Clay-mineral distribution in surface sediments of the Eurasian Arctic Ocean and continental margin as indicator for source areas and transport pathways — a synthesis

Clay-mineral distributions in the Arctic Ocean and the adjacent Eurasian shelf areas are discussed to identify source areas and transport pathways of terrigenous material in the Arctic Ocean. The main clay minerals in Eurasian Arctic Ocean sediments are illite and chlorite. Smectite and kaolinite occur in minor amounts in these sediments, but show strong variations in the shelf areas. These two minerals are therefore reliable in reconstructions of source areas of sediments from the Eurasian Arctic. The Kara Sea and the western part of the Laptev Sea are enriched in smectite, with highest values of up to 70% in the deltas of the Ob and Yenisey rivers. Illite is the dominant clay mineral in all the investigated sediments except for parts of the Kara Sea. The highest concentrations with more than 70% illite occur in the East Siberian Sea and around Svalbard. Chlorite represents the clay mineral with lowest concentration changes in the Eastern Arctic, ranging between 10 and 25%. The main source areas for kaolinite in the Eurasian Arctic are Mesozoic sedimentary rocks on Franz-Josef Land islands. Based on clay-mineral data, transport of the clay fraction via sea ice is of minor importance for the modern sedimentary budget in the Arctic basins.     

Distribution of clay minerals in surface sediments from the eastern Barents and south-western Kara seas

Surface samples from the eastern Barents and south-western Kara seas have been analysed for clay mineralogy. Transport paths, the role of regional sources and local bedrock outcrops and the influence of hydrodynamic and glacigenous processes for clay distribution on the shelves are discussed in relation to central Arctic Ocean deep sea and sea ice sediments. Franz Josef Land and Novaya Zemlya show significantly different clay mineral associations. Although smectite concentrations are fairly high, Franz Josef Land can be excluded as a source for central Arctic sea ice sediments, which are relatively rich in smectite. In the Kara Sea, smectite concentrations in coastal sediments surpass even the Franz Josef Land concentrations. The large cyclonic gyre in the eastern Barents Sea between Novaya Zemlya and Franz Josef Land, which serves as a mixing zone between Arctic and North Atlantic water, is apparently reflected within the smectite distribution pattern. With the exception of Franz Josef Land, the area of investigation is typically low in kaolinite. In particular, coastal areas and areas north of Novaya Zemlya, influenced by the inflow of Arctic waters, show the lowest kaolinite concentrations. A high kaolinite occurrence within the Nansen Basin is most probably related to Franz Josef Land and emphasizes the importance of long-range downslope transport of sediments across the continental slope. The surface water circulation pattern in close interaction with local outcrops onshore Novaya Zemlya and locally restricted occurrences within the eastern Barents Sea significantly alter the illite dispersal pattern. Illite concentrations are lowest around Franz Josef Land. Chlorite is generally low in the area of investigation. Submarine outcrops and important chlorite occurrences onshore Novaya Zemlya bias its distribution pattern.     

Sea-ice transport of riverine particles from the Laptev Sea to Fram Strait based on clay mineral studies

The aim of this study was to identify pathways and processes of modern sediment transport from the Siberian hinterland to the Laptev Sea and further to the Arctic Ocean. Clay mineral analyses were performed on riverine suspended particulate material (SPM), surface sediments of the Laptev Sea shelf, and sea-ice sediments (SIS). Material collected during seven expeditions was included in this study. Clay mineral assemblages are used to decipher the distribution of riverine sediments on the shallow Laptev Sea shelf, the entrainment of fine particles into newly forming ice, and the transport of SIS from the Laptev Sea towards the ablation areas. A cluster analysis of our data set shows that the clay mineral assemblages of Laptev Sea shelf sediments and SIS are controlled mainly by the input of riverine SPM supplied by the Khatanga, Lena, and Yana Rivers. Whereas the western shelf clay-mineral province is characterized by enhanced smectite concentrations supplied by the Khatanga River, the eastern Laptev Sea is dominated by illite discharged through the Lena and Yana Rivers. The SIS smectite concentration serves as an indicator for sediment source areas on the circum-Arctic shelves. Subsequently, the Transpolar Drift can be distinguished into a Siberian Branch fed from the eastern Kara Sea and the western Laptev Sea, and a Polar Branch originating from the eastern Laptev Sea.     

