苏北盆地码头庄油田阜宁组震积岩特征及形成模式

通过岩芯观察,码头庄油田阜宁组发育了大量的同生小断层、液化岩脉、泥火山、震动液化扭曲变形、震动液化卷曲变形、自碎角砾岩等震积岩沉积构造,该类沉积构造属于软沉积变形构造,具有典型的震积岩沉积特征。首次在同期震积岩中发现同生微型正/逆断层发育,2种不同类型断层的发现,说明区内震积岩存在不同的应力环境,在滑塌体上部易形成微正断层,在滑塌体下部易形成微逆断层。认为前人对震积岩微同沉积断裂层、微褶皱变形层、碎块层、液化均一层4段分层的完整垂向序列可能过于理论化,并提出水平液化变形段、拉张段、滑脱段、沉积段、水平沉积变形段5段式震积岩立体发育模式。     

惠民凹陷西部早第三纪沙河街组浊积扇及砂岩体沉积特征研究

惠民凹陷是渤海湾地区新生代断陷盆地之一，其西部地区下第三系发育完整。沙三组中、上段发育大量的浊积扇及典型的浊积岩，后者具深湖相、半深湖相泥岩、油页岩韵律，成因上与三角洲沉积体系的形成、演化关系密切。浊积岩砂体是油气聚集的有利地带，构成了研究区重要的油气储集体。本文阐述了区内沙三组中—上段浊积岩分布、发育样式、形成及演化规律。     

库车前陆盆地白垩系亚格列木组浊流沉积特征与意义

通过对库车前陆盆地西部卡普沙良河剖面上侏罗统喀拉扎组-下白垩统亚格列木组沉积相垂向演化分析、砂泥岩X射线荧光光谱分析、储层微观特征研究,认为喀拉扎组-亚格列木组发育一套干旱气候背景下的陆上季节性辫状河-半深湖浊积扇-浅湖相的沉积演化序列。上侏罗统喀拉扎组主要以季节性辫状河沉积为主,下白垩统亚格列木组下部发育早晚两期浊积扇沉积,浊积扇水道砂体中见槽模、沟模以及重荷模,并发育典型的鲍玛序列,该沉积时期的古气候偏干冷;亚格列木组上部主要发育浅湖相泥岩与沙坝沉积,此沉积时期古气候由湿热变化至干冷。亚格列木组浊积扇水道砂体中石英含量较高,一般介于62%~70%之间,粒间溶孔与构造缝较发育;浅湖相沙坝砂体石英含量降低,一般为55%~58%,沙坝砂体中溶蚀孔较浊积扇中溶蚀孔多。亚格列木组中浊流沉积的发现,不但丰富了库车前陆盆地重力流沉积的研究成果,也表明在早白垩世库车西部发育较深水的沉积环境,为该地区湖相深水沉积的油气勘探奠定了基础。     

根据孢粉组合推论西藏伦坡拉盆地第三纪地层时代及其古地理

伦坡拉盆地位于藏北高原南部,海拔4000多米,是藏北新生代地层甚为发育的地区,第三系沉积厚达三千米以上,自下而上划分为:迪欧组、牛堡组、丁青组和伦坡拉组。自1967年以来,我们先后分析了采自伦坡拉盆地的伦坡拉构造两个剖面,丁青构造两个剖面,牛堡构造两个剖面,阿利开拍构造一个剖面,猪头山一个剖面,伦坡拉西拗陷一个剖面以及四口钻井的岩心样品近300块。     

辽东湾辽中凹陷中部古近系东营组震浊积岩特征研究

辽东湾辽中凹陷中部古近系东营组地层中发育多期大规模浊积扇,利用岩芯、薄片、测井及地震资料,对这些浊积岩及其下伏地层的沉积成岩特征、沉积构造和岩石类型分析,认为研究区东营组浊积岩与典型的原地震积岩伴生,属于地震成因的浊积岩.这些浊积扇的扇中以长石砂岩和岩屑长石砂岩为主,埋深一般在1 500 m～2 500 m左右,为早成岩演化Bl期.测井解释孔隙度平均为27.5%,储层物性良好,并且具有良好的生储盖组合,钻探证实其良好的含油气性.此类浊积扇与地震活动紧密相关,其分布具有一定的等时性,因此可以推测渤海海域郯庐断裂两侧在活跃期发育的大规模浊积扇,具有良好的岩性油气藏勘探前景.     

