Sedimentology of the Old Red Sandstone (Siluro-Devonian) in the Clee Hills area,Shropshire, England

The sequence of approximately 1300 m is divided by a major unconformity (Middle Devonian) into the thick Lower Old Red Sandstone (Siluro-Devonian), resting disconformably on Ludlovian (Silurian) marine strata, and the much thinner Upper Old Red Sandstone (Upper Devonian) overlain by the Carboniferous.The Lower Old Red Sandstone commences with littoral sediments (Downton Castle Formation) followed by tidal mud-flat deposits (Temeside Formation) formed after a brief marine transgression. The predominant remainder of the sequence (Ledbury Formation, Ditton Group, Abdon Group, Woodbank Group), characterized by fining-upwards cyclothems, records the establishment during a marine regression of extensive and persistent alluvial plains. Prior to Ditton Group times, detritus came from relatively distant regionally metamorphosed rocks lying to the north or west of the Clee Hills. Subsequently, apparently as the result of river-capture or drainage-reversal consequent on the commencement of the final (mid-Devonian) phase of Caledonian movement, high-level crustal rocks closer at hand (largely Wales) replaced the metamorphics as the sources of sediment, the earlier Lower Old Red Sandstone itself being recycled. To judge from the calcretes preserved in the alluvial formations, the area lay near the Equator and experienced a relatively dry hot climate.The Upper Old Red Sandstone likewise reveals fining-upwards cyclothems. The overlying Carboniferous rocks evidence the renewed marine transgression of the area, after the removal of the effects of the mid-Devonian movements.     

地震沉积学在滨南浊积砂岩区的研究及应用

运用地震沉积学的理论,使用90°相位转换和地层切片等关键技术,结合钻测井资料,对滨南地区滨682井区古近纪沙河街组3个层序的砂体分布特征和沉积体系进行了精细研究。结果表明,该区东部和东南部浊积砂体较为发育。层序I早期浊积砂体分布面积较大,中期和晚期面积较小;层序Ⅱ早期和晚期浊积砂体分布范围较大,中期很小;层序Ⅲ主要分布在南部地区。证明该方法不但简单,而且减少了穿时问题,适合楔形沉积层序的分析研究。     

Sedimentology and depositional environments of the Maastrichtian Patti Formation, southeastern Bida Basin, Nigeria

The Maastrichtian Patti Formation, which consists of shale - claystone and sandstone members, constitutes one of the three Upper Cretaceous lithostratigraphic units of the intracratonic southeastern Bida Basin, in central Nigeria. Well exposed outcrops of this formation were investigated at various locations around the confluence of the Niger and Benue Rivers. The lithostratigraphic sections were measured and their peculiar sedimentological features such as textures, physical and biogenic sedimentary structures, facies variations and associations were documented and used to interpret the depositional environments and develop a paleogeographic model. Some selected representative samples of the sedimentary depositional facies were also subjected to grain size analysis.Three shoreline sedimentary depositional facies composed of shoreface, tidal channel, and tidal marsh to coastal swamp facies were recognized in the study area. Continental sedimentary depositional facies such as fluvial channel, swamp, and overbank were also documented. The sandstones of the shoreface and tidal channel facies are medium- to coarse-grained, moderately sorted (standard deviation ranges from 0.45–1.28 averaging 0.72), and quartzarenitic. The fluvial channel sandstone facies are coarse- to very coarse-grained, mostly poorly sorted (standard deviation ranges from 0.6–1.56 averaging 1.17), and subarkosic. Typical sedimentary structures displayed by the shoreface and tidal channel facies include burrows, clay drapes, hummocky and herringbone cross stratifications, whereas the fluvial channel sandstone facies are dominated by massive and planar cross beddings. The tidal marsh to coastal swamp shales and ferruginised siltstone facies are fossiliferous and bioturbated, whereas the nonmarine swamp siltstones contain vegetal imprints and lignite interbeds. The overbank claystone facies are massive and kaolinitic.In the study area, a regressive to transgressive model is proposed for the Patti Formation. This model correlates with stratigraphically equivalent sediments of the Ajali and Mamu Formations in the adjacent Anambra Basin to a great extent.     

