Geophysical methods for the study of sedimentary cycles

We present the wavelet depth-frequency analysis and variable-scale frequency cycle analysis methods to study sedimentary cycles. The spectrum analysis, variable-scale frequency cycle analysis, and wavelet depth-frequency analysis methods are mainly discussed to distinguish sedimentary cycles of different levels. The spectrum analysis method established the relationship between the spectrum characteristics and the thickness and number of sedimentary cycles. Both the variable-scale frequency cycle analysis and the wavelet depth-frequency analysis are based on the wavelet transform. The variable-scale frequency cycle analysis is used to obtain the relationship between the periodic changes of frequency in different scales and sedimentary cycles, and the wavelet depth-frequency analysis is used to obtain the relationship between migration changes of frequency energy clusters and sedimentary cycles. We designed a soft-ware system to process actual logging data from the Changqing Oilfield to analyze the sedimentary cycles, which verified the effectiveness of the three methods, and good results were obtained.

Study of sedimentary sequence cycles by well-seismic calibration

In order to solve the problems of the fine division of sedimentary sequence cycles and their change in two-dimensional space as well as lateral extension contrast, we developed a method of wavelet depth-frequency analysis. The single signal and composite signal of different Milankovitch cycles are obtained by numerical simulation. The simulated composite signal can be separated into single signals of a single frequency cycle. We also develop a well-seismic calibration insertion technology which helps to realize the calibration from the spectrum characteristics of a single well to the seismic profile. And then we determine the change and distribution characteristics of spectrum cycles in the two-dimensional space. It points out the direction in determining the variations of the regional sedimentary sequence cycles, underground strata structure and the contact relationship.

MAJOR SEDIMENTARY CYCLES AND BASIN EVOLUTION OF MESOZOIC IN NORTHERN HIMALAYAS, SOUTH TIBET

The northern Himalayas was situated on the north margin of the Indian plate and was part of the Gondwana. During Mesozoic and Cenozoic, the geological development of the region was mainly controlled by the evolution of the Neotethyan ocean as well as the movement of the plates (or blocks) on its two sides, showing as a typical passive continental margin [1] . The Mesozoic and Cenozoic sedimentation forms a giant transgression\|regression cycle in this region [2] . The strata have clearly recorded the processes that the Gondwana continent broke up, the Indian plate drifted northward, and consequently collided with the Eurasia, suggesting a Wilson cycle. They also reveals the evolution of the Neotethyan ocean from breakup to expanding, contracting and finally to closing. 1\ The major sedimentary cycles\;The marine Mesozoic and Cenozoic developed continuously in the northern Himalayas, south Tibet, with a total thickness of about 8000m. From the Triassic to Eocene, 70 third\|order sequences have been recognized [2] . Among them 12 are in the Triassic, 22 in the Jurassic, 27 in the Cretaceous and 9 in the Paleogene, with an average duration of 3m.y for each. These can in turn be grouped as 21 sequence sets and 6 mesosequences (2nd order). All of the mesosequences are bounded by prominent discontinuity at bottom, either with subaerial erosion or submarine truncation [2] , suggesting abrupt falls of sea\|level in long\|term changes. The approximate ages for the basal boundaries of these mesosequences are respectively at ca. 257Ma (latest Capitanian), 215Ma (latest Norian), 177Ma (early Aalenian), 138Ma (mid Tithonian), 103Ma (mid Albian) and 68Ma (late Maastrichtian). Each of mesosequences forms a major sedimentary cycles in the region and may result from the joint effects of global sea\|level changes and regional tectonic\|basin evolution.

Application of Activity and Wavelet Analysis on Well Logging Sedimentary Cycle Division

The method of sedimentary cycle division is studied based on comprehensive research and activity analysis of well logging, combined with wavelet analysis and characteristics of stratigraphic cycle. Based on the method above, this paper divided stratigraphic cycles and finely classified the tratifigraphic by taking H1518 in HSS oilfield as an example. The result shows that sedimentary cycle can be divided effectively based on key stratum study, activity and wavelet analysis of well log, and the research of sedimentary cycle characteristics. H1 formation can be divided into 1 sand group, 3 sand layers and 7 single layers.

