河南西峡盆地上白垩统河流及湖泊沉积中的遗迹组构

河南西峡盆地上白垩统马家村组沉积厚度巨大,达1 960 m,由辫状河沉积、曲流河沉积和湖泊沉积组成。在河流与湖泊沉积中,发育丰富的遗迹化石,共6种类型,分别为Skolithos linearis、Cylindricumichnosp、Palaeophycus tubularis“J”形潜穴、垂直分枝潜穴和垂直螺旋潜穴。从形态分析,大多数为居住迹,按照遗迹化石产出岩层的岩性、扰动特征和残留遗迹等总体特征,将所发现的遗迹化石层划分为两类遗迹组构,即软底组构和僵底组构。前者主要发育在纹层状极细砂岩和粉砂岩中,潜穴密度大,属种单一,包括Skolithos组构和Palaeophycus组构;后者主要发育在厚层泥岩中,潜穴密度较大,类型稍多,包括由Cylindricum ichnosp、垂直分枝潜穴J形潜穴和垂直螺旋潜穴所组成的遗迹组构。与报道过的其他地区陆相遗迹化石的对比表明,随着时间的推移,河流沉积中的组构特征在白垩纪有明显变化,而浅湖沉积中的遗迹组构表明造迹生物的扰动能力显著加强。     

豫西北奥陶系马家沟组三段遗迹组构及沉积演化规律

豫西北奥陶系马家沟组三段碳酸盐岩中遗迹化石丰富。在对野外露头实地观测的基础上,利用室内切片、薄片分析等对研究区奥陶系马家沟组三段遗迹化石、遗迹组构及沉积演化规律进行研究。结果表明:(1)研究区奥陶系马家沟组三段共鉴定出遗迹化石类型7属10种。(2)根据遗迹化石的分子组成、产状、共生关系、丰度与分异度以及生物扰动的程度,结合沉积学特征分析,共识别出遗迹组构4种:Psilonichnus遗迹组构主要发育在潮上带与潮间带上部(高潮坪)低能的沉积环境;Thalassinoides遗迹组构代表潮间带中-下部和台内滩等高能沉积环境;Helminthopsis遗迹组构反映局限碳酸盐岩台地内的潟湖和开阔台地内的滩间海等较低能的沉积环境。Helminthopsis-Chondrites遗迹组构揭示开阔碳酸盐岩台地中滩间海-台内洼地等非常低能的沉积环境。(3)建立了研究区马家沟组三段的层序地层格架,并在层序格架内对遗迹组构和沉积微环境的演化规律进行了研究,解译出研究区马家沟组三段经历了两次区域性的海侵—海退;综合岩石类型、岩石序列组合、沉积构造、生物化石、遗迹化石组合、遗迹组构等资料,建立了研究区奥陶系马家沟组三段各遗迹组构与沉积微环境的三维相模式。这对研究华北奥陶系沉积环境与沉积演化具有重要的借鉴意义。     

豫西地区下二叠统太原组遗迹组构及其沉积环境

豫西下二叠统太原组中发育丰富的遗迹化石,常见有Zoophycos,Taenidium,Thalassinoides,Teichichnus,Gordia,Nereites,Chondrites和Planolites等,部分灰岩层中还发育生物扰动构造。根据遗迹化石的形态、组成、产状、分布特征以及丰度、分异度、生物扰动程度的不同,在研究区太原组碳酸盐岩中共识别出5种遗迹组构,包括类型A--Gordia-Planolites遗迹组构、类型B--Rhizocorallium-Thalassinoides遗迹组构、类型C--Zoophycos-Taenidium遗迹组构、类型D--Zoophycos-Speckle burrow强生物扰动遗迹组构、类型E--Chondrites-Nereites遗迹组构。其中类型C根据Zoophycos在剖面上所展现的各种特征,又可细分为3种类型,即类型C-1,C-2和C-3。通过分析宿主岩的沉积特征,表明太原组碳酸盐岩中的遗迹组构主要分布于潟湖潮坪和台内浅滩(类型A)、正常天气浪基面之上的浅海上部或局限台地(类型B,类型C-1和类型C-2)、正常天气浪基面之下的开阔台地(类型C-3,类型D)和风暴浪基面之下的浅海下部或水动力条件类似的较闭塞的沉积环境中(类型E)。     

