Ruschi Anita Gomes, Rodrigues André Rosch, Cetto Paulo Henrique, Bastos Alex Cardoso
Departamento de Oceanografia - PPG Oceanografia Ambiental - LaboGeo Marine Geosciences, Universidade Federal do Espírito Santo, Avenida Fernando Ferrari 514, Vitória, 29090-600, ES, Brazil.
Sci Rep. 2024 Oct 18;14(1):24443. doi: 10.1038/s41598-024-75223-5.
The paleoenvironmental evolution of the Abrolhos Depression (AD) on the southern Abrolhos Shelf during the global post-Last Glacial Maximum (LGM) transgression is investigated through benthic foraminifera analysis. Downcore sediment samples (core DA03A-5B) collected at a depth of 63 m provide insights into the formation and paleoenvironmental variations of AD over the past 18 kyr BP. The core is divided into four biofacies based on foraminifera assemblages. At the base, the presence of carbonate concretions indicates a karstic surface, marking the initiation of the paleolagoon formation at approximately 13 kyr BP with low density of foraminifera, where species such as Elphidium sp. and Hanzawaia boueana (EH Biofacies) were more abundant. During the Younger Dryas (YD) (12.8-12.5 kyr BP), the AD exhibits two distinct phases: an initially confined lagoon environment with reduced circulation characterized by the dominance of the species Ammonia tepida (At Biofacies), followed by increased circulation characterized by higher density, richness, and diversity of benthic foraminifera. The end of the YD is identified by a significant biofacies change, indicative of a shallow marine environment, where the dominant species were A. tepida and Elphidium excavatum (AE Biofacies), supported by sedimentological and geochemical proxies. This paleoenvironmental shift is associated with Meltwater Pulse (MWP) -1B, suggesting a connection to a shallow marine environment. As sea levels continue to rise, the AD transitions into an open marine setting. However, around 8 kyr BP, a change occurs with the absence of A. tepida and the occurrence of planktonic and other benthic foraminifera typical of the outer shelf, indicating depths greater than 50 m (HQ Biofacies). The findings highlight the complex interplay between climate fluctuations, sea-level changes, and the formation of coastal environments during the LGM transgression. This study contributes to our understanding of paleoenvironmental dynamics, adding valuable insights to the evolutionary history of AD. The results emphasize the importance of integrating benthic foraminifera analysis, radiocarbon dating, and geochemical proxies to reconstruct paleoenvironments accurately. Overall, this research enhances our knowledge of global continental shelf evolution during the post-LGM transgression and provides valuable information for future paleoenvironmental studies.
通过底栖有孔虫分析，研究了末次盛冰期（LGM）后全球海侵期间阿布洛霍斯陆架南部阿布洛霍斯凹陷（AD）的古环境演变。在63米深度采集的柱状沉积物样本（DA03A - 5B岩芯）为了解过去18 kyr BP期间AD的形成和古环境变化提供了线索。根据有孔虫组合，该岩芯分为四个生物相。在底部，碳酸盐结核的存在表明存在岩溶面，标志着大约13 kyr BP时古泻湖开始形成，此时有孔虫密度较低，其中艾氏拟抱球虫（Elphidium sp.）和布氏汉泽有孔虫（Hanzawaia boueana）（EH生物相）等物种更为丰富。在新仙女木期（YD）（12.8 - 12.5 kyr BP），AD呈现出两个不同阶段：最初是一个封闭的泻湖环境，环流减弱，以温和半咸水单栏虫（Ammonia tepida）占主导（At生物相），随后环流增强，底栖有孔虫的密度、丰富度和多样性更高。YD末期通过显著的生物相变化得以确定，这表明是一个浅海环境，优势物种是温和半咸水单栏虫和挖掘艾氏有孔虫（Elphidium excavatum）（AE生物相），沉积物学和地球化学指标也证实了这一点。这种古环境转变与融水脉冲（MWP）-1B有关，表明与浅海环境存在联系。随着海平面持续上升，AD转变为开阔海洋环境。然而，在大约8 kyr BP时，情况发生了变化，温和半咸水单栏虫消失，出现了外陆架典型的浮游有孔虫和其他底栖有孔虫，表明深度大于50米（HQ生物相）。研究结果突出了末次盛冰期海侵期间气候波动、海平面变化与海岸环境形成之间的复杂相互作用。这项研究有助于我们理解古环境动态，为AD的演化历史增添了有价值的见解。结果强调了整合底栖有孔虫分析、放射性碳测年和地球化学指标以准确重建古环境的重要性。总体而言，这项研究增进了我们对末次盛冰期后海侵期间全球大陆架演化的认识，并为未来的古环境研究提供了有价值的信息。
