黄骅坳陷奥陶纪岩相古地理

LITHOFACIES PALAEOGEOGRAPHY OF THE ORDOVICIAN IN HUANGHUA DEPRESSION

黄骅坳陷地处埕宁隆起和沧县隆起之间 ,北与燕山褶皱带相连。区内奥陶系厚6 0 0～ 80 0m ,主要由石灰岩和白云岩组成。下奥陶统分冶里组和亮甲山组 ,中奥陶统分下马家沟组、上马家沟组和峰峰组 ,上奥陶统缺失。下马家沟组、上马家沟组和峰峰组又分别分下段和上段。早奥陶世冶里期和亮甲山期 ,本区以局限海环境为主 ,其内散布着一些潮坪和滩。中奥陶世 ,本区岩相古地理显示出明显的沉积旋回 ,早马家沟期早期潮坪广布 ,晚期以局限海为主 ;晚马家沟期早期又是潮坪广布 ,晚期以开阔海为主 ;峰峰期早期潮坪广布 ,晚期又以开阔海为主。在奥陶纪 ,本区经历了 4个大的海侵—海退旋回 ,其中晚马家沟期晚期是本区乃至整个华北地台的最大海侵期。

The Huanghua Depression is located between the Chengning Uplift and Cangxian Uplift, connecting with the Yanshan Fold Zone to the north. In the study area, the Ordovician is 600～800 m thick and mainly consists of limestones and dolostones. The Lower Ordovician can be divided into the Yeli Formation and Liangjiashan Formation, and the Middle Ordovician can be divided into the Lower Majiagou Formation, Upper Majiagou Formation, and Fengfeng Formation. The Lower Majiagou Formation, Upper Majiagou Formation, and Fengfeng Formation can each be further divided into the upper member and the lower member. The Upper Ordovician is missing. In the Yeli Age and Liangjiashan Age of the early Ordovician, the study area was mainly a shallow restricted platform, in which there were several tidal flats and banks. The lithofacies palaeogeography throughout the Middle Ordovician showed strong cyclicity. In the early Early Majiagou Age, transgression occurred, and the whole study area was occupied by tidal flats. In the late Early Majiagou Age, sea level rose further and most of the study area changed to a shallow restricted platform. In the early Late Majiagou Age, sea level fell, and tidal flats again dominated the area. In the late Late Majiagou Age, sea level rose quickly and most of the study area changed to a relatively deep open platform. In the early Fengfeng Age, the area changed to tidal flats. In the late Fengfeng Age, the whole study area changed to a relatively deep open platform again. During the Ordovician, the study area underwent 4 marine transgression-regression cycles. In the late Late Majiagou Age marine transgression reached maximum.