Quarternary evolution of the Colorado River at Lees Ferry, Arizona.

摘要

Eight deposits have been identified along the Colorado River at Lees Ferry using detailed mapping, sedimentology, and cross-sectional surveys. Geochronology of six of these deposits using optically stimulated luminescence and cosmogenic 10Be exposure techniques indicates a long-term bedrock incision rate of 290 to 470 m/my. Comparison of these incision rates to others reported throughout the Colorado River basin reveals a region of faster incision in the vicinity of Lees Ferry and Glen Canyon. This apparent increase in central plateau Pleistocene incision rates may be caused by either epeirogenic uplift or transient waves of incision in response to original drainage integration. In addition, chronostratigraphic analysis indicates that deposits at Lees Ferry are generally younger than correlative deposits in headwater catchments and in eastern Grand Canyon. Data from this study indicate that fluvial responses at Lees Ferry are a complicated integration of signals from climate change in headwater catchments and sediment production from local hillslopes and tributaries.