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精确约束印度-亚洲初始碰撞时间对于认识喜马拉雅造山过程、青藏高原隆升机制及其对环境、气候和生物的效应具有重要的意义.本文基于对西藏雅鲁藏布缝合带两侧沉积记录的研究,对印度-亚洲大陆初始碰撞时间研究进行了总结和评述,探讨了印度-亚洲大陆初始碰撞的穿时性,重建了大陆碰撞的沉积演化.在接受以大陆间洋壳消失、陆壳-陆壳初始接触作为初始碰撞定义的前提下,利用两种方法:(1)缝合带附近深水浊积岩物源区由印度物源向亚洲物源转变的时间,(2)喜马拉雅欠充填前陆盆地启动在缝合带两侧造成的沉积环境突变或不整合的时间,精确限定印度-亚洲大陆初始碰撞时间为古新世中期((5 9±1)Ma).从喜马拉雅造山带来看,真正的初始碰撞时间比正常海相沉积结束要早20~25Ma,而磨拉石出现比初始碰撞要晚30~40Ma.基于特提斯喜马拉雅古近系沉积记录,印度-亚洲大陆初始碰撞在喜马拉雅中部和西部不存在明显的穿时性.本文从喜马拉雅地区的沉积记录角度出发,将喜马拉雅造山作用划分为四个阶段:(1)始喜马拉雅初始阶段,古新世中期-早始新世(59~52Ma),初始碰撞发生,同碰撞盆地存在深海环境,印度大陆一侧发育碳酸盐缓坡;(2)始喜马拉雅早期阶段,始新世早-中期(52~41Ma或35Ma),以发育残留的浅海沉积为特征,新特提斯海湾自西向东逐渐消亡;(3)始喜马拉雅晚期阶段,始新世末期-渐新世(41~26Ma),整个喜马拉雅和藏南地区缺乏沉积作用;(4)新喜马拉雅早期阶段,渐新世末期-早中新世(2 6~17Ma),喜马拉雅隆升,陆相磨拉石快速堆积,沿缝合带东西向发育雅鲁藏布江和印度斯河.
Accurately Constraining Indo-Asian Initial Impact Time is of Great Significance for Understanding the Himalayan Orogenic Process, the Uplift Mechanism of the Tibetan Plateau and Its Effects on Environment, Climate and Biology.Based on the study of sedimentary records on both sides of the Yarlung Zangbo suture in Tibet, , This paper summarizes and comments on the study of the initial collision time in the Indo-Asian Continent, discusses the timeliness of the initial collision in the Indian-Asian continent and reconstructs the sedimentary evolution of the continental collision. After accepting the disappearance of the oceanic crust, continental crust- The initial contact of the shell is defined as the initial collision using two methods: (1) the time when the source region of deep-water turbidite near the suture is changed from an Indian source to an Asian source, (2) the time when the Himalayan underfilled foreland basin The initiation or abrupt change of sedimentary environment on both sides of the suture caused the initial collision time of India-Asia continent to be mid-Paleocene ((59 ± 1) Ma). From the Himalayan orogenic belt, the true The initial collision time is 20-25Ma earlier than the normal marine sedimentation and the molasse occur 30-40Ma later than the initial collision.Based on sedimentary records of the Tethyan Himalayan Paleogene, The initial continent collision in Himalayas does not have obvious time-passing features in the central and western Himalayas.This paper divides the Himalayan orogeny into four stages from the perspective of sedimentary records in the Himalayas: (1) In the initial Himalayan period, in the mid-Paleocene- In the early Eocene (59 ~ 52Ma), the initial collision occurred in the same collision basin with the deep sea environment, and the carbonate rock was developed on one side of the Indian continent. (2) In the early Himalayan period, the Eocene early-middle period (52 ~ 41Ma or 35Ma), characterized by the development of residual shallow sea sediments. The Neo-Tethys Bay gradually vanished from west to east. (3) Late Eocene-Oligocene (41-26Ma), the entire Himalayas and southern Tibet (4) In the early Neo-Himalaya, the late Oligoceses - Early Miocene (26 ~ 17Ma), Himalaya uplifts, rapid accumulation of terrazzo molasse, along the east-west development of the suture zone Brahmaputra and India River.