东濮地区中奥陶统层序格架及沉积演化

以层序地层学和沉积岩石学为指导，深入分析东濮地区野外、岩心、薄片和测录井等地质、地球化学和地球物理资料，恢复古气候及古海平面，结合区域地质背景，识别层序界面，建立了中奥陶统层序地层格架并阐述格架内沉积演化特征。结果表明，中奥陶统为一个二级层序（SSQ1），包含三个三级层序（SQ1、SQ2、SQ3）。SQ1为下马家沟组-上马家沟组下段，底为怀远运动不整合面，顶为岩性转换型界面（SB1）；SQ2为上马家沟组上段-峰峰组下段，顶为暴露型界面（SB2）；SQ3为峰峰组上段，顶为造山侵蚀型界面（SB3）。SQ1海侵体系域为局限台地向开阔台地过渡，发育开阔海、膏云坪和颗粒滩微相；高位体系域整体发育局限台地云坪、膏云坪和云灰坪，局部地区发育灰坪和颗粒滩；SQ2海侵体系域以开阔台地为主，发育开阔海微相，局部高地发育膏云坪、云坪和云灰坪，高位体系域为局限台地，整体发育云灰坪，局部发育膏云坪、灰云坪和颗粒滩微相；SQ3受风化剥蚀严重，仅能恢复海侵体系域早期沉积，以开阔台地为主

Sequence stratigraphic framework and sedimentary evolution of the Middle Ordovician in Dongpu Area

According to sequence stratigraphy and sedimentology theories, and based on thorough analysis of outcrops, cores, thin sections, logging and geochemical data, the paleoclimate and paleo sea-level are restored. Combining with the regional geological background, the sequence interface is identified, the sequence stratigraphic framework of the middle Ordovician system is established, and the sedimentary evolution characteristics in the framework are described. It is demonstrated that the Middle Ordovician is a second-order sequence ( SSQ1 ), composing of three third-order sequences ( SQ1, SQ2, SQ3 ). SQ1 included the Lower Majiagou Formation and the lower part of the Upper Majiagou Formation, the bottom surface of SQ1 is the Huaiyuan movement unconformity surface, and the top surface is a lithological transition boundary ( SB1 ); SQ2 included the upper part of the Upper Majiagou Formation and the lower part of the Fengfeng Formation, and the top surface of SQ2 is an exposure boundary ( SB2 ); SQ3 included the upper part of the Fengfeng Formation, and the top surface of SQ3 is an orogenic erosion boundary ( SB3 ). The transgressive system tract of SQ1 is a transition from restricted platform to open platform, with the microfacies of open sea, gypsiferous dolomitic flat and grain bank developed, while the high system tract is characterized by restricted platform, with the microfacies of dolomitic flat, gypsiferous dolomitic flat, and dolomitic calcific flat mainly developed, and the calcific flat and grain bank are developed in local areas. The transgressive system tract of SQ2 is recognized as open platform with the microfacies of open sea well developed, and the gypsiferous dolomitic flat, dolomitic flat and calcific dolomitic flat are developed in local highstand; the high system tract is mainly composed of restricted platform with the microfacies of dolomitic calcific flat developed, and the gypsiferous dolomitic flat, calcific dolomitic flat, and grain bank are developed in local areas. The SQ3 has been severely weathered and eroded, and only the early deposition of transgressive system tract is reconstructed, where the open platform is well develop.