Modern river discharge and pathways of supplied material in the Eurasian Arctic Ocean: evidence from mineral assemblages and major and minor element distribution

Clay-mineral, heavy-mineral, and elemental distributions in sediments from the Arctic Ocean and the adjacent Laptev and Kara seas can be attributed to the geology of the hinterland and the transport of terrigenous material by rivers onto the shelves. Kara Sea sediments are characterized by increased contents of smectite and elevated Ni/Al-, Ti/Al-, and Cr/Al ratios. In the western Laptev Sea sediments are enriched in smectite and clinopyroxene and increased in Ti/Al-, Cr/Al-, and Ca/Al ratios. The composition of the sediments reflects suspended matter input from the large trap basalt of the Putoran Mountains. The eastern Laptev Sea sediments display increased illite and amphibole contents as well as a chemical composition similar to average shale. This composition is due to the discharge from the Lena and Yana rivers, which drain a large catchment area consisting of sedimentary Mesozoic and Paleozoic rocks. Material from the eastern Laptev Sea is transported by ocean currents and sediment-laden sea ice along the Transpolar Drift into the central Arctic Ocean. This is indicated by similar values of Ti/Al-, Cr/Al-, Rb/Al-, and K/Al ratios as well as increased concentrations of amphibole and illite, determined in sediments from the Lomonosov Ridge. A minor input from the Beaufort Sea into the central Arctic Ocean is suggested from increased Ca/Al ratios and increased contents of opaque minerals.     

东海东北部海域表层沉积物黏土矿物来源及输运

利用X射线衍射,对东海东北部海域80个表层沉积物样品进行黏土矿物的相对含量分析.结果表明:东海东北部海域表层沉积物黏土矿物中伊利石（65.1%）含量最高,其次为绿泥石（26.6%）、高岭石（8.9%）和蒙皂石（4.3%）;矿物组合中伊利石-绿泥石-高岭石-蒙皂石型占绝对优势,伊利石-绿泥石-高岭石型较少.由外陆架至冲绳海槽,伊利石含量分布呈低-高-低-高;绿泥石呈低-高-低;高岭石分布趋势明显异于伊利石和绿泥石,含量值分布出现由高到低的趋势;蒙皂石在个别区域缺失,高值区呈斑块状分布在水深小于100 m的外陆架.快速聚类分析显示,黏土矿物可分为“类长江”、“类黄河”和“类台湾”3种类型,呈4个区域相间展布.“类黄河”型黏土矿物主要由黄海沿岸流将黄河、废黄河等物质再悬浮搬运而来,分布于29.5°N以北、127°E以西的外陆架区,并未越过东海外陆架进入冲绳海槽.外陆架区“类长江”型黏土矿物主要为低海平面时期古长江物质,并混有少量现代长江源悬浮物质;冲绳海槽区“类长江”型黏土矿物主要来自低海平面时期古长江物质.“类台湾”型黏土矿物主要由黑潮控制,由台湾经冲绳海槽南部搬运而来,沿陆坡附近沉积.      

台湾海峡表层沉积物中黏土矿物特征及物质来源

利用X射线衍射仪,对比分析台湾海峡及周边表层沉积物的黏土矿物特征,讨论长江、福建和台湾河流对海峡黏土矿物的贡献程度。福建河流（闽江）的黏土矿物以高岭石为主（>40％）,其次是伊利石（30％）和绿泥石,不含蒙脱石;长江和浙闽泥质区的黏土矿物特征是伊利石含量最高（61％～66％）,其次是绿泥石（16％～17％）和高岭石（10％～13％）,少量蒙脱石（6％～9％）。台湾河流（浊水溪）黏土矿物组合为伊利石（>70％）和绿泥石,不含高岭石和蒙脱石为特征。台湾海峡高岭石含量由西向东明显减少,说明高岭石主要来自福建的河流。〖JP2〗台湾海峡50 m等深线以东区域的黏土矿物具有高的伊利石和绿泥石含量,低的蒙脱石和高岭石含量,且伊利石的化学指数和结晶度值都明显低于长江和福建的河流,反映台湾河流的物质来源。在台湾暖流作用下,台湾河流为台湾海峡中北部提供了大量的伊利石和绿泥石。福建近海的黏土矿物主要是由福建河流提供的,但在平潭岛周边海域的黏土矿物可能有长江物质的混合。〖JP〗     

Mineralogy of Holocene Sediments from the Southwestern Black Sea Shelf (Turkey) in Relation to Provenance, Sea-level and Current Regimes

Grain size and mineral composition of core sediments were used to investigate influences of various terrestrial and marine conditions, which have prevailed on the southwestern Black Sea shelf during the Holocene. Siliciclastic mud with small amounts of sand and gravel from nearby coastal hinterland is the principal sediment type, whereas sediments deposited near the shelf edge and the Istanbul Strait and off the Duru Lake （a paleo-river mouth） constitued large quantities of sand and gravel of both biogenic and terrigenic origin. Variable amounts of aragonite, 1 nmmicas, quartz, feldspars, calcite and dolomite constitute the dominant non-clay minerals in bulk sediments. The clay mineral assemblage in the 〈 2 μm fraction is made up of smectite, illite, kaolinite and chlorite. Aragonite and calcite are mainly derived from benthic accumulations, whereas feldspars （mainly plagioclase） and smectite reflect magmaticvolcanic provenance and the distribution of 1 nm-micas and chlorite correlate with nearby metamorphic sources onland. Nevertheless, grain size and mineral distribution generally indicate a combination of effects of wind and wave climate, longshore and offshore cyclonic currents, changing sea-level stands and nearby source rock and morphological conditions. It is also suggested that at least part of clay minerals could be derived from the northwesterly Danube River input.     

