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南秦岭横丹浊积岩系是一套巨厚的浊流沉积,以向南或南东倾的单斜构造产出。由下而上,该沉积层序包括深水盆地、深水浊积扇和斜坡水道3个相序。相应地,沉积物粒度变粗,厚度变大,火山质组分含量增加,凝灰层大量发育,表明横丹浊积岩系为活动型浊积岩;其古水流方向为NNW—NNE向,物源区为南侧的碧口火山岩系。另外,横丹浊积岩系内还见石英岩、重结晶大理岩成分的砾石,说明其物源还包括被动陆缘环境的沉积物。相序、组构、沉积特征和物源区综合分析表明,横丹浊积岩系为弧前盆地充填物。构筑这一弧前盆地的动力学机制是洋壳板块向南俯冲于扬子板块被动陆缘之下,时代可能晚于中晚泥盆世。
The South Qinling Hengdan Turbidity Series is a set of thick turbidite sediments that are produced in monoclinic structures that are either southeastern or south-easterly inclined. From bottom to top, the sedimentary sequence includes three phases of deep-water basin, turbidite fan and slope channel. Correspondingly, the grain size of the sediment becomes thicker, the thickness becomes larger, the content of volcanic components increases and the tuff layer develops in a large scale, which indicates that the Hengdan turbidite is an active turbidite. The paleocurrent direction is NNW-NNE direction, The source area for the south of Bikou volcanic rock series. In addition, the Hengdan turbidite system also see quartzite, recrystallized marble composition of gravel, indicating its source also includes the passive continental margin sediments. The comprehensive analysis of facies, tectonics, sedimentary features and provenance shows that Hengdan turbidite is the filling of the forearc basin. The dynamic mechanism for constructing this pre-arcuate basin is that the oceanic plate subducted southward beneath the passive continental margin of the Yangtze Plateau, and may be later than the Middle Devonian.