Hydrothermal indications of Early Cretaceous red beds in lacustrine successions,North Yellow Sea Basin,eastern China

Controversies over the origin of globally distributed Cretaceous red beds have mainly focused on climate vs. weathering with potential hydrothermal influence. In comparison to Cretaceous Oceanic Red Beds, Cretaceous lacustrine red beds exhibit chronological inconsistencies and their diverse tectonic settings suggest differing genetic mechanisms. In this paper, Early Cretaceous red beds in the North Yellow Sea Basin, one of Mesozoic rift basins in eastern China that are associated with multi-phase magmatic activities, was chosen to document potential hydrothermal impact. Geological and geochemical analyses show that these red beds were syndepositional products developed in shallow to moderately deep lacustrine environments and that they were influenced by hydrothermal activity. Major and trace elements, including enhanced Al₂O₃-normalized Fe₂O₃ and Fe₂O₃ (total) values, Al/(Al + Fe + Mn) and (Fe + Mn)/Ti ratios, Ni-Co-Zn and Fe-Mn-(Ni + Co + Cu)*10, ∑REE-La/Yb, the concentrations of hydrothermally-related ions, invalid redox indicators of trace elements, abnormally high Fe₂O₃ (total) content, positive Eu anomaly, correlation of Fe₂O₃ (total) and Eu anomaly, and vitrinite reflectance (Ro) vs. total organic carbon (TOC), all show strong hydrothermal fluid influence and heating effects. By integrating and comparing data from previous studies, we propose a hydrothermally affected sedimentation model for Cretaceous red beds and associated sediments in magma-activated lacustrine basins, and conclude that the enriched metallic ions introduced by the hydrothermal fluids may be the most significant reason for the deposition of the red beds, and the flushed ferric ions, accompanied by hydrothermal fluid, are the main ions that are hosted inside hematite causing the red sediment. This model can be applied to similar lacustrine basins that experience strong magmatic activity.     

Tectono-stratigraphy of Lower Cretaceous Tanan sub-basin,Tamtsag Basin,Mongolia: Sequence architecture,depositional systems and controls on sediment infill

Tanan sub-basin is an active-fault bounded basin. The spatial distribution and temporal evolution of depositional systems were significantly influenced by tectonics. Fault movement and stages of basin development controlled the subsidence rates and the potential for erosion and the rate of sediment supply. Distinct stages of rift evolution during the early Cretaceous can be recognized, namely the early syn-rift, rift climax and late syn-rift stages. Three types of lacustrine sequence, consisting of distinctive depositional systems, are distinguished: (1) the early syn-rift sequences (SQ1 + SQ2), which are composed mainly of fan delta and shallow lacustrine depositional systems; (2) the rift climax sequences (SQ3) which developed in response to rapid and differential tectonic subsidence rates, and consist of fan delta, deep lacustrine and sublacustrine fan depositional systems; and (3) the late syn-rift sequences (SQ4) which are comprised of braided-delta and shallow lacustrine depositional systems. Each of the three lacustrine sequence architectures stands for a particular stage of basin fill and reflects variable rates of basin subsidence. Within each sequence, depositional systems and their stacking patterns are interpreted to have been a function of the interaction between tectonics and sediment supply. Differential subsidence across the basin, related to rotation of fault blocks, resulted in the formation of distinct paleomorphologies in different structural settings. These settings were fault-scarp zones controlling the development of fan-deltas, fault-terrace zones controlling the development of fan-delta and sublacustrine fans, half-graben dip-slope zones controlling the development of braided river and braided deltas, and intra-basinal fault-break zones controlling the development of sublacustrine fans. During the late syn-rift stage, active tectonism, displacement on the boundary faults had ceased. At this stage the depositional systems and their stacking patterns were dominantly related to the sediment supply rates, and not to tectonic activity.     