同生逆断层控制的砂砾岩沉积模式及有利储集相带分布--以玛湖凹陷南斜坡白25井区上乌尔禾组为例

通过岩芯相-测井相-地震相-分析化验数据对比,结合砂砾岩沉积野外考察实践综合归纳分析,认为上乌尔禾组同生逆断层控制的冲积扇-扇三角洲砂砾岩沉积体系整体呈进积式沉积,具"冲积扇扇根（槽流带）-冲积扇扇中/扇三角洲平原（辫流带）-扇三角洲前缘（水下分流带）-前扇三角洲/滨浅湖（夹杂水下扇）"相序特征,发育槽流、泥石流/砂质碎屑流、辫状河道、水下分流河道、扇面水道五种典型砂砾岩沉积微相类型。同生逆断层带不断抬升剥蚀的累积效应,使近物源区冲积扇扇根沉积整体减薄,同时使同生逆断层控制沉积相带分异的趋势越来越明显。泥质含量是控制挤压背景下砂砾岩储层质量的关键因素,贫泥砂砾岩储层成岩压实减孔效应弱,剩余粒间孔发育,且粗粒级颗粒内部多发育压碎缝沟通粒间孔隙,储层质量最佳。依据储集空间组合类型将有利储集相带分为原生粒间孔-压碎缝发育带、原生粒间孔-次生溶孔发育带两大类。前者主要分布于构造高部位近断裂带-中上斜坡带;后者主要分布于中下部斜坡带。     

涠西南凹陷A井区古近系流沙港组一段砂体沉积特征及分布规律

涠西南凹陷A井区古近系流沙港组一段下亚段发育了大规模的砂砾岩沉积。岩芯观察及分析化验资料表明砂砾岩沉积发育丰富的能够反映浊流沉积的鲍马序列、冲刷充填及变形构造等沉积构造并具有直线一段式和上拱一段式等粒度概率曲线类型。垂向以多个底部发育冲刷充填构造的正旋回叠加为特征,整体表现为正序。沉积特征表明砂砾岩为湖底扇沉积。综合利用地震反射特征及垂向地层叠加样式等方法,在流一段湖底扇内共识别出3个五级层序,将湖底扇沉积划分为3期。各旋回湖底扇砂体厚度与平均波峰振幅、能量半时及瞬时频率等地震属性有良好的相关关系。在高精度层序地层格架的约束下,结合钻井及录井资料分析与地震属性分析,对3期湖底扇砂体平面分布特征进行了研究,各期湖底扇具有左右迁移摆动、垂向叠置发育的特征。由于受到3号控盆断层和0号隐伏断层的影响,使得涠西南低突起北缘发育的5号断层幕式活动,导致研究区可容空间发生转换,构造运动控制的可容空间不均衡转换是控制流一段湖底扇砂体分布规律的主要因素。     

湘西王村剖面寒武系花桥组浊积岩特征及其大地构造意义

湘西王村地区的寒武系代表江南斜坡相沉积序列,传统的下寒武统划分为杷榔组、清虚洞组;中寒武统划分为敖溪组、花桥组（下部）;上寒武统划分为花桥组（上部）、追屯组。其中,花桥组中浊流沉积发育,可识别出7次规模较大的浊流活动期,第一期浊积岩包括69个浊积序列,分别归属于11个副层序;第二期浊积岩包括37个浊积序列,分别归属于7个副层序。每个副层序的下部表现为近源浊积岩,上部表现为远源浊积岩,所代表的海水深度变化由浅变深。第一期浊流活动发生在海平面上升时期,形成三级层序的海侵体系域;第二期浊流活动发生在海平面较低、斜坡较陡时期,形成三级层序的低水位体系域。江南斜坡带中—上寒武世浊积岩频繁出现反映台地边缘深大断裂周期性活动强,断裂两盘升降差异运动显著。     

