Large lakes provide key records of global environmental change because of their geographic distribution and the kinds of stratigraphic records that they contain. Large lakes range in age from more than 20 million to less than 20 thousand years. This temporal and spatial distribution is precisely what is required for regional and time-series reconstructions of climate and other environmental systems.
Large lakes vary greatly in their physical, chemical, biological, and geological characteristics.
They range in chemistry from highly dilute to highly saline and their waters may vary greatly in residence time. Depending on nutrient availability, their biological productivity may range from oligotrophic to hypereutrophic. Water levels in some lakes fluctuate rapidly, while others are hydrologically stable. Human impacts on large lakes range from dramatic to nil. Within a given large lake, depositional environments are varied and complex.