中扬子台地南侧下奥陶统等深岩沉积研究

发布时间：2018-07-03 20:44

本文选题：中扬子台地 + 下奥陶统　；参考：《长江大学》2015年硕士论文

【摘要】：深水环境下等深流沉积研究已经过去50多年,在这50多年里虽然取得了一些成果,但对等深岩的形成机理和沉积环境研究较少。中扬子台地南侧早奥陶世沉积格局稳定,沉积相分区明显,由西北至东南依次为浅水碳酸盐岩台地、深水斜坡和盆地沉积区,整体上该区属于华南古大陆边缘带成熟阶段环境的一部分。该区不仅深水重力流沉积发育,而且深水等深流沉积也十分发育。对中扬子台地南侧下奥陶统等深岩丘进行研究,不仅可以丰富等深流沉积研究的内容,促进深水牵引流沉积研究的发展,而且对于等深岩的形成机理及重新认识等深流形成时该地区古地理、古气候和古大地构造条件等也有重大意义,同时对于寻找该地区沉积矿产尤其是油气的勘探具有重要的实际意义。本文通过野外剖面实测、详细描述和碳氧同位素特征分析,对研究区形成等深岩的环流的特征、不同类型等深岩的形成环境有什么不同进行了探索。在野外地质工作的基础上,以现代沉积学理论和海洋学中关于等深流沉积的理论为指导,采取室内宏观与微观研究相结合、常规分析与先进的分析测试相结合的方法,对中扬子台地南侧下奥陶统等深岩丘实例进行重点解剖,深入研究其等深岩的类型及特征、沉积层序和纵横向分布规律,并通过对等深岩地化指标特征的测试结果分析,研究该区等深岩的形成机理及其形成时的古地形、古气候、古盐度等古环境条件。通过野外剖面实测和详细研究,认为中扬子台地南侧下奥陶统盘家咀组为一套以灰色泥晶灰岩、粉屑灰岩、砂屑灰岩和生物屑灰岩为主的深水碳酸盐岩沉积,主要发育垂向降落沉积、重力流沉积和等深流沉积3种沉积类型。根据岩性特征可将该等深流沉积划分为灰泥等深岩、粉屑等深岩、砂屑等深岩、细砾屑等深岩和生物屑等深岩5种类型,其中灰泥等深岩尤为发育,砂屑等深岩、生物屑等深岩次之；并对其发育特征、碳氧同位素特征以及垂向层序进行了归纳总结。研究表明,研究区主要存在由单一灰泥等深岩、单一生物屑等深岩、单一砂屑等深岩、生物屑等深岩与灰泥等深岩、砂屑等深岩与灰泥等深岩组成的5种不完整等深岩层序和极少的完整等深岩层序。在剖面上,根据等深岩发育类型及程度,将盘家咀组划分为三部分,从第1部分至第Ⅲ部分,等深岩沉积厚度所占比例呈增大趋势；结合区域沉积背景,认为该地区早奥陶世盘家咀组沉积期等深流活动的强度总体上呈由弱到强的变化规律。为了研究该等深流沉积形成时的古环境,分别对研究区不同类型等深岩与原地沉积进行系统采样做碳氧同位素分析。研究表明,工区下奥陶统盘家咀组等深岩的δ13C值分布于-0.83‰々2.31‰,δ13O值的范围为-10.93‰～-9.54‰,Z值介于为120.82～127.14之间,T为16.98～24.81℃。与原地沉积相比,研究区等深岩的δ13C值、Z值、T值均较高,且随着等深岩的粒度增大,其δ13C值、Z值、T值均逐渐增高；表明等深流沉积环境与原地沉积完全不同,等深岩主要形成于高盐度的较深水环境中,且盐度、水温越高,越有助于高能等深流沉积物砂屑等深岩、生物屑等深岩的形成。等深岩层序的形成周期均表现为古盐度、古水温、海平面先增大后减小的周期性变化。
[Abstract]:Deep water sedimentary study has been studied for more than 50 years. Although some achievements have been made in the past 50 years, the formation mechanism and sedimentary environment of peer-to-peer deep rock are less studied. The sedimentary pattern of Early Ordovician in the southern side of the middle Yangtze platform is stable and the sedimentary facies is distinct, from the northwest to the southeast, the shallow water carbonate platform and the deep water slope are in turn. As a whole, the basin is part of the mature stage of the paleo continental margin of Southern China. This area is not only deep-water gravity flow deposition and development, but also deep deep flow deposits are also very well developed. The development of the research on water tractive flow deposition is of great significance to the paleogeography, paleoclimate and paleotectonic conditions in the formation of the deep stream, as well as the formation mechanism and re understanding of the deep rocks. At the same time, it is of great importance to the exploration of the deposits in this area, especially the exploration of oil and gas. A detailed description and analysis of carbon and oxygen isotopes have been made to explore the characteristics of the circulation of the deep rocks in the study area and the difference in the forming environment of different types of deep rocks. On the basis of the field geological work, with the theory of modern sedimentology and the theory of the deep flow deposition in oceanography, the indoor macro and micro research is taken. Combined with the combination of the conventional analysis and the advanced analysis and testing method, the lower Ordovician deep rock colliculus in the southern side of the middle Yangtze platform are dissected, and the types and characteristics of the deep rock, the depositional sequence and the vertical and horizontal distribution law are studied, and the test results of the characteristics of the index characteristics of