上新世—早更新世青藏高原北缘隆升的磁性地层学证据

MAGNETOSTRATIGRAPHIC EVIDENCE FOR THE PLIOCENE-EARLY PLEISTOCENE UPLIFT OF THE NORTHERN TIBETAN PLATEAU

对新疆叶城剖面西域砾岩及下伏第三纪地层的磁性地层学研究表明 ,西域砾岩的沉积时代为晚上新世至早更新世 ,磁性地层年龄为 3.5至 <1.8Ma。阿图什组沉积于早上新世 ,古地磁年龄为 4 .6～ 3.5 Ma。阿图什组以砂岩和粉砂岩为主夹薄层砾岩 ,为河流相及冲积扇前缘相。西域砾岩以厚层砾岩为主夹风成粉砂岩 ,为典型洪积—冲积扇堆积。

Magnetostratigraphic study of the Xiyu conglomerate and underlying Tertiary strata of the Yecheng section,Xinjiang has revealed that the Xiyu Formation was deposited during the late Pliocene and early Pleistocene,with magnetostratigraphic ages from 3 5 Ma to younger than 1 8 Ma.The underlying Artux Formation was deposited during the early Pliocene,with magnetostratigraphic ages from 4 6 Ma to 3 5 Ma.The Artux Formation is dominated by sandstone and siltstone ,with minor gritstone layers,indicating a fluvial and distal fan environment.The Xiyu Formation is characterized by coarse conglomerate,typical of debris flow deposits,indicating a proximal fan environment.The deposition of Xiyu Formation indicates abrupt uplift of the northern Tibetan Plateau during the late Pliocene early Pleistocene.