Paleoclimatic Record in Carbonates from the Semiarid Region of Bahia

The paleoclimatology in the semi-arid region of the State of Bahia is examined based on the isotopic composition of carbonates. from the Caatinga Formation. The chronology of a profile across this Formation, based on the analysis of the activity ratios 230Th / 234U and 234U / 238U, covers the range from 250,000 years in the top to about 10,000 years in the bottom. It was identified two patterns on the stable isotope composition, one for wetter conditions coupled with higher organic activity, and other for drier periods. It is proposed a climate regime that is humid with a dense vegetation during the glacial cycle from 250,000 to 130,000 years; followed by a transition to a semi-arid regime from 130,000 years to about 80,000 years. From 80,000 to 10,000 years the environmental conditions are again similar to the conditions prevailing in the previous glacial cycle.