| Description |
A paleoenvironmental reconstruction is presented from the Bear River Range, southeast Idaho. Reconstructed environmental conditions are inferred from paleoecological proxies, including pollen, macrofossils, and macroscopic charcoal from lacustrine sediments taken from Plan B Pond. A second, complementary paleoenvironmental reconstruction is presented based on stable carbon and oxygen isotope measurements of speleothem calcite collected from Minnetonka Cave, located just 8 km from Plan B Pond. The paleoenvironmental reconstructions from the two Bear River Range records suggest that each record contains significant seasonal bias, with the speleothem and sedimentary charcoal records primarily recording winter-season variability over time, and the pollen and macrofossil data recording summer conditions. Together, the Bear River Range data show a comprehensive picture of Holocene hydroclimatic conditions, and refines our understanding of controls on water resource variability in the region. Based on the Bear River Range records, the study area experienced cool, wet winters, and hot, dry summers in the early Holocene (prior to ~7500 BP), as compared to modern. The middle Holocene (7500-4000 BP) was characterized by dry and consistently warming winters, with dry, warm summers. The Late Holocene (4500 BP-Modern) has been characterized by cooler summers, with generally wetter, but increasingly variable, winter conditions. The results of this study indicate that previously published paleoclimate reconstructions from the Western United States must be considered carefully when using them to understand large-scale ocean atmosphere teleconnection patterns such as El-Nino Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO). Because these teleconnection patterns are associated with spatially consistent seasonal precipitation and temperature anomalies, paleoclimate records must be evaluated for seasonal bias, if they are to be used for reconstructing past strength or presence of the teleconnection anomalies. |
