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1.
Maxime Virolle Benjamin Brigaud Raphaël Bourillot Hugues Fnis Eric Portier Thibault Duteil Julius Nouet Patricia Patrier Daniel Beaufort 《Sedimentology》2019,66(3):859-894
Porosity and permeability may be preserved in deep sandstone reservoirs by clay coating (mainly chlorite) which limits quartz overgrowths. Chloritization around quartz grains results mainly from mineralogical transformations of pre‐existing clays. It is fundamental to study those clay precursors to better understand and predict the location and distribution of clay coatings in subsurface sandstones for petroleum or geothermal prospecting. This paper reports a high‐resolution analysis of the composition, distribution and fabric of clays along a modern estuary, the Gironde (south‐west France). The scale of the study ranges from thin sections, through sand bar bodies, up to the entire estuary. Results show that clays are detrital and deposited at the same time as sand grains despite strong hydrodynamic conditions. Clays bind to medium‐grained sands forming detrital clay grain coats. On average, 26% of detrital sand grains are coated along the entire length of the estuary. Coat thickness varies from 1 μm to more than 200 μm, and coat coverage exceeds 30% in some samples. The turbidity maximum zone position (surface water turbidity from 1 to 10 g l?1) in the estuary, which is controlled by seasonal variations in hydrodynamic processes, significantly impacts the location of the maximum clay content and the abundance of coated grains in sandy facies along the estuary. Flocculation in the water column results in the accumulation of suspended matter and contributes to the high turbidity in the estuary. Exopolymeric substances produced by diatoms are observed both in the field and by cryo‐scanning electron microscopy, suggesting that they may play a major role in binding detrital clay around sand grains. Finally, tidal bars and heterolithic point bars in the estuary funnel and estuarine channels are prime sedimentological targets for finding clay coatings and potentially good reservoir quality in deeply buried sandstones. 相似文献
2.
Joshua Griffiths Richard H. Worden Luke J. Wooldridge James E. P. Utley Robert A. Duller Rhiannon L. Edge 《Sedimentology》2019,66(6):2011-2047
The spatial distribution of clay minerals in sandstones, which may both enhance or degrade reservoir quality, is poorly understood. To address this, clay mineral distribution patterns and host‐sediment properties (grain size, sorting, clay fraction abundance and bioturbation intensity) have, for the first time, been determined and mapped at an unprecedentedly high‐resolution in a modern estuarine setting (Ravenglass Estuary, UK). Results show that the estuary sediment is dominated by illite with subordinate chlorite and kaolinite, although the rivers supply sediment with less illite and significantly more chlorite than found in the estuary. Fluvial‐supplied sediment has been locally diluted by sediment derived from glaciogenic drift deposits on the margins of the estuary. Detailed clay mineral maps and statistical analyses reveal that the estuary has a heterogeneous distribution of illite, chlorite and kaolinite. Chlorite is relatively most abundant on the northern foreshore and backshore and is concentrated in coarse‐grained inner estuary dunes and tidal bars. Illite is relatively most abundant (as well as being most crystalline and most Fe–Mg‐rich) in fine‐grained inner estuary and central basin mud and mixed flats. Kaolinite has the highest abundance in fluvial sediment and is relatively homogenous in tidally‐influenced environments. Clay mineral distribution patterns in the Ravenglass Estuary have been strongly influenced by sediment supply (residence time) and subsequently modified by hydrodynamic processes. There is no relationship between macro‐faunal bioturbation intensity and the abundance of chlorite, illite or kaolinite. Based on this modern‐analogue study, outer estuarine sediments are likely to be heavily quartz cemented in deeply‐buried (burial temperatures exceeding 80 to 100°C) sandstone reservoirs due to a paucity of clay grade material (<0·5%) to form complete grain coats. In contrast, chlorite‐enriched tidal bars and dunes in the inner estuary, with their well‐developed detrital clay coats, are likely to have quartz cement inhibiting authigenic clay coats in deeply‐buried sandstones. 相似文献
3.
