地理学报 ›› 2018, Vol. 73 ›› Issue (9): 1728-1736.doi: 10.11821/dlxb201809009

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金沙江金江街段河流阶地年代及对河谷水系演化历史的启示

董铭1(),苏怀1(),史正涛1,明庆忠2,何回丽3   

  1. 1. 云南师范大学旅游与地理科学学院,昆明 650500
    2. 云南财经大学旅游文化产业研究院,昆明 650221
    3. 中国科学院昆明植物研究所,昆明 650201
  • 收稿日期:2017-09-18 出版日期:2018-09-25 发布日期:2018-09-19
  • 基金资助:
    国家自然科学基金项目(41762014, 41462007, 41362010, 41001010);云南省应用基础研究计划项目(2013FZ047)

The age of river terraces in the Jinjiangjie reach of the Jinsha River and its implications for valley and drainage evolution

DONG Ming1(),SU Huai1(),SHI Zhengtao1,MING Qingzhong2,HE Huili3   

  1. 1. College of Tourism and Geography Sciences, Yunnan Normal University, Kunming 650500, China
    2. Research Institute of Tourism and Culture Industry, Yunnan University of Finance and Economics, Kunming 650221, China
    3. Kunming Institute of Botany, CAS, Kunming 650201, China
  • Received:2017-09-18 Published:2018-09-25 Online:2018-09-19
  • Supported by:
    National Natural Science Foundation of China, No.41762014, No.41462007, No.41362010, No.41001010;Applied Basic Research Project of Yunnan Province, No.2013FZ047

摘要:

100多年来,关于金沙江独特水系格局的形成历史一直是地学界争论的重要话题之一。多数学者认为,现代金沙江水系是古长江袭夺古红河上游发展过来的。红河海底扇5.5 Ma泥沙供给中断被认为与这一袭夺事件有关。然而,长期以来人们一直没有找到与这一时代相匹配的地貌证据。最近在金沙江金江街段找到了多达8级的河流阶地序列,ESR测年结果显示这些阶地的形成年代为1.07 Ma、0.70 Ma、0.65 Ma、0.51 Ma、0.47 Ma、0.44 Ma、0.30 Ma和0.18 Ma,结合GPS高程测量数据,推算最近1.0 Ma以来的河谷平均下切速率为147 mm/ka。以填充河谷地形为主要手段的古地形恢复结果(基于DEM数据)显示,古长江袭夺古红河上游形成现代金沙江水系发生在这一区域内海拔2000 m左右的古地形面解体之后,依照河谷平均下切速率外推,古地形面解体时代为5.5 Ma,即现代金沙江水系形成于5.5 Ma之后。我们的研究结果与红河海底扇的资料形成一个相互呼应的证据链,为重建现代金沙江水系格局形成历史提供重要依据。

关键词: 金沙江, 金江街, 阶地, 水系演化

Abstract:

The Jinsha River has attracted considerable attention for nearly a century due to its unusual drainage basin morphology. Most models describing its evolution suggest that the modern Jinsha River, draining the Tibetan Plateau margin, was once a tributary to a single, southward river system called "Paleo-Red River", which drained into the South China Sea and then its flow direction changed to east to join the Yangtze River due to river capture. The Red River submarine fan, considered to have been primarily fed by the Paleo-Red River system, suddenly disappeared at 5.5 Ma provides an important chronological constraint on this reorganization of drainage lines and reversal event. However, no geomorphic evidence has been found to agree with this hypothesized timeframe. Here, we present electron spin resonance (ESR) ages from eight terraces preserved in the Jinjiangjie reach of the Jinsha River together with their GPS altimetry data. Their ages from old to young are 1.07 Ma, 0.70 Ma, 0.65 Ma, 0.51 Ma, 0.47 Ma, 0.44 Ma, 0.30 Ma and 0.18 Ma, with a calculated average river incision rate of 147 mm/ka since 1.0 Ma. The paleo-topography, reconstructed by filling the deeply incised river gorges with digital elevation model (DEM) data, shows that the upper reach of the Paleo-Red River was captured by the Yangtze River and changed its flow direction eastward at the time of disruption of the 2000 m asl paleo-topographic surface in the Jinsha River drainage basin. The age of the paleo-topographic surface formation would be approximately 5.5 Ma using the average river incision rate extrapolation, suggesting that the present Jinsha River system was born after 5.5 Ma. This data support the chronological constraint from the Red River submarine fan, and hypothesized evolution of the Jinsha River.

Key words: Jinsha River, Jinjiangjie reach, terrace, drainage evolution