the peer-to-peer deep rock geochemistry are analyzed, and the study area and so on are studied. The formation mechanism of deep rock and its paleoclimate, paleoclimate, paleosalinity and other paleoenvironmental conditions. Through field survey and detailed study, it is believed that the lower Ordovician Pan Jia Tsui formation on the southern side of the middle Yangtze platform is a set of deep-water carbonate deposits mainly of gray muddy limestone, silt limestone, sand clastic limestone and bioclastic limestone. There are 3 types of sedimentary types: vertical descent deposition, gravity flow deposition and equal deep flow deposition. According to the lithologic characteristics, the same deep flow deposits can be divided into 5 deep rocks, such as plaster, deep rock, sand and other deep rocks, fine gravel and other deep rocks, such as deep rock and other deep rocks, of which the plaster and other deep rocks are particularly developed, sand and other deep rocks, and other deep rocks, and so on. The characteristics of its development, carbon and oxygen isotopes and vertical sequences are summarized. The study shows that there are 5 incomplete sequences and poles of deep rocks composed of deep rocks such as single plaster, single biochip and other deep rocks, single sand and other deep rocks, deep rocks such as deep rock and plaster, sand and other deep rocks such as plaster and other deep rocks. In the section, according to the type and degree of the development of the same deep rock, the Pan Jia Tsui formation is divided into three parts. From the first to the third part, the proportion of the sedimentary thickness of the deep rock is increasing, and the sedimentary background of the region is considered to be the overall intensity of the deep flow activity in the early Ordovician of the early Ordovician. In order to study the Paleoenvironment in the formation of the same deep flow deposits, the carbon and oxygen isotopes of different types of deep rocks and original deposits in the study area are systematically sampled and analyzed. The study shows that the delta 13C value of the deep rock in the lower Ordovician of the Ordovician of the Ordovician is 2.31 per thousand and the range of the delta 13O value is -10.93. The value of Z is between 120.82 and -9.54 per thousand, and the value of Z is between 120.82 and 127.14 and 16.98 ~ 24.81 C. Compared with the original deposit, the delta 13C value, Z value and T value of the deep rock in the study area are all higher, and with the increase of the granularity of the isodeep rocks, the delta 13C value, Z value and T value are all increased gradually, indicating that the sedimentary environment of the equal depth is completely different from the original deposit, and the isodeep rock is mainly formed at the high level. In the deepwater environment of salinity, the higher the salinity, the higher the water temperature, the more helpful to the formation of deep rock and other deep rocks such as the high energy and other deep stream sediments. The formation period of the sequence of the same deep rock is manifested by the paleo salinity, the paleo water temperature, and the decrease of the sea level and then the decrease of the periodicity.
【学位授予单位】：长江大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P534.42

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