粤北晚泥盆世天子岭组遗迹组构及其环境解释

遗迹组构是由生物成因改造的沉积岩组构,它是物理过程和生物过程相互作用的产物。本文在广东韶关晚泥盆世天子岭组碳酸盐岩沉积中建立了4个遗迹组构,即反映局限台地或封闭海湾环境的Planolies montanus遗迹组构,反映台地潮下低能环境的Thalassinoides—Planolites遗迹组构,反映潮上-潮间环境的．Skolithos遗迹组构和受固底底质控制的Thalassinoides遗迹组构。对遗迹化石和生物扰动构造进行阶层分析,从中识别出受固底底质控制的遗迹化石Thalassinoides.sp,这类遗迹化石常常代表层序地层学中的重要界面。     

大港油田中部滩海新近纪古湖泊发育的证据

大港中部滩海新近系层系是重要的油气后备勘探领域和战略接替区.前人普遍认为新近系层系发育曲流河和辫状河沉积.借鉴渤海海域浅层油气勘探经验, 基于遗迹组构、微古生物、生物有机化合物、碳氧同位素以及地震等地质资料分析, 认为中部滩海东部发育开阔的古湖泊, 其证据为: 发育见于国内外浅湖环境的典型的Palaeophycus遗迹组构; 发现丰富的见于正常浅湖环境的浮游绿藻化石; 发现较多的仅分布在古代和现代湖泊中的介形类——Candona、Cypris; 干酪根类型、生物有机化合物、碳氧同位素以及地震等地质资料也证明了古湖泊的存在.馆陶组中、晚期至明化镇组沉积早期为湖泊逐渐扩张达到鼎盛发育的时期.      

Ichnofabrics and their Sedimentary Environment of the Lower Permian Taiyuan Formation, Western Henan

豫西下二叠统太原组中发育丰富的遗迹化石,常见有Zoophycos,Taenidium,Thalassinoides,Teichichnus,Gordia,Nereites,Chondrites和Planolites等,部分灰岩层中还发育生物扰动构造.根据遗迹化石的形态、组成、产状、分布特征以及丰度、分异度、生物扰动程度的不同,在研究区太原组碳酸盐岩中共识别出5种遗迹组构,包括类型A——Gordia-Planolites遗迹组构、类型B—— Rhizocoralliurn- Thalassinoides遗迹组构、类型C—— Zoophycos- Taenidium遗迹组构、类型D——Zoophycos- Speckle burrow强生物扰动遗迹组构、类型E——Chondrites- Nereites遗迹组构.其中类型C根据Zoophycos在剖面上所展现的各种特征,又可细分为3种类型,即类型C-1,C-2和C-3.通过分析宿主岩的沉积特征,表明太原组碳酸盐岩中的遗迹组构主要分布于潟湖潮坪和台内浅滩(类型A)、正常天气浪基面之上的浅海上部或局限台地(类型B,类型C-1和类型C-2)、正常天气浪基面之下的开阔台地(类型C-3,类型D)和风暴浪基面之下的浅海下部或水动力条件类似的较闭塞的沉积环境中(类型E).     

豫西济源地区中三叠世油房庄组遗迹组构及其环境解释

河南济源地区中三叠世油房庄组发育了一套滨浅湖相的砂泥岩沉积，在该组上段紫红色与黄绿色砂泥岩沉积中发现了大量的遗迹化石。其中高能砂质滨湖沉积中识别出6种遗迹组构:斑状生物扰动组构、Skolithos isp.-Planolites montanus组构、Skolithos verticalis组构、Planolites beverleyensis组构、Skolithos isp.组构和Palaeophycus annulatus 遗迹组构，它们可归入陆相Skolithos遗迹相；极浅湖泥岩夹粉砂岩沉积中识别出3种遗迹组构: Skolithos linearis遗迹组构、Taenidium barretti遗迹组构和植物根迹组构，它们可归入陆相Scoyenia遗迹相。     

