泥石流堆积物的粒度特征及分形结构:以金沙江上游干热河谷区瓦卡泥石流沟为例

以金沙江上游干热河谷区瓦卡泥石流沟为例,引入沉积相的概念,按沉积相特征对泥石流沉积剖面进行地层单元划分。把沉积亚相划为A相粗砾泥石流层、A1相细砾泥石流层和B相表泥层。每层采集3~4个样品,共采集61个样品,并对其粒度特征及分形结构进行分析。结果表明:(1)3种沉积亚相的粒度分布曲线均呈多峰型,反映出泥石流堆积物颗粒组成分选性差的特点。(2)A、A1相为粗、细混杂砾石层堆积,颗粒分布较不均匀,而B相为不含或极少含砾石的亚黏土层沉积,各组分颗粒百分含量分布较均匀。(3)多砾石的A、A1相分形特征较好,分维值区间为2.692 1~2.697 1,相关系数为0.868 2~0.832 2,体现出混杂堆积结构特点;B相分维值为2.900 7,其相关系数为0.43。B相表泥层与A相粗砾泥石流层、A1相细砾泥石流层的粒度分布与分形结构特征很好地反映了泥石流沉积亚相不同类型的沉积环境差异。     

湖北松滋大冶组深水碳酸盐岩沉积

湖北松滋下三叠统大冶组主要为一套深水碳酸盐岩,与下伏上二叠统长兴组灰色中厚层状灰岩呈整合接触,它以深水原地沉积为主,夹有深水异地沉积。深水原地沉积以深灰色薄层泥晶灰岩和页岩互层为主,异地沉积以浊流沉积和碎屑流沉积为主。浊流沉积鲍玛层序C、D、E段发育,以粉屑灰岩、泥晶灰岩为主;碎屑流沉积以泥晶砾屑灰岩为主。其岩相类型有泥晶灰岩(M1)、泥晶粉屑灰岩(M2)、泥晶砾屑灰岩(M3)、泥页岩(C1),可组合为盆地—盆地边缘相(M1+C1)、下斜坡亚相、上斜坡亚相(M1或M1+M3)、开阔台地相(M1+C1)四种组合。从早三叠世早期到晚期,水体逐渐变浅,但总体表现为深水沉积环境。     

海南岛东部阳江红盆的沉积相研究

研究区沉积物自下而上可划分为白垩系鹿母湾组、抱万组、白石岭组，据红盆沉积物的性质、结构及原生沉积构造，将盆内沉积物划分为冲积扇相、瓣状河流相、洪冲积平原相及湖相4种不同的沉积相，河道、片汜、泥石流、泥流、筛积沉积等10种不同的成因类型。盆内沉积作用形成了冲积扇相、瓣状河流相和滨湖相3种不同的沉积体。     

泌阳凹陷东南缘下第三系杂砾岩的沉积学特征

摘要：本文首次对区内杂砾岩（又称红层）的沉积学特征进行研究。据成因之不同,把杂砾岩区分为６类：泥石流、颗粒流、泥流、冲刷砾石层、河道及片流沉积。讨论了各类沉积之特点,尤其是砾石的粒度分布特征。结果表明,不同成因的杂砾岩砾石的粒度分布曲线形态,尤其是量化粒度参数存在明显差异。     

西昆仑山北缘下更新统西域组中上部泥石流沉积 的发现及其意义

报道了在西昆仑山北缘的恰哈、桑株、柯克亚等地的西域组中上部地层中发现数十层泥石流沉积。容重测量表明,泥石流以粘性泥石流为主,典型沉积相组合为AC、AA1C、DAA1BC、AA1BC、AA1B、A1BC,反映泥石流沉积从上游向下游由扇顶向扇缘环境演化,泥石流沉积时代对比为早更新世早中期。青藏高原西北缘西域组中上部泥石流沉积的发现,为分析该区西域组沉积时期的构造背景、地貌条件、气候特征提供了重要的新资料,为研究青藏高原隆升及其引发的地质灾害效应提供了新的证据,对泥石流地质灾害的防治提出了预警。     

贵阳乌当地区奥陶系湄潭组风暴岩特征

贵阳乌当地区奥陶系湄潭组下部的页岩中所夹的一层生物碎屑泥晶灰岩,是一个完整的风暴岩层,整个风暴岩厚约130cm,其沉积序列由下而上分为粒序段A、块段层段B、平行层理段C、丘状交错层理段D、小型沙纹层理段E以及泥岩段F,其A段+B段厚度小于D段+E段,为一下陆棚环境的远积风暴岩.     