Sedimentology of a Proterozoic erg: the Venkatpur Sandstone, Pranhita-Godavari Valley, south India

Reappraisal of the Late Proterozoic Venkatpur Sandstone indicates that the bulk of the sandstone is aeolian in origin. Aeolian stratification types, namely (i) inverse graded translatent strata, (ii) adhesion laminae, (iii) grainflow strata and (iv) grainfall strata, are present throughout the outcrop belt. Nine facies have been identified that represent both aeolian and related aqueous environments within a well-developed erg. Cosets of large cross-beds at the Bellampalli section in the NW of the study area record dune fields in the interior of the sand sea. To the SE, at the Godavari River and Ramgundam sections, a progressive increase in the relative proportion of the flat-bedded to cross-bedded facies and intercalated non-aeolian facies delineates the transition from the dune-field to sand-sheet environment. An alternating sequence of aeolian and marine sediments at Laknavaram, in the extreme SE, marks the termination of the sand sea. Palaeocurrent data suggest that the NW-SE trend of the sections represents a transect across the sand sea in a direction normal to the resultant primary palaeowind direction. Abundant horizontally stratified units in the Vankatpur Sandstone do not always represent the interdune sediments. On the basis of the thickness and geometry of the units, nature of bounding surfaces and associated facies sequence, the facies is variously interpreted to represent interdune, inland sabkha, sand sheet and coastal sand flat deposits.     

Cyclostratigraphic Correlation of Cenomanian and Turonian Deposits of the Eastern European Platform

Depositional conditions at the Cenomanian–Turonian time have been specified and a cyclostratigraphic scheme of the correlation of the Turonian sections has been proposed based upon generalizations of our own results concerning sections of Voronezh anteclise, Ulyanovsk–Saratov trough, Crimea, and the Caucasus.     

Sedimentology and depositional environments of the Ordovician Umm Sahm Sandstone Formation in southern Jordan

The Ordovician Umm Sahm Sandstone Formation of Jordan comprises approximately 200-m-thick succession of fluvial quartzarenites with subordinate claystone and siltstone lithologies of shallow marine conditions. The Umm Sahm Formation is characterized by its dark brown color, frequent jointing, and steep scarps. The Umm Sahm Formation is bounded by the marine claystones of Hiswah Formation at the top and the fluvial sandstones of the Disi Formation at the bottom. The Umm Sahm Formation is composed of two main facies: fluvial facies and tidal facies. The fluvial facies constitutes about 93% of the total thickness. The lower few meters of the succession passes upward from the Disi Sandstone Formation into similar massive white sandstone facies exhibiting similar white color, fine- to coarse-grained sandstone, with round-shaped pebbles. Trough and planar cross-bedding show a northwest unidirectional palaeocurrent trend. Light brown colored quartzarenites similar to those of the Cambrian Umm Ishrin Sandstone Formation are most common in the upper part of the succession. The tidal facies occupies three intervals in the middle part of the succession. It is composed of laminated and thin-bedded sandstones, siltstones, and claystones. They are rippled and varicolored with abundant trace fossils (Cruziana, Harlania, ruzophycus). The presence of hummocky cross stratification indicates the earliest short-lived tempestite conditions during the Paleozoic erathem of Jordan. The first appearance of Graptolites in the Ordovician rocks of Jordan was recorded during this study in the tidal facies of the Umm Sahm Formation. The vertical arrangement of both fluvial and tidal facies indicates three successive short-lived transgressions and regressions. These marine incursions indicate the successive shoreline advances of the Tethys Ocean, which was located northward, and inundated the southern braid plain. The three short-lived transgressive events took place, and the Tethys marine margin was displaced southward, giving rise to deposition of tidal facies in an open coast tidal flat. Following the transgressive events, renewed progradation and strandline retreat took place, fed by large amounts of siliciclastics derived from the continent and transported by braided streams across the intertidal zone.     

