Paleoclimate reconstruction derived from speleothem strontium and δ13C in Central Florida

Variability of strontium and carbon isotopes are reported from a speleothem from Central Florida, USA. Thermal ionization mass spectrometry of uranium–thorium isotopes indicate the speleothem was precipitated during the last 4000 years. Sr concentrations are negatively correlated with δ13C, a relationship inferred to record changes in soil productivity. Coeval changes in the Sr content and δ13C signals, as induced by soil productivity, are explained by changing precipitation above the cave. Both proxies record a 170–180-year solar cycle that has also been found in the Gulf of Mexico marine records and elsewhere. Consequently, this result provides evidence of an extraterrestrially driven modulator of precipitation in Central Florida.