中文摘要：

野外露头岩石学与地层学研究表明,青藏高原东北缘囊谦古近纪盆地贡觉组自下而上可分为5个岩性段,它们构成两套由粗变细的沉积序列,主要形成于冲积扇-河流-湖泊-三角洲沉积环境。不同的岩性段具有不同的岩石组合,反映其形成于不同的沉积环境：第一岩性段分布局限,为滨浅湖相沉积;第二岩性段、第四岩性段和第五岩性段形成于近源、快速堆积环境;第三岩性段为面积分布广泛的干旱-炎热气候条件下的河流-湖泊沉积环境产物。由于盆地沉积的不对称性及所处沉积环境的不同,各岩性段在盆地内的出露也不相同,总体反映盆地经历了早期挤压推覆前陆盆地、中期走滑拉分盆地、晚期走滑挤压推覆前陆盆地的演化历史。

英文摘要：

With the uplifting and large-scale thrusting and striking of Qinghai-Tibet Plateau,a lot of Tertiary intracontinental red basins were formed on the basis of Palaeo-Tethys multi-island ocean framework around Yushu area in the northeast of the Plateau.In these basins a set of such fluvial-lacustrine sediments as red clasolite,marlite and gypsum were deposited,accompanied by magmatism in some basins,with Nangqen basin being most typical in this aspect.Based on field petrologic and stratigraphic study,the authors divided the Gonjo Formation of Nangqen Paleogene basin in northeastern Qinghai-Tibet Plateau into five sections of different sedimentary environments such as alluvial fans,fluvialite,lake and delta facies,which formed two sequences characterized by coarse grains in the lower part and fine grains in the upper part.Different sections have different rock assemblages,suggesting that they were formed in different sedimentary environments.The first section has a limited distribution and is only exposed on the west side of the middle part of the basin;it consists of siltstone,mudstone,argillaceous limestone,shale and slate,implying lake facie deposition.The second section exposed on the north part of the basin shows a proximal and rapid deposition environment composed of red conglomerate,glutenite and sandstone.The third section has a large distribution area and is exposed all over the basin;it is composed of dark purple mudstone,silty mudstone and gypsum deposited in alluvial and fluviatile fans under the condition of dry and hot weather.The fourth and fifth sections only exposed in the middle and south parts of the basin are composed of fluvial-lacustrine sediments composed of red conglomerate,glutenite and sandstone deposited in a proximal and rapid deposition environment.An analysis of sediment sources has revealed that the material sources evolved from stable interior of craton through debris recyclic orogenic zone to mixed recyclic orogenic zone.Owing to the asymmetry of the basin and dissimilar depositional