地质学
海底扩张
裂谷
古生物学
不整合
结壳
地幔(地质学)
大陆地壳
构造学
地震学
大陆边缘
反演(地质)
地堑
作者
Weiwei Ding,Dieter Franke,Jiabiao Li,Stephan Steuer
出处
期刊:Tectonophysics
[Elsevier]
日期:2013-01-01
卷期号:582: 162-176
被引量:107
标识
DOI:10.1016/j.tecto.2012.09.026
摘要
We interpret a more than 500 km long composite multi-channel seismic reflection profile across the entire Dangerous Grounds, the South China Sea. Five tectonostratigraphic units are determined, together with seven sequence boundaries. Detailed analysis of extensional features, based on measurements of fault heaves, revealed two major phases of extension, separated by a distinct unconformity, which likely correspond with the beginning of sea-floor spreading in the South China Sea. Early extension occurred during continental rifting (Late Cretaceous–Early Oligocene), and resulted in formation of half-grabens and rotated blocks, controlled by a deeply rooted detachment system. Extension continued in our study area during the drifting phase of the East Subbasin of the South China Sea (Late Oligocene–Early Miocene) until the subsequent opening of the Southwest Subbasin at about 25 Ma, but its intensity decreased markedly thereafter. Deeply rooted detachment systems evolved possibly during this second phase of extension at the continent–ocean transition area. From a coincidence of the lowermost reflections and Moho depth as derived from gravity inversion we tentatively interpret the flattened part of this detachment system as the crust–mantle boundary. It is suggested that the Dangerous Grounds reflect a magma-poor rift system at the initial stage of mantle unroofing. We suggest that a widespread carbonate platform developed across the Dangerous Grounds, concurrent with the period of seafloor spreading in the Southwest Subbasin of the South China Sea. Fault-related stretching factors (βf) along the line show discrepancies with the whole crustal stretching factors (βc). The continental crust of the Dangerous Grounds may have experienced nonuniform thinning.
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