滇西保山金鸡地区三叠系上统大水塘组震积岩的发现及意义

以往认为保山地区三叠系上统大水塘组为浅海沉积,通过1∶5万金鸡村等幅区域地质调查,本文认为保山三叠系上统大水塘组的背景沉积主体为一套钙质浊积岩,主要由A、E段组成,中部夹薄层状硅质岩（饥饿沉积）,并伴有滑塌岩块,属斜坡-盆地环境,是永德-黑山裂谷（海槽）的一部分。笔者在大水塘组中首次发现了震积岩,包括振动液化卷曲变形构造、微同沉积断层、液化泥晶脉、震积不整合、地裂缝、液化角砾、液化眼球及由地震使沉积物液化流动形成的滑（流）积岩、滑（流）褶皱等资料,这些现象组合规律性极差,仅有少量有垂向组合层序,显示出地方性属种的色彩。微同沉积断层、液化泥晶脉几乎充满沉积的全过程。岩石遭敲击时,都会散发出极浓的油气味,显示出良好的烃源岩特征。因此,研究大水塘组震积岩的分布和形成对于恢复三叠系上统大水塘组古地理环境及寻找烃源岩都具有非常重要的现实意义。     

远源缓坡型薄层细粒浊积岩沉积规律--以松南西斜坡大布苏地区青一段地层为例

以松南西斜坡大布苏地区青一段薄层细粒浊积岩地层为例,以高分辨率层序地层学和沉积学理论为指导,建立了五级层序的高精度等时地层格架,并用最大熵频谱分析进行验证。利用岩芯、测井和地震手段,总结了研究区浊积岩的沉积特征及与三角洲前缘沉积相的区别,通过单井、连井以及RMS振幅确定了坡折带的位置及浊积岩沉积分布规律,得出该区浊积岩属于三角洲前缘河口坝远源缓坡滑塌成因,为线物源、砂泥混合型。薄层细粒浊积岩沉积规律研究表明:①滑塌浊积体主要分布于基准面下降期,靠近层序界面,厚度较大,垂向上表现为叠加或与浊积水道呈互层,且向上厚度增大;②上升期浊积水道往往靠近层序界面,厚度较大,表现为“箱状”水道主体,下降期浊积水道靠近湖泛面,厚度较小,表现为“尖指状”水道侧翼;浊积水道随基准面上升厚度减薄,随基准面下降厚度增加;③浊积席状砂主要分布在较深水、最大湖泛面附近,厚度较薄,或表现为垂向上叠加,或与湖相泥岩、浊积水道侧翼及滑塌浊积体呈互层关系。勘探实践表明研究区薄层细粒浊积岩可以获得较高的油气产量。     

某地下第三系T层粒度分布特征及沉积环境

碎屑沉积的粒度研究,已有七十余年历史。近二十年来,无论分析方法及资料解释,都有长足进步,因而已经成为岩石定量研究和环境(相)推断方面的重要手段。     

Earthquake‐induced turbidites triggered by sea level oscillations in the Upper Cretaceous and Paleocene of Italy

Earthquakes are widely recognized as triggers for turbidites, submarine debris flows and slumps. In tectonically active areas, surprisingly small changes in stress can trigger seismic events, implying that past sea level changes may be important in controlling the timing of seismicity and the occurrence of turbidites. We apply this idea in an analysis of turbidites from the upper Cretaceous–Paleocene Scaglia Rossa Formation of the Umbria‐Marches region of Italy. These turbidites are composed of resedimented foraminiferal tests derived from fluidizing deep‐water (∼1500 m), pelagic sediments; seismic triggering is the most likely triggering mechanism given this setting and composition. The timing of these turbidites (and associated synsedimentary slumps), constrained by biostratigraphy and magnetostratigraphy, reveals an unusual, non‐random temporal pattern that appears to correlate well with proposed eustatic fluctuations. This correlation between turbidites and eustatic fluctuations leads us to suggest that stress and pore fluid pressure changes associated with changing sea level may trigger periods of increased seismicity in the geological past.     