Correspondence Between Astronomical Periods and Sedimentary Cycles

It is shown from detailed study that there are some genetic relationships between outer events of celestial bodies and inner geological events of the earth, such as some kinds of correspondences between astronomical periods and sedimentary cycles. The time spans of movement periods of the solar.system around the center of the galaxy and cross the plain of the galaxy, the periods of the earth orbit (Milankovitch period) and periods of sunspot are coincided with that of respective sedimentary cycles. It is suggested that the gravity and magnetic changes of the earth leading up to the global climatic and sea level changes are the dynamics of sedimentary cycles.

Characteristics of Milankovitch Cycles in the Mid-Permian Liangshan and Qixia Formations of the Sichuan Basin——Examples from Well-Long17 and Well-Wujia1

The Liangshan and Qixia formations in the Sichuan Basin of central China were formed in the earlier middle Permian. Based on outcrop observation of the Changjianggou section at Shangsi, Guangyuan region and 3 rd -order sequence division in typical drillings, one-dimensional spectrum analysis has been used to choose the better curve between the natural gamma ray spectrometry log（ln （Th/K）） in Well-Long17 and the gamma ray log（GR） in Well-Wujia1, respectively, for identifying Milankovitch cycles in Sequence PSQ1 which comprises the Liangshan and Qixia formations, and then to identify the variation in the Milankovitch cycle sequences. On this basis, the system tract and 4 th -order sequence interfaces in Sequence PSQ1 were found via two-dimensional spectral analysis and digital filtering. Finally, a high-frequency sequence division program was established. Among these cycles, long eccentricity （413.0 ka） and short eccentricity （123.0 ka） are the most unambiguous, and they are separately the major control factors in forming 4 th -order （parasequence sets） and 5 th -order （parasequences） sequences, with the average thicknesses corresponding to the main cycles being 11.47 m and 3.32 m in Well-Long17, and 14.21 m and 3.79 m in Well-Wujia1, respectively. In other words, the deposition rate in the beach subfacies is faster than that of the inner ramp facies. The ln（Th/K） curve is more sensitive than the GR as the index of relatively ancient water depth in carbonate deposition. One-dimensional spectrum analysis of ln（Th/K） curve could distinguish the Milankovitch cycle sequences that arose from the Precession cycle （20.90 ka）, with a much higher credibility. Sequence PSQ1 in Well-Long17 contains 10 4 th -order sequences, and the growth span of Sequence PSQ1 consisting of the Liangshan and Qixia formations is about 4.13 Ma. The single deposition thickness of the long eccentricity cycle sequence has the characteristics of thinning and then thickening in the two-dimensional spectrum, which could be used to identify the system tract interface of the 3 rd -order sequence. The precession sequence thickness remains stationary. As a result, the early deposition rate in the mid-Permian of the Sichuan basin was very slow, remaining nearly stationary, and this reflects a sustained depositional environment. Whole-rock carbon and oxygen isotope curves could also prove this point. Milankovitch cycle sequence studies provide a basis for paleoenvironmental analysis and, as such, can be used to analyze ancient climate change, calculate deposition rate and deposition time, and carry out fine isochronous stratigraphic correlation.

Breeding and Simple-rapid Regeneration Protocol for Jisheng 1 with Glandless Trait and High-frequency Somatic Embryo Production Ability

Most of model cotton varieties used in tissue culture have glands on both the reproductive and vegetative parts of the plant.These glands contain compounds that are toxic to human and non-ruminant animals.The presence of these compounds limits their usage as food and feed.To obtain a glandless cotton variety with high-frequency somatic embryo production ability,27 glandless varieties

Cycles of fine-grained sedimentation and their influences on organic matter distribution in the second member of Paleogene Kongdian Formation in Cangdong Sag,Bohai Bay Basin,East China

