δ¹³C and ⁸⁷Sr/⁸⁶Sr stalagmite records from Northeastern Brazil

Changes in insolation driven by precession and obliquity are considered the major driver of tropical precipitation on orbital time scales, and responsible for vegetation and physical landscape changes during the Late Holocene over tropical South America and these changes are recorded in speleothems from Northeastern Brazil (NEB). We investigated the environmental changes in the last 26 ky in the karst region of Chapada do Apodi - NEB, and present here the results of carbon (δ13C) and strontium (87Sr/86Sr) isotopes obtained in five speleothems from caves Trapiá, Rainha, Abissal and Furna Nova.

This approach reveals that the balance between soil formation and erosion and their alternating impact on vegetation and precipitation changes occurred in response to variations in the position and intensity of the Intertropical Convergence Zone over the region. The data also reveals the beginning of the Meghalayan chronozone in NEB, characterized as the aridification of this region, decline in soil production, drying out of underground drainages, and increased dominance of dry-adapted flora species, characteristic of a more open vegetation (caatinga).