INFLUENCE OF BASE LEVEL AND CLIMATIC CHANGES OF THE LITTLE DOLORES RIVER, COLORADO

Studies of arroyos in western Colorado have received little attention compared to the more studied arroyos of the southwest. The Little Dolores River, a tributary of the Colorado River on the Uncompahgre Plateau has recently been studied to understand the dynamics that shape the history around arroyo formation. Geologic mapping, 14C dating, and GPS gradient transects were used to conduct this study. This study was part of a larger research effort conducted in the summer of 2006 as part of a NSF-REU funded to Mesa State College.

Gradient transect geometry reveals the Little Dolores River is not influenced by base level changes from the nearby Colorado River. The transect also reveals a series of knickpoints along the stream which represent structural changes of nearby faults. Furthermore, gradient transect also reveals these faults do not offset the fill terraces.

A geologic map constructed in this study displays the distribution of fill terraces. Also mapped are tributaries that join into the Little Dolores from the south. These tributaries push the main channel up against its bed rock canyon walls to the north. Charcoal fragments and snails are seen within the fill terraces. These probably represent recent fires and flooding within the tributaries carrying sediment to the main channel.

Two cycles of incision and aggredation are reflected within the two fill terraces. Due to structural observations of the main channel it is suggested that the arroyo formation is due to regional and local climatic changes. Local flooding reflects periods of rainy seasons and regionally wetter years.