Applying seismic geomorphology to delineate switched sequence stratigraphic architecture in lacustrine rift basins: An example from the Pearl River Mouth Basin,northern South China Sea

Switched sequence stratigraphic architectural units were developed in the Eocene Wenchang Formation stratigraphic section of the Pearl River Mouth Basin (PRMB), northern South China Sea. Utilizing a high-quality 3D seismic data set, well logs and restored paleogeomorphology, the architecture and genesis of switched sequence stratigraphic units have been systematically investigated. The Wenchang Formation, a second-order sequence, can be subdivided into seven third-order sequences (from base to top: SQ1, SQ2, SQ3, SQ4, SQ5, SQ6, and SQ7). The sequence stratigraphic architecture of the Wenchang Formation is characterized by continuous lateral stacking patterns from sequences SQ1 to SQ7. Sequences SQ1–SQ4 mainly developed in the HZ26 sag, whereas sequences SQ5–SQ7 mainly developed in the XJ24 sag. The depositional centres of the Wenchang Formation appear to have migrated from the HZ26 sag to the XJ24 sag-along the northwest direction from sequences SQ1 to SQ7. Multiple tectonic activation episodes or alternating tectonic subsidence of the HZ26 and XJ24 sags resulted in the distinctive geomorphological features that effected the development of the switched sequence stratigraphic architecture in the study area. The switched sequence stratigraphic architecture presented in this study may provide new insights into a better understanding of sequence stratigraphic stacking patterns in continental lacustrine rift basins.     

Sedimentary facies associations and sequence stratigraphy of source and reservoir rocks of the lacustrine Eocene Niubao Formation (Lunpola Basin,central Tibet)

The Eocene Niubao Formation of the Lunpola Basin, a large Cenozoic intermontane basin in central Tibet, is an important potential hydrocarbon source and reservoir unit. It represents ∼20 Myr of lacustrine sedimentation in a half-graben with a sharply fault-bounded northern margin and a low-angle flexural southern margin, resulting in a highly asymmetric distribution of depositional facies and sediment thicknesses along the N-S axis of the basin. An integrated investigation of well-logs, seismic data, cores and outcrops revealed three third-order sequences (SQ1 to SQ3), each representing a cycle of rising and falling lake levels yielding lowstand, transgressive, and highstand systems tracts. Lowstand systems tracts (LST) include delta and fan delta facies spread widely along the gentle southern margin and concentrated narrowly along the steep northern margin of the basin, with sublacustrine fan sand bodies extending into the basin center. Highstand systems tracts (HST) include expanded areas of basin-center shale deposition, with sublacustrine fans, deltas and fan deltas locally developed along the basin margins. Sequence development may reflect episodes of tectonic uplift and base-level changes. The southern margin of the basin exhibits two different structural styles that locally influenced sequence development, i.e., a multi-step fault belt in the south-central sector and a flexure belt in the southeastern sector. The sedimentary model and sequence stratigraphic framework developed in this study demonstrate that N2 (the middle member of Niubao Formation) exhibits superior hydrocarbon potential, characterized by thicker source rocks and a wider distribution of sand-body reservoirs, although N3 (the upper member of Niubao Formation) also has good potential. Fault-controlled lithologic traps are plentiful along the basin margins, representing attractive targets for future exploratory drilling for hydrocarbons.     

南大西洋被动陆缘共轭盆地烃源岩分布与油气富集规律——以巴西桑托斯盆地和西非纳米贝盆地为例

巴西桑托斯盆地与西非纳米贝盆地属于南大西洋中部被动大陆边缘共轭盆地,其构造演化可划分为3个阶段:裂谷期、过渡期和后裂谷期,过渡期发育阿普特阶盐。南大西洋不对称裂开控制了桑托斯盆地和纳米贝盆地在盐下早白垩世裂谷地堑、盐发育和盐上晚白垩世地层厚度等方面的差异,这些差异控制了桑托斯盆地和纳米贝盆地盐下早白垩世湖相烃源岩发育及盐上晚白垩世海相烃源岩成熟度,进而控制了桑托斯盆地和纳米贝盆地油气富集规律。桑托斯盆地深水区盐下下白垩统构造或岩性圈闭是寻找巨型油气田的有利勘探方向;浅水区盐上上白垩统地堑深凹陷盐活动相关构造或岩性圈闭是寻找大中型油气田的有利勘探方向。     

