摘要
青藏高原经过古近纪挤压缩短和增厚地壳均衡隆升,晚新生代形成了以走滑和伸展为主的相对稳定构造环境。中新世早期与晚更新世分别发育巨型古大湖,上新世—早更新世发育很多规模较大的古湖泊,古大湖对夷平面形成演化具有重要的控制作用。中新世早期((24.1±0.6)^(14.5±0.5)Ma)以古大湖的湖面为侵蚀基准面,经过隆起区剥蚀夷平和长期湖相沉积,在高海拔环境下形成早期夷平面。中新世晚期—第四纪以湖面与五道梁群湖相沉积顶面为基准,在高海拔环境下继续发生剥蚀夷平和准平原化,逐步形成主夷平面或高原面。第四纪河流溯源侵蚀导致内外流水系分界线自东向西迁移,在青藏高原东部形成高山峡谷地貌。
The Tibetan Plateau isostatically uplifted after contractional shortening and crustal thickening in Paleogene and is dominated by strike-slip and extension in Late Cenozoic. Very vast lakes formed in Early Miocene and Late Pleistocene in central Tibetan Plateau respectively, and large paleo-lakes formed in Pliocene and Early Pleistocene alternatively in northern and eastern Tibetan Plateau. Level of vast lakes had been base surface for incision in Early Miocene from （ -24. 1±0.6） Ma to （ - 14.5±0.5） Ma, and lakes and top lacustrine deposits of Wudaoliang Group became base surface for erosion and peneplanation since Late Miocene, which formed planation surface or peneplain of the Tibetan Plateau. Upstream incision of rivers led to westward motion of boundary between internally and externally drained regions and disappearance of paleo-lakes in Quaternary, and Quaternary incision of external rivers gradually formed present topography characterized by deep valleys, high mountains and remained peneplain in eastern Tibetan Plateau.
出处
《现代地质》
CAS
CSCD
北大核心
2009年第6期993-1002,共10页
Geoscience
基金
科技部国际科技合作项目(2006DFB211330
2001CB711001)
中国地质调查局项目(1212010711510)
关键词
古大湖
侵蚀基准面
夷平面
准平原化
青藏高原
vast palco-lake
base surface for incision
planation surface
peneplanation
the Tibetan Plateau
