DOI: 10.1016/j.epsl.2020.116651
论文题名: Geochemical evidence of Milankovitch cycles in Atlantic Ocean ferromanganese crusts
作者: Josso P. ; van Peer T. ; Horstwood M.S.A. ; Lusty P. ; Murton B.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2021
卷: 553 语种: 英语
中文关键词: astronomical parameters
; astronomical tuning
; Fe-Mn crust
; ITCZ
; Pb isotopes
; West African Craton
英文关键词: Binary alloys
; Ferroalloys
; Inductively coupled plasma
; Iron alloys
; Iron metallography
; Iron ores
; Iron oxides
; Isotopes
; Laser ablation
; Lead
; Manganese alloys
; Manganese metallography
; Manganese nodules
; Mass spectrometers
; Radioactive elements
; Titanium oxides
; Weathering
; Ferromanganese crusts
; Geochemical evidence
; High spatial resolution
; Inductively coupled plasma mass spectrometer
; Isotopic composition
; North East Atlantic
; Spatial and temporal resolutions
; Time frequency analysis
; Lead metallography
; chemostratigraphy
; crustal structure
; ferromanganese deposit
; geochemistry
; intertropical convergence zone
; isotopic composition
; lead isotope
; Milankovitch cycle
; mixing
; paleoclimate
; rainfall
; seawater
; water mass
; Atlantic Ocean
; West African Craton
; Lamiinae
英文摘要: Hydrogenetic ferromanganese crusts are considered a faithful record of the isotopic composition of seawater influenced by weathering processes of continental masses. Given their ubiquitous presence in all oceans of the planet at depths of 400–7000 meters, they form one of the most well-distributed and accessible records of water-mass mixing and climate. However, their slow accumulation rate and poor age constraints have to date limited their use to explore 100 ka paleoclimatic phenomena. Here it is shown how the Pb isotope signature and major element content of a Fe-Mn crust from the north-east Atlantic responded to changes in the intensity and geographic extent of monsoonal rainfall over West Africa, as controlled by climatic precession during the Paleocene. The studied high-spatial resolution (4 μm) laser-ablation multi-collector inductively coupled plasma mass spectrometer (LA-MC-ICP-MS) Pb isotope data is a nearly 2 order of magnitude improvement in spatial and temporal resolution compared to micro-drill subsamples. The record demonstrates cyclicity of the 206Pb/204Pb and 208, 207Pb/206Pb ratios at the scale of single Fe-Mn oxide laminae, in conjunction with variations in the Fe/Mn ratio, Al, Si and Ti content. Time-frequency analysis and astronomical tuning of the Pb isotope data demonstrates the imprint of climatic precession (∼20 ka) modulated by eccentricity (∼100 and 405 ka), yielding growth rates of 1.5–3.5 mm/Ma consistent with previous chemostratigraphic age models. In this context, boreal summer at the perihelion causes stronger insolation over West Africa, resulting in more intense and geographically extended monsoonal rainfalls compared to aphelion boreal summer conditions. This, in turn, influences the balance between the weathering endmembers feeding the north-east Atlantic basin. These results provide a new approach for calibrating Fe-Mn crust records to astronomical solutions, and allow their isotopic and chemical archive to be exploited with an improved temporal resolution of 1000–5000 years. © 2020 Copyright British Geological Survey (c) UKRI 2020 Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/165535
Appears in Collections: 气候变化与战略
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作者单位: British Geological Survey, Environmental Science Centre, Keyworth, Nottingham, NG12 5GG, United Kingdom; University of Southampton, Waterfront Campus, European Way, Southampton, SO14 3ZH, United Kingdom; National Oceanography Centre, Waterfront Campus, European Way, Southampton, SO14 3ZH, United Kingdom
Recommended Citation:
Josso P.,van Peer T.,Horstwood M.S.A.,et al. Geochemical evidence of Milankovitch cycles in Atlantic Ocean ferromanganese crusts[J]. Earth and Planetary Science Letters,2021-01-01,553