According to the theory of sequence stratigraphy based on continental transgressive-regressive(T-R)cycles,a 500 m continuous core taken from the second member of Kongdian Formation(Kong 2 Member)of Paleogene in Well G108-8 in the Cangdong Sag,Bohai Bay Basin,was tested and analyzed to clarify the high-frequency cycles of deep-water fine-grained sedimentary rocks in lacustrine basins.A logging vectorgraph in red pattern was plotted,and then a sequence stratigraphic framework with five-order high-frequency cycles was formed for the fine-grained sedimentary rocks in the Kong 2 Member.The high-frequency cycles of fine-grained sedimentary rocks were characterized by using different methods and at different scales.It is found that the fifth-order T cycles record a high content of terrigenous clastic minerals,a low paleosalinity,a relatively humid paleoclimate and a high density of laminae,while the fifth-order R cycles display a high content of carbonate minerals,a high paleosalinity,a dry paleoclimate and a low density of laminae.The changes in high-frequency cycles controlled the abundance and type of organic matter.The T cycles exhibit relatively high TOC and abundant endogenous organic matters in water in addition to terrigenous organic matters,implying a high primary productivity of lake for the generation and enrichment of shale oil.

Griesbachian Cyclostratigraphy at MajiashanSection, Anhui Province, China

The Lower Triassic at Majiashan Section, deposited in the deep part of the Lower Yangtze carbonate ramp, is the only outcrop of the deep Lower Triassic preserved in the present Lower Yangtze region. Even so, the alternations of mudrock of mudrock and marl (or limestone) are still very distinct and recognizableable, though usually more or less condensed. The lithological and geochemical cycles at Majiashan Section are discussed in terms of the sedimentary characters and the contents of some elements analyzed at a 2-centimeter-interval with no hiatus of the Lower Triassic. The division resolution of the Griesbachian stratigraphy may increase to the scale of ten thousand years by the mudrock-marl (or limestone) bundles and the geochemical cycles. The analysis of the relationship between the sedimentary cycles/the geochemical cycles and the Milankovitch cycles may suggest the time limit and the sedimentary rates.

Sedimentary system characteristics and depositional filling model of Upper Permian——Lower Triassic in South Yellow Sea Basin

In the South Yellow Sea Basin,Mesozoic–Paleozoic marine strata are generally well developed with large thickness,and no substantial breakthroughs have been made in hydrocarbon exploration.Through research,it is believed that the Upper Permian–Lower Triassic can be regarded as a long-term base-level cycle.Based on drilling data,characteristics of the lithology–electric property combination cyclicity,and the special lithology,the long-term base-level cycle was divided into five medium-term base-level cycles(MC1–MC5).On this basis,the Permian–Triassic sedimentary systems and their filling model were analyzed in accordance with the change of base-level cycle and transition of sedimentary environment,as well as characteristics of the drilling sedimentary facies and seismic facies.The results show that there were six sedimentary systems(fluvial,delta,tidal flat,open platform,restricted platform,and continental shelf)developed in the Upper Permian–Lower Triassic,the sedimentary systems were distributed such that the water was deep in the northwest and shallow in the southeast,and there were two base-level cycle filling models(a relatively stable tidal flat facies and a rapidly transgressive continental shelf facies to stable platform facies)developed in the Upper Permian–Lower Triassic.These models can provide a basis for evaluation of the Mesozoic–Paleozoic hydrocarbon geology in the South Yellow Sea Basin.

Lateral downslope transport and tentative sedimentary organic carbon box model in the southern Yap Trench,western Pacific Ocean

Sediment collapse and subsequent lateral downslope migration play important roles in shaping the habitats and regulating sedimentary organic carbon(SOC)cycling in hadal trenches.In this study,three sediment cores were collected using a human-occupied vehicle across the axis of the southern Yap Trench(SYT).The total organic carbon(TOC)and total nitrogen(TN)contents,δ13C,radiocarbon ages,specific surface areas,and grain size compositions of sediments from three cores were measured.We explored the influence of the lateral downslope transport on the dispersal of the sediments and established a tentative box model for the SOC balance.In the SYT,the surface TOC content decreased with water depth and was decoupled by the funneling effect of the V-shaped hadal trench.However,the sedimentation(0.0025 cm/a)and SOC accumulation rates(∼0.038 g/(m^(2)·a)(in terms of OC))were approximately 50%higher in the deeper hadal region than in the abyssal region(0.0016 cm/a and∼0.026 g/(m^(2)·a)(in terms of OC),respectively),indicating the occurrence of lateral downslope transport.The fluctuating variations in the prokaryotic abundances and the SOC accumulation rate suggest the periodic input of surficial sediments from the shallow region.The similar average TOC(0.31%–0.38%),TN(0.06%–0.07%)contents,and SOC compositions(terrestrial OC(11%–18%),marine phytoplanktonic OC(45%–53%),and microbial OC(32%–44%))of the three sites indicate that the lateral downslope transport has a significant mixing effect on the SOC composition.The output fluxes of the laterally transported SOC(0.44–0.56 g/(m^(2)·a)(in terms of OC))contributed approximately(47%–73%)of the total SOC input,and this proportion increased with water depth.The results of this study demonstrate the importance of lateral downslope transport in the spatial distribution and development of biomes.

