东营凹陷滑塌型重力流沉积分布特征及三角洲沉积对其影响

三角洲沉积为滑塌型重力流的形成提供了物质来源,它对前端滑塌型重力流的沉积分布特征具有重要影响.以东营凹陷洼陷带沙三中亚段三角洲-前端滑塌型重力流沉积为研究对象,综合利用钻井岩心、三维地震、测录井及分析测试等资料,总结不同类型滑塌型重力流沉积特征、识别标志和分布特征,分析三角洲作为物源对滑塌型重力流的形成、沉积类型、沉积特征和分布特征的影响.研究表明,研究区滑塌型重力流沉积主要发育滑动岩、滑塌岩、碎屑流沉积和浊积岩4种类型,不同类型其沉积构造、粒度特征、地球物理特征差异显著.研究区砂质碎屑流沉积最为发育,滑动滑塌沉积次之,浊流沉积和泥质碎屑流沉积少量发育.不同地区重力流沉积发育程度及常见垂向序列存在差异,博兴南坡与辛133区块重力流类型以砂质碎屑流沉积为主,常见多期次砂质碎屑流沉积相邻或相间垂向组合;牛庄南坡与中央隆起带地区类似,由近及远,重力流类型及垂向序列存在较大差异;营11区块以砂质碎屑流沉积和浊流沉积为主,浊流比例相对其他区块较高;丰14区块单井重力流类型整体较单一,为砂质碎屑流沉积或滑塌沉积.三角洲砂泥百分含量控制了滑塌型重力流的沉积类型和沉积特征;三角洲沉积物粒径控制原始前积角大小,前积角越大,滑塌型重力流越发育,但滑移距离相对越近;三角洲的坡折点控制下,滑动滑塌沉积主要分布在斜坡坡脚和同沉积断层附近,浊流沉积主要分布在深水平原,碎屑流沉积在斜坡坡脚-深水平原均有分布;三角洲高的堆积速率通过减小内摩擦力促使滑塌型重力流的形成,其堆积速率与构造沉降速率的差异对滑塌型重力流沉积的垂向叠置和侧向连续性也具有重要影响.      

渤中25-1油田沙三段重力流沉积模式及油气地质意义

运用最新重力流沉积理论,以钻井岩芯、地震资料为基础,系统研究了渤海海域渤中25-1油田沙三段重力流沉积特征、类型、岩相组合、砂体空间展布特征以及沉积模式。结果表明,研究区主要发育滑塌重力流、砂质碎屑流、浊流3种重力流沉积类型,并构成5种典型的岩相组合,包括湖相细粒沉积与滑塌重力流组合（MS）、砂质碎屑流与滑塌重力流组合（DS）、砂质碎屑流与浊流组合（DT）、浊流与砂质碎屑流组合（TD）、湖相细粒沉积与浊流组合（MT）。研究区重力流沉积具有"源-坡-断-流"联控的"滑塌-砂质碎屑流-浊流"沉积过程与发育模式,其中砂质碎屑流砂体呈舌状体分布,浊流砂体则具有朵状体形态特征。储层综合评价表明,砂质碎屑流砂体粒度粗、宽厚比小、泥质含量低、物性好,是优质的重力流储层类型。对不同重力流类型沉积特征、展布形态以及储层性质的精细研究,对深水优质砂岩储层的预测具有重要的指导意义。     

