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.

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.

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.

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

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.

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.

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。

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。

泛巽他盆山体系北部湾古泥沼旋回与古生态效应

南海西北部北部湾在地质环境方面与狭义巽他陆架相似而成为一体构成泛巽他,同属青藏高原及其挤出阶梯地貌盆山体系。然而,关于其指示环境变化和碳循环的古泥沼分布及其气候-构造驱动机制、作用与联系等缺乏关注,其研究滞后于上述热点巽他陆架相关进展。为加强对这些内容的认识,本文的研究在北部湾北部华南陆缘沉降带进行了80.05 m进尺第四系全岩心钻取,立足于沉积物微体古生物、粒度、碎屑矿物组分、微量元素含量等基础沉积环境指标的实验测试、鉴定以及测年数据,并结合前人相关资料和结果进行综合分析。结果表明,岩心底部年龄为中更新世后期171.0 ka,孢粉化石呈热带和亚热带植被面貌,主要有栲属、栎属等以及鳞盖蕨属、水龙骨科等,其含量变化显示出3个主要气候变化阶段,与倒数第二冰盛期、末次间冰期、末次冰期以及冰消期等相联系,从56.0 ka始见有半咸水种硅藻化石条纹小环藻、柱状小环藻等,有孔虫化石出现于中全新世6.0 ka接受海进。总体上以砂为主,但局部粉砂和黏土(泥)含量较高,最高依次可达65.78%、59.71%,元素含量为2.6×10^(-6)~347×10^(-6),碎屑矿物稳定出现石英、长石、风化矿物,以前者占优,平均含量88.57%,余下矿物相间出现,具有陆源性,各要素随气候阶段而变化。存在5个泥沼旋回,沉积环境有所差异,在冰期和间冰期均有分布,出现炭化腐木以及邻区炭化层。青藏高原隆起导致的区域强烈地形落差在中—晚更新世业已构建,盆山体系成为海洋暖湿气流与地形作用的水热有效利用地带,北部湾冰期出露地表古水系广布,森林和草地植被共存,有助于泥沼的维护发展。气候波动性是泥沼的本质驱动因素,除了间冰期之外,冰期的强烈暖阶振荡亦为其成因;泛巽他北部湾在冰期同样具有碳库意义,具有转移与弥补中高纬度生产力衰减之作用。

川东地区寒武系洗象池群下段厚层白云岩特征及成因

四川盆地东部寒武系洗象池群厚层白云岩分布广泛,具有勘探潜力。文中以川东地区南川三泉洗象池群野外剖面为研究对象,基于其岩石学、沉积学、岩石地球化学和矿物学特征,分析其在沉积旋回中的变化,探讨白云岩化流体性质、来源与迁移路径。结果表明:洗象池群白云岩阴极发光弱,δ^(13)C,^(87)Sr/^(86)Sr值与洗象池群同期海水区间重叠,表明白云岩化流体来源于同期海水,白云岩化作用发生在准同生—浅埋藏时期;岩石地球化学和矿物学特征与沉积旋回具有相关性,在向上变浅的旋回中,白云石含量、化学计量数和δ^(18)O升高,有序度降低,表明随相对海平面下降,白云岩化流体的温度、盐度和Mg/Ca值升高,旋回顶部白云岩化程度高;相对海平面较高时,研究区西北侧潟湖中的咸化海水穿过刚形成不久的泥晶灰岩和先期形成的孔渗性好的颗粒灰/白云岩,发生以横向远源渗透回流为主的白云岩化作用;随着相对海平面逐渐下降,潟湖水体循环逐渐变差、盐度升高,潮间—潮下带古地貌高地处形成颗粒灰岩,发生暴露溶蚀;暴露区域经波浪和潮汐作用带来潟湖中的咸化海水,白云岩化流体向下流动,发生以垂向近源渗透回流为主的白云岩化作用;多期横向远源和垂向近源渗透回流白云岩化事件持续叠加,形成川东洗象池群下段潮间—潮下带厚层白云岩。

早始新世温室气候与海侵作用对库车坳陷库姆格列木群含盐层系沉积的协同控制作用

塔里木盆地北部库车坳陷库姆格列木群(54-46 Ma)厚层含盐层系为油气成藏的优质区域盖层,但该套含盐层系的原始时空展布、古地理环境和沉积控制因素尚不明确,给盐下油气藏钻井施工造成了较大困难。通过盆缘野外露头剖面实测与盆内录井元素分析相结合,开展盐湖中心与边缘沉积旋回对比研究,探讨库姆格列木群含盐层系发育的主控因素。库姆格列木群发育3个Ⅲ级旋回:第1个Ⅲ级旋回Ⅰ_(1)以盆缘砂砾岩—泥岩—石膏岩组合、湖盆中心泥岩—石膏岩—盐岩—碳酸盐岩组合为特征,指示陆内盆地向陆缘盆地的古地理环境转变。第2个Ⅲ级旋回Ⅰ_(2)以盆缘砂砾岩—泥岩—石膏岩组合、湖盆中心厚层盐岩加泥岩组合为特征,为陆缘盆地盐湖沉积模式。第3个Ⅲ级旋回Ⅰ_(3)盆缘—盆内沉积具有相似的膏质泥岩和泥岩组合特征,为陆内干盐湖沉积模式。结合早始新世全球气候和海平面升降变化历史,认为Ⅰ_(1)旋回(约54-51 Ma)由陆内向陆缘环境的转变及厚层石膏岩的沉积受早始新世气候适宜期(53-51 Ma)和全球海平面升高的影响,Ⅰ_(2)旋回(约51-48 Ma)厚层盐岩的沉积受全球持续干旱气候和海平面再次升高的影响,而Ⅰ_(3)旋回(约48-46 Ma)厚层含盐层系沉积的缺失与全球气候持续干旱和海平面下降有关。

基于连续薄片统计的须二段岩石相组合及沉积旋回分析

目前对川西地区三叠系须家河组二段(须二段)已开展了沉积微相层面研究,但不同微相背景下岩石相特征与沉积旋回存在差异。为了更加精细刻画岩石相特征并揭示其对有利储层的指示意义,基于连续岩屑及岩心薄片鉴定的岩石学特征分析,通过地质学手段及聚类分析技术,结合测井数据等资料,建立须二段更精细的物质组成、岩石相类型及沉积微相演化序列。须二段砂体划分为六个岩石相,并识别出16个水下分流河道-分流间湾、水下分流河道-河口坝沉积旋回。统计显示水下分流河道下部的A1类岩石相、A4类岩石相物性较好,因此水下分流河道的下部物性通常高于上部,且普遍优于河口坝。须二段中亚段物性最好,上亚段次之,下亚段较差。水下分流河道物性普遍比河口坝好;物性变化与旋回、岩石相的变化存在一定的相关性;发育于水下分流河道中下部的A1、A4类岩石相更易形成有利储层。

沿海高铁滨海平原软土力学特性研究

根据沿海高铁汕头至汕尾段定测勘探成果,对上千组土工试验数据进行统计分析,研究不同沉积成因的软土工程地质特性,并结合实际工程分析软土对工程建设的影响。结果表明:滨海沉积相、泻湖相、三角洲冲积相软土含水量约40%~60%、孔隙比大于1.2、压缩系数大于0.5,结构松散软弱,属于高压缩性土;榕江三角洲冲积相软土分为两层,形成于两个海潮沉积旋回,其承载力特征值分别为60、80 kPa,两层淤泥质土需考虑软土震陷;三角洲沉积相粉细砂层多夹淤泥或淤泥质土,属层状构造土,力学性质具有横观各向同性,采用砂井或插塑板处理地基的效果较好。