Sediment accumulation rates in subarctic lakes: Insights into age-depth modeling from 22 dated lake records from the Northwest Territories,Canada     

《Quaternary Geochronology》2015

Age-depth modeling using Bayesian statistics requires well-informed prior information about the behavior of sediment accumulation. Here we present average sediment accumulation rates (represented as deposition times, DT, in yr/cm) for lakes in an Arctic setting, and we examine the variability across space (intra- and inter-lake) and time (late Holocene). The dataset includes over 100 radiocarbon dates, primarily on bulk sediment, from 22 sediment cores obtained from 18 lakes spanning the boreal to tundra ecotone gradients in subarctic Canada. There are four to twenty-five radiocarbon dates per core, depending on the length and character of the sediment records. Deposition times were calculated at 100-year intervals from age-depth models constructed using the ‘classical’ age-depth modeling software Clam. Lakes in boreal settings have the most rapid accumulation (mean DT 20 ± 10 yr/cm), whereas lakes in tundra settings accumulate at moderate (mean DT 70 ± 10 yr/cm) to very slow rates, (>100 yr/cm). Many of the age-depth models demonstrate fluctuations in accumulation that coincide with lake evolution and post-glacial climate change. Ten of our sediment cores yielded sediments as old as c. 9000 cal BP (BP = years before AD 1950). From between c. 9000 cal BP and c. 6000 cal BP, sediment accumulation was relatively rapid (DT of 20–60 yr/cm). Accumulation slowed between c. 5500 and c. 4000 cal BP as vegetation expanded northward in response to warming. A short period of rapid accumulation occurred near 1200 cal BP at three lakes. Our research will help inform priors in Bayesian age modeling.  相似文献   

塔里木盆地冷盆热改造的地震学证据          下载免费PDF全文

王腾飞  黄少英  程日辉  肖中尧  王典  能源  蒋飞  杨宝俊 《地球物理学报》2016,59(3):992-1002

塔里木盆地是我国最大的沉积盆地,对我国油气战略选区具有较大的意义.自震旦系成盆以来,塔里木盆地表现为一个低温的冷盆.在覆盖全盆的20条地震长剖面上,识别出83处特殊的地震反射结构,其特征为同相轴向上凸起呈尖角状,形态为直立或近直立,故名地震反射尖角直立结构.共识别出四种基本类型的地震反射尖角直立结构,平缓型、正常型、巨幅型、刺穿型,两个形态基本一致的基本型紧邻而组合为双相位型,两个或多个不同类型、不同形态的集中于某处则构成复合型.平缓型、正常型、巨幅型、刺穿型依次反映了变形增强的序列,理想状态下该反射结构由深至浅存在从刺穿型至平缓型的渐变序列,故基本类型的划分只是反映某处地震反射尖角直立结构的整体形态特点.地震反射尖角直立结构部位可能发育火成岩,与盆内钻遇火成岩钻井平面分布具有较高的相关度.地幔物质上涌至岩石圈,巨大的上拱能量造成了地层的变形,叠加构造因素的改造,地震反射尖角直立结构正是这一系列作用于地震反射上的响应.地震反射尖角直立结构是"热上涌"作用的产物.有机质的成熟、油气藏的形成和破坏与盆地热作用关系密切,对照塔里木盆地已有的油气田与"尖角直立"地震反射结构的平面分布,发现二者具有较高的相关性.地震反射尖角直立结构所反映的"热上涌"现象,促进了塔里木盆地"冷盆"背景下丰富油气资源的形成.  相似文献   

郯庐断裂渤南段各分支新生代构造特征及其对油气聚集的控制作用   总被引：1，自引：0，他引：1       下载免费PDF全文

肖述光韦阿娟  王粤川赵志平 吴庆勋 《地质科学》2017,(2):375-389

通过对郯庐断裂渤南段3 个分支几何构造样式、断裂活动速率和伸展量、优势伸展方向等运动学特征,以及构造演化特征等方面的对比分析,总结了与之对应的斜向伸展-弱走滑改造、斜向伸展-强走滑叠加、持续强走滑拉分3 种构造成因类型,并阐明了不同成因演化模式对圈闭形成、储层发育和油气运移的控制作用,建立了各分支构造-成藏响应关系。结果表明,新生代以来渤海南部海域处于地幔隆升导致的南北向引张和太平洋板块斜向俯冲形成的北东向右旋剪切双重应力场中,郯庐断裂的3 个分支具有相同的构造演化阶段,但各个时期局部应力场的不同导致了它们构造特征的差异,进而影响和控制了各分支在油气聚集时期、层位、规模等方面的成藏差异性。  相似文献   