鄂尔多斯盆地南部三叠系延长组深水重力流沉积特征及其石油地质意义

通过大量岩心观察、钻测井资料分析及野外露头观察,对鄂尔多斯盆地南部延长组长6—长7深水重力流沉积特征、触发机制、沉积过程、沉积模式及石油地质意义进行了系统分析。研究结果表明:研究区共存在滑动岩体、滑塌沉积、砂质碎屑流沉积、浊流沉积及泥质碎屑流沉积5种类型的重力流沉积物,各类型的沉积物特征明显。不同类型重力流沉积物垂向组合可分为5类,研究区重力流的形成过程可分为5个阶段:三角洲前缘沉积阶段、滑动阶段、滑塌变形阶段、砂质碎屑流及泥质碎屑流形成阶段以及浊流形成阶段。滑动、滑塌砂体多呈孤立透镜体状,砂质碎屑流砂体多以扇沟道的形式展现出来,浊流砂体多分布在扇沟道的前端或侧翼,呈席状砂展布。深水重力流砂体垂向叠置厚度大,可形成规模大的油藏,大大扩展了深湖的勘探范围。研究区长6、长7油层组砂质碎屑流砂体储集层物性较好,含油性好,是重点勘探层位。     

鄂尔多斯盆地南部三叠系延长组深水重力流沉积特征及其石油地质意义*

通过大量岩心观察、钻测井资料分析及野外露头观察,对鄂尔多斯盆地南部延长组长6—长7深水重力流沉积特征、触发机制、沉积过程、沉积模式及石油地质意义进行了系统分析。研究结果表明:研究区共存在滑动岩体、滑塌沉积、砂质碎屑流沉积、浊流沉积及泥质碎屑流沉积5种类型的重力流沉积物,各类型的沉积物特征明显。不同类型重力流沉积物垂向组合可分为5类,研究区重力流的形成过程可分为5个阶段:三角洲前缘沉积阶段、滑动阶段、滑塌变形阶段、砂质碎屑流及泥质碎屑流形成阶段以及浊流形成阶段。滑动、滑塌砂体多呈孤立透镜体状,砂质碎屑流砂体多以扇沟道的形式展现出来,浊流砂体多分布在扇沟道的前端或侧翼,呈席状砂展布。深水重力流砂体垂向叠置厚度大,可形成规模大的油藏,大大扩展了深湖的勘探范围。研究区长6、长7油层组砂质碎屑流砂体储集层物性较好,含油性好,是重点勘探层位。     

晚三叠世鄂尔多斯盆地湖盆沉积中心厚层砂体特征及形成机制分析

晚三叠世延长组长6、长7油层组沉积期鄂尔多斯盆地湖盆中部深水区稳定发育厚层砂岩,局部地区连续厚度可达上百米。在盆地西南沉积体系,巨型砂带北西—南东向平行于相带界线展布,与三角洲前缘砂体呈现出“断根”的现象;在东北沉积体系,砂带围绕三角洲呈群状、带状分布。厚层砂体成因复杂,总体上可称作深水重力流—牵引流沉积复合体,包括滑塌砂体、砂质碎屑流砂体、浊积砂体、三角洲砂体及底流改造砂体5种成因类型,其中以重力流沉积组合为主,但白豹及其北部主要为三角洲沉积夹重力流沉积。不同成因的砂体纵向叠加,横向复合连片形成了稳定分布、规模宏大的砂带。厚层砂体的形成、展布方向、分布范围主要受控于沉积物的供给速率、湖盆底形及构造活动等因素。     

珠江口盆地惠州地区新生界珠海组和珠江组重力流沉积特征*

通过2口井的岩心观察,在珠江口盆地惠州地区新生界珠海组和珠江组,发现有重力流沉积。该地区重力流沉积的主要特征是：滑塌构造发育广泛,是本区最主要的重力流沉积;液化沉积中泄水构造发育;浊流沉积中鲍马序列不完整。惠州地区的重力流沉积是三角洲前缘砂体垮塌再搬运沉积而形成的。在重力流沉积中还发现有潮汐作用的存在,潮汐作用和重力流沉积伴生。通过对惠州地区重力流沉积特征的研究,认为不能简单地将重力流沉积等同于浊流沉积;重力流沉积不仅局限在深水地区,在相对浅水地区也会发育。建议正确理解鲍马序列并予以合理使用。     