云南思茅地区上石炭统沉积特征及其构造背景

思茅地区位于东特提斯构造域的东段,晚古生代时期属扬子地台西缘的一部分。晚石炭世具有台盆相间的沉积格局,形成了三类不同的沉积：滨岸沉积、浅海台地沉积和深水浊流沉积。其中深水浊流沉积以火山源浊流沉积为特征,是在平缓的碳酸盐台地或陆棚之上通过断陷事件发展起来的,包括了５个沉积旋回,表现出强烈的火山活动期与火山休眠期交递进行的沉积旋回特征。自晚石炭世早期到晚期,火山活动期逐渐增长,休眠期逐渐缩短,反映出盆地性质自稳定向活动的转化过程。火山岩具有岛弧型火山岩特征,说明晚石炭世,思茅地区具有活动型大陆边缘沉积特征     

Upslope flow of turbidity currents on the northwest flank of the Cearà Rise: western Equatorial Atlantic*

A piston core (RC16-57) raised from the northwestern flank of the Ceará Rise contained several turbidites up to 62 cm thick with grain sizes ranging from clay to coarse sand. These turbidites were similar in composition to terrigenous turbidites found throughout the Amazon Cone, continental rise and abyssal plains of the western Equatorial Atlantic. The core site (RC16-57) on the Ceará Rise, however, was 156 m above the level of the adjacent Amazon Cone (the source of the turbidites). Thus the turbidity currents which deposited these beds apparently had to flow upslope for 17 km to reach the core site. Sub-bottom reflectors observed on a 3.5 kHz echogram that extended from the Amazon Cone upslope past the core site suggested that these and deeper turbidites extended from the cone up the rise flank to distances of up to 40 km from the cone/rise boundary and to elevations up to 400 m above the level of the cone at the base of the rise. An equally plausible explanation could be that the turbidity currents that deposited these sediments were in excess of 400 m in thickness and thus would not require uphill flow to reach their observed location on the rise flank. The absence of terrigenous turbidites from the bases of topographic knolls on the continental rise and abyssal plains throughout the western Equatorial Atlantic indicated, however, that turbidity currents were normally less than 100 m thick and hence would seem to rule out this explanation. The average gradient of the rise flank in this region was about 1 : 1000 (\sim 0.5°).     

论古代海洋碳酸盐沉积环境基本模式

我国碳酸盐地层分布广泛,厚度巨大,类型复杂,从而为我国碳酸盐研究提供广阔前景。解放以后,我国首先在四川盆地的二、三叠系碳酸盐岩中获得高产气田,推动了碳酸盐岩的研究。     

北山造山带古生代浊积岩构造环境探讨及其大地构造意义

北山造山带是研究中亚造山带增生造山的关键地区之一,浊积岩是增生造山带的重要组成部分。北山古生代浊积岩主要出露于营毛沱、柳园和黑山口地区。营毛沱浊积岩发育于下奥陶统,古水流方向由南向北,内部砂岩具中高等风化程度的长英质源区,构造背景为被动陆缘。早二叠世柳园浊积岩内部砂岩具低到中等风化程度的中基性源区,构造背景为大洋岛弧。早二叠世黑山口浊积岩中的砂岩源区具中等风化程度,环境相对柳园砂岩较为稳定,和长英质源区的沉积岩具相似性,构造环境可能为活动陆缘弧。对北山古生代浊积岩的解剖揭示北山古生代经历了复杂的俯冲增生过程。早古生代花牛山-火石山一带发育向北的俯冲,火石山南部被动陆缘形成营毛沱浊积岩,之后的俯冲带局部后撤形成泥盆纪墩墩山岛弧。柳园地区晚古生代洋壳向花牛山和石板山岛弧带俯冲分别形成了柳园和黑山口浊积岩。本研究支持北山增生时间持续到早二叠世的观点,对认识天山、索伦缝合带的衔接对比研究具有重要的意义。     

新疆北部泥盆系火山碎屑浊积岩层序结构特征及其地质意义

新疆北部泥盆系火山碎屑浊积岩包括粗粒、中粒和细粒火山碎屑浊积岩三大类,后者尚可进一步划分为粉砂质、泥质和生物成因浊积岩。岩性上以含火山物质有别于陆屑、钙屑浊积岩。在火山碎屑浊积岩中识别出20种层序结构,它们可归并为完整鲍马序列、连续不完整鲍马序列和间断不完整鲍马序列三类。文章认为:间断不完整鲍马序列是多个浊流事件或浊流事件与其他事件相互叠加、干扰的产物,为活动构造环境,特别是火山岛弧海中非单源、单方向浊流沉积或火山碎屑浊积岩或细粒浊积岩的重要特征。     

