Climate changes in Northeastern Brazil from deglacial to Meghalayan periods and related environmental impacts

• Published in: Quaternary science reviews 2020-12, Vol.250, p.106655, Article 106655
• Main Authors: Utida, Giselle, Cruz, Francisco W., Santos, Roberto V., Sawakuchi, André O., Wang, Hong, Pessenda, Luiz C.R., Novello, Valdir F., Vuille, Mathias, Strauss, André M., Borella, Ana Claudia, Stríkis, Nicolás M., Guedes, Carlos C.F., Dias De Andrade, Fábio Ramos, Zhang, Haiwei, Cheng, Hai, Edwards, R. Lawrence
• Format: Article
• Language: English
• Subjects: Archaeology; Demographic impacts; Holocene; ITCZ; Northeastern Brazil; Speleothems; Stable isotopes
• ISSN: 0277-3791; 1873-457X
• DOI: 10.1016/j.quascirev.2020.106655

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. Here we investigate the environmental changes in the karst region of Chapada do Apodi - Northeastern Brazil (NEB), using a multi-proxy approach including carbon (δ13C), oxygen (δ18O) and strontium (87Sr/86Sr) isotopic analyses on speleothems from different caves, carbonate bedrock, and clastic cave deposits. 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 (ITCZ) over the region. The high δ13C and δ18O and low 87Sr/86Sr values at 4,200 yrs BP indicate a massive episode of soil erosion, resulting in the exposure of carbonate bedrocks over a large area of the karst terrain. This event marks the beginning of the Meghalayan chronozone, 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). We investigated if the Holocene climatic changes affected human occupation in the NEB and found that the overall demographic course is virtually identical to the well-established curve characterized by population deflation during Middle Holocene. •The combined use of speleothem δ18O, δ13C and 87Sr/86Sr records for paleoenvironmental reconstruction.•Relative changes in soil turnover in response to ITCZ rainfall in Northeastern Brazil.•Evidences of hydrological changes in the ITCZ region from multiproxy cave records.•Increased aridification in Northeastern Brazil coincident with Meghalayan chronozone.•The 4.2 event as marker of abrupt changes in climate and its impact in human population.