西非宽扎盆地烃源岩分布及油气成藏

宽扎盆地为南大西洋被动大陆边缘盆地,构造演化可划分为裂谷期、过渡期和后裂谷期3个阶段,过渡期发育阿普特阶盐岩。宽扎盆地主要发育3套烃源岩:盐下下白垩统阿普特阶湖相烃源岩、盐间早白垩世阿普特期海相烃源岩和盐上古近纪始新世海相烃源岩。宽扎盆地油气田均围绕烃源灶分布,烃源岩是该盆地油气藏形成与分布的主控因素。宽扎盆地发育4套含油气系统(盐下下白垩统、盐间下白垩统、盐上上白垩统和盐上古近系)以及2种成藏模式(古生新储和自生自储)。宽扎盆地深水21区块Cameia-1井、Cameia-2井以及21区块Azul-1井盐下地层获得重大油气勘探突破,表明该盆地深水区存在盐下下白垩统含油气系统并发育优质湖相烃源岩,提高了宽扎盆地深水区油气勘探潜力。     

北黄海盆地中生代地层的地质特征和油气潜力(英文)

位于山东半岛东北部的北黄海盆地沿东北方向可以延伸到朝鲜的西朝鲜湾盆地和安州盆地 ,而沿西南方向可以延伸到中国的胶莱盆地。长期以来该盆地的找油重点为第三系 ,结果收效甚微。2 0世纪 80年代末朝鲜在西朝鲜湾靠北黄海盆地一侧钻井数口且在中生代地层中发现了商业性油气流 ,自此中生代地层替代新生代第三纪地层成为人们关注的焦点 ,人们希望在北黄海盆地的中生代地层中也能找出商业性油气流。本文以李四光 ( 1 979)划分的新华夏系第二隆起带理论为指导 ,将胶莱盆地、北黄海盆地、西朝鲜湾盆地和安州盆地作为一个整体进行考虑 ,在详细分析了安州盆地、西朝鲜湾盆地和胶莱盆地的中生代地层分布、油气潜力及其类比关系后认为 ,北黄海盆地在基底结构及其上覆盖层的沉积特征上应具有与安州盆地、西朝鲜湾盆地和胶莱盆地相似的特征。目前 ,西朝鲜湾盆地和胶莱盆地在中生代地层中已取得重要的油气发现和油气显示 ,而它们主要是由下白垩统和上侏罗统组成。因此 ,我们有理由相信 ,北黄海盆地的中生代地层很可能成为有远景的勘探靶区。     

北黄海盆地东部M隆起构造特征及演化

北黄海盆地是中国东部近海中生代断陷型盆地,详细记载着中国东部复杂的构造活动信息,期间经历了多期岩浆活动和构造反转。M隆起位于北黄海盆地东部,其构造活动记录比周边的坳陷更为详细。为充分认识M隆起的地质结构及沉积响应关系,在充分利用地震、钻测井等资料的基础上,结合区域构造背景,从构造运动学和动力学等方面探讨分析其构造演化历程,进而为北黄海盆地乃至中国东部地区的构造演化提供新的依据。高精度三维地震资料及地质分析揭示,该隆起区发育有5个典型的不整合面,纵向上可划分为5个构造层。结合北黄海盆地所处构造位置、构造变形和沉积充填特征,及板块运动和区域构造演化史,将北黄海盆地东部M隆起自中侏罗世至今的构造演化划分为5个阶段(共9期):裂陷阶段(稳定沉积期、掀斜形成期、早白垩世凹陷沉积期)、构造反转阶段(晚白垩世抬升剥蚀期)、再次裂陷阶段(早渐新世初沉积期、早渐新世末剥蚀期、F2断层活跃期)、再次构造反转阶段(整体抬升期)、区域沉降阶段(区域沉降期)。     