靖边油田南部延长组长2段沉积相研究

基于前人对研究区延长组长2段沉积相成岩作用等研究较少,应用现代沉积学原理,对靖边油田南部延长组长2段沉积相进行系统分析。研究表明,长2段的沉积物颜色为灰白色、浅灰色,显示出一种水体较浅、水上的沉积环境;发育有板状交错层理、槽状交错层理、平行层理、砂纹层理等构造;沉积时水动力条件较强,发育曲流河和辫状河沉积。曲流河沉积主要发育在长2~1油层组。根据河道砂坝的沉积物组成,可将其区分为两种类型:以砾质沉积为主的砾质辫状河和以砂质沉积为主的辫状河流。研究区长2~2、长2~3沉积类型表现为砂质辫状河流沉积。以河道砂坝为主,局部发育不完整泛滥平原。在长2~1时期,研究区的沉积类型由辫状河变为曲流河,侧向加积形成较宽的河道砂体。长2~2时期延续了长2~3时期的辫状河沉积类型。整体砂体厚度较厚。     

鄂尔多斯盆地华池地区中侏罗统延安组延9油层组河流沉积及演化

据新的地层划分方案及大量钻井、露头和岩心资料,详细研究了鄂尔多斯盆地华池地区延安组延9油层组（Y9）沉积体系特征及演化,认为延9油层组主要为河流沉积,是延10油层组的继承与发展,发育有辫状河、辫状型曲流河和网状河3种类型的河流。Y39油层是辫状河发育的油层,Y29油层在继承Y39油层河流的基础上发育辫状型曲流河,Y19油层则是在前两期逐渐填平补齐之后,在准平原条件下发育的网状河沉积。华池地区延9油层组发育辫状河-辫状型曲流河和网状河两种河流沉积模式。     

琼东南盆地北部新近系三亚组遗迹组构特征及其沉积环境

琼东南盆地北部新近系地层厚度巨大,遗迹化石非常发育。在对7口取心井岩心详细观测的基础上,综合利用薄片分析、成像测井与相关实验等资料,对琼东南盆地北部新近系三亚组遗迹组构特征及其沉积环境进行了研究。结果表明:(1)琼东南盆地北部新近系三亚组共识别出遗迹化石14属,根据遗迹化石的类型、产状、丰度和分异度、扰动程度、生物潜穴之间的共生关系等,可划分出5种遗迹组构,其中OphiomorphaThalassinoides遗迹组构主要发育在临滨上部沉积环境中,Palaeophycus遗迹组构主要发育在临滨中部沉积环境中,Planolites-Thalassinoides遗迹组构主要发育在临滨下部沉积环境中,Phycosiphon-Planolites遗迹组构主要发育在浅海上部沉积环境中,Phycosiphon-Chondrites遗迹组构主要发育在浅海下部沉积环境中;(2)根据遗迹组构和测井相分析认为琼东南盆地北部新近系三亚组沉积环境为滨-浅海,三亚组一段的沉积环境为由滨岸向浅海过渡,而三亚组二段的沉积环境为浅海;(3)综合岩相、生物化石、遗迹组构、测井相和沉积微相分析结果,建立了琼东南盆地北部新...     

中国现代网状河流沉积特征和沉积模式

中国境内的许多河流发育有网状河段,从长江、黑龙江、珠江等这样的大型河流到嫩江、赣江等中小型河流都有。依据这些网状河的地理和构造背景的不同,可以把它们划分为:平原网状河流、山谷网状河流、入湖三角洲平原网状河流和入海三角洲平原网状河流四大类型。作者通过实地挖掘探槽、密集采样,对嫩江齐齐哈尔平原网状河段、赣江入湖三角洲平原网状河段、珠江入海三角洲平原网状河段沉积特征进行了详细描述和研究,并建立了网状河的沉积模式,探讨了网状河的成因。认为网状河流体系的发育不受气候和地理位置的限制,低坡降是形成网状河的必要条件,相对稳定的网状河道不同于曲流河和辫状河,湿地环境是网状河流体系中最发育的地貌单元,堤岸植被繁茂、粘结性高是河道稳定的重要因素,与曲流河和辫状河相比,网状河出现的几率较低。     

大庆油田北部河流相储层沉积微相与水淹特征

大庆油田北部发育砂质辫状河道、曲流河道、高弯度分流河道和低弯度分流河道等砂体类型。以井间可对比的单一河流沉积物为研究单元 ,从河流相储层成因特征入手 ,应用油田开发后期密井网资料开展各类河流砂体细分微相研究。重点阐述了各类砂体的规模、宽厚比、发育的主要微相、物性特征及层内非均质特点。应用不同时期密闭取心检查井资料、测井水淹解释、生产动态测试资料 ,结合不同砂体和微相的非均质特点研究了不同微相的水淹变化特征。研究结果表明 ,不同阶段各类砂体层内及平面水淹变化特征不同 ,高含水后期剩余油主要分布于河间薄层砂、部分决口水道和废弃河道微相中 ,低弯度分流河道砂体中剩余油相对发育     

