DETERMINING THE IMPACT OF LAKE POWELL LEVELS AND SEASONAL VARIATIONS ON THE COLORADO RIVER BY ANALYZING USGS CORES TO LINK SEDIMENTARY FACIES, DEPOSITIONAL ENVIRONMENTS, AND PRE-2018 EVENTS IN LAKE POWELL'S HISTORY

The Colorado River and its tributaries, whether experienced from its waters or observed from above, are a geologic marvel. These iconic canyon systems trace their origins to ancient sedimentary layers, deposited over 300 million years ago during the Pennsylvanian period, which were later uplifted and carved by the younger Colorado River. More recently, the construction of Glen Canyon Dam in 1963 created Lake Powell. Since then lake levels have been monitored, seasonal tributary discharge has been recorded and average daily temperatures reported. In 2018, the Utah Geological Survey (USGA) collected core samples along the Colorado River near a newly forming delta, which is actively migrating southward toward the dam. These cores reveal meter-scale stratigraphic packages comprising pre-reservoir fluvial sands, thickly bedded muds (5–10 cm), and thinly bedded muds (2–5 cm). Preliminary analysis shows consistent patterns across multiple cores, enabling the identification of sedimentary facies that reflect distinct depositional environments. By correlating these environments with historical lake levels and discharge data, we aim to better understand how fluvial and deltaic systems respond to varying parameters. Given the Colorado River’s large and relatively steady discharge rates, it is hypothesized that facies development is primarily influenced by changes in Lake Powell’s reservoir levels. The stratigraphic sequences observed in the cores are expected to correspond directly to fluctuations in lake levels, offering insights into the interplay between sedimentary processes and reservoir dynamics.