川西北地区早志留世风暴岩及其环境与古生态意义

研究区为扬子地块西北缘的一套巨厚页岩、泥岩层,间夹生物礁、生物丘及透镜状和不规则层状风暴生屑灰岩。根据风暴岩的地层分布及岩石学特征,作者将三类不同层位的风暴岩划分为A,B,C,D,E五类:A、B型为近源风暴岩,C、D及E型为远源风暴岩。从A型到E型反映出风暴能量逐渐减弱,水体加深的趋势。由于生物碎屑层形成在泥质陆架上,使生境的底质性质发生变化,造成底栖生物群落从适于泥底生活的内栖生物群落通过埋藏反馈作用转变为表栖固着生物群落,形成众多的礁及丘。一般A型风暴岩是本区礁的基底;B型因其沉积位置较A型深且规模小,仅在少数地方可见其上发育丘₁C型风暴岩之上可见生物层;而D、E型不适于表栖固着生物发育,其上均为泥页岩所覆盖。     

吉木萨尔凹陷二叠统芦草沟组地层与沉积环境特征研究

准噶尔盆地吉木萨尔凹陷芦草沟组是我国近些年致密油气勘探开发的热点地区之一。本文利用岩心、岩石薄片、测井和地震等资料,在识别和分析芦草沟组主要岩石类型的基础上,对芦草沟组的沉积演化特征、层序地层格架和沉积环境的变迁等方面进行了综合研究。研究表明,芦草沟组岩性主要为碎屑岩和碳酸盐岩两个大类,其中碎屑岩以泥页岩和粉（细）砂岩为主,碳酸盐岩主要为白云岩和灰岩。沉积特征表现为：下部（F 段）、中部（C+D段）和上部（A 段）的泥页岩层段,发育于湖进时期的深湖至半深湖相沉积,为烃源岩层段;下部致密储集层段（E 段）和上部致密储集层段（B 段）,发育于湖退期的浅湖相、三角洲前缘相沉积。由于后期的构造隆升,芦草沟组的沉积环境由早期的开阔湖盆逐渐向后期封闭的局限湖盆转变,沉积水体也逐渐向咸化和还原环境转变。     

东濮凹陷古近系沙河街组三段河口湾沉积亚相之沉积学与痕迹学识别与油气储层

沉积学结合痕迹学研究,识别出东濮凹陷古近系沙河街组三段,存在五类河口湾沉积亚相。这五类亚相都含有斜向异源碎屑层理及海相或咸水痕迹化石。现代和古代河口湾研究证明,斜向异源碎屑层理（Inclined Heterolithic Stratification）,是潮汐水流进入河流式河口湾引发波动震荡机制形成的。表现为重复出现,厚在数厘米到数分米的泥/砂对偶层。东濮凹陷文留地区沙河街组三段岩芯研究显示,不同类型的泥/砂对偶层及其所含海相和咸水成因痕迹化石,记录下河口湾上游,受潮汐影响产生水下收缩裂隙和滨岸痕迹化石Diplocraterion的河流成因砂（亚相A）;河口湾中部,因与最大紊流带相关,出现变形层理和痕迹化石Palaeophycos、Planolites和Chondrites的泥质沉积（亚相B、C）;河口湾下游,则显示Terebellina、Rhizocrallium、Ophiomorpha、Diplocraterion等高分异度痕迹化石的海相成因砂（亚相D、E）。文留地区古近纪油田与北美白垩纪油田的研究和勘探开发说明,河流式河口湾油气资源丰富,识别这类古环境,对寻找油气储层,意义重大。     