Sedimentology and paleogeographic evolution of the intermontane Kathmandu basin, Nepal, during the Pliocene and Quaternary. Implications for formation of deposits of economic interest

The Kathmandu Valley is an intermontane basin in the center of a large syncline of the Lesser Himalayas. The sedimentary basin fill comprises three units of Plio-Pleistocene to Holocene age. The study aimed at modeling the paleogeographic evolution of the basin, with emphasis on sedimentary series of fossil fuels and non-metallic deposits. The lithological setting of the basin and the tectonic framework were instrumental to basin subsidence. Alluvial through lacustrine sedimentation during incipient stages is a direct response to uplift in the hinge zone of the synclinorium. Axial parallel sediment dispersal gave way to fluviodeltaic sedimentation mainly from the limbs of the synclinorium. Ongoing compression and renewed uplift in the core zone of the synclinorium drove the uplift of a NW–SE running divide and a subdivision of the mono-lake into two basins. This ridge blocked the flow of transverse rivers and the northern subbasin became gradually choked. Ongoing uplift of the entire basin during the recent geological history caused a reorganization of the drainage pattern and triggered linear erosion in the southern mountain range. Step-by-step the remaining lacustrine basins disappeared. Fan aggradation coincide with cold dry or warm seasons, fluvial dissection and discharge increased during warmer and more humid periods. High lake levels exist during phases of increased humidity. The results of this basin analysis may be used predictively in the exploration for coal, natural gas, diatomaceous earths and quarrying for sand or clay. The gas potential is at its maximum in the lacustrine facies, sand and clay for construction purposes may be quarried economically from various fluvial and deltaic deposits. Diatomaceous earths predominantly accumulated in marginal parts of the lake and some landslide-dammed ponds. Lignitic brown coal can be mined together with combustible shales from poorly drained swamps.     

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.     

青藏高原东缘古近纪粗碎屑岩沉积学及其构造意义

青藏高原东缘古近纪盆地的填图和沉积学研究表明,在青藏高原东缘区域性走滑-挤压构造背景下形成的古近纪盆地内广泛发育厚层—巨厚层状的紫红色粗碎屑岩系。其沉积特征指示为一种近源快速堆积的泥石流和辫状河道沉积体,形成于干旱炎热气候条件下的典型陆内冲积扇环境。盆地充填序列、粗碎屑岩层序、动植物化石和盆地内岩浆岩~(40)Ar-~(39)Ar年代学等综合研究结果表明,古近纪盆地内粗碎屑岩大约形成于38～29 Ma。该时期与青藏高原东缘北段(横断山地区)古近纪盆地的形成和南段(兰坪—思茅地区)大盆地的裂解时间基本一致,这很可能预示着青藏高原在晚始新世—早渐新世期间曾发生过整体的快速构造隆升。     

四川省阿坝地区大骨结病区地球化学特征

大骨结病是中国分布较广的地方病，在四川省阿坝州流行，特别在若尔盖的包座地区严重流行。笔者通过以往专家对于大骨结病病因研究、生命元素特征分析和大骨结病病区和非病区的元素背景的研究认为，四川阿坝地区大骨结病可能是病区腐植酸富集，Se、Mo、Cu、V的偏低和Ba、Sr、P对于CaO的拮抗作用造成Ca的缺乏所引起的地方病。与此同时，通过1：20万内江幅“趴病”区的土壤和水化学元素地球化学研究，认为有类似之处。因此，上述因素可能是这种骨骼病的地球化学的病因。     

The effect of diagenesis on reservoir quality of Mamu Sandstone,Anambra basin,Nigeria

The petrography and powder diffraction analyses were integrated to study the effect of diagenesis on the reservoir quality of the Mamu Sandstone in areas around Enugu, southeastern Nigeria. The sands are moderately to well sorted, very fine to fine grained feldspathic arenite deposited in diverse environments of upper to lower shoreface and sub-environments of delta plain. Pressure solutions, authigenic clays and quartz and feldspar overgrowths are the main diagenetic features of the sandstones in the area. These diagenetic features result in mechanical and chemical compaction, alteration of framework grains and precipitation of dissolved grains. In varying degrees, coating of clasts and filling of pore-spaces by clay and heavy minerals reduced the pore throat diameter, which caused mild reduction of the porosity and permeability of sands. Despite these observed diagenetic effects, the Mamu sands still have the potential to serve as good hydrocarbons reservoir especially for gas.     