鄂尔多斯盆地南部长7页岩沉积特征和有机质富集因素研究          下载免费PDF全文

马　瑜周世新  陶辉飞付德亮 李　靖李源遽  李成成杨亚南 《地质科学》2017,(1):106-122

对鄂尔多斯盆地南部瑶科1（YK1）井延长组长7段页岩45件样品进行了总有机碳、Rock-Eval热解分析,并且对其中的15个样品进行了有机碳同位素组成分析、氯仿沥青“A”含量和微量元素分析。结果显示,长7段有机质丰度指标（TOC、氯仿沥青“A”、生烃潜量）之间具有良好的相关性,长73有机质丰度高于长71,长72有机质丰度最低;有机碳同位素指示长73层有机质类型好,以Ⅰ型为主,长72和长71层有机质以Ⅰ和Ⅱ型为主;氧化还原指标U/Th、δU和V/(V+Ni)值指示长7沉积时期水体整体为还原-强还原环境,其中,相比长72和长71的沉积环境,长 73的沉积环境还原性更强,可能达到厌氧、硫化细菌发育的程度。页岩中高P元素含量,指示YK1井长7段页岩沉积时期具有高古生产力特征。有机碳含量（TOC）与氧化还原指标和P元素呈良好的正相关关系,表明有机质含量的变化同时受控于古生产力高低和氧化还原的保存条件。因此,长7段页岩有机质富集模式可能属于“生产力模式”,即长7页岩有机质的富集是由于较高的初始生产力通过消耗水体中的氧气而形成易于保存有机质的缺氧环境。综合前人的页岩气研究成果,认为富有机质的长73层是鄂尔多斯盆地南部页岩气富集的最有利层段。  相似文献   

中国海相盆地油气保存条件主控因素与评价思路   总被引：1，自引：0，他引：1  

何治亮  李双建  沃玉进  张殿伟  顾忆  周雁 《岩石学报》2017,33(4):1221-1232

中国海相盆地具有多旋回演化、盆-山结构复杂、稳定性差的特点,油气保存条件是制约油气勘探的关键因素。本文在对中国海相盆地构造改造特征和油气藏破坏方式分析的基础上,对影响油气保存条件的主控因素进行了总结,提出了海相多旋回强改造盆地油气保存条件评价的思路方法。中国海相盆地构造演化具有"五世同堂、同序异时"的特点,燕山中晚期和喜马拉雅期是影响油气保存的关键构造变革期。海相油气藏的破坏方式主要有断裂切割、抬升剥蚀、褶皱变动、深埋裂解、岩浆烘烤、流体冲洗、生物降解和长期扩散等8种主要方式。构造、盖层、热体制、流体活动和时间是控制保存环境及其动态演化的主控因素。中国海相盆地油气保存系统的评价思路为,以上述5种主控因素动态分析评价为基础,以地质结构和源-盖组合为依据划分评价单元,以源-盖动态演化,今、古流体系统演化和油气藏动态成藏过程研究为重点,动态地评价油气保存系统,进而优选有利的保存单元。  相似文献   

四川海相克拉通盆地显生宙演化阶段及其特征   总被引：2，自引：1，他引：1  

刘树根  孙玮  钟勇  邓宾  宋金民  冉波  罗志立  韩克猷 《岩石学报》2017,33(4):1058-1072

四川叠合盆地是在四川海相克拉通盆地基础上形成的。本文利用最新的钻井资料、地震资料及其研究成果,详细阐述了四川海相克拉通盆地在显生宙的演化阶段及其特征。研究结果发现,四川海相克拉通盆地显生宙演化可分为早晚两期,早期为晚震旦世-石炭纪,晚期为二叠纪-中三叠世。两期克拉通演化都经历了早期弱拉张,后期弱挤压阶段。弱拉张初始阶段都有一次海相碳酸盐岩的大面积稳定沉积(震旦系灯影组和二叠系栖霞-茅口组)和随后的隆升剥蚀作用及风化壳岩溶作用。其后进入弱拉张期,发育拉张槽,拉张强度最大的部位均位于克拉通的西北部,都是从克拉通的西北部边缘向克拉通内部减弱。然而,两期拉张槽的充填特征不同,早寒武世绵阳-长宁拉张槽是补偿型充填,与拉张槽周缘相比,拉张槽内沉积厚度巨大;晚二叠世-早三叠世开江-梁平拉张槽为欠补偿型充填,与拉张槽周缘相比,拉张槽内沉积厚度非常薄。拉张期结束后进入弱挤压阶段,形成古隆起,挤压强度最大的部位均位于克拉通的西南部,都是从克拉通的西南边缘向克拉通内部减弱。弱拉张阶段的拉张槽与弱挤压阶段的古隆起均为大角度相交关系;然而,拉张槽和古隆起的规模差别较大,早寒武世绵阳-长宁拉张槽面积约5.4×10~4km~2,对应的加里东期乐山-龙女寺古隆起面积6×10~4km~2;晚二叠世-早三叠世开江-梁平拉张槽面积约2.0×10~4km~2,对应的印支期开江古隆起面积0.8×10~4km~2;晚二叠世-早三叠世蓬溪-武胜拉张槽面积约1.5×10~4km~2,对应的印支期泸州古隆起面积4.2×10~4km~2。绵阳-长宁拉张槽的规模比开江-梁平拉张槽、蓬溪-武胜拉张槽要大,乐山-龙女寺古隆起的规模也大于泸州-开江古隆起的规模。四川海相克拉通盆地显生宙演化特征在很大程度上控制了四川叠合盆地海相油气地质条件的发育和油气藏的形成分布。  相似文献   