川北下寒武统仙女洞组台缘斜坡碳酸盐岩重力流沉积

基于重力流剖面的野外观察、露头解剖及镜下鉴定等分析手段,对四川盆地北部下寒武统仙女洞组台缘斜坡碳酸盐 岩重力流沉积及发育机制进行了研究。研究区位于仙女洞组,主要沉积粉砂质泥岩、生屑泥晶灰岩、藻灰岩等3种岩石类 型;根据层面上产出形态的不同,将该区碳酸盐岩重力流沉积分为似瘤状碳酸盐岩重力流沉积和角砾型碳酸盐岩重力流沉 积2类。结合露头区重力流沉积物粒度及岩性变化,将碳酸盐岩重力流沉积由下至上划分出5个发育期次,期次内部重力流 沉积物由细变粗,纵向上呈现出明显的叠置关系,与仙女洞组时期所经历的海退环境大致吻合。地震、风暴浪等触发机制 导致台缘斜坡上部松散沉积的灰泥丘块体发生破碎并沿斜坡发生滑塌,伴随水体注入,大块砾石在沉积物-水体混合的环 境中发生破碎搅动,形成大小不等的块体,深水底流等作用对未固结或弱固结的砾屑灰岩进行溶蚀、改造,最终形成了层 面形态特征不同的2类似瘤状碳酸盐岩重力流沉积。角砾型碳酸盐岩重力流沉积则主要是未破碎的巨型灰泥丘块体经搬运 和短距离滑塌,最终与似瘤状砾屑灰岩共同沉积而成。     

鄂尔多斯盆地西南部延长组6段重力流沉积特征及其油气地质意义

鄂尔多斯盆地南部延长组长6油层组中发现大量块状无层理砂岩,属陡坡带处堆积的三角洲前缘沉积物沿斜坡滑塌形成的重力流沉积。综合岩芯、露头、测井及分析化验资料,认为延长组发育滑塌岩、液化沉积物流、砂质碎屑流和经典浊流等多种类型的重力流,不同类型重力流沉积特征差异明显;其中地形坡度、物源供给和一定的触发机制是形成长6重力流沉积的基本条件;在流动过程中由于水的混入和沉积物卸载,重力流沉积物发生浓度变化和流态转换,形成滑塌岩-砂质碎屑流、砂质碎屑流-浊流、浊流等不同组合类型;重力流砂岩延伸至半深湖-深湖相泥岩中,与长7烃源岩侧向连通,形成有利的成藏组合,是研究区延长组重要的勘探目标区。     

重力流主导的深水沉积特征及其模式——以共和盆地下三叠统为例

深水沉积具有良好的油气勘探前景,近年来已成为沉积学研究的前缘和油气工业界关注的焦点。以共和盆地下三叠统为例,通过野外剖面的详细观察描述,结合室内镜下薄片鉴定与粒度分析,对深水沉积类型、沉积特征、垂向组合、成因机制以及沉积模式进行系统研究。共和盆地早三叠世深水沉积类型主要有滑塌型深水重力流沉积、底流沉积以及深水悬浮沉积,其中滑塌型深水重力流沉积又可识别出滑塌沉积、砂质碎屑流沉积与浊流沉积三种类型。滑塌沉积常见以同沉积褶皱为代表的多种软沉积物变形构造;砂质碎屑流沉积以块状砂岩为主,内部可见砂质团块、泥砾或泥质撕裂屑,块状砂岩顶底与相邻岩层均为突变接触;浊流沉积普遍发育正粒序,可见不完整的鲍马序列,底面常见多种类型的底模构造;底流沉积发育多种牵引流沉积构造。研究区软沉积物变形构造类型丰富,其中滑塌层内的软沉积物变形构造主要在斜坡滑塌过程中形成;未发生滑塌层内的软沉积物变形构造主要因地震使沉积物发生液化作用及流体化作用而形成。在综合分析盆地构造背景、深水沉积分布规律、重力流触发机制的基础上,建立了共和盆地早三叠世滑塌型重力流主导的深水沉积模式。滑塌型重力流主要由地震以及火山事件触发,水道化的地区会形成大面积的海底扇沉积体系。底流作为深水环境中不可忽视的动力因素,往往会对重力流沉积进行后期改造而使其物性变好。深水悬浮沉积作为一种背景沉积,在重力流事件的间歇期成为主要的深水沉积物。研究显示内扇、中扇可作为致密砂岩油气的勘探区,外扇可进行页岩油气勘探。     

