| 西藏山南地区琼结南部上三叠统郎杰学群的沉积学岩相特征与浊积扇模式 |
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| 引用本文： | 李祥辉,曾庆高,王成善.西藏山南地区琼结南部上三叠统郎杰学群的沉积学岩相特征与浊积扇模式[J].现代地质,2003,17(1):52-58. |
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| 作者姓名： | 李祥辉 曾庆高 王成善 |
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| 作者单位： | 1. 成都理工大学,地球科学学院,四川,成都,610059
2. 西藏国土资源厅,区域地质调查队,西藏,拉萨,850000 |
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| 基金项目： | 国家自然科学基金项目(40272102). |
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| 摘 要： | 西藏山南地区琼结南部上三叠统郎杰学群由轻微变质的泥质岩和碎屑岩组成,其中,砂岩主要为(岩屑)长石(杂)砂岩和(长石)岩屑(杂)砂岩,碎屑的分选和磨圆度较差,成分和结构成熟度较低,经历了压溶、交代及胶结等成岩作用;发育与浊积岩相关的层面、层理构造及沉积旋回发育。研究表明,按照宋热组、江雄组和姐德秀组地层层序,郎杰学群岩相总体呈现外—中扇砂板岩相向中—内扇砂板岩含砾岩相演化,向上变粗变浅,中源和近源/分支水道亚相增加;以姐德秀组下段中部为界可分为A和B两个层序,它们分属浊积扇演化的两个不同阶段;推测研究区及邻近地区可能存在一个较大规模向南迁移进积的舌状浊积扇。
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| 关 键 词： | 浊积扇 岩相 郎杰学群 上三叠统 琼结 西藏 |
| 文章编号： | 1000-8527(2003)01-0052-07 |
| 修稿时间： | 2002年7月8日 |
SEDIMENTARY CHARACTERISTICS OF THE UPPER TRIASSIC LANGJIEXUE GROUP IN SOUTHERN QIONGJIE, TIBET |
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| Abstract: | The Langjiexue Group, herein refers to the lightly metamorphosed Upper Triassic terrigenous rocks exposing to the east of the north south directed and active Yangbajing Qiongdui Fault, and being constrained by faults both southern and northern sides. It is mainly composed of slate (phyllite) and lightly metamorphic clastic rock, in which the sandstone is of lithoclastic and / or feldsparthic graywack. The clastic grains in sandstone are of worse sorting and roundness, and both the component and texture maturities are relatively low, somewhat due to diagenesis. There are many sedimentary structures such as flute, load cast, parallel cross bedding, ripple, etc. remained in the strata, and varieties of the Bouma sequence and depositional cycles are readily recognizable in the field. According to a postulated normal stratigraphic sequence of the Songre Formation, Jiangxiong Formation to Jiedexiu Formation in the Langjiexue Group, it is proposed that the lithofacies evolution has a tendency of outer middle fan sandstone slate package to middle inner fan gravel sandstone slate, which could be separated by sandstone and conglomerate series at the middle Lower Member of the Jiedexiu Formation. By combination of herein lithofacies, and southward paleocurrent and recycled orogenic belt tectonic background of sources cited in an unpublished report, it is supposed that there could be a bigger lobular turbiditic fan progressed southward in the study area and its vicinity. |
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| Keywords: | turbidite fan lithofacies the Langjiexue Group Upper Triassic Qiongjie Tibet |
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