南黄海盆地南五凹阜宁组“广湖咸水”烃源岩及其油气勘探意义

通过对南五凹钻井所揭示的阜宁组进行岩性、地球化学、古生物及地震相等综合分析证实,南五凹阜宁组发育中深湖相泥质烃源岩,且该套烃源岩形成于"广湖咸水"沉积环境。"广湖"即湖盆分布广泛,中深湖相泥质烃源岩在凹陷深洼处和缓坡带均有发育,平面上面积大,纵向上厚度大,具备生成油气的物质基础。"咸水"即烃源岩形成时期湖盆受到了海侵影响,致使水体性质偏咸。南五凹与中国东部古新世—始新世期间曾遭受海侵影响的其他湖盆类似,其形成的咸化烃源岩具有"排烃早"的特征。南五凹阜宁组湖相烃源岩"广湖咸水"沉积特征对于油气勘探具有重要意义。     

南黄海北部坳陷及周缘地区白垩纪以来构造研究进展

南黄海北部坳陷是在印支期前陆盆地基底上发育的白垩纪—新生代大型伸展盆地。笔者系统总结了国内外学者南黄海北部坳陷周缘大地构造学研究、盆地内构造变形—陆相层序充填研究近年来的研究成果,对比了中韩两国学者对于北部坳陷的陆相层序划分方案的异同点,列举了目前研究的薄弱点,提出了一些亟待解决的问题。此研究对于东亚陆缘断陷盆地群地球动力学机制分析、扬子—华北碰撞造山带垮塌研究以及南黄海油气勘探突破均有重要的科学和经济意义。     

Three-dimensional facies architecture analysis using sequence stratigraphy and seismic sedimentology: Example from the Paleogene Dongying Formation in the BZ3-1 block of the Bozhong Sag,Bohai Bay Basin,China

The Bohai Bay Basin is a classic non-marine rift basin in eastern China. The Paleogene Dongying sequences are the main hydrocarbon-bearing stratigraphic unit in the basin. Using three-dimensional (3-D) seismic data and one well control in the BZ3-1 Block in the western slope of the Bozhong Sag, we analyzed 3-D facies architectures of the Dongying sequences. The Dongying Formation, a second-order sequence, can be subdivided into four third-order sequences (from base to top: SQ1, SQ2, SQ3, and SQ4). The facies architecture was analyzed by using the seismic sedimentology approach based on 3-D seismic data. Sediment of the Dongying sequences was derived from the northern Shijiutuo Uplift via four major configurations of incised valleys, namely “V”, “U”, “W”, and composite shaped incised valleys. Seismic stratal slices reveal branching and converging characteristics of the channels from upstream to downstream. On the basis of an integrated analysis of well log, core data, seismic facies based on multi-seismic attributes, three sedimentary facies (e.g., “delta”, “fan-delta”, and “shore” or “shallow lacustrine” facies) have been recognized. The four types of incised valleys and their evolution control the sedimentary systems in the sedimentation area. The numbers and sizes of the fans are controlled by the sedimentary systems at various scales. Incised valley-fill and deltaic sand bodies are excellent hydrocarbon reservoirs and potentially good exploration targets for the study area. The reservoir quality of sequences SQ1, SQ2, and SQ3 become better gradually from base to top. The proposed sediment dispersal patterns may aid in the prediction of potential reservoir distribution. This study also demonstrates that facies architecture analysis using sequence stratigraphy and seismic sedimentology may serve as an effective approach for constructing 3D facies models for petroleum exploration in areas lacking of well or outcrop data.     