Sedimentary filling characteristics and controlling factors of lacustrine microbial carbonates sequence in the Santos Basin,Brazil

Based on comprehensive analysis of seismic,logging,core,thin section data,and stable isotopic compositions of carbon and oxygen,the sedimentary filling characteristics of the Lower Cretaceous Barra Velha Formation sequence in H oil field,Santos Basin,are studied,and the high-frequency sequence stratigraphic framework is established,and the spatial distribution of reef-shoal bodies are predicted and the controlling factors are discussed.During the depositional period of the Barra Velha Formation,the study area is a slope-isolated platform-slope sedimentary pattern from southwest to northeast and the change of climate background from rift to depression periods has resulted in the variation of sedimentary characteristics from the lower third-order sequence SQ1(BVE 300 Member)of low-energy deep water to the upper third-order sequence SQ2(BVE 200 and 100 members)of high-energy shallow water in the Barra Velha Formation.The activities of extensional faults and strike-slip faults in rift period and the sedimentary differentiation from platform margin to intra-platform in depression period made the sedimentary paleogeomorphology in these two periods show features of“three ridges and two depressions”.The reef-shoal bodies mainly developed in the SQ2-LHST period,with vertical development positions restricted by the periodic oscillation of the lake level,and developed on the top of each high-frequency sequence stratigraphic unit in SQ2-LHST in the platform.The strike-slip fault activity controlled the distribution of the reef-shoal bodies on the plane by changing the sedimentary paleogeomorphology.The positive flower-shaped strike-slip faults made the formation of local highlands at the margins of and inside the shallow water platforms and which became high-energy sedimentary zones,creating conditions for the development of reef-shoal bodies.

Classification and exploration potential of sedimentary basins based on the superposition and evolution process of prototype basins

Classification,superimposed evolution and sedimentary filling of prototype basins are analyzed based on the Wilson cycle principle of plate theory,by dissecting the evolution history of 483 sedimentary basins around the world since the Pre-cambrian,combined with the three stress environments of tension,compression and shear.It is found that plate tectonic evo-lution controls the superimposed development process and petroleum-bearing conditions of the prototype basins in three as-pects:first,more than 85%of the sedimentary basins in the world are developed from the superimposed development of two or more prototype basins;second,the superposition evolution process of the prototype basin takes Wilson cycle as the cycle and cycles in a fixed trajectory repeatedly.In each stage of a cycle,a specific type of prototype basin can be formed;third,each prototype basin can form a unique tectonic-sedimentary system,which determines its unique source,reservoir,cap conditions etc.For hydrocarbon accumulation,the later superimposed prototype basin can change the oil and gas accumulation conditions of the earlier prototype basin,and may form new petroleum systems.Based on this,by defining the type of a current basin as its prototype basin formed by the latest plate tectonic movement,14 types of prototype basins can be classified in the world,namely,intracontinental growth rift,intr acontinental aborted rift,intercontinental rift,passive continental margin,interior craton,trench,fore-arc rift,ba ck-arc rift,back-arc de pression,back-arc small ocean,peri pheral foreland,back-arc foreland,strike-slip pull-apart,and strike-slip flexural basins.The classification scheme can ensure the uniqueness of the types of in di-vidual sedimentary basin,and make it possible to predict their oil and gas potential scientifically through analogy.