辽西凌源地区中侏罗统邓杖子组沉积环境探讨

通过对辽西凌源地区牛营子盆地邓杖子组地层剖面测制,结合岩石组合、沉积构造及相序叠置关系等因素分析研究,认为邓杖子组沉积环境为冲积扇相.邓杖子组下部岩性为灰色厚层—巨厚层中—粗粒石灰岩质砾岩,沉积环境为扇根亚相,由筛积物沉积、泥石流沉积组成;中部主要为灰绿色薄层中细粒长石砂岩、细粒钙质砂岩,夹灰色石灰岩质砾岩、含砂质灰岩等,由扇中亚相和扇端亚相组成;上部岩性为灰色中厚层—厚层夹厚层—巨厚层石灰岩质砾岩,沉积环境可识别出扇中亚相和扇根亚相,二亚相均由河道沉积和漫流沉积组成.     

Quaternary sedimentology of the Rose Creek fan delta, Walker Lake, Nevada, USA, and implications to fan-delta facies models

The 3·2 km long Rose Creek fan delta of west‐central Nevada is prograding from an active rift margin into the 32 m deep Walker Lake. A case study of the forms, processes and facies of this fan delta reveals that the proximal and medial zones mainly are of sub‐aerial origin, and the distal zone is of lacustrine origin. Pebbly to bouldery rock‐avalanche mounds >100 m thick (Facies A) and muddy to bouldery debris flow levées 0·5 to 2·0 m thick (Facies B) dominate the proximal zone, whereas mostly matrix‐supported cobbly pebbly debris flow lobes 0·1 to 1·0 m thick (Facies C) typify the medial zone. Surficial pebble lags and gully fills (Facies D) are widespread in both zones but, in exposures, comprise only partings or lenticles between debris flow units. The distal fan delta mainly consists of lakeshore to lake‐bottom tracts formed by extensive wave reworking of debris flow facies. Nearshore deposits include erosional cobbly boulder lag beaches (Facies E), pebbly constructional beaches attached at headcuts or on barrier spits (Facies F), pebbly upper shoreface (Facies G) and sandy lower shoreface (Facies H) tracts positioned lakeward of the beach, and pebbly landward‐dipping foresets (Facies I) and backshore‐pond sand and mud (Facies J) present landward of the spits. Erosional lag beaches fringe the windward north side of the fan‐delta front, attached constructional beaches characterize the central zone, and southward‐elongating barrier spits typify the leeward south side, extending from the zone of greatest projection of the fan delta into the lake. Shoreline facies asymmetry results from largely unidirectional longshore drift caused by high fetch to the north and minimal fetch to the south, combined with the arcuate shape of the fan‐delta front. The spits overlie a platform deposited below common wave base consisting of south‐east‐trending cones of pebbly Gilbert foresets (Facies K) and sandy toesets (Facies L). Typically slumped silt and mud (Facies M) fringe both this platform and lower shoreface sand in deeper water. This case demonstrates facies types and patterns that are inconsistent with the widely promoted fan‐delta facies model having a front consisting of an apron of radially directed Gilbert foresets deposited where sub‐aerial flows enter the lake. The Rose Creek fan‐delta front instead features a sharp contact between sub‐aerial and lakeshore facies formed where waves erode, sort and redistribute heterogeneous debris flow sediment into the various shallow‐to‐deep lake facies. Gilbert foresets are present only in the lee of the fan delta where sediment moving by longshore drift reaches the brink of the spit front. This facies scenario results from the infrequency of fan‐building events versus nearly constant wind‐induced waves, a scenario that, in contrast to the popular Gilbert model, probably is the norm for fan deltas. The level of Walker Lake, and thus the position of wave reworking on the Rose Creek fan delta, fluctuated over a range of ～157 m during the last 18 kyr, producing complex interfingering between sub‐aerial and lakeshore facies across a 1700 m wide radial belt, typifying a wave‐modified, freestand lacustrine fan delta.     

