Climate changes in Northeastern Brazil from deglacial to Meghalayan periods and related environmental impacts. (15th December 2020)

• Record Type: Journal Article
• 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
• Is Part Of: Quaternary science reviews. Volume 250(2020)
• Publication Date: 2020-12-15
• Subjects: Stable isotopes -- ITCZ -- Speleothems -- Holocene -- Northeastern Brazil -- Archaeology -- Demographic impacts; Geology, Stratigraphic -- Quaternary -- Periodicals; Stratigraphie -- Quaternaire -- Périodiques; 551.79
• DOI: 10.1016/j.quascirev.2020.106655
• Languages: English
• ISSNs: 0277-3791

Abstract

Abstract: 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 (δ 13 C), oxygen (δ 18 O) and strontium ( 87 Sr/ 86 Sr) 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 δ 13 C and δ 18 O and low 87 Sr/ 86 Sr 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. Highlights: The combined use of speleothem δ 18 O, δ 13 C and 87 Sr/ 86 Sr 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.