Late Cenozoic landscape evolution on lava flow surfaces of the Cima volcanic field, Mojave Desert, California

Landscape evolution in the eastern Mojave Desert is recorded by sys1ematic changes in Pliocene to latest Pleistocene volcanic: land· forms that show discrete periods of eolian deposition, surface stabilization, drainage-network expansion, and erosion on basaltic lava nows. These processes are documented by K·Ar dating in conjunction with morphometric, sedimentologic. pedologic, and geophysica1 studies. Lava-Dow surfaces are composed of constructional bedrock highs and accretionary eolian mantles with overlying stone pave-ments. The stratigrapby of these mantles records episodic, climaticaJJy induced influxes of eolian rmes derived from playa floors and distal piedmont regions. 1De relative proportions of mantle and exposed bedrock vary with flowage, and Dows between 0.25 and 0.7S m.y. old support the most extensive eolian mantle and pavement reflecting landscape stability. Drainage networks evolve on nows by (1) rapid initial extension, (2) maximum extension and elaboration, and (3) abstraction of drainage. Increases in bedrock exposures and erosion of the eolian mantle on Oows > 0.70 m.y. old coincide with maximum drainage extension and significant changes in soil and hydrologic properties within this mantle. Increasing the content of pedogenic clay and CaC03 causes the accretionary mantle's penneability to decr,ease; decreased mantle permeability promotes increased runoff, surface erosion, and drainage development. In the late Cenozoic. landscape evolution of lava nows, four major stages reneet variations in land· scape stability that are contTOlled by the impact of episodic influxes of eolian fmes and increasing soi1-profile development on infiltration· runoff properties of the Dow surfaces.