滑塌堆积在逆冲构造中的作用——以宁夏牛首山中奥陶统米钵山组为例

宁夏中南部发育的中奥陶统米钵山组中普遍发育着滑塌堆积。综合米钵山组内滑塌堆积的沉积及后期的变形特征,我们认为滑塌堆积在逆冲变形中起着重要的作用,在逆冲构造中滑脱层的发育往往和岩性有关,滑塌堆积也是一种重要而潜在的滑脱层,不仅由于大尺度上其显著的横向不均匀性,中小尺度上其内部也表现出不均一性,因此它的存在使得应力得以在该层集中,变形因此也主要发生在该层中,从而产生滑脱层,而滑塌堆积的围岩变形则很微弱。结合宁夏中宁中南部地区强烈的逆冲推覆作用,我们认为中奥陶统中的滑塌堆积是该区逆冲推覆构造的重要滑脱层,这些滑脱层控制着该地区下古生界的变形。由于这种构造作用的叠加,先前的那些外来岩块逐渐“细粒化”,逆冲作用使得滑脱堆积中的砾石变形成为构造透镜体,这解决了该地区长期存在的有关这些砾石或透镜体是外来体还是本地的争论。我们的研究表明,在宁夏地区中奥陶统中大部分以外来体为主,但也有一定的本地岩层因构造作用成为透镜体,因此在不同地区应该仔细分析。由于牛首山地区逆冲构造比较发育,滑塌堆积转化成广义上的混杂堆积,而同样有滑塌堆积产出的贺兰山地区由于远离祁连山造山带,滑塌堆积得以保存,其中的砾石基本上没有变形。宁夏地区中奥陶统中的滑塌堆积从区域上为我们提供了一个区别滑塌堆积与混杂堆积的例子。     

Ore-Clastic Olistostromes, Ore Clasts, and Allochthonous Antimony–Mercury Deposits in the Alay Range, Southern Tien Shan

Based on the detailed study of outcrops, two generations of ore clasts were recognized in clastic haloes around allochthonous antimony–mercury deposits: (1) early generation composed of in situ fragments of older autochthonous deposits (ore clasts) and (2) late generation of fragments related to the destruction of ore-bearing allochthons and found as exotic inclusions in flysch and olistostromes. Ore clasts reside in the terrigenous (pre-flysch) sequence that makes up the upper part of terrigenous–carbonate nappes and olistoplaques in the lower flysch–olistostrome sequence. Thus, they belong to allochthonous units. The terrigenous sequence differs from the younger flysch sediments by a relatively small thickness, predominantly clayey composition, and absence of rhythmic bedding and large erratic blocks. It is also characterized by the synsedimentary volcanic activity with the eruption of intermediate and acid igneous rocks, silicification, and ore mineralization in the lower part of the sequence, the maximal mineralization being confined to the boundary with underlying limestones. Relative to the terrigenous sequence the flysch–olistostrome sequence, which hosts ore-bearing allochthons, is distinguished by the primary attitude, greater abundance of ore clasts, and higher extent of ore disintegration. Some genetic features of autochthonous and allochtonous jasperoid deposits are considered. Their differences in age, host environment, formation depth, vertical extent of ore deposition, and zoning are also outlined.     

