层序地层框架下的鲕粒滩形成样式:以北京西郊下苇甸剖面寒武系第三统为例

发布时间：2018-10-09 18:40

【摘要】：华北地台寒武系第三统,大致包括毛庄组、徐庄组、张夏组和崮山组,在其中上部大面积发育鲕粒滩相灰岩,从而不符合标准的威尔逊碳酸盐相带中"台地边缘颗粒滩相"的概念。在北京西郊下苇甸剖面,基于沉积相序列的层序地层划分表明,这些鲕粒滩相地层,常常构成层序的晚期高水位体系域或强迫型海退体系域,表现出层序地层框架下特别的鲕粒滩形成样式,成为相对快速沉降背景下的相对海平面缓慢下降的沉积响应,从而不符合标准的层序地层学模式,因为在标准的层序地层学模式中沉积作用主要发生在相对海平面上升和停滞阶段,而且在海平面下降期将形成一个连续的侵蚀作用不整合面。再者,与海侵作用期的陆棚相钙质泥岩和深缓坡相条带状泥晶灰岩、及其所代表的泥质碳酸盐沉积物主导的浅海陆架型台地相对应,强迫型海退过程之中发育的大面积分布的鲕粒滩,代表着寒武纪类型多样的碳酸盐台地类型中的一种新的碳酸盐台地类型,即鲕粒砂所主导的浅海碳酸盐陆架为特征的一种特别的碳酸盐台地,即浅海陆架被颗粒质的鲕粒沉积物大面积覆盖,向海一侧为缓坡、向陆一侧为潮坪。所以说,北京西郊下苇甸剖面的寒武系第三统,鲕粒滩的层序地层位置所代表的特别的形成样式,以及所蕴含的寒武纪碳酸盐台地的类型,将为更大区域的追索和对比、以及华北地台第三世的古地理重建提供重要的线索和思考途径。
[Abstract]:The third series of Cambrian system in North China platform, including Maozhuang formation, Xuzhuang formation, Zhangxia formation and Gushan formation, developed oolitic beach limestone in the upper part of the platform. Therefore, the concept of "platform marginal granular beach facies" in Wilson carbonate facies zone is not conformed to the standard. In the Xiweidian section of the western suburb of Beijing, sequence stratigraphy based on sedimentary facies sequence shows that these oolitic beach facies strata often form late high water level system tracts or forced regressive system tracts of sequences. The formation pattern of oolitic beach under sequence stratigraphic framework is shown to be the sedimentary response of slow decline of relative sea level in the context of relatively rapid subsidence, which does not conform to the standard sequence stratigraphic model. Because in the standard sequence stratigraphic model sedimentation mainly occurs at the stage of relative sea level rise and stagnation and a continuous erosive unconformity surface will be formed during the sea level fall. Furthermore, it corresponds to the continental shelf facies calcareous mudstone and deep gentle slope facies banded marl limestone during transgression, as well as shallow-sea shelf type platform, which is dominated by muddy carbonate sediments. The large-scale oolitic beach developed during the process of forced regression represents a new type of carbonate platform among the various types of carbonate platform in the Cambrian. That is, a special carbonate platform characterized by the oolitic sand dominated by the shallow sea carbonate shelf, that is, the shallow sea shelf is covered by a large area of granular oolitic sediments, with a gentle slope on one side of the sea and a tidal flat on one side of the land. Therefore, the Cambrian third Series, the sequence stratigraphic location of the oolitic beach, and the type of Cambrian carbonate platform contained in the lower Weidian section of the western suburb of Beijing will be the pursuit and correlation of a larger area. The paleogeographic reconstruction of the third North China platform provides important clues and ways of thinking.
【作者单位】：中国石油化工集团;中国地质大学地球科学与资源学院;
【基金】：国家自然科学基金项目(41472090、40472065、49802012)资助
【分类号】：P534.41;P539.2

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