徐州地区新元古界下部具臼齿构造碳酸盐岩事件成因探讨  

Study on the Origin of Molar-tooth Structure-bearing Carbonates in the Lower Neoproterozoic in Xuzhou Area

作　　者：冯乐[1] 李壮福[1] 陆鹿[1] 窦鲁星[2] 师庆民[1] 周晏召 

机构地区：[1]中国矿业大学资源与地球科学学院,徐州221000 [2]中国石油大学(北京)地球科学学院,北京102249

出　　处：《高校地质学报》2015年第2期203-214,共12页Geological Journal of China Universities

基　　金：中国矿业大学研究生实践与科研创新项目(GSF121101)资助

摘　　要：徐州地区新元古界贾园组-赵圩组发育陆棚-缓坡-台地边缘的碳酸盐沉积,记录有广泛的风暴事件,并在其中发现大量具"臼齿构造"碳酸盐岩。依据野外剖面系统观察与室内综合分析,将臼齿碳酸盐岩划分为原地型:条带状M1(平直条带状M1-a、分叉条带状M1-b)、蠕虫状M2(短小蠕虫状M2-a及长条蠕虫状M2-b)、丝状M3、悬针状M4;异地型:碎屑状M5等五种形态类型,主要发育于缓斜坡下部到潮坪环境。以水体深度及水动力条件下的七种代表性风暴序列为背景,将臼齿碳酸盐岩的形态及分布与瞬时高能事件沉积做关联分析。研究发现,臼齿构造与风暴事件有密切联系,表征晴好天气下的块状层中以M3为主,风暴期动荡水体序列层段以M1,M2为主,而在表征风暴高潮期序列层段以异地型的M4,M5为主。风暴的强弱及水深变化控制了风暴序列的分布,进一步控制了臼齿构造的形态与规模。由此推断,臼齿构造形成是在中-新元古代特殊的古大气古海洋背景下,在风暴周期的不同阶段,经历具有裂缝形成与微亮晶充填的紧密联系的过程。风暴前期和风暴高潮期,风暴浪对臼齿构造的形成主要体现在造缝阶段,而风暴后期则主要为微亮晶的填充阶段。最终形成广泛分布的具臼齿构造碳酸盐岩这一地质历史内特殊的事件型碳酸盐岩类型。Molar-tooth structures（MTS） and storm deposits were widely developed in the carbonate sedimentary system ofshelf-ramp-platform margin from the Jiayuan Formation to the Zhaowei Formation of Neoproterozoic in Xuzhou area. Based on fieldobservations of outcrops and indoor comprehensive analysis, MTS were divided into autochthonous MTS containing banded M1（straightbanded M1-a; branched banded M1-b）, worm-like M2（short wormlike M2-a; long wormlike M2-b）, filiform M3, suspension needle-likeM4, and allochthonous MTS containing clastic M5. The five types mainly occur in the area from the lower area of gentle ramp to thetidal flat. Based on the background of seven typical storm sequences of different water depths and hydrodynamic conditions, correlationanalysis was performed between morphology, distribution of the MTS, and the instantaneous high-energy event deposits. The analysisshows that close correlation was found between MTS and the storm events, indicating that M3 is mainly present in the massive layers infine weather. The M1 and M2 were mainly formed in turbulent environment during fluctuating period with frequent earthquakes andstorms. While the M4 and M5 are the principal types in the layers formed during the storm upsurge period, the strength of the storm and the water depth control the scale of the storm sequence, and further control the morphology and distribution of the MTS. Therefore,during the different stages of the storm cycle, the form of MTS includes two interrelated processes： crack formation and microspar fillingunder the special marine and atmospheric paleoenvironment during the Middle-late Proterozoic. During the early period and the climaxperiod of a storm, the storm wave has influenced mainly on the crack opening stage of the MTS formation; while the storm waves mainlyinfluence the filling stage during the later period. Finally, Molar-tooth structure-bearing carbonate, a special type of an event carbonatein the geological history, was formed and widely distributed.

关 键 词：新元古界 臼齿构造 地震 风暴沉积 

分 类 号：P588.245[天文地球—岩石学]