View article

Branched glycerol dialkyl glycerol tetraethers (brGDGTs) in lake sediment are increasingly being used to reconstruct past mean annual temperatures. These compounds have been most extensively studied in tropical regions, but the potential to use these compounds to study the temperature history of alpine settings and mid-latitudes, such as the Rocky Mountain region of the United States, has not yet been examined. We present a new temperature calibration based on brGDGTs and PRISM temperature data from 34 small alpine lakes in the Southern Rocky Mountains in Wyoming and Colorado. The lakes vary in elevation with mean annual temperatures (MAT) ranging between-1 and 2.7 C and lake depths ranging from 1 to 25 m. Our results indicate that both mean annual air temperature and lake depth were important controls on the degree of methylation of the suite of brGDGTs found in the sediments. When we …