Reconstructing Paleoenvironmental Conditions of Northern Alabama Utilizing Guano Cores

Abstract

The need to understand long-term precipitation patterns in the southeast United States are of great concern considering human population increase, climate change, agricultural production and environmental stressors. Current management strategies are typically based on records with short chronologies, spanning the past hundreds of years. One paleoclimate archive capable of tracking moisture regimes and other paleoenvironmental conditions over millennial timescales is guano deposits in cave systems. Guano deposits record moisture and precipitation and are commonly found in many caves systems throughout the southeastern United States. However, this potentially useful tool has received little attention. Here, I present a 9,000-year record of moisture and rainfall variability based upon stable isotopes systematics (δ15N, 13C, D) in a guano core collected from a cave system named Cave Springs, located near the city of Priceville, Alabama. Moisture variability was inferred from nitrogen and carbon stable isotope records. Deuterium was measured from bulk guano and used as a proxy of the evaporation to precipitation balance. Results show two periods of low moisture in the early (11,151 – 13,764 YBP) and late (0 – 4,177 YBP) Holocene separated by a period of high moisture during the middle (4,388 – 10,916 YBP) Holocene, which correspond to nearby pollen reconstructions. Furthermore, this study suggests that future research investigating guano deposits from caves can provide a reliable long-term record of local paleoclimate where other records such as lake sediments are not available.