巴基斯坦盐岭东部新生代演化过程及对喜山运动幕次的响应

摘要

The Salt Range lies in the northern part of the India plate sharing the same sedimentary environment with the Potwar basin in the early Cenozoic.In the Paleocene and Eocene Epochs,marine life covered the Salt Range and Potwar basin to form carbonate and offshore clastic rock sediments.However,regional uplift at the end of the Oligocene Epoch destroyed the marine sedimentary environment,causing denudation of deposited sediments.From the Miocene Epoch onward,the Salt Range and Potwar basin turned into a sedimentary environment for continental foreland,where thick alluvion sediments covered the area.The Salt Range and Potwar basin remained connected until the end of the Pleistocene Epoch when the Salt Range became a mountain after southward thrust motion,while a new foredeep buildup at the south side of the Salt Range and Potwar basin turned into a broken-foreland basin at the same time.Each end of the Oligocene and Pliocene Epochs marked a key point in time from the Cenozoic to Salt Range:at the end of the Oligocene Epoch,sedimentary environment turned into continental facies from marine facies after a short uplift period;and at the end of the Pliocene Epoch,the Salt Range became a mountain and the surrounding tectonic settings changed accordingly.These two points in time coincided with the critical time-in-point of the Himalayan movement associated with the convergence and collision of the India and Eurasia plates.%巴基斯坦盐岭地区位于印度板块北部,与其北部的波特瓦尔盆地一同接受了新生代早期沉积.区内自古新世和始新世的滨海相-海相沉积起,经渐新世抬升剥蚀,中新世以来转为陆相前陆沉积,沉积了巨厚层河流-冲积相碎屑岩,至更新世后期开始逆冲成山,而其北部波特瓦尔盆地相应地进入破裂前陆盆地演化期,在其南部形成新的前陆沉积区.盐岭新生代演化过程中两个关键时间点分别为渐新世末和上新世末,前者完成了沉积环境由洋到陆的转变,后者使盐岭隆升成山,改变了区域构造格局,这两个时间点对应喜马拉雅运动工幕和Ⅱ幕.盐岭东部地区新生代的演化与印度-欧亚板块的俯冲-碰撞息息相关,且在演化的关键时间点上密切呼应,其新生代演化过程对我国青藏高原隆升意义重大.