拉萨地块北缘中晚侏罗世周缘前陆盆地的厘定

研究拉萨地块北缘中晚侏罗世盆地类型、演化对重塑班公湖?怒江结合带及邻区构造?古地理和含油气盆地评价具有重要的意义.通过对那曲县城北部的中上侏罗统拉贡塘组进行了沉积特征分析和碎屑锆石U-Pb测年.结果表明,该组一段为陡坡型三角洲沉积,下部的碎屑流显示出向南东流动的特点;二段主要为潮坪?混积陆棚沉积;一段下部的石英杂砂岩、...

Definition of Mid-Late Jurassic Peripheral Foreland Basin in the Northern Margin of Lhasa Block

To identify its types and evolution features of the Mid-Late Jurassic basin located in northern margin of Lhasa block is of great significance for reconstructing its tectonic-paleogeography and assessing the petroliferous basins in Bangonghu-Nujiang junction zone and its adjacent area. In this paper, the sedimetary features and provenance area of Mid-Late Jurassic Lagongtang Fm which is exposed in north of Nagqu county, was studied. The results shows that the Member 1 of Lagongtang Fm belongs to steep-slope delta deposition, and debris flow deposits located in its lower part has the characterisitics of southward flow, and Member 2 of the Fm was deposted in tidal flats and mixed shelf, and the detrital zircon ages of greywackes in the lower part of Member 1 and quartz fine sandstone in the lower part of Member 2 range from 2 611 Ma to 216 Ma and from 2 800 Ma to 152 Ma respectively. Comprehensive research results shows that the basin located in northern marigin of Lhasa block is a peripheral foreland one controlled by Bangonghu-Nujiang junction zone, and had dual source supply, and experienced the conversion from flysch basin to molasses one at 152 Ma or so. Meanwhile, the overthrust which took place in Bangonghu-Nujiang junction zone become stronger than before since that time, and caused a new foreland basin marked by the Shamuluo Formation form in it.