孟加拉扇上扇某区块深水沉积体的特征及演化模式

利用高分辨率三维地震资料分析了孟加拉扇上扇某区块的深水沉积体特征。发现了六种典型地震相:下切充填相、海鸥翼状相、楔形发散相、透明相、强振幅平行相和弱振幅平行相。下切充填相代表粗粒的水道充填沉积;海鸥翼状相代表水道-天然堤复合体;楔形发散相代表细粒的天然堤沉积;透明相代表块体搬运沉积;强振幅平行相代表朵叶体沉积;弱振幅平行相代表深海披覆沉积。通过对典型地震剖面特征和平面属性分布分析可知:上扇垂向上依次沉积了朵叶体、水道和堤岸、朵叶体、水道-天然堤复合体。     

吉林新立油田下白垩统泉头组成岩储集相及储集空间演化

吉林新立油田位于吉林省松原市郭县以北新庙乡境内。综合应用25口取心井薄片、镜质体反射率、铸体、电镜、X衍射等岩心分析资料，研究了泉头组的成岩作用、成岩演化序列、成岩阶段划分及储集空间类型。根据成岩作用及特有的储集空间组合，划分了4种成岩储集相类型，即A相(不稳定组分强溶解次生孔隙成岩储集相)、B相(中等压实弱-中胶结混合孔隙成岩储集相)、C相(强压实中等胶结残余粒间孔成岩储集相)、D相(碳酸盐强胶结微孔隙成岩储集相)；并阐述了各类成岩储集相的特征，其中A相储集物性最好，B相次之，C相较差，D相最差。最后探讨了泉头组储集空间演化，在中成岩阶段A期形成了大量次生溶蚀孔隙，为首次在该区泉头组特低渗储层中预测相对有利的成岩储集相带提供了研究思路和科学依据，也为改善特低渗油田的开发效果奠定了坚实的地质基础。     

Sedimentology of the debris-flow-dominated Warm Spring Canyon alluvial fan, Death Valley, California

Facies analysis of widely distributed exposures of the 32·6 km² and 8·1-km-long Warm Spring Canyon fan, central Death Valley, shows that it has been built principally by debris-flow deposits. These deposits were derived from a mature Panamint Range catchment mostly underlain by Precambrian mudrock, quartzite and dolomite. Stacked, clast-rich and matrix-supported debris-flow lobes of slightly bouldery, muddy, pebble–cobble gravel in beds 20–150 cm thick dominate the fan from apex to toe, accounting for 75–98% of most exposures. Interstratified with the debris flows are less abundant (2–25% of cuts), thinner (5–30 cm) and more discontinuous beds of clast-supported and imbricated, pebble–cobble gravel deposited by overland flows and gully flows. This facies formed by the surficial fine-fraction water winnowing of the debris flows primarily during recessional flood stage of the debris-flow events. Two other facies associations make up a small part of the fan. The incised-channel tract consists of a 250-m-wide clast-supported ribbon of irregularly to thickly bedded, boulder, pebble, cobble gravel nested within debris-flow deposits. This channel fill is oriented generally perpendicular to the Panamint range front. It formed by extensive erosion and winnowing of debris flows deposited within the incised channel, into which all water discharge from the catchment is funnelled. The limited presence of this facies only straddling the present incised channel indicates that this channel overall has maintained a consistent position on the fan except for slight lateral shifts, some caused by strike-slip offset. Fault offset temporarily closed the upper incised channel, causing recessional debris-flow mud to be ponded behind the dam. The other local facies assemblage consists of subrounded to rounded, moderately sorted pebble gravel in low-angle cross-beds that slope both basinwards and fanwards. This gravel was deposited in beachface, backshore and shoreface barrier-spit environments that developed where Lake Manly impinged on the Warm Spring fan during late Pleistocene time. These deposits straddle headcuts into, and were derived from, erosion of the debris-flow deposits. Wave energy sorted finer sediment from the shore zone, concentrated coarser sediment and rounded the coarse to very coarse pebble fraction by selective reworking.     