The Gramscatho Basin, south Cornwall, UK: Devonian active margin successions

Deep marine deposits of the Gramscatho Basin of south Cornwall reflect two tectonic regimes; Early to Middle Devonian rifting of continental lithosphere with formation of oceanic lithosphere to the south, and Middle Devonian to earliest Carboniferous convergence along its southern margin. Sediments on thinned continental crust to the north and oceanic lithosphere to the south were juxtaposed in the Late Devonian when nappes of deep water flysch and olistostrome were thrust up on to the northern continental margin of the basin. Basin closure was accommodated by forward propagating thrust nappes, accompanied by penecontemporaneous sedimentation. The stratigraphical sequences of major nappes illustrate the progradation of flysch with climactic sedimentation of olistostrome in late Mid- to Late Devonian times. The Lizard Complex, including the Lizard ophiolite, within that nappe stack, constitutes part of one of the GCR sites which are largely in the allochthonous rocks. Many of those sites feature the olistostrome, Roseland Breccia Formation, with its great variety of sedimentary, igneous and metamorphic clasts (up to 1.5 km), and the association of ocean floor basalt and penecontemporaneous acidic volcanics indicative of the coming together of oceanic and continental plates. A site at the top of the parautochthonous continental margin succession displays the erosion products of the youngest nappe as it emerged and advanced across the sediment surface, marking closure of the oceanised Gramscatho Basin and continental collision.     

白云鄂博群哈拉霍疙特组滑塌堆积的 发现及其地质意义

笔者等在白云鄂博矿田北西部查干楚鲁附近白云鄂博群哈拉霍疙特组上段发现了典型的滑塌堆积。重点研究了同一滑塌层位中的两个滑塌堆积露头。整个滑塌堆积层岩性单一,内部结构杂乱,不见原始沉积层理。根据野外观察和室内薄片鉴定结果,该处岩性主要有两种：形状不一、大小混杂的灰黄色白云岩岩块（滑积岩块）杂乱无序地分布在深灰色纹层状碳质微晶灰岩（本地沉积）中。最大的透镜状白云岩滑积岩块露头长27m,宽58m。深灰色纹层状碳质微晶灰岩岩层产状基本稳定,整体北倾,倾角较大。深灰色灰岩层与灰黄色白云岩的接触界面附近发育软沉积物变形构造,白云岩滑积岩块本身棱角不明显,两端有明显的细颈拉长现象,表明滑塌发生时,白云岩处于半固结和不完全成岩状态。滑积岩块位于不同的背景沉积层位中,揭示露头区存在多次的滑塌堆积事件。根据滑塌堆积的内部结构特征,初步判断其为被动大陆边缘靠近多岛洋或碳酸盐台地的深水盆地边缘,主要触发因素可能为地震活动。此外,白云鄂博群中滑塌岩块的发现表明白云鄂博群与腮林忽洞群沉积时具有相似的构造、古地理环境,这为白云鄂博群与腮林忽洞群相当（均为早古生代）提供了新的佐证。     

Franciscan Complex olistostrome at Crescent City, northern California

An olistostrome and bounding turbidites are exposed within the late Mesozoic Franciscan Complex along the Crescent City (California) coastline. Facies grade in character from Mutti & Ricci Lucchi (1978) mixed facies B, C and D, to F (the olistostrome), to mixed A, B and E, progressing upwards within the Franciscan stratigraphic section. The facies F unit outcrop is up to 600 m thick and extends 12 km along strike. It consists of oblate to tabular blocks, up to 200 m in maximum dimension, of greenstone, tonalite, radiolarian chert, limestone, phyllite and greywacke dispersed in a scaly argillite matrix. The olistostromal origin of the unit is indicated by depositional contacts with bounding turbidites, by the presence of abundant recycled sedimentary clasts within the unit, and by the presence of sedimentary breccias and associated dismembered, slump-folded turbidites both within the olistostrome and among subjacent turbidites. Sandstones are chiefly feldspathic litharenites that were very likely derived from the partially dissected, late Mesozoic Sierran-Klamath magmatic are. Franciscan rocks record an early pervasive, layer-parallel flattening strain in such features as extensional faults, necking and pinch-and-swell structures. Several scales of extensional faulting account for the juxtaposition of turbidites of different facies and/or with varying degrees of stratal disruption, the formation of sandstone lozenges, and the formation of scaly foliation in the olistostrome matrix. The latter resulted from the juxtaposition of lenticles with varying concentrations of silt and clay. These were ultimately derived from the finer divisions of turbidite beds that were incorporated into the olistostrome. The presence of gradational contacts between some sandstone olistoliths and the olistostrome matrix, and of sandstone dykes that intrude fractures and associated drag-folded turbidite beds indicate that Franciscan sediments were not lithified during their early deformation. These sediments were deposited in either a trench or trench slope basin, and were first deformed either by gravity collapse of the trench slope cover or, less likely, by vertical loading beneath the toe of the accretionary wedge. They later were folded during internal shortening of the growing Franciscan accretionary prism.     