基于连续小波变换的黑北凹地砂砾储卤层沉积特征研究

柴达木盆地西部中深层“砂砾型”钾盐储卤层与沉积水体变化息息相关,高密度网状二维地震资料包含的频率信息,有助于识别发育砂砾储卤层的沉积环境,为深层富钾卤水储层研究提供支撑。采用连续小波变换时频分析技术将地震信号从一维的时间域拓展到二维的时间-频率域上,能够在频谱中更清晰地刻画沉积体内部岩性组合的旋回结构特征。基于正演数据和实际钻井数据,总结了低水位体系域、水进体系域、高水位体系域和水退体系域层序框架下,沉积体的地震时频谱旋回响应特征:低水位体系域的时频谱能量主要聚集在低频,高水体系域的时频谱能量主要聚集在高频,水进体系域的时频谱能量随时间减小向高频方向移动,水退体系域的时频谱能量随时间减小向低频方向移动,指出35 Hz是划分有利沉积旋回——水退体系域末期、低水位体系域和水进体系域初期的频率阈值。选择合适频率区间重构地震数据能突出弱振幅砂砾层的反射特征,结合全频带数据有助于快速识别有利沉积旋回,为寻找砂砾型深层卤水钾矿提供依据。

马里亚纳海沟挑战者深渊南坡JL7KBC03短柱样硅质软泥沉积的物源、沉积环境和碳储库效应

海斗深渊是影响地球系统演化的关键一环,但由于超深水深导致的样品匮乏,对其沉积过程的精细研究仅见零星报道。本研究基于马里亚纳海沟挑战者深渊南坡JL7KBC03插管柱样系统的微体古生物、沉积学、矿物学研究,对该区沉积档案的物源、沉积环境记录进行解读。结果显示:(1)沉积物以第四纪硅藻软泥为主,其中大筛盘藻(Ethmodiscus rex)含量达99%以上。大筛盘藻的激发,可能为晚更新世冰期时段南极中层水入侵西北太平洋期间,南极“硅溢漏”效应对低纬水体溶解硅的补充,以及冰期风尘铁元素的激发所致。(2)沉积柱样中夹杂的数层暗色薄层,指示了研究区频繁的火山、热液活动。沉积物矿物、元素地球化学物源分析结果表明:研究区非生物组分物质与九州-帕劳海脊和马里亚纳海槽物质相近,陆源风尘和太平洋热液物质的贡献则相对较小。(3)海斗深渊独特的地形特征与水动力条件,利于有机质的快速沉降与埋藏,以硅藻软泥等形式将大量有机碳封存在深渊底部,动态调节着海洋碳储库与岩石圈碳储库之间的相互转化,是研究全球碳循环和碳封存的重要组成部分。

吐哈盆地胜北洼陷中下侏罗统水西沟群天文旋回地层划分

根据自然伽马测井数据,对吐哈盆地胜北洼陷沁探1井中下侏罗统水西沟群开展旋回地层学分析和沉积噪声模拟,并利用识别出的地层中的米兰科维奇旋回信号来研究地球轨道周期对湖平面变化的驱动作用,进而进行天文旋回地层划分。研究结果表明:①吐哈盆地胜北洼陷中下侏罗统水西沟群在自然伽马曲线中可识别出12.8~51.1 m,3.0~11.9 m,1.1~3.6 m和1.3~2.4 m的沉积旋回,比例关系为21.0∶5.0∶1.5∶1.0。根据天文调谐与相关系数估算出水西沟群沉积速率为3.3~11.7 cm·ka-1。②天文调谐后的时间域序列显示水西沟群长偏心率周期为405 ka、短偏心率周期为99~131 ka、斜率周期为32.6~35.0 ka、岁差周期为20.0~24.8 ka,证明吐哈盆地中下侏罗统沉积过程受到米兰科维奇旋回控制。沁探1井八道湾组(未钻穿)、三工河组和西山窑组的持续时间分别为3.0±0.1 Ma,4.1±0.1 Ma和9.0±0.1 Ma。③地球轨道旋回对陆相湖盆的湖平面升降具有明显的驱动作用,沁探1井水西沟群的沉积噪声模拟证明了~1.5 Ma超长周期可控制台北凹陷早—中侏罗世湖平面的变化。