Cross-section restoration and one-dimensional basin modeling of the Central Subbasin in the southern Kunsan Basin,Yellow Sea

The petroleum system of the Kunsan Basin in the Northern South Yellow Sea Basin is not well known, compared to other continental rift basins in the Yellow Sea, despite its substantial hydrocarbon potential. Restoration of two depth-converted seismic profiles across the Central Subbasin in the southern Kunsan Basin shows that extension was interrupted by inversions in the Late Oligocene-Middle Miocene that created anticlinal structures. One-dimensional basin modeling of the IIH-1Xa well suggests that hydrocarbon expulsion in the northeastern margin of the depocenter of the Central Subbasin peaked in the Early Oligocene, predating the inversions. Hydrocarbon generation at the dummy well location in the depocenter of the subbasin began in the Late Paleocene. Most source rocks in the depocenter passed the main expulsion phase except for the shallowest source rocks. Hydrocarbons generated from the depocenter are likely to have migrated southward toward the anticlinal structure and faults away from the traps along the northern and northeastern margins of the depocenter because the basin-fill strata are dipping north. Faulting that continued during the rift phase (∼ Middle Miocene) of the subbasin probably acted as conduits for the escape of hydrocarbons. Thus, the anticlinal structure and associated faults to the south of the dummy well may trap hydrocarbons that have been charged from the shallow source rocks in the depocenter since the Middle Miocene.     

Geomorphology and sedimentary sequence evolution during the buried stage of paleo-uplift in the Lower Cretaceous Qingshuihe Formation,Junggar Basin,northwestern China: Implications for reservoir lithofacies and hydrocarbon distribution

The evolution of large-scale paleo-uplifts within sedimentary basins controls the sedimentary provenance, depositional systems and hydrocarbon distributions. This study aims to unravel changes in paleo-geomorphology, interpret sedimentary sequence evolution, and investigate favourable reservoir types and the hydrocarbon distribution during the buried stage of a long-term eroded paleo-uplift, taking the Lower Cretaceous Qingshuihe Formation (K₁q) in the Junggar Basin as an example. These research topics have rarely been studied or are poorly understood. This study integrates current drilling production data with outcrop and core analyses, drilling well logs, 3D seismic data interpretations, grading data, physical property comparisons and identified hydrocarbon distributions.After more than 20 million years of differential river erosion and weathering in arid conditions, the large-scale Chemo paleo-uplift within the hinterland area of the basin formed a distinctive valley–monadnock paleo-geomorphology prior to the deposition of K₁q. Since the Early Cretaceous, tectonic subsidence and humid conditions have caused the base level (lake level) to rise, leading to backfilling of valleys and burial processes. Two systems tracts in the target strata of K₁q, consisting of distinctive depositional systems, can be identified: (1) a lowstand systems tract (LST), which is confined within incised valleys and is mainly composed of gravelly braided rivers and rarely occurring debris flows and (2) an extensive transgressive systems tract (TST), which developed into an almost flat landform and consists of braided river delta to lacustrine depositional systems. Overall, the physical properties of braided river reservoirs in the LST are better than those of the braided river delta reservoirs in the TST. However, the inhomogeneous distributions of carbonate cements cause differences in the physical properties of conglomerate reservoirs in the LST. However, for sandstones in both the LST and TST, coarser grain sizes and better sorting result in better physical properties. Altogether, four types of reservoir can be identified in the study area: Jurassic inner monadnock reservoirs, K₁q LST stratigraphic onlap reservoirs, LST structural reservoirs and TST structural reservoirs.     

低勘探程度盆地模拟研究——以南黄海盆地北部坳陷为例

盆地模拟已成为当前沉积盆地研究的重要工具。南黄海盆地北部坳陷自裂陷期演化以来沉积了巨厚的中-新生代碎屑沉积,近年来的地质调查获取的数据为其盆地模拟研究提供了条件,本次研究在收集相关基础数据的基础上,首先对盆地构造热演化史进行了模拟,重建了盆地热史,模拟结果显示其古热流在中-晚侏罗世平均值约为61mW/m²,在约145-74Ma间不断上升至约80 mW/m²,随后缓慢下降至65 mW/m²,并持续到渐新世末期,据此将盆地演化阶段划分为裂前期、裂陷期及裂后期。盆地模拟结果显示北部坳陷在白垩纪逐步进入强裂陷演化阶段并经历快速沉积过程,至晚白垩纪裂陷发育程度中等,在此基础上,对研究区进行了三维盆地模拟,结果显示北部坳陷生烃门限深度大致位于古近系阜宁组顶部,下伏的侏罗系及白垩系烃源岩基本完成生排烃过程,其中侏罗系烃源岩生排烃主要发生在盆地发育的裂陷期及裂后期,而白垩系及古近系烃源岩生排烃主要发生在裂后期。尽管研究区尚处在低勘探程度阶段,但盆地模拟结果已能为研究区下一步的勘探提供重要的信息,此外,本次研究对模拟过程中的主要不确定性也进行了分析。     