河型转化研究进展综述

河型研究是河流动力学及河流工程学中的一个基本问题,也是沉积学家判别地下不同成因砂体的一个关键问题。目前河型的分类大都基于河流的平面形态,而这一分类受到了越来越多的质疑,并提出了一些新的分类方案,许多研究者注意到河型并不是离散的,存在一系列连续变化的河型,同时,顺直河、曲流河以及辫状河这些常见的河型之间可能发生突变,河型转化是当前国际河流学界研究的前缘和薄弱环节。本文通过综述河型转化在现代沉积、模拟实验、露头以及地震四个方面的研究进展,认为河型转化主要受到构造作用、沉积物供给、气候条件和海(湖)平面变化四大因素控制,其中前三个因素对于古河型的演化至关重要。在上述因素的影响下,一条河流从上游往下游,往往具有由辫状河→低弯度曲流河→高弯度曲流河→网状河的演化规律。但是河流的位置并不是决定上述变化的主要因素,只要符合条件,即构造作用、沉积物供给及气候等因素发生重大变化的情况下,河型就可能发生转化。然而,河型转化的研究成果尚未引起石油地质学家们的足够重视,并没有被充分的应用到古代河流的解释中去,这将是今后的一个重点研究方向。     

Sedimentological and ichnological signatures of changes in wave,river and tidal influence along a Neogene tropical deltaic shoreline

Analysis of Neogene cores from the Eastern Venezuela Basin along 65 km of a west–east trending shoreline allows characterization of the sedimentological and ichnological signatures of wave, river and tidal processes. The area displays deltas prograding northward from the Guyana Shield. Twenty‐three facies are defined and grouped into four categories (wave‐influenced, river‐influenced, tide‐influenced and basinal). Wave‐dominated deltaic deposits occur mostly in the Tácata Field. The delta plain was characterized by tide‐influenced distributary channels separated by interdistributary bays. Fluvial discharge in the delta front and prodelta was repeatedly interrupted by storm‐wave reworking and suspended sediment fallout. Delta‐front and prodelta deposits contain some ichnotaxa that typically do not occur in brackish water (for example, Chondrites and Phycosiphon). Amalgamated storm deposits are unburrowed or contain vertical Ophiomorpha. Lateral (especially on the updrift side) to the river mouths, waves caused nearly continuous accretion of the associated strandplains. These deposits are the most intensely bioturbated, and are dominated by the estenohaline echinoid‐generated ichnogenus Scolicia. River‐dominated deltaic deposits are present in the Santa Bárbara, Mulata, Carito and El Furrial Fields. Low‐sinuosity rivers characterized the alluvial plain, whereas the subaerial delta plain was occupied by higher‐sinuosity rivers. The subaqueous delta plain includes distributary channels and tide‐influenced interdistributary bays. Further seaward, successions are characterized by terminal distributary‐channel and distributary mouth‐bar deposits, as well as by delta‐front and prodelta deposits showing evidence of sediment gravity‐flow and fluid‐mud emplacement. Delta‐front and prodelta deposits are unbioturbated to sparsely bioturbated, suggesting extreme stress, mostly as a result of high fluvial discharge and generation of sediment gravity flows. Tidal influence is restricted to interdistributary bays, lagoons and some distributary channels. From an ichnological perspective, and in order of decreasing stress levels, four main depositional settings are identified: river‐dominated deltas, tide‐influenced delta plains, wave‐dominated deltas and wave‐dominated strandplain–offshore complexes.     