Surficial geophysical deduction of the geomaterial and aquifer distributions at Ngor-Okpala local government area of Imo State, South Eastern Nigeria

Twenty seven vertical electrical sounding (VES) profiles surrounding four known traverses were obtained in Ngor-Okpala local government area of Imo state to examine the subsurface geomaterials and the associated groundwater potential. The VES data, constrained by borehole data, provided useful information about the subsurface hydrogeologic and lithologic conditions. From the validated interpretation, the area assessed has loamy soil, medium grained sands, well-sorted medium-grained/gravelly sands and river sand as the lithologic succession from top to the bottom of the depth penetrated. The aquifers in the area were found in the medium-grained sands and well-sorted medium-coarse-grained sands. The aquifer depth for all-season groundwater that would be devoid of draw-down can be found at a depth range of 42–50 m. The resistivity maps of selected depths exhibit sharp resistivity changes at depth due mainly to undulating subsurface topography. A map of the distribution of the kσ-values shows that good quality groundwater can be found in most parts of the area.     

藏北安多地区侏罗纪菊石动物群及其古地理意义

藏北安多地区新发现2套以黑色页岩、深灰色钙质泥岩和泥灰岩为主的舍菊石化石的侏罗纪地层，它们与羌塘地区广泛分布的雁石坪群无论在化石组合或沉积特征方面都明显不同．岗尼乡剖面地层中产太阳菊石科的菊石，主要有Sonninia，Dorsetensia，Witchellia等。、这套地层是双湖地区色哇组的东延部分，时代确定为中侏罗世早中巴柔期114道班剖面中羌姆勒曲组的菊石化石大多归属于Virgatosphinctinae科，计有Aulacosphinctes、Virgatosphinctes等，均为上侏罗统菊石化石的典型分子，产出层位应归于提塘阶中、上部。藏北安多-改则以北一线的侏罗系深水黑色岩系虽不十分连续，但从有化石证据的土阿辛阶到巴柔阶再到提塘阶都有零星出露，它们同属一个沉积相区。侏罗纪时羌塘南部可能存在一套大陆边缘型沉积地层，因此有必要对该区的构造属性和演化历史重新进行解释。     

Groundwater quality assessment in parts of Eastern Niger Delta, Nigeria

Hydrogeochemical analyses were carried out on groundwater samples collected from 20 producing wells in different parts of the Eastern Niger Delta. Results show that the concentrations of the major cations (Na⁺, K⁺, Ca²⁺, Mg²⁺) and anions (Cl^–, SO ₄ ^2– , HCO ₃ ^– ) are below the World Health Organization (WHO) standards set for domestic purposes. The occurrence of slightly saline water in certain areas is attributed to local hydrogeological processes occurring in the area. On the basis of the analytical results, two hydrogeochemical facies are delineated. These are calcium-magnesium-chloride-sulfate-bicarbonate (Ca-Mg-Cl-SO₄-HCO₃) and calcium-sodium-chloride-sulfatebicarbonate (Ca-Na-Cl-SO₄-HCO₃) to the west and east of the study area, respectively.     

Further evidence of marine Cenomanian,lower Turonian and Maastrichtian in the Upper Benue basin of Nigeria (West Africa)