Turbidite stratigraphy in proglacial lakes: Deciphering trigger mechanisms using a statistical approach

Turbidites embedded in lacustrine sediment sequences are commonly used to reconstruct regional flood or earthquake histories. A critical step for this method to be successful is that turbidites and their trigger mechanisms are determined unambiguously. The latter is particularly challenging for prehistoric proglacial lake records in high-seismicity settings where both earthquake-generated and flood-generated turbidites interrupt the background varved sedimentation. This calls for a new method to allow efficient and objective identification and classification of turbidites. This study examined turbidites in five long (9 to 17 m) sediment cores from Eklutna Lake, a proglacial lake in south-central Alaska, using standard core logging and grain-size data. A novel statistical approach is presented, in which varve-thickness distributions were first analyzed to objectively identify the thickest turbidites and distinguish them from background sedimentation. For each turbidite, a selection of variables were then measured, including: basal grain-size, thickness, magnetic susceptibility and spectrophotometric variables. Triggering mechanisms were discriminated by a combination of principal component analysis and clustering, and by calibration with historical events. Using this approach, a 2250 year long lake-wide event stratigraphy was constructed, with 94 prehistoric events, including 24 earthquake and 70 flood events. Basal grain-size and thickness variables turn out to be the most effective proxies for discrimination. This statistical approach is a powerful and new method to identify turbidites and their triggering mechanisms in long prehistoric sediment records. It opens up new prospects for palaeoseismological, palaeohydrological and palaeoclimate studies in proglacial lakes worldwide.     

Simple estimates for the magnitude of bedload transport under a turbid surge

Characteristic length and timescales for a turbid surge are used to estimate bedload transport by the surge, deriving estimates for the conditions under which deposited material will be mobilized as bedload, and of the relative importance of bedload in determining the overall deposit geometry. A critique is provided of the common modelling assumptions which underlie these estimates and of how their consistency can be checked. For large turbidity currents, such as those which emplaced the Marnoso Arenacea turbidites in northern Italy, model predictions of overall geometry are not easy to reconcile with the field data: some possible reasons for this are discussed. The estimates obtained from these characteristic scales are consistent with the widespread presence in turbidites of sedimentary structures which indicate bedload transport; some of these structures from the Marnoso Arenacea Formation are reviewed briefly. However, the estimates suggest that bedload transport is not a major factor responsible for the geometry of the large turbidites in this formation, which exhibit a broad thickness maximum in their proximal region that contrasts with the downstream-thinning geometry of smaller beds. This effect suggests that the explanation for this theoretically unexpected geometry should be sought in other physical mechanisms.     

Announcement

The Precambrian rocks of the St. Malo region are grouped into two tectono-stratigraphical units which are correlated with the Pentevrian Complex (a pre-900 Ma basement) and the Brioverian succession (a cover sequence deposited sometime during the interval 900-650 Ma) recognized elsewhere within the Precambrian of the Armorican Massif of France and the Channel Islands. The Pentevrian Complex in this region is composed of metasediments, metatexites (migmatites) and diatexites (anatectic granodiorites). The Brioverian succession is represented by a sequence of turbidites which have undergone only greenschist facies metamorphism. Rocks assigned to the Pentevrian Complex in the St. Malo region preserve the effects of at least four episodes of deformation and two episodes of migmatization all of which occurred prior to the deposition of the turbidites. Three episodes of deformation have affected the Brioverian succession in response to the late Precambrian Cadomian orogeny. Thus two distinct groups of Precambrian metasediments, with different structural-metamorphic histories, are present in the St. Malo region. Cadomian deformation of the Pentevrian Complex is heterogeneous, the strain being largely confined to ductile shear belts. Brief comparison is made with other areas of Precambrian rocks in the northern part of the Armorican Massif.