Alina Shchepetkina Murray K. Gingras John-Paul Zonneveld S. George Pemberton 《Estuaries and Coasts》2017,40(4):947-966
Fine-grained sediment deposition is often conceived to happen in still water conditions and to represent slow sedimentation rates. However, it has been increasingly noted that mud sedimentation commonly occurs under high-energy conditions. The macrotidal Petitcodiac River estuary is used as an example to investigate the significance of flocculation as an important process in the rapid removal of large amounts of sediments from suspension under turbulent flow conditions. A range of physical sedimentary structures was observed at the Petitcodiac River estuary intertidal flats and bars, including low-angle and horizontal planar lamination, current and climbing ripples, surficial fluid mud, soft-sediment deformation, microfaults, and mud rip-up clasts. Fluid mud within the study area contains considerable proportions of clay (21–67%) and contributes to the formation of creeping fluid-mud sheets and streams. Detailed examination of the naturally occurring clay flocs shows that they contain up to 77% of the entangled silt- and sand-sized grains. SEM and microscopic imaging of fluid mud reveal a substantial amount of bioclastic material within the flocs and dispersed among the sediments. These observations show that physicochemical and biological processes influence silt, plankton, and clay aggregation. Water samples and observations from the Petitcodiac River estuary confirm that flocs form in the water column and then settle to the tidal-channel floor and flanking intertidal flats. Laboratory experiments, using Petitcodiac sediment, show how the clay flocs have the potential to sweep the water of silt-sized suspended grains. Additionally, diatoms and their associated extracellular polymeric substance (EPS) sheaths might play a role in mineral aggregation and increased sediment cohesiveness. 相似文献
4.
Spatial and depth-wise distribution of sediment components, organic carbon and selected metals (Fe, Mn, Al, Ni, Cr, Co, Zn and Pb) is studied across upper and middle tidal flats from lower and middle estuarine regions of Kundalika Estuary, central west coast of India. Silt and clay form the major components in lower and middle estuary, respectively. Sand, silt, clay and organic carbon showed band-type distribution along the estuary. The sediment deposition over the years took place in varying hydrodynamic conditions in lower and middle estuarine regions. Upper flats of the lower estuary represent mud while middle flats of the lower estuary facilitated the deposition of sandy mud. Correlation results indicated the importance of clay and organic carbon in removal and trapping of metals at lower and middle estuary, respectively. Factor analysis indicated that the distribution of metals is largely controlled by Fe–Mn oxyhydroxides and organic carbon. The middle flats of the lower estuary showed an anthropogenic source for Ni, Cr and Co while middle flats of the middle estuary showed a mainly lithogenic source. 相似文献
5.
Senapathi Venkatramanan Thirunavukkarasu Ramkumar Irudhayanathan Anithamary 《Arabian Journal of Geosciences》2013,6(5):1371-1380
The aim of this study is to understand the various sources and factors controlling the abundance and distribution of clay minerals, sand, silt, clay and organic matter of the surface sediments of Tirumalairajanar Estuary in two different seasons. The study was undertaken for two seasons, based on ten selected stations all along the estuary, mouth and freshwater zone. Furthermore, along the estuary region, clay and silt were observed and also at few stations in the upstream end. Organic matters in the sediments appeared to be the main mechanisms for the distribution of clay minerals in estuary indicated that the distributions of clay minerals were comparatively higher during postmonsoon than in premonsoon season. The clay mineral assemblage consists mainly of chlorite, kaolinite, montmorillonite, illite and very scarce gibbsite. The clay from the sediments has been separated and studied for mineral identification using X-ray diffraction analysis. The present study also reveals that sediment texture is one of the main controlling factors for the distribution of organic matter. 相似文献
6.
珠江口晚第四纪埋藏风化层及其环境意义* 总被引：4，自引：0，他引：4
风化层是沉积间断和环境变迁的明显标志。在珠江三角洲平原以及珠江口海域都见有晚第四纪的埋藏风化层。珠江口外伶仃岛海域2个钻孔岩芯4个样品的AMS年龄表明,在第四系剖面中,MIS 3以来通常有两个风化层。下风化层的年龄为\{31060~\}28754aB.P. ,属于MIS 3; 上风化层为\{14320~\}11500aB.P. ,属于MIS 2。风化层的岩性因地而异,包括粘土、砂质粘土、中细砂和砂砾等。色调为红褐色、褐色或杂色。2个岩芯上、下风化层4个样品的氧化物分析表明,上风化层的风化强度比下风化层大。1个岩芯的硅藻分析表明,风化层主要是陆相层经风化而成,两个风化层分别反映MIS 3和MIS 2的两个陆相—海相的沉积旋回。 相似文献
7.
