中新世晚期至上新世早期南部非洲季风的轨道强迫与演化

IF 3.2 2区 地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY
Allana Queiroz de Azevedo, F. Jiménez‐Espejo, F. Bulian, F. Sierro, D. Tangunan, Y. Takashimizu, A. Albuquerque, K. Kubota, C. Escutia, R. Norris, S. Hemming, I. Hall
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引用次数: 0

摘要

中新世晚期-上新世早期(7.4-4.5 Ma)是地球历史上的一个关键时期,在全球降温的情况下,大气和海洋环流发生了剧烈重组。在此期间,南部非洲季风(SAFM)可能在气候系统变化中发挥重要作用。然而,由于缺乏连续记录,人们对这一重要大气系统的动力学了解甚少。在这里,我们根据元素地球化学(Ca/Ti和Si/K比率)、稳定同位素地球化学(奥布力纳宇宙浮游有孔虫中记录的δ18O和δ13C),以及来自位于莫桑比克海峡入口处的国际海洋发现计划U1476站点的海洋沉积物粒度数据。Si/K比(河流输入)的光谱特征用于识别控制SAFM的主要轨道强迫。进动旋回控制着7.4至~6.9 Ma的降水,以及上新世早期的降水。从~6.9到~5.9 Ma,进动和长偏心周期驱动SAFM。南极冰盖在这段时间内的主要扩张似乎影响了O.universa的同位素记录,作为对海洋和大气重组的反应,该记录留下了其长期变化信号。进动周期从5.9到5.3 Ma明显减弱,几乎与地中海流出水停止的时期相同。这些发现突出了SAFM、地中海和其他热带地区之间的重要遥相关。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Orbital Forcing and Evolution of the Southern African Monsoon From Late Miocene to Early Pliocene
The late Miocene‐early Pliocene (7.4‐4.5 Ma) is a key interval in Earth's history where intense reorganization of atmospheric and ocean circulation occurred within a global cooling scenario. The Southern African monsoon (SAFM) potentially played an important role in climate systems variability during this interval. However, the dynamics of this important atmospheric system is poorly understood due to the scarcity of continuous records. Here, we present an exceptional continuous late Miocene to early Pliocene reconstruction of SAFM based on elemental geochemistry (Ca/Ti and Si/K ratios), stable isotope geochemistry (δ18O and δ13C recorded in the planktonic foraminifera Orbulina universa), and marine sediment grain size data from the International Ocean Discovery Program (IODP) Site U1476 located at the entrance of the Mozambique Channel. Spectral characteristics of the Si/K ratio (fluvial input) was used to identify the main orbital forcing controlling SAFM. Precession cycles governed precipitation from 7.4 to ∼6.9 Ma and during the early Pliocene. From ∼6.9 to ∼5.9 Ma, the precession and long eccentricity cycles drove the SAFM. The major Antarctic ice sheet expansion across this interval appear to influence the isotopic records of O. universa imprinting its long‐term variability signal as a response to the ocean and atmospheric reorganization. Precession cycles markedly weakened from 5.9 to 5.3 Ma, almost the same period when the Mediterranean Outflow Water ceased. These findings highlight important teleconnections among the SAFM, Mediterranean Sea, and other tropical regions.
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来源期刊
Paleoceanography and Paleoclimatology
Paleoceanography and Paleoclimatology Earth and Planetary Sciences-Atmospheric Science
CiteScore
6.20
自引率
11.40%
发文量
107
期刊介绍: Paleoceanography and Paleoclimatology (PALO) publishes papers dealing with records of past environments, biota and climate. Understanding of the Earth system as it was in the past requires the employment of a wide range of approaches including marine and lacustrine sedimentology and speleothems; ice sheet formation and flow; stable isotope, trace element, and organic geochemistry; paleontology and molecular paleontology; evolutionary processes; mineralization in organisms; understanding tree-ring formation; seismic stratigraphy; physical, chemical, and biological oceanography; geochemical, climate and earth system modeling, and many others. The scope of this journal is regional to global, rather than local, and includes studies of any geologic age (Precambrian to Quaternary, including modern analogs). Within this framework, papers on the following topics are to be included: chronology, stratigraphy (where relevant to correlation of paleoceanographic events), paleoreconstructions, paleoceanographic modeling, paleocirculation (deep, intermediate, and shallow), paleoclimatology (e.g., paleowinds and cryosphere history), global sediment and geochemical cycles, anoxia, sea level changes and effects, relations between biotic evolution and paleoceanography, biotic crises, paleobiology (e.g., ecology of “microfossils” used in paleoceanography), techniques and approaches in paleoceanographic inferences, and modern paleoceanographic analogs, and quantitative and integrative analysis of coupled ocean-atmosphere-biosphere processes. Paleoceanographic and Paleoclimate studies enable us to use the past in order to gain information on possible future climatic and biotic developments: the past is the key to the future, just as much and maybe more than the present is the key to the past.
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