柳江地区奥陶系碳酸盐岩沉积特征及沉积演化

Sedimentary Characteristics and Evolution of Ordovician Carbonate Rocks in Liujiang Area, China

秦皇岛柳江地区是研究奥陶系碳酸盐岩沉积地层的重要场所。通过对奥陶系开展野外地层剖面测制和室内岩矿鉴定,综合分析了奥陶系碳酸盐岩沉积特征和沉积演化,结果表明奥陶系碳酸盐岩沉积相类型为潮坪相、局限台地相和开阔陆棚相,并可进一步划分为潮上带、潮间带、潟湖、浅滩、滩间海和浅海风暴沉积等6种亚相类型;奥陶系碳酸盐岩形成于两个较长周期的海侵—海退过程,发育了两个完整的沉积旋回,即:早奥陶世冶里期到亮甲山早期,经历了局限台地→开阔陆棚→局限台地的沉积演化过程;早奥陶世亮甲山中期到中奥陶世马家沟期,经历了局限台地→开阔陆棚→局限台地→潮坪的沉积演化过程。在此基础上,建立了柳江地区奥陶系碳酸盐岩沉积模式。

Liujiang area of Qinhuangdao is an important place to study the sedimentary strata of Ordovician carbonate rocks.Based on field profile measurement and rock-mineral identification of Ordovician,a comprehensive analysis of the sedimentary characteristics and evolution shows that the sedimentary facies of the Ordovician carbonate rocks are tidal flat facies,restricted platform facies and open shelf facies.It can be further divided into six subfacies types:supratidal zone,intertidal zone,lagoon,shoal,intercoastal subfacies and neritic storm deposits.The Ordovician carbonate rocks were formed in two long-term Transgression-Regression processes and developed two complete sedimentary cycles.From the early Ordovician Yeli period to the early Liangjiashan period,the sedimentary evolution process was from restricted platform→open shelf→restricted platform.From the middle Liangjiashan period of early Ordovician to Majiagou period of middle Ordovician,the sedimentary evolution process was from restricted platform→open shelf→restricted platform→tidal flat.On this basis,the sedimentary model of Ordovician carbonate rocks in Liujiang area is established.