塔中地良奥陶系地层格架与沉积演化

Stratigraphic Framework and Sedimentary Evolution of Ordovician Strata in Tazhong Area,Tarim Basin

塔里木中部地区奥陶系大致以Ⅰ号断裂为界分东北和西南两个地层分区,自下而上分白云岩段、灰岩段、泥质灰岩段、泥岩夹灰岩段、泥岩夹砂岩段、砂砾岩段、泥岩夹砂岩段、泥岩灰岩互层段和砂岩段等9个岩性段。早奥陶世,塔中地区以碳酸盐岩台地相为主,自西向东为局限台地相、开阔台地相、台地边缘相和深水斜坡相。中——晚奥陶世,塔中地区西部以混积陆架相为主,东部以深水斜坡相为主。中—晚奥陶世,塔中东部及塔东地区在构造上具弧后前陆盆地性质。中—上奥陶统地层完整地记录了该盆地从形成发展到消亡的过程,即早期为深水斜坡相复理石活动沉积,晚期演化为浅海陆架相稳定沉积。

There are two stratigraphic zones of Ordovician strata, northeast and southwest ones,which are bounded by fault F1, in Tazhong area,Tarim Basin.Nine Ordovician lithologic members are divided upwards,namely limestone,muddy limestone,mudstone intercalated with limestone,mudstone intercalated with sandstone,sandstone/conglomerate, mudstone intercalated with sandstone,mudstone interbedded with limestone,and sandstone members.In Early Ordovician, there mainly was carbonate rock platform facies which includes restricted sea platform facies,open sea platform,platform margin facies and deep-water slope facies from the west to the east in Tazhong area.In Middle-Late Ordovician,there mainly were carbonate-classic mixed rock shelf facies in the west part and deep-water slope facies in the east part.Tectonically,it is characterestic of a back-arc foreland basin in the eastern Tazhong-Tadong area during the Middle-Late Ordovician.The Ordovician strata completely record the evolution of this foreland basin that formed,developed and consumed.That is, there were active flysch sediments of deep-water slope facies during the early phrase and stable sediments of neritic shelf facies during the late phrase.