雅鲁藏布中新生代深水沉积盆地形成和演化(Ⅱ)——喜马拉雅碳酸盐台地动力演化

FORMATION AND EVOLUTION OF THE MESOZOIC AND CENOZOIC DEEP-WATER SEDIMENTARY BASINS ALONG THE YARLUNG ZANGBO RIVER(Ⅱ): DYNAMICS OF THE HIMALAYAN CARBONATE PLATFORMS

关键词:  喜马拉雅造山带  碳酸盐台地  “喷溢流”  高频海平面振荡

Key words:  Himalayan orogenic belt  carbonate platform  “shedding flow”  high-fre-quency sea-level oscillations

摘要:

喜马拉雅地区的碳酸盐台地产生、发展和消亡与特提斯造山带形成的动力演化息息相关。三叠纪时,碳酸盐台地较稳定地在聂拉木陆架边缘发展起来,主要受陆源碎屑强烈干扰,碳酸盐台地在其生长面附近发育。早、中侏罗世,碳酸盐台地受构造沉降和海平面变化强烈影响,从潮下低能带向高能变浅的镶边台地旋回性发展。在台地边缘斜坡—盆地中发育一套特殊的碳酸盐“喷溢流”沉积。晚侏罗世,碳酸盐台地受被动大陆边缘初期快速热沉降影响,被黑色页岩覆盖,台地被淹没死亡。早白垩世,陆架边缘台地可能以孤立台地为特征,相当多的碳酸盐台地碎裂或崩塌,靠大陆一侧则主要为末端变陡缓坡。晚白垩世开始,碳酸盐台地主要在岗巴一带发育,发育向上变深的沉积序列,为受前陆挠曲影响产物。第三纪初,碳酸盐台地主要为缓坡,属于前陆盆地远离造山带一侧的碳酸盐台地沉积。喜马拉雅碳酸盐台地的最终消亡是由于造山抬升暴露。

Abstract:

The initiation, development and termination of the Himalayan carbonate platforms are closely related to the dynamic evolution of the Tethyan orogenic belt. In the Triassic, the carbonate platforms were firstly born on the shelf margins in the Nyalam area. In the meantime, they were also developed on and near the critical growing surfaces of the carbonate platforms because of the interference of the terrigenous clastics. Later in the Early and Middle Jurassic, the carbonate platforms, influenced by the tectonic subsidence and sea-level changes, evolved cyclically from the low-energy subtidal zone to the high-energy shallowing rimmed platform. A sequence of especial carbonate "shedding flow" deposits were laid down in the slope-basin environment of the platform margins. In the Late Jurassic, the carbonate platforms were covered by black shale and drowned to the death as a result of the rapid thermal subsidence during the early stage of the passive continental margin development. Till the Early Cretaceous, the platforms on the shelf margins may be characterized by the isolated platforms, a lot of which were destroyed and slumped into the marginal deeper basins, and then the platforms became the distally steepened ramps near the landward side of the Indian Continent. Beginning from the Late Cretaceous, the carbonate platforms were well developed mainly in the Gamba area, with deepening-upward sedimentary sequences in the foreland wedges. At the beginning of the Tertiary, the carbonate platforms passed gradually into ramps, belonging to the carbonate platorm sediments far from the orogenic side of the foreland basins. The termination of the Himalayan carbonate platforms may be attributed to the uplifting and exposure by the orogenic movements.