华北地区中北部寒武系层序地层格架

华北地台寒武系碳酸盐岩是华北地区重要的深部油气勘探目标,加强寒武系层序格架及其充填样式的研究对于指导潜山油气藏和潜山内幕油气藏勘探具有重要的理论与现实意义。在系统分析典型露头剖面岩性和沉积序列发育特征的基础上,结合典型钻井、测井资料和地震资料,共识别出3种层序边界类型,即暴露成因的I型和II型层序边界以及淹没不整合型(III型)层序边界;将华北地区中北部寒武系划分为7个可区域性对比的三级层序,并建立层序地层格架。利用碳酸盐岩全岩碳同位素对全球海平面变化的良好表征性,与露头沉积微相分析得到的相对水深变化规律进行对比,探讨了三级层序发育的主控因素。认为在古气候和沉积充填速率影响不大的背景下,下寒武统CSQ1层序(相当于府君山组或昌平组)、CSQ2层序(相当于馒头组)和上寒武统CSQ5层序(相当于崮山组)的发育受全球海平面变化和板块内差异沉降等构造背景综合控制,特别是CSQ5层序属于典型的淹没不整合型三级层序;CSQ3层序(相当于毛庄组)、CSQ4层序(相当于徐庄组及张夏组)、CSQ6层序(相当于长山组)和CSQ7层序(相当于凤山组)的发育主要受控于全球海平面变化。

Cambrian sequence stratigraphic framework in the middle-northern North China

Cambrian carbonate rocks in North China platform are well developed reservoirs for deep hydrocarbon accumulation. It is of significance to study the Cambrian sequence stratigraphy and filling pattern for exploration of both buried hills and buried hill inner curtain hydrocarbon accumulations. Synthesizing the lithofacies and sedimentary cycles' characteristics of outcrop, typical drilling log and seismic data, three kinds of sequence boundaries are identified, including not only the types I and type II related to the exposure but also the boundary indicating the drowned unconformity. Furthermore, the 3rd order sequence stratigraphic framework of Cambrian in the middle-northern North China has been established, and the Cambrian can be divided into seven 3rd order sequences tracing regionally. Through analyzing the carbon isotope cycles of whole rock reflecting the global sea level change and sedimentary cycles implying the depositing water depth, the dominating factors for the 3rd order sequences development of Cambrian in the middle-northern North China are clarified. The paleoclimate and sedimentation rate were relatively stable, inferring the tectonic setting and global sea level were vital for sequence development. The forming of sequence CSQ1(Fujunshan Formation or Changping Formation), sequence CSQ2(Mantou Formation) and sequence CSQ5(Gushan Formation) are comprehensively controlled by global sea level changes and regional tectonic subsidence, especially the sequence CSQ5 which is dominated by the drowned unconformity. While the stably aggradated sequences CSQ3(Maozhuang Formation), CSQ4(Xuzhuang Formation or Zhangxia Formation), CSQ6(Changshan Formation) and CSQ7(Fengshan Formation) are mainly dominated by the global sea level change.