Abstract:
A quantitative model is proposed for the long-term evolution of lakes and internally drained basins resulting from tectonic vertical motions, sediment infill, outlet erosion, and climatic regime. The model accounts for the formation of a water body in the topographic basin created by tectonic uplift across a river, where incision capability is calculated using a stream power-law. The model also addresses the notion that, after cessation of tectonic forcing, lakes are transitory phenomena over geological time scales. High uplift rates across an antecedent river, in combination with low upstream precipitation, result in river defeat and lake formation. In addition to geometrical, lithological, and tectonic parameters, the evaporation rate at the lake surface is revealed as a key factor triggering drainage closure (endorheism) and significant lake life extension by preventing outlet erosion. Post-tectonic lake extinction is ensured by sediment overfill and/or outlet erosion. Once uplift comes to an end and drainage reopens (lake capture), shallow lakes at high altitudes undergo a faster reintegration into the drainage network and extinction. Vertical isostatic movements of the lithosphere significantly delay this process in lakes larger than 50-200 km. The development of an internally drained basin out of an open lacustrine basin requires that uplift across the outlet persists until the lake is large enough to evaporate all collected water. The evolution of tectonic lakes has, therefore, similar dependency on geometrical constraints (initial relief, length of the river, hypsometry of the catchment), lithological parameters (rock erodibility), tectonics (uplift rate, duration, and its spatial distribution), and climate (precipitation and evaporation rates). ©2006 Geological Society of America.
