Evidence for Climate Change FromDesert Basin Palaeolakes

Lakes have long been recognized as being rich storehouses of environmental information. A lake basin collects water, but also sediment, much of which has been weathered and transported via fluvial processes from the near and far reaches of its drainage basin. The amount of water held in a lake is recorded on the landscape in coastal erosional and depositional landforms created at the water’s edge. The sediments deposited on the bottom of the lake can be clastic, geochemical, or biogenic, and include materials derived within the standing water body itself, such as through coastal erosion, chemical precipitation, or biogenic concentration, as well as those delivered to the lake from the surrounding drainage basin. In most cases only a small percentage of a lake’s sediment load is delivered from outside of the drainage basin as aeolian fallout. Because, under natural conditions, climate is the main determinant of the amount of water in a lake and because it influences some important characteristics of the lacustrine sediments and biota, changing climatic conditions are represented in the suites of abandoned shorelines and accumulations of sediments left by the lake over time (Fig. 25.1). This archival property makes the geomorphic and sedimentologic evidence of present and past lakes valuable as environmental and palaeoenvironmental indicators. Such evidence from late Quaternary palaeolakes, in fact, ranks among of the most complete and accessible sources of palaeoclimatic proxy