西藏那曲地区中晚侏罗世拉贡塘组深水碎屑流沉积特征和沉积模式
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中国地质调查局成都地质调查中心

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国家自然科学基金项目(面上项目,重点项目,重大项目)


Depositional characteristics and model of the deepwater debris flow of the MidLate Jurassic Lagongtang Formation in the Nagqu area, Tibet
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Chengdu center of China Geological Survey

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    摘要:

    本文报道了那曲地区拉贡塘组深水碎屑流的沉积特征,并进行了控制因素、沉积过程分析,建立了沉积模式,对深化海相碎屑流研究和含油气盆地评价具有重要的意义。碎屑流沉积下部为砾质碎屑流,上部为砂质碎屑流与泥质碎屑流沉积的交替,其内发育不同类型、大小的软沉积变形构造,如软沉积变形褶皱、布丁构造和软双重构造。砾质碎屑流、砂质碎屑流沉积体内可见滑塌、滑动体。研究表明,班公湖―怒江洋闭合后,随着木嘎岗日岩群在中侏罗世逐步暴露地表并遭受剥蚀,很可能在班公湖―怒江结合带与拉萨地块的过渡部位形成三角洲,为拉贡塘组碎屑流的形成奠定了物质基础。同时,班公湖―怒江结合带背驮三角洲向南逆冲,三角洲水道转化为深切河道,陡岸带未固结沉积物脉动式沙崩,崩落物在自身重力作用下沿深切河道向盆地方向搬运。流经沟口后,受地形等因素影响,碎屑流发生分流,最后冻结式沉积。

    Abstract:

    This paper reports depositional characteristics of deep?water debris flow of Lagongtang Formation in Nagqu area, Tibet, and points out that it is significant for its controlling factors, depositional process analyzed and depositional model proposed to improve marine theories of gravity flow, to assess petroliferous basins. The debris flow deposit consists of gravel debrites in its lower and sandy one alternating with muddy one in its upper, and soft depositional deformation structures with varying types, scales are developed in it like soft depositional deformation folds, boudinages and soft dual structures. And many slumps and slides are identified in the gravel? and sandy debites. The research shows that along with Mugagangri Group gradually being exposed and denuded in Middle Jurassic, a delta was developed at the tectonic transition from Bangong Co?Nujiang suture zone to Lhasa blok after closure of Bangong Co?Nujiang ocean, forthurmore, it laid a material foundation for the formation of gravity flow deposits of Lagongtang Formation. Futhurmore, the main delta river turned into a canon channel, along with the junction zone thrusting southwards and delta lifting continuously on it. Loose deposits resulted from unconsolidated sediments of the delta collapsed in the channel steep bank flows towards basin along the channel under self?gravity. The debrites diversion took place under the influence of several factors such as terrain when it passed by the mizoguchi, and 2 sub-debrites formed and deposited frozenly at last.

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  • 收稿日期:2020-12-14
  • 最后修改日期:2022-01-20
  • 录用日期:2022-03-12
  • 在线发布日期: 2023-02-16
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