贵州兴义地区早三叠世沉积环境演化及其生物响应

发布时间：2018-04-21 11:07

本文选题：贵州 + 早三叠世　；参考：《成都理工大学》2017年博士论文

【摘要】：兴义地区位于南盘江盆地西北边缘,保存有较完整的早三叠世浅水沉积记录,该地区晚二叠末至中三叠世生物演化经历了由灭绝到复苏的演化过程,是研究早三叠世沉积环境变迁及生物演化的理想地区。研究区早三叠世主要由飞仙关组及嘉陵江组沉积地层组成。飞仙关组以局限台地潮坪相陆源碎屑岩沉积为主,夹混积碳酸盐岩沉积;而嘉陵江组则以浅水台地、蒸发台地相碳酸盐岩沉积为主,夹混积陆源碎屑岩沉积。浅水相沉积结构与沉积构造主要包括:波状层理、透镜状层理、脉状层理及平行层理,局部见小型交错层理等,常见石膏假晶,电镜下见草莓状黄铁矿、自生石英颗粒等。不同种类的错时相具有不同的环境意义,其在空间上的交叉分布,指示研究区海洋环境经历多次改善-恶化过程。研究区错时相主要包括:叠层石、蠕虫状灰岩、条带状灰岩、巨鲕灰岩。叠层石中大量的微生物化石和草莓状黄铁矿反映叠层石形成于贫氧-低氧的沉积环境;条带灰岩良好的韵律性可能与海平面周期性波动有关,灰质条带中大量微生物化石,指示灰质条带形成于贫氧的海洋环境;蠕虫状灰岩的成因较为复杂,反映多种沉积环境,其中似层状、不规则粒状、椭圆状蠕虫状灰岩反映缺氧的沉积环境,变形柱状蠕虫状灰岩反映有氧的海洋环境。地球化学分析表明研究区早三叠世海洋环境具有多期次改善-恶化的演化过程。碳同位素研究表明,研究区早三叠世经历了3次负漂与3次正漂,说明早三叠世海洋环境经历了多次改善-衰退过程。硫同位素研究表明,研究区硫同位素值剧烈波动(飞仙关组从-25.5‰至26.3‰,嘉陵江组从-3.9‰至37.3‰),反映当时多变的海洋生态环境。Sr87/Sr86值表现出快速上升的趋势,从0.707203至0.708107,其百万年内的变化速率自显生宙来最大。MgO/CaO值指示研究区从格瑞斯巴赫期末(飞仙关组一段沉积期)至斯潘斯期末(嘉陵江组三段沉积期)气候比较潮湿,嘉陵江组三段沉积期后期,气候相对较干燥。镁铝比值指示早三叠世处于正常浅海环境,未受到陆地淡水的影响。早三叠世碳同位素不仅在横向上表现为剧烈的波动,还在纵向上表现出显著的离散分异。通过统计全球范围内30余条碳同位素剖面,发现早三叠世碳同位素具有显著的离散系数(标准方差)。研究表明海洋初级生产力和海水分层共同导致了早三叠世碳同位素在纵向上的显著变化,其中海水分层是主要原因。综合碳同位素在纵向上和横向上的相关性,将早三叠世海洋环境划分为是10个阶段。研究区早三叠世氧化还原界面主要出现了3次上移,分别在N1(P-T界线附近)、Smithian中期、Spathian中晚期,其中前两个时期氧化还原界面向上迁移幅度最大。N2、P2、P3时期,透光带Δδ13C值大于深水Δδ13C值,海洋初级生产力是影响碳同位素水深梯度的主要因素。早三叠世海洋沉积环境演化过程,与研究区古生物多次复苏-残存-灭绝响应过程具有较好的耦合关系。具体表现为二叠纪-三叠纪界线附近,缺少生物化石,岩石以青灰色泥岩为主,反映海洋恶化;Griesbachian早期,数层双壳化石层指示海洋环境存在一次短暂的复苏;在Griesbachian中期,粉砂岩中紫红色条带开始增多,双壳化石分异度的升高指示浅水海洋环境改善;Griesbachian晚期至Dienerian早期,岩石主要为青灰色细砂岩-粗砂岩,缺乏生物化石反映海洋环境恶化;Dienerian中晚期,草莓状黄铁矿粒径增大,化石分异度升高,指示海洋环境逐渐改善。在Smithian早期,硫同位素正漂、碳同位素负漂、黄铁矿颗粒增多,反映海洋环境恶化。在Smithian中期,化石分异度减少、硫同位素达到最高值,指示海洋环境恶化;Smithian晚期,变形柱状蠕虫状灰岩、海洋红层、化石分异度升高,指示海洋环境改善;Spathian早期,叠层石中保存大量微生物化石、硫同位素负漂,生物化石减少,指示海洋环境恶化。Spathian晚期,生物化石分异度提高,指示海洋环境改善。
[Abstract]:The Xingyi area is located on the northwest edge of the South Pan River Basin, and has a relatively complete record of early three fold shallow water deposits. The evolution of the late two and middle three stages of the region experienced the evolution process from extinction to resuscitation. It is a study area to study the sedimentary environment changes and biological evolution of the early three fold. The early three fold of the study area was mainly from Feixianguan. The formation of sedimentary strata in the group and the Jialingjiang formation. The Feixianguan formation is mainly composed of the terrigenous clastic rocks of the tidal flat facies in the limited platform, and the sedimentary carbonatite deposits, while the Jialingjiang formation is based on the shallow water platform, the evaporative platform facies carbonate deposits are the main deposits, and the sediments are mixed with the terrigenous clastic rocks. The shallow water facies sedimentation structure and sedimentary structure mainly include wave bedding and penetration. Mirror bedding, pulse bedding and parallel bedding, small staggered bedding, common gypsum pseudo crystal, strawberry like pyrite and autogenic quartz particles under electron microscope. Different kinds of wrong phases have different environmental significance. The cross distribution in space indicates that the marine environment has experienced many improvement and deterioration process in the study area. The fault of the study area is wrong. The time phase mainly includes: the fossils, vermicular limestone, banded limestone, and giant Oolitic Limestone. A large number of microorganism fossils and strawberry like pyrite in the raspite reflect the formation of the depositional environment of the oxygen poor hypoxia. The good rhythm of the strip may be related to the periodic wave of the sea level, and a large number of microorganism fossils in the gray matter band are indicated. The gray matter bands are formed in the oxygen poor marine environment; the cause of the wormlike limestone is more complex, reflecting a variety of sedimentary environments, in which the stratiform, irregular granular, elliptical vermicular limestone reflects the anoxic sedimentary environment, and the deformed columnar wormlike limestone reflects the aerobics of the marine environment. The geochemical analysis shows the early three fold marine rings in the study area. The carbon isotope