贵州紫云晚二叠世——早三叠世初火山作用与生物礁的沉积演化

发布时间：2018-05-30 13:37

本文选题：长兴期 + 生物礁　；参考：《沉积学报》2017年01期

【摘要】：晚二叠世长兴期是华南地区重要的成礁期,也是火山事件频发的一个时期。生物礁是一种对海洋环境十分敏感的生态系,晚二叠世的火山作用势必影响到当时生物礁的生长和沉积相的演化。然而,前人有关晚二叠世火山事件的研究主要集中在二叠系与三叠系界线附近,而对整个长兴期生物礁的演化与火山事件关系的研究则较少。选择贵州紫云的台地边缘礁为研究对象,通过大量磁化率的测试,分析整个晚二叠世生物礁的沉积演化与火山作用的关系。分析结果显示,长兴早期和末期岩石的磁化率值明显偏高,反映较强的火山活动。在这两个时期,造架生物相对不发育。长兴中期,岩石的磁化率值相较于长兴早期和长兴晚期总体偏低,表明火山活动相对较弱,导致生物礁的快速生长。但长兴中期生物礁灰岩中夹有几层生物碎屑灰岩,其磁化率值有小幅度的升高,说明短时期小规模的火山作用虽然导致了生物礁生长的暂时中断,但礁相动荡的环境使得火山灰中细小的铁磁性物质难以沉积下来。研究发现,尽管早三叠世早期泥岩具有高的磁化率值,但泥质岩中多层火山黏土具有异常高的磁化率值,火山灰物质对磁化率大小的影响远远超过陆源物质的贡献。
[Abstract]:The Changxing period of late Permian is an important reefing period in South China, and it is also a time of frequent volcanic events. The reef is a very sensitive ecosystem to the marine environment. The volcanism of the late Permian will affect the growth of the reef and the evolution of the sedimentary facies at that time. However, previous studies on the late Permian volcanic events mainly focus on the Permian and Triassic boundary, but the relationship between the evolution of the whole Changxing reef and volcanic events is less. The platform marginal reef of Ziyun in Guizhou Province was selected as the research object. The relationship between the sedimentary evolution and volcanism of the entire late Permian reef was analyzed by a large number of magnetic susceptibility tests. The results show that the magnetic susceptibility of the early and late Changxing rocks is obviously higher, which reflects the strong volcanic activity. During these two periods, the scaffolding organisms were relatively undeveloped. In the middle period of Changxing, the magnetic susceptibility of rocks is lower than that of early and late Changxing, indicating that the volcanic activity is relatively weak, which leads to the rapid growth of reefs. However, there are several layers of bioclastic limestone in the reef limestone of the middle period of Changxing, and its magnetic susceptibility is increased by a small margin, which indicates that the small-scale volcanism caused the temporary interruption of the growth of the reef in a short period of time. But the turbulent reef environment makes it difficult to deposit the fine ferromagnetic material in the volcanic ash. It is found that although the early Triassic mudstone has a high magnetic susceptibility value, the multilayer volcanic clay in the mudstone has an unusually high magnetic susceptibility value, and the influence of volcanic ash on the magnetic susceptibility is far greater than that of the continental source material.
【作者单位】：广州海洋地质调查局;中国地质大学地质过程与矿产资源国家重点实验室;湖北省地质调查院;
【基金】：国家自然科学基金项目(41572001)~~
【分类号】：P317;P512.2

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