Influence of refractory organic matter on source rock hydrocarbon potential: A case study from the Second White Specks and Belle Fourche formations,Alberta, Canada     

《Marine and Petroleum Geology》2017

Dilution by inert, refractory organic carbon can have a significant impact on the hydrocarbon potential of source rocks. In this study, a correction of total organic carbon, based on petrographic observations, is proposed to give a better indication of hydrocarbon generation potential. This correction shows that although the Second White Specks Formation is an excellent hydrocarbon source rock, hydrogen index and total organic carbon are influenced by dilution from refractory organic carbon of various sources. The results show that a higher degree of dilution occurs within the Belle Fourche Formation than the Second White Specks Formation. This dilution can have a significant impact on the hydrocarbon potential of the rock.Volumetric calculation of the inert carbon fraction using organic petrographic methods provides a semi quantitative method to correct total organic carbon values for the refractory organic carbon dilution effect. Incorporation of the dilution corrected organic carbon value in hydrogen index calculations allows a greater understanding of source rock hydrocarbon potential. This method provides better differentiation of the small scale variation between micro-facies and formation, as observed in the Second White Specks and Belle Fourche formations, than traditional bulk geochemical methodologies and previously proposed correction methodologies. Degree of dilution, either through transport of recycled allochthonous or autochthonous reworking of organic matter in-situ is highly variable and represents a significant challenge in the characterization of heterogeneous source rocks.This study investigates the organic petrology and geochemistry of a sediment core from the thermally immature area of the Upper Cretaceous Second White Specks Formation and Belle Fourche Formation. Reflectance and relative abundance of three maceral groups (bituminite, alginite, and refractory organic carbon macerals) showed significant organic matter compositional differences between micro-facies in the Second White Specks Formation. A change is also observed in organic matter composition from the upper part of the Belle Fourche Formation to the Second White Specks Formation. These compositional changes represent shifts in sediment source, sea floor oxygen levels, and depositional energy levels. These changes can be episodic, as observed between micro-facies, or longer time scale trends, as observed between the studied formations.  相似文献   

Concept and Intension of Natural Gas Hydrate Petroleum System and Case Analysis     

Xiao Hongping  Lin Changsong  Peng Yong  Wei Wei  Zhang Jinhua  Zhang Qiaozhen 《地球科学进展》2017,32(1):21-33

According to the hot topics of the natural gas hydrate distribution regularity,formation conditions,accumulation process and accumulation pattern, gas hydrates reservoir forming conditions including gas source, gas hydrate stability zone, reservoir stratum, water source and migration passage were summarized by literature review first. Then, three main factors, geological structure condition, sedimentary condition and geographical climate change were summarized and analyzed, which control the accumulation and distribution of gas hydrates. On basis of this,basic concepts and research methods of natural gas hydrate petroleum system were analyzed and discussed by the example of gas hydrate accumulation conditions and process in permafrost regions of Kunlun mountain pass. The results show that the key of studying gas hydrate accumulation process and evaluating gas hydrate reservoir forming potential is analyzing how the static accumulation elements couple and match in geological time and space.  相似文献   

巴楚—麦盖提斜坡区油、气、水成因分析及其勘探意义     

刘军  田雷  崔海峰  陈永权  张年春 《海相油气地质》2017,22(1)

针对巴楚—麦盖提斜坡区油气田的油、气、水特征存在较大差异性的现象,在对比油、气、地层水地球化学特征的基础之上,探讨分析了它们的成因。研究认为,和田河气田原油裂解气和干酪根裂解气的混合气在中—下寒武统膏岩封闭作用下发生硫酸盐热还原反应以后,以水溶气的方式运移至上覆奥陶系—石炭系圈闭中,形成了现今高干燥系数、重碳同位素特征的气藏,以及奥陶系风化壳顶面附近低矿化度、高变质系数的Na2SO4型地层水。中—下寒武统膏岩层对巴楚—麦盖提斜坡区油气形成、演化和分布有重要影响,膏岩层之下可以作为一个潜在的勘探领域。  相似文献   

Floating marine debris surface drift: Convergence and accumulation toward the South Pacific subtropical gyre   总被引：2，自引：1，他引：1  

Elodie Martinez  Keitapu Maamaatuaiahutapu  Vincent Taillandier 《Marine pollution bulletin》2009,58(9):1347-1355

Whatever its origin is, a floating particle at the sea surface is advected by ocean currents. Surface currents could be derived from in situ observations or combined with satellite data. For a better resolution in time and space, we use satellite-derived sea-surface height and wind stress fields with a 1/3° grid from 1993 to 2001 to determine the surface circulation of the South Pacific Ocean. Surface currents are then used to compute the Lagrangian trajectories of floating debris. Results show an accumulation of the debris in the eastern-centre region of the South Pacific subtropical gyre ([120°W; 80°W]–[20°S; 40°S]), resulting from a three-step process: in the first two years, mostly forced by Ekman drift, the debris drift towards the tropical convergence zone (30°S). Then they are advected eastward mostly forced by geostrophic currents. They finally reach the eastern-centre region of the South Pacific subtropical gyre from where they could not escape.  相似文献