塔东地区寒武纪—奥陶纪碳酸盐岩台缘带迁移与相对海平面变化关系

MIGRATION OF CAMBRIAN-ORDOVICIAN CARBONATE PLATFORM MARGIN AND ITS RELATIONSHIP WITH THE RELATIVE SEA-LEVEL CHANGE IN EAST TARIM BASIN

通过识别和追踪寒武纪—奥陶纪不同期的台地—台地边缘界线揭示不同期台地边缘相带的变迁,通过识别碳酸盐岩岩性和沉积能量并结合有机碳及碳氧同位素等资料编制塔东地区相对海平面变化曲线,探讨海平面变化对不同时期台地边缘迁移的控制作用。研究表明:早寒武世塔东地区以斜坡相—盆地相为主,台地边缘相不发育;中晚寒武世海平面不断下降,台地类型为局限台地,台地边缘相发育且向盆地方向迁移;早奥陶世全球海平面开始上升,蓬莱坝组沉积期台地边缘宽度变窄,鹰山组下段沉积期海平面下降,台地类型变为开阔台地,台地边缘相带变宽,鹰山组上段沉积期经历了快速的水进,海平面又开始下降,台地边缘相带向盆地内侧进一步加宽,一间房组沉积期之后,随海平面快速上升,台地被淹没。

With the help of the identification and trace of the platform-platform margin boundary in different peri- ods of Cambrian-Ordovician period, the changes of the marginal facies belt were revealed, by means of the identifi- cation of the lithologies of the carbonate rock and sedimentary energy, and moreover integrating with the data such as the organic carbon, carbon-oxygen isotopes and so forth, the changed relations of the relative sea level were com- piled and mapped, and furthermore the controlling actions of the changes on the migration of the platform margin in different periods were discussed. The study achievements show that the slope facies-basin facies is the main form in East Tarim Basin in Early Cambrian, but the platform margin phase is not well-developed; in Middle and Lower Or- dovician, the sea level gradually dropped, the platform type was limited platform, the platform margin was well-de-veloped and migrated to the basin; in Early Ordovician Epoch, the global sea level began to rise, in the sedimenta- ry period of Penglaiba Formation, the platform margin become narrow ; for the period in Lower Member of Yingshan Formation, the sea level dropped, the platform type turned into the open one, and moreover its margin began wi- der; for the period in Upper Member of Yingshan Formation, the rapid water transgression occurred, the sea level began to drop once more, the platform margin facies belt further widened towards the basin internal part; after de- positing period of Yijianfang Formation, the platform was submerged with the rapid rise of the sea level.