Evolution of the Paleogene succession of the western Himalayan foreland basin

The Paleogene succession of the Himalayan foreland basin is immensely important as it preserves evidence of India-Asia collision and related records of the Himalayan orogenesis.In this paper,the depositional regime of the Paleogene succession of the Himalayan foreland basin and variations in composition of the hinterland at different stages of the basin developments are presented.The Paleogene succession of the western Himalayan foreland basin developed in two stages,i.e.syncollisional stage and post-collisional stage.At the onset,chert breccia containing fragments derived from the hanging walls of faults and reworked bauxite developed as a result of erosion of the forebulge. The overlying early Eocene succession possibly deposited in a coastal system,where carbonates represent barriers and shales represent lagoons.Up-section,the middle Eocene marl beds likely deposited on a tidal flat.The late Eocene/Oligocene basal Murree beds,containing tidal bundles,indicate that a mixed or semi-diurnal tidal system deposited the sediments and the sedimentation took place in a tidedominated estuary.In the higher-up,the succession likely deposited in a river-dominated estuary or in meandering rivers.In the beginning of the basin evolution,the sediments were derived from the Precambrian basement or from the metasediments/volcanic rocks possessing terrains of the south.The early and middle Eocene（54.7-41.3 Ma） succession of the embryonic foreland possibly developed from the sediments derived from the Trans-Himalayan schists and phyllites and Indus ophiolite of the north during syn-collisional stage.The detrital minerals especially the lithic fragments and the heavy minerals suggest the provenance for the late Eocene/Oligocene sequences to be from the recycled orogenic belt of the Higher Himalaya,Tethyan Himalaya and the Indus-suture zone from the north during post-collisional stage.This is also supported by the paleocurrent measurements those suggest main flows directed towards southeast,south and east with minor variations.This implies that the river system stabilized later than 41 Ma and the Higher Himalaya attained sufficient height around this time.The chemical composition of the sandstones and mudstones occurring in the early foreland basin sequences are intermediate between the active and passive continental margins and/or same as the passive continental margins.The sedimentary succession of this basin has sustained a temperature of about 200 C and undergone a burial depth of about 6 km.

India Collided with Asia at Least 72 Ma:Recognition of An Underfilled Foreland Basin in Central Himalaya

The Himalayan peripheral foreland basin developed when India and Asia collided.Previous studies in the Himalayan foreland were mostly concentrated on Neogene continental clastic sedimentation in sub-Himalaya or Paleogene shallow marine sedimentation along Pakistan,India,and Nepal in Lesser Himalaya. The lack of early stage of underfilled。

环青藏高原盆山体系东段新构造变形特征——以川西为例

介于扬子板块与青藏高原之间的川西前陆冲断带是环青藏高原盆山体系东段的重要组成部分,它是研究喜马拉雅构造运动对青藏高原东缘沉积盆地构造作用的重要场所。本文分别选取川西南段、川西北段和川北西段米仓山前的区域构造地质剖面来研究沉积地层在喜马拉雅运动中发生的构造变形特征。通过前陆冲断构造变形带的宽度、水平缩短量,山体隆升、盆地沉降,新构造对早期古构造的叠加与改造关系的研究,揭示出在环青藏高原盆山体系内,造山带与盆地边缘的冲断构造变形从造山带向克拉通盆地内扩展的同时受欧亚大陆与印度板块碰撞及其远程效应的空间位置限制,靠近青藏高原的川西南段到远离它的川北西段,新构造变形强度、新构造变形范围、盆山耦合程度具有依次降低等特征。这种受环青藏高原盆山体系控制的前陆冲断带构造变形具有明显的资环效应,特别是对油气资源的聚集与分布有重要的影响,控制了川西南段晚期次生气藏发育,川西北段和川北西段的早期原生气藏的发育。

雅鲁藏布中新生代深水沉积盆地形成和演化(Ⅰ)——喜马拉雅造山带沉积特征及演化

通过对喜马拉雅三叠纪到第三纪区域沉积特征分析,阐明了雅鲁藏布喜马拉雅特提斯造山带从裂谷—被动大陆边缘—前陆盆地的沉积盆地演化史。随着以雅鲁藏布带为代表的喜马拉雅特提斯打开,三叠纪到早侏罗世为特提斯早期裂开的大陆边缘裂谷盆地。早期裂谷中心部位不是现在大陆缝合线的雅鲁藏布一带,而在低分水岭带。晚侏罗世到早白垩世,雅鲁藏布江南测为典型被动大陆边缘,其沉积盆地沉降、海平面变化与沉积作用相吻合。晚白垩世到第三纪为前陆盆地演化阶段,从沉积作用可以识别出晚白垩世晚期为造山第一暮,第三纪初为第二幕。

库车前陆盆地喜马拉雅运动特征及其油气地质意义

根据构造变形解析和岩石记忆信息 ,库车前陆盆地的喜马拉雅运动可以划分为 3期 ,它们对应的时间分别为渐新世末、上新世末和早更新世末 ,其构造挤压强度依次由弱变强 ,在喜马拉雅晚期达到高峰 ,是该区构造的主要变形期和定格期 ,也是该区异常高压形成和油气成藏的主要时期。中更新世以来为新构造运动阶段 ,主要表现为 2～ 3次重要的抬升和相对较弱的褶皱逆冲变形 ,并对该区的油气藏主要起破坏作用。库车前陆盆地的构造变形从喜马拉雅早期开始发育 ,各构造带的发育时间从北往南依次由早变晚 ,它控制了该区断层相关褶皱、构造圈闭及其油气藏的带状分布规律。喜马拉雅晚期强烈的水平构造挤压是该区异常高压形成的主要因素 ,是该区油气形成分布的主要控制因素和驱动力 。

龙门山中段中生代前陆盆地的构造演化史

依据龙门山中段中生代盆地的基底性质、沉积构造组合和构造变形，论证了川西拗陷是在印支期发育于扬子板块活动大陆边缘的弧背（前陆）盆地，前陆盆地的构造变形是经印支期构造变动和喜马拉雅期叠加改造形成的推覆构造；并讨论了龙门山中段中生代前陆盆地的构造演化历史。

喜马拉雅前渊和孟加拉湾盆地形成演化

通过区域地质、地球物理、板块重建及地球动力学背景综合研究,揭示了喜马拉雅前渊和孟加拉湾盆地形成演化及动力学背景。喜马拉雅前渊与孟加拉湾盆地被西隆(Shillong)高原分隔。喜马拉雅前渊位于西隆高原北侧,主要以拉萨地块前白垩系为基底,晚白垩世—早始新世为新特提斯洋向洋内岛弧、拉萨板块俯冲形成的弧前和弧后盆地;中始新世—中新世早期,新特提斯洋逐渐俯冲消亡,印度板块与拉萨地块的陆陆碰撞逐渐加剧,形成前陆盆地;中新世中期以来,随着印度板块与欧亚板块陆陆碰撞的加剧,喜马拉雅前陆盆地隆升、剥蚀,只保留了前陆盆地的前渊。孟加拉湾(Bengal)盆地位于西隆高原南侧,其西北部以印度板块的前寒武系为基底,石炭—二叠纪为裂谷盆地,三叠纪为剥蚀区,侏罗纪—早白垩世以火山作用为主,晚白垩世—早始新世为被动大陆边缘盆地,中始新世以来随着印度板块向拉萨板块俯冲加剧,印度洋板块向缅甸大陆俯冲,孟加拉湾盆地演化为陆缘碎屑供应逐渐增强的残留洋盆。孟加拉湾东南部的基底为前古近系洋壳,始新世以来形成巨厚的残留洋盆充填序列。