The Casanova Complex of the Northern Apennines: A mélange formed on a distal passive continental margin

The Cretaceous-Palaeocene Casanova Complex occurs in two thrust sheets of the eugeosynclinal Ligurids of the Northern Apennines. It is a sedimentary mélange with ophiolitic and quartzose turbidites or limestone-shale olistostrome (submarine debris flows) as matrix. Exotic blocks of ophiolite and granite, serpentinite breccias and lenticular ophiolitic breccias and olistostromes contribute to the mélange character of the complex. Deformational structures include soft-sediment slump folds (indicating a SW-dipping palaeoslope) and boudins, a gradational slumped top to the mélange, small-scale faults in chert blocks and deformation associated with the emplacement of the exotic slide blocks. The blocks were shed as rotational slides from submarine fault scarps and are surrounded by haloes of debris created by submarine weathering. The stacking pattern of the blocks, with the originally stratigraphically highest ophiolite lithologies lowest in the pile of blocks, is explained by a diverticulation model with progressively deeper erosion. Mechanical analysis shows that the blocks were stable when partly exposed resting on a soft sediment substratum. Criteria which distinguish the Casanova Complex from a tectonic mélange, and which may be of value in other mélanges, are discussed. Previous interpretations of the complex as a precursor olistostrome to northeastward nappe emplacement (the Bracco ridge model) are rejected. The mélange is believed to have formed on ocean crust as a result of turbidite and debris flow sedimentation, soft sediment deformation, block faulting, gravity sliding and submarine erosion at the distal edge of a uniformly SW-dipping continental margin.     

利用陆面岩石中生成的宇生同位素重建冰川漂砾运动历史的尝试

冰川漂砾的形成年代通常难以直接测定，并且漂砾形成以后是否被再次搬运或者移动过，更是无法知道。本文研究发现，通过测试砾石不同部位的宇生同位素，不仅可以测定砾石形成的时代，而且可以确定砾石再次被搬运或者被翻转的年代，从而恢复砾石运动的历史。本文以石英中生成的宇生同位素^10Be，对青藏高原东南部海子山的冰川漂砾进行了探讨，结果表明该砾石形成于倒数第二次冰期(186～128ka BP之间)，在末次冰期中再次被冰川搬运，使之反转。该方法不局限于^10Be和冰川漂砾，也适用于其他陆面岩石中生成的宇生同位素以及其他成因的石块或者砾石。因此为探讨冰川作用、泥石流活动、重力崩塌等过程提供了一种重要的方法和技术途径。     

Ordovician volcanic and plutonic complexes of the Sakmara allochthon in the southern Urals

The Ordovician terrigenous, volcanic–sedimentary and volcanic sequences that formed in rifts of the active continental margin and igneous complexes of intraoceanic suprasubduction settings structurally related to ophiolites are closely spaced in allochthons of the Sakmara Zone in the southern Urals. The stratigraphic relationships of the Ordovician sequences have been established. Their age and facies features have been specified on the basis of biostratigraphic and geochronological data. The gabbro–tonalite–trondhjemite complex and the basalt–andesite–rhyolite sequence with massive sulfide mineralization make up a volcanic–plutonic association. These rock complexes vary in age from Late Ordovician to Early Silurian in certain structural units of the Sakmara Allochthon and to the east in the southern Urals. The proposed geodynamic model for the Ordovician in Paleozoides of the southern Urals reconstructs the active continental margin, whose complexes formed under extension settings, and the intraoceanic suprasubduction structures. The intraoceanic complexes display the evolution of a volcanic arc, back-, or interarc trough.     

