SURFICIAL GEOLOGIC MAP ALONG THE KANAB CREEK ALLUVIAL CORRIDOR IN SOUTHERN UTAH: EVIDENCE OF MULTIPLE CYCLES OF ARROYO CUTTING AND FILLING

Kanab Creek is a north-south trending catchment that drains part of the Grand Staircase landscape in Southern Utah, and terminates in western Grand Canyon. An approximately 21-km long and 5-km wide corridor centered on Kanab Creek was mapped in the White Cliffs and Kanab 7.5 minute quadrangles between the Jurassic White Cliffs and Vermillion Cliffs. Bedrock is composed primarily of very thick Navajo Sandstone, and some Kayenta formation at the south end of the field area. Along this 21-km stretch, Kanab Creek can be divided into 3 unique geomorphic reaches. The upstream reach is a bedrock controlled, gravel-bedded channel that is dry most of the year. Here, Quaternary basalt flows crop out at river level. The middle terraced reach is a bedrock canyon where 3 terraces are preserved at 40, 20 and 5 meters above modern river level. The channel is sand dominated, is engulfed by woody riparian vegetation today, and contains some amount of water most of the year. The southern reach of Kanab Creek, where it exits the Vermillion Cliffs, is characterized by a deep arroyo that has cut 30-40 meters into its basin-fill deposits. Kanab Creek incised to its modern level in the early 1880s during a series of large floods, which is well documented through historical accounts.

The goal of this research is to provide a 1:12000-scale surficial geologic map of the Kanab Creek corridor from the White Cliffs to the Vermillion Cliffs. Mapping includes river and eolian deposits, as well as colluvium and alluvial fans. In addition to mapping, terrace and basin-fill deposits were dated using Optically Stimulated Luminescence (OSL) dating. Mapping, geochronology, and sedimentary facies interpretation are important for understanding the timing and duration of arroyo cut and fill cycles along Kanab Creek. Outcomes of this mapping will help to test the hypothesis that cycles of incision and aggradation may be linked to changes in regional climate. Comparison of this alluvial record to other alluvial and regional paleoclimate records may relate these processes to changes in sediment supply, regional precipitation regime, and flood frequency.