Field investigations in the Upper Benue rift basin of Nigeria highlight the necessity for a review of the Cenomanian-Turonian biostratigraphy of the area. Three ammonite zones of Vascoceras bulbosum (Reyment), Paravascoceras costatum (Reyment) and Pseudotissotia (Bauchioceras) nigeriensis (Woods) have been recognized at sections exposed at the quarry of the cement factory near the village of Ashaka. The sediments within the Vascoceras bulbosum zone also contain specimens of Exogyra olisiponensis (Sharpe), Kanabiceras septemseriatum (Cragin) and Epengonoceras dumbli (Cragin). These are all indicative of an uppermost Cenomanian age and reveal that at least the lower portion of the Gongila Formation as exposed at Ashaka is faunistically equivalent to the Pindiga Formation as exposed in the type section at Pindiga.The shales in the Gombe region in which Libycoceras ismaeli (Zittel) was found are probably part of the Maastrichtian Fika shales outcropping extensively in the northern part of the area. The discovery of Cyclolithes nov. sp. within Gombe sandstones at Dakiti near Kumo confirm that they are at least partially marine in origin and Maastrichtian in age. This could be considered as an additional evidence in favour of the presence of marine waters in the Upper Benue during the last part of the Cretaceous.     

塔里木盆地巴楚–麦盖提地区寒武纪沉积序列与古地理演化

塔里木盆地巴楚–麦盖提地区（巴麦地区）是重要的含油气地区。基于最新的钻井和地震资料,本文将该地区寒武系划分为13个三级层序,同时,总结了三级层序界面及层序内部特征,对层序格架下的沉积序列及各时期的岩相古地理进行了精细刻画,并且提出,巴麦地区经历了从碳酸盐缓坡到镶边碳酸盐台地的演化过程。通过对巴楚隆起上的钻井、测井资料和地震相应特征的研究,对缺乏钻井等实物资料的麦盖提斜坡地区沉积环境进行了合理的推测,最终以组为单位编制了岩相古地理图。研究结果显示,塔里木盆地巴楚–麦盖提地区在寒武纪的沉积演化中（SQ1-SQ13）经历了两次大规模海侵,形成寒武系盐下良好的生储盖组合,其中,麦盖提地区是塔里木盆地西南部寒武系勘探领域形成大型油气藏的最有利区带,具有良好的勘探前景。

     

Depositional System of the Carboniferous Huanglong Formation, Eastern Sichuan Basin: Constraints from Sedimentology and Geochemistry

Using analyses of the lithology, sequences, paleoenvironment, and tectonic setting, the depositional system of the Carboniferous Huanglong Formation in the eastern Sichuan Basin was identified. The lithological characteristics of the Lower Member, Middle Member, and Upper Member were analyzed and classified. Before the use of carbon, oxygen, and strontium isotopes in the analysis, all of the geochemical data were tested for validity. On the basis of the Z values obtained from carbon and oxygen isotopes, the paleoenvironments of the three members were elucidated. Lower Member was dominantly an enclosed marine environment with intense evaporation and little freshwater input into the sea. Middle Member developed in a semi-enclosed to normal marine environment with many rivers. Upper Member was formed in a normal marine environment. The east Sichuan Basin was enclosed by paleouplifts before the deposition of the Huanglong Formation, forming a relatively enclosed depositional setting. Paleogullies developed in the Silurian strata that underlie the Carboniferous rocks; these paleogullies can be identified. On the basis of a comprehensive analysis, we propose that the Huanglong Formation developed in a platform system. Four microfacies were identified: supratidal flat, dolostone flat, grain shoal, and shelf microfacies. The high-permeability and high-porosity characteristics of the grain shoal microfacies are favorable for hydrocarbon accumulation, while the supratidal flat and shelf microfacies developed very few high-quality reservoirs. The paleogullies, in which increased amounts of grain shoal microfacies developed, controlled the distribution of high-quality reservoirs.     

Oil-spill disasters and the rural hazardscape of Eastern Nigeria

The objective of the paper is to investigate the links between the patterns of incidents, the amount of hazardous materials locally present and capability of local emergency preparedness in rural local government councils. Four states Abia, Akwa Ibom, Bayelsa and Rivers State were used to examine the nature and pattern of oil-spill disasters in rural Nigeria. It is argued that oil-spill hazards are more than isolated engineering malfunctions. They can be alternatively understood as reflections of the social, economic and political contexts in which they occur. Discriminant analysis is used to examine the relationship between 71 country risk-related and preparedness variables and incident frequency. The findings illustrate the usefulness of contextual analysis in examining the restructuring of rural life and the capacity of fiscally and socially stressed rural communities to respond to environmental change.