Conditioning Channel Meanders to Well Observations

Assessment of uncertainty in the performance of fluvial reservoirs often requires the ability to generate realizations of channel sands that are conditional to well observations. For channels with low sinuosity this problem has been effectively solved. When the sinuosity is large, however, the standard stochastic models for fluvial reservoirs are not valid, because the deviation of the channel from a principal direction line is multivalued. In this paper, I show how the method of randomized maximum likelihood can be used to generate conditional realizations of channels with large sinuosity. In one example, a Gaussian random field model is used to generate an unconditional realization of a channel with large sinuosity, and this realization is then conditioned to well observations. Channels generated in the second approach are less realistic, but may be sufficient for modeling reservoir connectivity in a realistic way. In the second example, an unconditional realization of a channel is generated by a complex geologic model with random forcing. It is then adjusted in a meaningful way to honor well observations. The key feature in the solution is the use of channel direction instead of channel deviation as the characteristic random function describing the geometry of the channel.     

Architecture and morphodynamics of a 1·6 Ga fluvial sandstone: Ellice Formation of Elu Basin,Arctic Canada

Precambrian fluvial deposits have been traditionally described as architecturally simple, forming shallow and wide braidplains with sheet‐like geometry. The varied architecture and morphodynamics of the 1·6 Ga Ellice Formation of Elu Basin, Nunavut, Canada, are examined from detailed studies of section and planform exposures along coastal platforms and stepped cliffs. The Ellice Formation overlies older Proterozoic sandstones and Archean crystalline rocks, recording sedimentation in fluvial, aeolian, coastal and nearshore‐marine environments. The fluvial deposits display palaeoflow towards the west/north‐west, while overlying shallow‐marine deposits record transgression towards the east/south‐east. The Ellice Formation displays dispersed palaeoflow at its base, and also at higher stratigraphic levels, where fluvial and aeolian deposits are associated. Elsewhere, mainly unimodal palaeoflow points to extensive low‐sinuosity fluvial deposition. Within the terrestrial deposits, fluvial, fluvial–aeolian and coastal architectural elements are recognized. Fluvial elements comprise cross‐bedded sandstone and minor conglomerate, exhibiting an overall fining‐upward trend with associated decrease in preservation, dimension and amalgamation of channel bodies. These motifs are interpreted to portray a shift in depositional environment from proximal trunk rivers to distal alluvial plains. Low‐sinuosity fluvial elements are the most common, and include major channel bodies, elongate side bars and mid‐channel bars with well‐developed scroll topography. High‐sinuosity channel‐bar complexes exhibit upbar‐flow rotation and yield evidence of bar expansion coupled with rotation and translation. Fluvial–aeolian elements are composed of aeolian dunes juxtaposed with isolated channel bodies and bank‐attached bars. Minor mixed fluvial–aeolian sheets record local deposition in unconfined settings (possibly floodbasins) or inter‐distributary highlands. Finally, coastal elements comprise small deltaic complexes composed of sand‐rich distributary‐channel bodies feeding heterolithic mouth bars. Overall, the sedimentary record of the Ellice Formation demonstrates an example from the Precambrian where alluvium was locally characterized by a higher geomorphic variability than previously recognized.     

Fluvial response to active extension: evidence from 3D seismic data from the Frio Formation (Oligo-Miocene) of the Texas Gulf of Mexico Coast, USA

Tectonic deformation of the land surface is known to influence the gradient, water and sediment discharge and the grain-size of modern fluvial systems. Any change in these variables alters the equilibrium of a fluvial system, potentially causing a change in channel morphology. 3D seismic data from the Tertiary (Miocene) age, Upper Frio Formation, Kelsey Field, South Texas, in the US are used to examine changing fluvial channel morphology through time during a period of active growth of a rollover anticline in the hangingwall of a normal fault (the Vicksburg Fault). The studied interval varies between 22 and 47 m thick, and spans several hundred thousand years. It consists of an alternation of fluvial sandstones, overbank mudstones and coal. Seismic extractions show the evolution of sinuous fluvial channels during a phase of growth fault activity. Prior to growth, a single sinuous channel is imaged. During growth, the fluvial system became decapitated by a developing rollover anticline, and a highly sinuous drainage network formed, with frequent avulsion events, headward propagation of streams and related stream capture. Increased channel sinuosity was spatially associated with increased avulsion frequency in the area down dip to the east of the rollover anticline, more than 10 km from the active fault. More than 25 m of relative accommodation developed on the flank of the growing rollover anticline compared with on the crest. The increased channel sinuosity is interpreted as reflecting an increase in longitudinal valley slope analogous to observations made in flume experiments and modern river systems. The increase in avulsion frequency is attributed to increased aggradation as the rivers adjusted back to equilibrium grade following the increase in slope.