of paleolakes to test the validity of the climatic and topographic models, and 2) predict the past occurrence of paleolakes for regions where the lacustrine deposits are either deeply buried or have been removed by uplift and erosion. Finally, both known paleolakes and predicted paleolakes were plotted on a set of revised paleogeographic reconstructions produced by the PALEOMAP Project. A set of these plate tectonic and paleogeographic reconstructions can be downloaded from: http://www.earthbyte.org/paleomap-paleoatlas-for-gplates/