南阳凹陷砂砾岩体甜点区预测及效果

南阳凹陷黑龙庙地区砂砾岩体规模小,多期砂体叠置,沉积期次划分难,非均质性强、甜点区难以预测。为此,利用可视化技术对三维地震资料进行精细构造解析与古构造恢复,研究砂砾岩体成因。在对5口井层序地层划分基础上,依据砂组-砂体的沉积旋回性与地震反射结构,划分砂砾岩体沉积期次;通过岩石物理分析与正演模拟明确砂砾岩体地球物理响应特征。通过井点处扇根、扇中、扇端地震反射特征与相同层位其他点处的地震反射特征进行相关分析,确定扇根、扇中、扇端的平面分布;实测砂砾岩体岩性、物性参数与波阻抗属性,交汇分析确定有效区分砂砾岩与泥岩的波阻抗属性的值域。依据高精度反演得到的波阻抗数据体,在砂砾岩体储层波阻抗值域及顶底反射层位控制下,求出有效储层厚度与分布,圈定砂砾岩体储层甜点区的范围。以此为依据在其甜点区上部署的HL1井日产油5.46 m 3,预测结果与实钻井一致。

桑干河流域淤地坝沉积泥沙特征及其来源解析

[目的]为查明桑干河流域的泥沙主要策源地和侵蚀产沙变化。[方法]选取阳原县高墙乡典型淤地坝沉积泥沙为研究对象,利用复合指纹识别技术,测定沉积泥沙及其源地的土壤粒径、SOC、TN、137 Cs、低频质量磁化率等9种指纹因子,研究了不同淤积阶段的泥沙策源地及坝控小流域侵蚀产沙演变规律。[结果](1)沉积泥沙中137 Cs平均含量较低,与沟壁土壤无显著差异(p>0.05),但极显著小于林草地和耕地的137 Cs含量(p<0.01),这指示淤地坝沉积泥沙主要来源于沟壁;(2)由于沟壁中大部分137 Cs含量低于检出限,137 Cs较好地指示泥沙主要来源沟谷地中的沟壁,但难以用于小流域多种策源地的判别,经Kruskal-Wallis H非参数检验和多元逐步判别分析筛选,确定TN+X lfb+SOC构成最佳指纹因子组合,有效地判别小流域2006—2017年泥沙源地的平均贡献率为沟壁(82.68%±8.20%)>耕地(15.36%±8.46%)>林草地(1.96%±0.33%);(3)在小流域侵蚀产沙过程中,沟壁长期是主要的泥沙贡献区,林草地对侵蚀性降雨的响应较弱,耕地在极端暴雨发生时其泥沙贡献率显著上升。[结论]137 Cs核素示踪技术有效地适用于该区小流域主要泥沙策源地判别,复合指纹技术则可以更好地厘定多元泥沙策源地。沟蚀引起的沟壁崩塌是桑干河流域土壤侵蚀严重的主要原因。

湘渝黔地区奥陶系红色岩溶地貌与沉积作用关系

文章基于野外露头观测、薄片观察、牙形石研究以及X射线衍射分析,从沉积角度探讨了风化作用与湘渝黔地区奥陶系红色岩溶地貌之间的关系。结果表明:同生成岩阶段,大气氧含量的增加,浅海陆棚水底氧化,陆源碎屑中铁离子被氧化形成Fe_(2)O_(3)进入沉积地层,奠定了地貌颜色;受岩相古地理的影响,早中奥陶世大湾期中上扬子地块自西向东岩相存在分带性,岩溶地貌仅出现在以武汉-松滋-松桃-黄平为中心的浅海陆棚碳酸盐岩弧形相带上;沉积微相决定碳酸盐岩孔隙大小与结构影响风化作用,岩石之间差异风化造就地貌凹凸形;米兰科维奇旋回导致牯牛潭组泥质灰岩与生物碎屑泥晶灰岩相互叠置,环潮坪型米级旋回造就出岩溶地貌的韵律性;灰岩中不溶残余物黏土矿物种类及含量暗示其沉积物源与埋藏史的差异,并影响岩层水化膨胀律和抗风化能力。