【摘要】 藏南岗巴—定日地区发育着西藏最晚期的海相沉积,对这套海相沉积的研究,可提供关于西藏特提斯演化晚期的良好信息。本文对岗巴—定日地区始新世遮普惹组的化石碳酸盐岩微相进行了较为详细的分析和研究,参考Wilson(1975)的标准微相,初步识别出10种微相和5种生物相类型。同时对遮普惹组中的砾状灰岩的成因机制作了有益的探讨,它完全是由沉积作用而成;胶结物不是源于物质的重新分配,而是台地边缘斜坡的等深流沉积。以此为基础,对西藏特提斯晚期沉积环境的演变进行了较为详细的分析。笔者认为:岗巴—定日盆地在始新世Ypresian—Lutetian早期接受海侵;自Lutetian晚期开始,区内总体处于一种海退环境,但由于受板块碰撞作用的影响,岗巴地区在Lutetian晚期—Bartonian晚期成为一深水坳陷盆地;至Priabonian早期,海水完全退出本区。更多还原

【Abstract】 The Youngest marine strata are exposed in the Gamba-Tingri area, southern Tibet.The study of this succession of marine strata may provide good information about the late evolutional history and closing age of the Tibet-Tethys remnant sea.On the basis of detailed fieldwork and laboratory thin-s ection identification,the authors studied the fossil carbonate microfacies of the Eocene Zhepure Formation in the Gamba-Tingri area.Ten types of microfacie s(MF1-MF10)and five types of biofacies are recognized.The genetic mechan ism of conglomeratic limestone of the Zhepure Formation is also discussed in t his paper.It is suggested that the conglomeratic limestone formed completely by contour current sediments on the plat-form-margin marine slope,rather than by redistribution of materials.Based on the above study,a detailed analysis is made on the late phase of the sedimentary evolution of Tibet-Tethys.The a uthors consider that a transgression took place in the Gamba-Tingri basin durin g the Eocene Ypresian-early Lutetian.In the late Lutetian,the Gamba-Tingri a rea was generally in a regressive environment.At that time ,however,the Gamb a area became a restricted deep-water depression as a consequence of continen tal compression due to plate collision.In the early Priabonian seawater complet ely withdrew from this area.更多还原