Depositional features of a late Weichselian outwash fan; central East Jylland,Denmark

Four major sedimentary facies are present in coarse-grained, ice-marginal deposits from central East Jylland, Denmark. Facies A and B are matrix-supported gravels deposited by subaerial sediment gravity flows as mudflows (facies A) and debris flows (facies B). Facies C consists of clast-supported, water-laid gravels and facies D are cross-bedded sand and granules. The facies can be grouped into three facies associations related to the supraglacial and proglacial environments: (1) the flow-till association is made up of alternating beds of remobilized glacial mixton (facies A) and well-sorted cross-bedded sand (facies D); (2) the outwash apron association resembles the sediments of alluvial fans in containing coarse-grained debris-flow deposits (facies B), water-laid gravel deposited by sheet floods (facies C) and cross-bedded sand and granules (facies D) from braided distributaries; (3) the valley sandur association comprises water-laid gravel (facies C) interpreted as sheet bars and longitudinal bars interbedded with cross-bedded sand and granules (facies D) deposited in channels between bars in a braided environment.The general coarsening-upward trend of the sedimentary sequences caused by the transition of bars and channel-dominated facies to debris-flow-dominated facies indicate an increasing proximality of the outwash deposits, picturing the advance and still stand of a large continental lowland ice-sheet. The depositional properties suggest that sedimentation was caused by melting along a relatively steep, active glacier margin as a first step towards the final vanishing of the Late Weichselian icesheet (the East Jylland ice) covering eastern Denmark.     

Sedimentology of an ancient erg margin: the Lower Jurassic Aztec Sandstone, southern Nevada and southern California

The Lower Jurassic Aztec Sandstone is an aeolian-deposited quartzose sandstone that represents the western margin of the southerly-migrating Navajo-Nugget sand sea (or erg). Vertical and lateral facies relations suggest that the erg margin encroached upon volcanic highlands, alluvial fan, wadi and sabkha environments. In southern Nevada, 700 m thick facies successions record the arrival of the Aztec sand sea. Initial erg sedimentation in the Valley of Fire consists of lenticular or tongue-shaped aeolian sand bodies interstratified with fluvially-deposited coarse sandstone and mudstone. Above, evaporite-rich fine sandstone and mudstone are overlain by thick, cross-stratified aeolian sandstone that shows an upsection increase in set thickness. The lithofacies succession represents aeolian sand sheets and small dunes that migrated over a siliciclastic sabkha traversed by ephemeral wadis. These deposits were ultimately buried by large dunes and draas of the erg. In the Spring Mountains, a similar facies succession also contains thin, lenticular volcaniclastic conglomerate and sandstone. These sediments represent the distal margin of an alluvial fan complex sourced from the west. Thin aeolian sequences are interbedded with volcanic flow rocks, ash-flow tuffs, debris flows, and fluvial deposits in the Mojave Desert of southern California. These aeolian strata represent erg migration up the eastern flanks of a magmatic arc. The westward diminution of aeolian-deposited units may reflect incomplete erg migration, thin accumulation of aeolian sediment succeptible to erosion, and stratigraphic dilution by arc-derived sediment. A two-part division of the Aztec erg is suggested by lithofacies associations, the size and geometry of aeolian cross-strata, and sediment dispersal data. The leading or downwind margin of the erg, here termed the fore-erg, is represented by a 10–100 m thick succession of isolated pods, lenses, and tongues of aeolian-deposited sediment encased in fluvial and sabkha deposits. Continued sand-sea migration brought large dunes and draas of the erg interior into the study area; these 150–500 m thick central-erg sediments buried the fore-erg deposits. The trailing, upwind margin of the erg is represented by back-erg deposits in northern Utah and Wyoming.     

Can liquefied debris flows deposit clean sand over large areas of sea floor? Field evidence from the Marnoso‐arenacea Formation,Italian Apennines

