8 Paleoclimate Records and Future Climate Trends in the American Southwest I

Tuesday, 15 May 2018
8:20 AM - 10:20 AM
Kaibab Room

CHRONOSTRATIGRAPHY OF TWO DUNE FIELDS IN SOUTHERN UTAH - IMPLICATIONS FOR DROUGHT PATTERNS IN THE CENTRAL COLORADO PLATEAU

Paper number: 8-4
Program: Theme Sessions
Time: 9:05 AM – 9:25 AM

Authors

Abstract

Sand dunes are threshold systems capable of recording past changes in effective moisture and aridity, sensitive to sustained, decadal-scale drought. Records of past drought can provide a reference to natural climate variability and expected extremes in an area. Such records provide data for refining climate models, as well as regional and community adaptive planning.

Records of past eolian activity were reconstructed for the Kanab and San Rafael dune fields in southern Utah using geomorphic mapping and stratigraphic description of outcrops and auger profiles. Age control for periods of dune activity comes from optically stimulated luminescence (OSL) dating of sand packages and radiocarbon dating of charcoal. Chronostratigraphic reconstructions are based on grain size analysis and description of buried soils (representing periods of dune stability).

Kanab dune field, located 13 km northwest of Kanab, Utah, covers about 12.5 km2 and is dominated by vegetated sand sheets and active and stabilized parabolic dunes. Initial OSL results have identified at least four periods of dune activation between 8 ka and 0.3 ka. The San Rafael Desert dune field, located approximately 25 km southwest of Green River, Utah encompasses a greater area (>2500 km2) and is composed of multiple active and stabilized barchanoid and parabolic dune fields. This region also contains isolated linear low-relief (<2 m) sand ridges, oriented NNE. Preliminary OSL ages identify at least three periods of dune formation between 8 ka and 0.5 ka.

We hypothesize that persistent (at least decadal scale) regional droughts would be recorded by coeval dune activity in these two dune fields (separated by 250 km). Conversely, non-correlative periods of dune activity likely reflect local disturbances, changes in vegetative cover or sand supply. Preliminary results suggest at least three periods of regional dune activity at 8 ka, 2 ka and 0.7 ka. Further analyses will refine chronologies of both sites and allow for regional comparison to tree-ring and other climate records.

Geological Society of America Abstracts with Programs. Vol. 50, No. 5

doi: 10.1130/abs/2018RM-314190

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