由上下扬子对比探讨南黄海中—古生界油气保存条件

为了探讨南黄海中—古生界油气保存条件,开展了上下扬子中—古生界构造演化、生储盖组合等对比分析。结果显示：印支和燕山运动对南黄海中—古生界的影响大大强于上扬子四川盆地,致使三叠系残留厚度较薄;推测南黄海中—古生界盖层以泥岩为主,膏盐岩为辅,其中泥岩盖层以下寒武统、下志留统和上二叠统为主,膏盐岩盖层则以中下三叠统为主。综合研究认为,烟台坳陷和崂山隆起以下寒武统或下志留统的泥岩为主要盖层,推测可形成威远型气藏;而青岛坳陷和勿南沙隆起以上二叠统泥岩为直接盖层,中下三叠统膏盐岩为间接盖层,推测可形成五百梯型或建南型气藏。南黄海盆地间接盖层缺乏,但下古生界具有良好的生烃潜力和保存条件,因此,南黄海盆地应重视下古生界页岩气的勘探和开发。     

南黄海盆地下三叠统层序地层格架

南黄海盆地是下扬子地块向海洋的延伸,中、古生界海相地层研究程度较低,仍未开展过系统的地层格架研究,制约了研究区的油气勘探进程。结合陆域下扬子的研究成果,利用研究区以及陆上苏北盆地的地质、钻井、测井、岩心等资料建立起下三叠统的三级层序地层格架。研究结果表明:三级层序边界为岩性转换界面或者不整合面;下三叠统可以划分为3个三级层序,其中每个三级层序又可以划分为海侵和高位体系域,低位体系域均不发育。以上研究为后期沉积相划分、储层预测等提供了可靠的地质依据。     

北部湾盆地海中凹陷流二段沉积体系及沉积模式

北部湾盆地北部涠西南凹陷多口钻井已获得高产油气流系列突破,其主力烃源岩层系为始新统流沙港组二段（流二段）,但紧邻南侧的海中凹陷目前暂无商业油气发现。流二段既发育有深湖—半深湖相的烃源岩,同时在主力烃源岩段也发育有湖底扇储层,因此,研究海中凹陷潜在生烃层系（烃源岩、湖底扇储层）沉积体系发育规律对今后勘探开发具有指导意义。以高精度三维地震资料及测井资料为基础,通过岩芯相、测井相、地震相、地震属性的综合分析,探讨流二段沉积体系发育规律,建立沉积模式。研究表明：流二段主要发育滨浅湖、深湖—半深湖、湖底扇及辫状河三角洲4种沉积体系类型;在北陡南缓的半地堑构造样式控制下,北部陡坡带及洼槽带发育深湖—半深湖相,同时接受北部、东部2个物源方向的供源,分别在西洼、东洼发育湖底扇相,南部缓坡带发育滨浅湖及辫状河三角洲相。海中凹陷流二段好烃源岩主要发育在初始湖泛面层序位置（ts）,湖底扇主要发育在湖泊扩张体系域内（TST）,反映了在断陷湖盆背景下,构造沉降因素控制烃源岩发育程度强于湖平面变化因素。研究可为半地堑型断陷湖盆深湖—半深湖相烃源岩与湖底扇储层发育层序位置及共生模式的建立提供参考。     