The Marnoso‐arenacea Formation in the Italian Apennines is the only ancient rock sequence where individual submarine sediment density flow deposits have been mapped out in detail for over 100 km. Bed correlations provide new insight into how submarine flows deposit sand, because bed architecture and sandstone shape provide an independent test of depositional process models. This test is important because it can be difficult or impossible to infer depositional process unambiguously from characteristics seen at just one outcrop, especially for massive clean‐sandstone intervals whose origin has been controversial. Beds have three different types of geometries (facies tracts) in downflow oriented transects. Facies tracts 1 and 2 contain clean graded and ungraded massive sandstone deposited incrementally by turbidity currents, and these intervals taper relatively gradually downflow. Mud‐rich sand deposited by cohesive debris flow occurs in the distal part of Facies tract 2. Facies tract 3 contains clean sandstone with a distinctive swirly fabric formed by patches of coarser and better‐sorted grains that most likely records pervasive liquefaction. This type of clean sandstone can extend for up to 30 km before pinching out relatively abruptly. This abrupt pinch out suggests that this clean sand was deposited by debris flow. In some beds there are downflow transitions from turbidite sandstone into clean debrite sandstone, suggesting that debris flows formed by transformation from high‐density turbidity currents. However, outsize clasts in one particular debrite are too large and dense to have been carried by an initial turbidity current, suggesting that this debris flow ran out for at least 15 km. Field data indicate that liquefied debris flows can sometimes deposit clean sand over large (10 to 30 km) expanses of sea floor, and that these clean debrite sand layers can terminate abruptly.     

Pleistocene fluvial sediments,palaeontology and archaeology of the upper River Thames at Latton,Wiltshire, England

Pleistocene fluvial sediments of the Northmoor Member of the Upper Thames Formation exposed at Latton, Wiltshire, record episodic deposition close to the Churn–Thames confluence possibly spanning the interval from Marine Isotope Stages (MIS) 7 to 2. The sequence is dominated by gravel facies, indicating deposition by a high‐energy, gravel‐bed river. A number of fine‐grained organic sediment bodies within the sequence have yielded palaeoenvironmental and biostratigraphical data from Mollusca, Coleoptera, vertebrates, pollen and plant macrofossils. The basal deposit (Facies Association A) contains faunal material indicating temperate conditions. Most of the palaeontological evidence including a distinctive small form of mammoth (Mammuthus cf. trogontherii), together with the U‐series age estimate of >147.4 ± 20 kyr suggest correlation with MIS 7. The overlying deposits (Facies Associations B and C) represent deposition under a range of climatic conditions. Two fine‐grained organic deposits occurred within Association B; one (Association Ba) in the northern part of the pit as a channel fill and the other (Association Bb) in its southern part as a scour‐fill deposit. The coleopteran assemblages from Ba, indicate that it accumulated under temperate oceanic conditions, while Bb, which also yielded a radiocarbon age estimate of 39 560 ± 780 ¹⁴C yr BP, was formed under much colder and more continental climatic conditions. The sequence is considered to represent deposition within an alluvial fan formed at the Churn–Thames confluence; a depositional scenario which may account for the juxtaposition of sediments and fossils of widely differing age within the same altitudinal range. Copyright © 2006 John Wiley & Sons, Ltd.     

Tectono sedimentary evolution of the Umm Ghaddah Formation (late Ediacaran-early Cambrian) in Jordan

The terrestrial Umm Ghaddah Formation of late Ediacaran-early Cambrian age was deposited in NE–SW elongated intracontinental rift system basins and sub-basins bounded by active listric half-graben faults. Basin fill consists of conglomerate facies association A, deposited in a fault-controlled transverse alluvial fan system that drained northwestward and graded laterally into sandstone facies association B, deposited by a braided river system flowing northeastward axial to the rift basin. The alluvial fan facies association was deposited by rock falls and non-cohesive debris flows of sediment gravity flow origin, and by sheetflood processes.The Umm Ghaddah Formation is dominated by a large-scale fining upward succession interpreted to reflect a gradual cessation of the Pan African Orogeny. Within this large-scale trend there are also minor fining and coarsening upward cycles that are attributed to repeated minor tectonic pulses and autocyclic shifting of the system.The distribution pattern of the Umm Ghaddah Formation and the underlying Ediacaran Sarmuj Conglomerates, Hiyala Volcaniclastics and Aheimir Volcanics in Jordan and adjacent countries in isolated extensional half-grabens and grabens formed during the extensional collapse phase of Arabia associated with the Najd Fault System seems to be unrelated to the present day Wadi Araba-Dead Sea transform fault system.