study showed that the early three fold of the study area had undergone 3 negative drift and 3 positive drift, indicating that the early three fold marine environment had experienced many improvement and decline processes. The sulfur isotope study showed that the sulfur isotope value of the study area was intense wave (Feixianguan group from -25.5 per thousand to 26.3 per thousand, Jialingjiang group) From -3.9 per thousand to 37.3 per thousand, the.Sr87/Sr86 value of the marine ecological environment at that time showed a rapid rising trend. From 0.707203 to 0.708107, the rate of change within millions of years from the Phanerozoic maximum.MgO/CaO value indicated that the study area was from the end of Garces Bach period (a period of Feixianguan group deposition) to the end of span period (third section of the Jialing River Group). The climate is relatively humid, and the climate is relatively dry in the late period of the third stage of the Jialingjiang group. The ratio of magnesium to aluminum indicates that the early three fold world was in the normal shallow sea environment and was not affected by the land fresh water. The early three fold carbon isotopes not only displayed violent fluctuations in the transverse direction, but also showed significant discretization in the longitudinal direction. More than 30 carbon isotopic profiles in the range have found that early three fold carbon isotopes have significant discrete coefficients (standard variance). The study shows that marine primary productivity and seawater stratification jointly lead to significant longitudinal changes in carbon isotopes in the early three stages, in which the stratification of sea water is the main reason. The correlation of the early three fold marine environment is divided into 10 stages. The early three redox interface in the study area was mainly moved up 3 times, respectively, at N1 (P-T boundary), mid Smithian, and late Spathian, of which the first two redox interfaces moved up to the maximum.N2, P2, P3 period, and the transmittance Delta 13C value was greater than depth. Water delta delta 13C value, marine primary productivity is the main factor affecting the carbon isotope water depth gradient. The evolution process of the early three fold marine sedimentary environment has a good coupling relationship with the multiple resuscitation - residual and extinction response process of Paleontology in the study area. It is characterized by the Permian Triassic boundary line, the lack of biological fossils, and the green and gray rocks. Mudstone mainly reflects marine deterioration; in the early period of Griesbachian, several layers of double shell fossils indicate a brief resuscitation in the marine environment; in the middle of Griesbachian, the purple red bands in the siltstone began to increase, and the elevation of the bivalve fossils indicated the improvement of the shallow water marine environment; the late Griesbachian to the early Dienerian, the rocks were mainly green ash. Fine sandstone - coarse sand rock, the lack of biological fossils reflect the deterioration of the marine environment. In the late Dienerian, the size of the strawberry pyrite increased and the fossil diversity increased, indicating the gradual improvement of the marine environment. In the early stage of Smithian, the sulfur isotopes were positive drift, carbon isotope drift, and pyrite particles increased, reflecting the deterioration of the marine environment. In the middle of Smithian, fossils were divided. In the late Smithian, the deformed columnar vermicular limestone, the marine red layer, the marine red layer, the fossils were increased, and the marine environment was improved. In the early stage of Spathian, the fossils were preserved in a large number of fossils in the stanus, the sulphur was negatively bleached and the biological fossils decreased, indicating the deterioration of the marine environment in the late.Spathian late period. During the period, the biologic fossils increased, indicating the improvement of marine environment.

【学位授予单位】：成都理工大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：P512.2;P534.51

【参考文献】