Debris flow (olistostromes) and slumping on a distal passive continental margin: the Palombini limestone–shale sequence of the northern Apennines

An olistostrome accumulation up to 530 m thick occurs in the Casanova area of the northern Apennines. It lies within or above the calciturbiditic Palombini limestone-shale sequence, and is part of the allochthonous Vara Complex—sediments originally deposited on oceanic crust. The olistostromes are poorly sorted, monomict, matrix-supported, submarine debris flow deposits with rigid plugs. They have a compactional foliation and a compaction-modified, planar clast fabric created during flow. Although diachronous in the main part of the area, the olistostromes have a vertical gradational contact with the overlying slumped Palombini, in which recumbent asymmetric fold hinges and trains and slump boudins are present. Many criteria indicate soft-sediment deformation. Fold asymmetry indicates a uniformly SW-dipping palaeoslope. The textural gradation from slumps to olistostrome beds, plus slump folds and boudins as olistostrome clasts show that the olistostromes are dismembered slumps. In vertical sections, variations in limestone petrography, volume percentage and size of clasts confirm that the olistostromes were derived from the Palombini as a series of bed-by-bed slumps keeping pace with sedimentation of the Palombini. From olistostrome clast sizes and bed thicknesses, a depositional slope of ～ 4° is estimated. The olistostromes are not precursor sediments shed from advancing nappes, as in the Bracco ridge model of some authors; rather, they were formed at the foot of a distal, block-faulted passive continental margin, long before nappe emplacement.     

Geodynamics of ophiolites and formation of hydrocarbon fields on the shelf of eastern Sakhalin

A model is proposed showing the formation of hydrocarbon fields on the shelf of eastern Sakhalin as being caused by sustained (from the Late Cretaceous to the present) extension in the adjacent deepwater Deryugin Basin with exposure of the upper mantle rocks at the bottom of the sedimentary basin. The thrust faults and detachments formed through this process facilitated the penetration of seawater into ultramafic rocks, thus providing large-scale serpentinization accompanied by generation of hydrocarbons. Extension in the Deryugin Basin was compensated by horizontal shortening at its margins, and as a result, by the formation of ophiolitic allochthons as constituents of the accretionary prism of eastern Sakhalin. Hydrocarbons were injected and pumped in the root zones of the allochthons, giving rise to their westward migration and the formation of petroleum pools in fault-line and underthrust traps on the shelf of Sakhalin Island. The Deryugin Basin is a petroleum-collecting area for oil and gas fields localized in the upper part of its western margin. More broadly, the work considers interrelations between hydrocarbon generation and the geodynamics of tectonic couples of ophiolitic allochthons and adjacent deepwater basins of marginal seas, in particular, in the western Pacific.     

Correlation of Neopleistocene tills in the northern Russian plain: Evidence from petrography of the coarse-clastic material

The petrographic composition of boulder–pebble material from numerous till sections of the Timan–Pechora–Vychegda region was scrutinized to establish locations of glacial provenances and pathways of the terrigenous material transport during different Neopleistocene glaciations. Analysis of a great body of factual materials confirmed high feasibility of the application of petrographic data on the coarse-clastic material and the ratio of distal and proximal components in tills for their subdivision and correlation. The most reliable and regionally consistent criteria are represented by index boulders and orientation of elongated rock clasts, as well as isotope datings of rock clasts in till horizons.