Tiju Itty Varghese Prakash Thirumali Nageshrao Nagendra Raghavendramurthy Nagarajan Ramasamy 《Arabian Journal of Geosciences》2018,11(3):61
Late Quaternary sediments representing the floodplain, estuary and offshore environments of southern Kerala were investigated to infer provenance. The grain size reveals the dominance of sand to silty clay, clay to clayey silt and clayey silt in the floodplain, estuary and offshore sediments, respectively. The chemical index of alteration (CIA) values and A-CN-K plot attributes to high, moderate and low weathering in floodplain, estuary and offshore regions, respectively. The SiO2/Al2O3 values lesser than Post-Archean Australian Shale indicate low to moderate maturity for the estuarine and offshore sediments. The geochemical immaturity indicates its derivation from low to moderately weathered source rocks. The major and trace elemental ratios and discriminant function diagrams attribute that the sediments were derived from intermediate to felsic source rocks. The enrichment of Cr and Ni concentration in the sediments compared to the upper continental crust, related to the contribution of orthopyroxenes, weathered from charnockite and garnets from the granulite terrain, respectively. 相似文献
8.
The Changjiang and the Jiulong Estuaries, located in eastern and southeastern China, respectively, have different geomorphologic
and tidal processes as well as anthropogenic development in their associated watersheds. Sediments in the Changjiang estuary
mostly consist of SiO2, CaO and MgO (mean percentages of 63.9, 4.34 and 2.35%), whereas sediments from the Jiulong estuary mostly consist of Al2O3, Fe2O3 and organic matter (mean percentages 19.2, 6.82 and 4.14%). The Jiulong estuarine sediments contain more than twice the concentrations
of Pb, Zn, Cu, than those from the Changjiang estuary. In the Jiulong estuary, these heavy metals are associated with carbonates
and organic matter, whereas in the Changjiang estuary, they are associated with residual fractions or clay. Sediments from
the Changjiang estuary, mostly sediments with little organic matter, do not efficiently sequester anthropogenic-derived trace
metals. In contrast, sediments from the Jiulong estuary consist of a mixture of fluvial and marine matter which can sequester
heavy metals contributed by larger landscapes with industrial and municipal wastewater. 相似文献
9.
通过X射线衍射系统分析了杭州湾地区SE2孔全新世沉积物的黏土矿物组成,结果显示研究层段黏土矿物主要由伊利石、绿泥石、高岭石和蒙脱石组成;伊利石结晶度较好,化学风化指数普遍大于0.5,表明以化学风化为主,且风化趋势自下而上呈递减趋势。通过对比中国东南部主要河流沉积物的黏土矿物组成,认为钱塘江下切河谷全新世沉积物的黏土矿物组成具有较好的物源指示意义: 全新世 Ⅰ 段(即古河口湾和河漫滩)沉积物主要来自钱塘江上游,特征黏土矿物为高岭石,河口外物质贡献不大;Ⅱ 段(即现代河口湾和近岸浅海)沉积物包含较多蒙脱石,表明不仅包括钱塘江上游物质,河口外长江物质也开始进入钱塘江河口。黏土矿物中,高岭石对气候有较好的指示作用:中全新世高岭石含量达到最高值,反映气候最为湿热,化学风化程度最高;晚全新世含量逐渐降低,反映气候逐渐回冷,化学风化强度降低。 相似文献
10.
