Climate changes in Northeastern Brazil from deglacial to Meghalayan periods and related environmental impacts
Climate changes in Northeastern Brazil from deglacial to Meghalayan periods and related environmental impacts
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DOI：
10.1016/j.quascirev.2020.106655
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发表时间：
2020-12-15
影响因子：
4
通讯作者：
Edwards, R. Lawrence
中科院分区：
文献类型：
--
作者：
Utida, Giselle;Cruz, Francisco W.;Edwards, R. Lawrence
由岁差和倾角驱动的日照变化被认为是热带降水在轨道时间尺度上的主要驱动因素，也是南美洲热带地区全新世晚期植被和自然景观变化的原因。在这里，我们研究了巴西东北部Chapada do Apodi(NEB)喀斯特地区的环境变化，采用多代理方法，包括对不同洞穴、碳酸盐基岩和碎屑洞穴沉积的洞穴进行碳(三角洲C-13)、氧(三角洲O-18)和锶(锶-87/锶-86)同位素分析。这一方法揭示了土壤形成和侵蚀之间的平衡及其对植被和降水变化的交替影响，响应于该地区热带辐合带(ITCZ)位置和强度的变化。4200年BP时高的C-13和O-18三角洲和低的Sr-87/Sr-86值指示了大规模的土壤侵蚀，导致碳酸盐岩基岩在大片岩溶地区露头。这一事件标志着Meghalayan时间臭氧的开始，其特点是该地区干旱，土壤生产下降，地下排水系统干涸，以更开阔的植被(Caatinga)为特征的干旱适应植物物种的优势增加。我们调查了全新世气候变化是否影响了人类在NEB的占领，发现总体人口过程实际上与以中全新世人口通货紧缩为特征的既定曲线相同。(C)2020爱思唯尔有限公司。保留所有权利。
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 (delta C-13), oxygen (delta O-18) and strontium (Sr-87/Sr-86) 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 delta C-13 and delta O-18 and low Sr-87/Sr-86 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. (C) 2020 Elsevier Ltd. All rights reserved.