DOI: 10.1016/j.earscirev.2020.103106
论文题名: Continent size revisited: Geophysical evidence for West Antarctica as a back-arc system
作者: Artemieva I.M. ; Thybo H.
刊名: Earth Science Reviews
ISSN: 00128252
出版年: 2020
卷: 202 语种: 英语
中文关键词: Back-arc extension
; Continental crust
; Lithosphere
; Paleosubduction
; Upper mantle
英文关键词: backarc basin
; continental crust
; data interpretation
; geodynamics
; gravity anomaly
; hypsometry
; seismicity
; subduction
; upper mantle
; Antarctica
; Pacific Ocean
; West Antarctica
英文摘要: Antarctica has traditionally been considered continental inside the coastline of ice and bedrock since Press and Dewart (1959). Sixty years later, we reconsider the conventional extent of this sixth continent. Geochemical observations show that subduction was active along the whole western coast of West Antarctica until the mid-Cretaceous after which it gradually ceased towards the tip of the Antarctic Peninsula. We propose that the entire West Antarctica formed as a back-arc basin system flanked by a volcanic arc, similar to e.g. the Japan Sea, instead of a continental rift system as conventionally interpreted. Globally, the fundamental difference between oceanic and continental lithosphere is reflected in hypsometry, largely controlled by lithosphere buoyancy. The equivalent hypsometry in West Antarctica (−580 ± 335 m on average, extending down to −1.6 km) is much deeper than in any continent, but corresponds to back-arc basins and oceans proper. This first order observation questions the conventional interpretation of West Antarctica as continental, since even continental shelves do not extend deeper than −200 m in equivalent hypsometry. We present a suite of geophysical observations that supports our geodynamic interpretation: a linear belt of seismicity sub-parallel to the volcanic arc along the Pacific margin of West Antarctica; a pattern of free air gravity anomalies typical of subduction systems; and extremely thin crystalline crust typical of back-arc basins. We calculate residual mantle gravity anomalies and demonstrate that they require the presence of (1) a thick sedimentary sequence of up to ca. 50% of the total crustal thickness or (2) extremely low density mantle below the deep basins of West Antarctica and, possibly, the Wilkes Basin in East Antarctica. Case (2) requires the presence of anomalously hot mantle below the entire West Antarctica with a size much larger than around continental rifts. We propose, by analogy with back-arc basins in the Western Pacific, the existence of rotated back-arc basins caused by differential slab roll-back during subduction of the Phoenix plate under the West Antarctica margin. Our finding reduces the continental lithosphere in Antarctica to 2/3 of its traditional area. It has significant implications for global models of lithosphere-mantle dynamics and models of the ice sheet evolution. © 2020 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/165995
Appears in Collections: 气候变化与战略
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作者单位: State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Sciences, China University of Geosciences, Wuhan, China; Department of Geophysics, Stanford UniversityCA, United States; Section of Marine Geodynamics, GEOMAR Helmholtz Center for Ocean Research, Kiel, Germany; Eurasia Institute of Earth Sciences, Istanbul Technical University, Turkey; Center for Earth Evolution and Dynamics (CEED), University of Oslo, Norway
Recommended Citation:
Artemieva I.M.,Thybo H.. Continent size revisited: Geophysical evidence for West Antarctica as a back-arc system[J]. Earth Science Reviews,2020-01-01,202