The Tinto and Odiel rivers drain 100 km from the Rio Tinto sulphide mining district, and join at a 20-km long estuary entering the Atlantic Ocean. A reconnaissance study of heavy metal anomalies in channel sand and overbank mud of the river and estuary by semi-quantitative emission dc-arc spectrographic analysis shows the following upstream to downstream ranges in ppm (μg g?1): As 3,000 to <200, Cd 30 to <0.1, Cu 1,500 to 10, Pb 2,000 to <10, Sb 3000 to <150, and Zn 3,000 to <200. Organic-rich (1.3–2.6% total organic carbon, TOC), sandysilty overbank clay has been analyzed to represent suspended load materials. The high content of heavy metals in the overbank clay throughout the river and estuary systems indicates the importance of suspended sediment transport for dispersing heavy metals from natural erosion and anthropogenic mining activities of the sulfide deposit. The organic-poor (0.21–0.37% TOC) river bed sand has been analyzed to represent bedload transport of naturally-occurring sulfide minerals. The sand has high concentrations of metals upstream but these decrease an order of magnitude in the lower estuary. Although heavy metal contamination of estuary mouth beach sand has been diluted to background levels estuary mud exhibits increased contamination apparently related to finer grain size, higher organic carbon content, precipitation of river-borne dissolved solids, and input of anthropogenic heavy metals from industrial sources. The contaminated estuary mud disperses to the inner shelf mud belt and offshore suspended sediment, which exhibit metal anomalies from natural erosion and mining of upstream Rio Tinto sulphide lode sources (Pb, Cu, Zn) and industrial activities within the estuary (Fe, Cr, Ti). Because heavy metal contamination of Tinto-Odiel river sediment reaches or exceeds the highest levels encountered in other river sediments of Spain and Europe, a detailed analysis of metals in water and suspended sediment throughout the system, and epidemiological analysis of heavy metal effects in humans is appropriate. 相似文献
11.
通过X射线衍射系统分析了杭州湾地区SE2孔全新世沉积物的黏土矿物组成,结果显示研究层段黏土矿物主要由伊利石、绿泥石、高岭石和蒙脱石组成;伊利石结晶度较好,化学风化指数普遍大于0.5,表明以化学风化为主,且风化趋势自下而上呈递减趋势。通过对比中国东南部主要河流沉积物的黏土矿物组成,认为钱塘江下切河谷全新世沉积物的黏土矿物组成具有较好的物源指示意义: 全新世 Ⅰ 段(即古河口湾和河漫滩)沉积物主要来自钱塘江上游,特征黏土矿物为高岭石,河口外物质贡献不大;Ⅱ 段(即现代河口湾和近岸浅海)沉积物包含较多蒙脱石,表明不仅包括钱塘江上游物质,河口外长江物质也开始进入钱塘江河口。黏土矿物中,高岭石对气候有较好的指示作用:中全新世高岭石含量达到最高值,反映气候最为湿热,化学风化程度最高;晚全新世含量逐渐降低,反映气候逐渐回冷,化学风化强度降低。 相似文献
12.
Geochemistry of Cu, Co, Ni, Zn, Cd and Cr in the surficial sediments of a tropical estuary, southwest coast of India: a granulometric approach 总被引：3，自引：0，他引：3
Geochemical characteristics of six trace metals – Cu, Co, Ni, Zn, Cd and Cr – in the bulk sediment and sand, silt and clay
fractions of a tropical estuary on the southwest coast of India have been studied and discussed. In bulk sediment, the trace
metal concentration is controlled mainly by the textural composition of the sample. Mud, sandy mud and sandy silt register
higher concentrations of trace metals than that in sand-dominant sediments. The granulometric partitioning studies also re-affirmed
the role of particle size in enriching the trace metals. The silt and clay fractions exhibit 7–8 times the enrichment of Cu
and Cd compared to that in sand. The enrichment factors of Zn, Cr, Ni and Co in the silt and clay fractions, compared to that
in sand, are 5–6, 4–5, 2–5 and 2–3 times, respectively. The trace metals in the sand fraction, particularly Ni and Cr, exhibit
strong positive correlation with the heavy mineral content of the samples. It clearly indicates a heavy mineral pathway to
the trace metals in the sand fraction. Cu and Co in silt and clay fractions exhibit a marked decrease towards the high saline
zones of the estuary. This is attributed to the desorption of Cu and Co from particulate phases during estuarine mixing. Contrary
to Cu and Co, the content of Zn in the clay fraction shows a marginal increase towards the estuarine mouth. This could be
explained by the influx of Zn-rich contaminant discharges from Zn-smelting industries located slightly north of the estuarine
mouth. The released Zn will effectively be held in the lattices of the clay mineral montmorillonite, which also exhibits a
marked increase towards the estuarine mouth. The anomalously high values of Cd in some places of the Central Vembanad estuary
is attributed to the local pollution.