南海深水盆地油气地质特征及勘探方向

在深入调研南海深水盆地油气地质条件的基础上,系统分析了油气分布规律和成藏主控因素,明确了油气资源潜力和有利勘探方向,旨在为南海深水油气勘探决策提供科学依据。研究结果表明：南海深水盆地发育在非典型边缘海大陆边缘,其石油地质条件具有特殊性,油气分布特征存在显著的南北差异。其中,南海北部深水的珠江口盆地和琼东南盆地,以构造圈闭型油气藏为主;南海中南部深水的曾母盆地南部和文莱-沙巴盆地,主要为构造圈闭型油气藏,曾母盆地北部以岩性油气藏（生物礁滩型油气藏）为主,万安盆地主要为构造圈闭型和基岩潜山型油气藏。南海北部深水盆地和中南部深水盆地的烃源岩、储盖和圈闭等油气地质特征表明,南海深水盆地具有巨大的油气勘探潜力。南海深水的有利勘探方向为：①琼东南盆地乐东-陵水凹陷的中央峡谷、陵南斜坡带,松南-宝岛凹陷的反转构造带,宝岛凹陷北坡海底扇,长昌凹陷的环A洼圈闭带（海底扇）;珠江口盆地白云凹陷的主洼深水扇、主洼两翼、西南断阶带,荔湾凹陷的深水扇。②南海中南部深水盆地的文莱-沙巴、曾母和万安盆地。     

南海东北部陆架边缘第四纪高分辨率层序地层和沉积体系演化及其控制因素

The northeastern shelf margin of the South China Sea(SCS) is characterized by the development of large scale foresets complexes since Quaternary. Based on integral analysis of the seismic, well logging and paleontological data, successions since ～3.0 Ma can be defined as one composite sequence, consist of a set of regional transgressive to regressive sequences. They can be further divided into six 3 rd order sequences(SQ0–SQ5) based on the Exxon sequence stratigraphic model. Since ～1.6 Ma, five sets of deltaic systems characterized by development of wedge-shaped foresets complexes or clinoforms had been identified. High-resolution seismic data and the thick foresets allowed further divided of sub-depositional sequences(4 th order) of regression to transgression, which is basically consistent with published stacked benthic foram O-isotope records. Depositional systems identified in the study area include deltaic deposits(inner-shelf deltas and shelf-edge deltas), incised valleys, and slope slumping massive deposits. Since ～1.6 Ma, clinoforms prograded from the southern Panyu Lower Uplift toward the northern Baiyun Depression, shelf slope break migrated seaward, whereas the shelf edge of SQ0 migrated landward. The development of incised valleys in the continental shelf increased upward,especially intensive on the SB3 and SB2. The slumping massive deposits increased abruptly since SB2, which corresponds to the development of incised valleys. The evolution of depositional systems of continental slope mainly controlled by the combined influence of sea level changes, tectonic movements, sediment supply and climate changes. Since ～3.0 Ma, relative sea level of the northern SCS had been experienced transgression(～3.0 Ma BP) to regression(～1.6 Ma BP). The regional regression and maximum transgressions of the composite sequences were apparently enhanced by uplift or subsidence related to tectono-thermal events. In addition,climatic variations including monsoon intensification and the mid-Pleistocene transition may have enhanced sediment supply by increasing erosion rate and have an indispensable influence on the development of the incised valleys and 5 sets of deltaic systems since ～1.6 Ma.     

始新统油气系统:泰国湾东北部油气勘探新层系

泰国湾区域经历了前裂谷期、裂谷期、裂后期的构造演化阶段,形成了多个裂谷盆地。泰国湾区域东北部在渐新世经历了一次明显构造反转,较泰国湾区域大部分地区强烈。通过对比区内钻井,结合地震解释,对该区的沉积特征和构造演化进行了分析,认为这次反转构造导致了反转构造带上构造、沉积特征与邻区有较大的不同。由于这次反转构造,泰国湾东北部在新层系发育新类型的油气系统,即深部的始新统油气系统:烃源岩为中始新统湖相泥岩,储层为上始新统-渐新统三角洲相砂岩,盖层为下中新统三角洲前缘相泥岩和上中新统以上的海相泥岩。该油气成藏系统已被钻井钻遇油气显示,是本区有效油气成藏系统。