Received: 10 July 1995 · Accepted: 3 June 1996 相似文献
13.
The Nature and Distribution of Particulate Matter in the Mandovi Estuary,Central West Coast of India
Pratima Mohan Kessarkar Venigalla Purnachandra Rao Ranjan Shynu Prakash Mehra Blossom E. Viegas 《Estuaries and Coasts》2010,33(1):30-44
Systematic seasonal variations of suspended particulate matter (SPM) along a 44-km transect of the Mandovi estuary reveal
that the concentrations of SPM are low at river-end stations, increase generally seaward, and are highest at sea-end stations
of the estuary. An estuarine turbidity maximum (ETM) occurs at sea-end stations during June–September when river discharge
is high and also in February–May when river discharge is low. These are the two windiest times of year, the former associated
with the southwest monsoon and the latter characterized by a persistent sea breeze. The salinity vs. SPM plot shows that high
SPM is a seaward deposit and skewed landward. Suspended matter comprised of floccules, fecal pellets, and aggregates that
consist of clay and biogenic particles occur everywhere in the estuary. Diatoms are the most common and are of marine type
at the sea-end and freshwater-dominated at river-end stations of the estuary. SPM is characterized by kaolinite- and smectite-rich
clay mineral suites at the river- and sea-end stations, respectively. Smectite concentrations increase seawards with the increase
in SPM content and are not influenced by salinity. Wind-driven waves and currents and biogeochemical processes at the mouth
of estuary likely play an important role in the formation of ETM in resuspension and transformation of SPM into floccules
and aggregates and in their upkeep or removal. 相似文献
14.
《International Geology Review》2012,54(2):145-165
Two sediment cores from the inner continental shelf of SW India, SK‐148/13 (4.66 m long; from 50 m water depth) and SK‐148/14 (5.37 m long; from 22 m water depth), were studied for provenance and palaeomonsoonal implications. Sediment layers at different depth intervals in these cores were estimated for clay minerals and organic matter content. Five surface sediment samples from the nearby Kali River estuary of the adjacent hinterland were also analysed for clay mineral contents. In both cores and Kali River sediments, smectite is the dominant clay followed by illite, and kaolinite or chlorite. Based on the similarities of the abundances of clay minerals and their relative wt‐% in the inner shelf sediment cores and in surface sediments of the estuary as demonstrated by significance tests, Al‐rich illite, and negligible contribution of clay from the deep‐sea and aeolian sources, it can be inferred that the sediments of the two inner continental shelf cores were derived from the adjacent hinterland. Application of statistical discordancy and significance tests on the down‐core variations in the crystallinity index (CI) of illite and organic matter content in the sediment cores indicates intense monsoonal (high rainfall) conditions at the adjacent hinterland during about 4300–6200 and 9300–10,400 years BP. These inferences are comparable to those from other well‐established palaeomonsoonal indicators such as sedimentation rates and mineral magnetic properties. The CI of illite, an easily determinable and climatically sensitive parameter, can thus be a reliable palaemonsoonal indicator for inner shelf sediment cores. The statistical methodology used in this work highlights the advantages of a quantitative interpretation of the data instead of the conventional qualitative visual examination. 相似文献
15.
Colloidal-sized material from the Patuxent River estuary, Maryland, was analyzed for more than 30 elements by instrumental neutron activation analysis. Sample data from stations ranging in salinity from 0.04 g/kg to 12 g/kg indicate that the winter colloidal material is dominated upstream by poorly crystallized clay minerals and iron oxide, but above a salinity of 10 g/kg, it consists primarily of carbonaceous material. Winter colloidal material decreases non-conservatively seaward from 29 to 0.6 mg/l. The summer colloidal material, however, is carbon-rich throughout the estuary and the amount of colloidal material in the upper water column does not change appreciably with increasing salinity. Many trace elements (Cs, Hf, Rb, Se, Th, V and the REE) covary with Al and probably are associated with the clay component. Other elements (As, Ba, Sb, Se, U and Zn) are considerably enriched relative to Al and may covary with the organic component. The results suggest that the freshwater winter colloidal system is a product of continental weathering processes, whereas the summer colloidal material is derived primarily from estuarine biological processes. 相似文献
16.
Depositional environment of mudflats and mangroves and bioavailability of selected metals within mudflats in a tropical estuary 总被引：1，自引：1，他引：0
M. C. Fernandes G. N. Nayak A. Pande S. P. Volvoikar D. R. G. Dessai 《Environmental Earth Sciences》2014,72(6):1861-1875
Four sediment cores representing adjacent mudflat and mangrove sub-environments of middle estuary (Shastri) were analyzed for sand, silt, clay, and organic carbon. Total metal concentration of iron (Fe), manganese (Mn), nickel (Ni), zinc (Zn), chromium (Cr), copper (Cu), cobalt (Co), and lead (Pb) and chemical speciation of Fe, Mn, and Co on selected samples was also carried out on mudflat cores. The sediments in the upper middle estuary were found to be deposited under highly varying hydrodynamic energy conditions; whereas lower middle estuary experienced relatively stable hydrodynamic energy conditions with time. The tributary joining the river near the upper middle estuary is found to be responsible for the addition of enhanced organic carbon and metal concentrations. Speciation study indicated Fe and Co are from natural lithogenic origin while Mn is derived from anthropogenic sources. Higher Mn and Co than apparent effects threshold can pose a high risk of toxicity to organisms associated with these sediments. 相似文献
17.
18.
杭州湾及其邻近海域沉积物中Fe、Mn、Ca、Mg的地球化学研究 总被引：2，自引：0，他引：2
本文通过对杭州湾及其邻近海域29个站位的表层沉积物化学、粘土矿物及碎屑矿物资料的分析,详细研究了开放型海湾沉积物中Fe、Mn、Ca、Mg元素地球化学特征。研究表明,1)与同类型海湾相比,杭州湾显示高Fe、Mn、Mg低Ca的特点。表明物质来源丰富,而生物作用较弱;2)Fe、Mn主要来自长江和钱塘江径流搬运,受粘土控制。Mg主要来自粘土对海水中Mg2+的吸附,同时受上覆水盐度的影响;3)北区元素间关系明显的比南区强烈,表明南区物质来源较北区复杂;4)主断面沉积物中Mg/Ca由河口向海洋增加,并与有机碳呈明显的正相关,显示杭州湾及邻近陆架区可能发生着原始碳酸盐（钙）白云岩化的反应。 相似文献
19.
扫描电镜(SEM)与X射线能量色散分析(EDX)联用,可获得粘土矿物微区成分和全样平均成分,并求出样品中的矿物含量,实验采用纯矿物人工配比组合样,进行SEM/EDX条件试验,矿物定量的相对误差小于5%.为考察该方法的实用性,做了湖南风化型矿石海泡石定量,还对安徽嘉山和江苏金层凹凸棒石进行矿物定量,均得到满意的结果,为了解矿区矿物组合特点和评价粘土矿床提供了依据. 相似文献
20.
Geochemical characteristics of Fe and Mn in sand, silt, and clay fractions as well as in bulk sediments of the tropical perennial Muvattupuzha river and the Central Vembanad estuary of the southwest coast of India have been studied and discussed. The results of a physical fractionation study of Fe and Mn indicated a substantial increase in the content of these metals in silt and clay fractions above that in sand. The riverine silt and clay fractions account for two to three times the enrichment of Fe and Mn than the corresponding sand fraction; the estuarine counterparts indicate four to eight times the enrichment. The observed enrichment of Fe and Mn towards the more finer size grades is mainly due to the increased surface area of the finer clastics, which in turn increase the absorptive ability. However, the mineralogical diversities of the three size fractions also influence the enrichment of Fe and Mn. The spatial distribution of Fe and Mn indicates a marked decrease in the content of the latter than the former towards the high saline zones of the river and the estuary. This variation could be due to the higher solubility of Mn towards the high saline zones of the aquatic environment where reducing condition prevails most of the year. 相似文献