南海北部陆架海域表层沉积物黏土矿物分布特征及物源分析

应用X射线衍射(XRD)对南海北部陆架海域225个站位表层沉积物黏土组分进行分析,结果表明,研究区黏土矿物总体以伊利石和绿泥石为主,高岭石和蒙脱石质量分数少,绿泥石、高岭石与蒙脱石质量分数呈明显的负相关关系。根据南海北部陆架海域表层沉积物中黏土矿物空间分布特征,结合邻近河流的黏土矿物组分以及洋流搬运作用,雷州半岛东部海域伊利石主要来源于广东沿海河流和珠江,绿泥石来自台湾岛,蒙脱石主要由吕宋河流提供,高岭石则由广东沿海河流和海南岛入海河流提供;雷州半岛西部海域伊利石来源于珠江,绿泥石和高岭石由红河提供,蒙脱石可能受广西入海河流携带的沉积物影响。     

海南岛周边海域表层沉积物中粘土矿物组合及其气候环境意义

X射线衍射分析结果显示,海南岛周边海域表层沉积物中粘土矿物主要由伊-蒙混层矿物、伊利石、高岭石和绿泥石等组成,其含量分别为34.2%,27.3%,21.1%和17.4%。采用人工判别分区和Q型聚类分析分区相结合的方法,将研究区按粘土矿物的相对含量和分布水深,划分出3个粘土矿物组合区,各分区的矿物组合特点显示它们的赋存现状受控于各种粘土矿物本身的粒度、形态特征、水动力条件和水深等因素。在南海海域首次鉴别出有较高含量的伊-蒙混层矿物存在,根据前人对伊-蒙混层矿物、伊利石和高岭石所指示气候条件的研究结果和本研究区内这些表层粘土矿物的含量、组合特征,判断海南岛及周边区域1 500 a以来一直处于比较温湿的气候环境。     

Trace metals in sediments from the inner continental shelf of the western Beaufort Sea

Increased development and changing climate have enhanced global interest in the Arctic Ocean and adjacent seas. Using a large, 3-yr data base, we have determined the distribution of trace metals in sediments from the inner shelf of the western Beaufort Sea. Metal concentrations in these sediments reflect pristine conditions, consistent with those for most coastal areas in the Arctic and with predictions based on average continental crust. Geographic variations in metal values are primarily related to sediment grainsize distribution. However, grain-size patterns are a complex function of several variables including source areas, ice and water movement, as well as physical and chemical weathering. Future identification of any metal contamination in Beaufort Sea sediments will be simplified by understanding the predictable natural patterns.     

Utility of clay Minerals in the Determination of Sedimentary Transport Patterns in the Bay of Cadiz and the Adjoining Continental Shelf (SW-Spain)

The contents and the distribution of clay minerals in modern sediments of the Cadiz bay and the continental shelf have been studied aiming to establish the sedimentary exchange model and the pathways followed by the clay fraction between the bay and the adjoining continental shelf. The most abundant clay minerals in the muddy sediments consist mainly of illite, smectite, interstratified illite-smectite, kaolinite and chlorite. The application of factor analysis method (PCA) to clay minerals data are considered to be useful in the determination of sedimentary transport patterns. The data from clay mineral assemblages, and their distribution map, make possible to establish the fine sediments transport paths in the study area using clay mineral as natural tracers. This model of transport takes in consideration the facies distribution, the supplies sources and the way of fine sediments are incorporated to the marine environment.

Two flows paths have been established: the outflows coming from Cadiz bay and the littoral zones; and the inflows coming from external marine zones of the bay. These flows are controlled by tidal currents and the morphology of the coast. The action of surge and the marine currents, specially the Atlantic Surface Water flow, are also important in the transport of fine sediments coming from sources located to the north of the study zone.     

Rare Earth Elements in the Bottom Sediments of the East Arctic Seas of Russia as Indicators of Terrigenous Input

The REE distribution was studied in the bottom sediments of the East Arctic shelf of Russia. It is established that sediments of the Laptev and western East Siberian seas are significantly enriched in REEs, the contents of which are much higher than those of other near-continental basins. The main REE sources are runoff of the Lena River, the basin of which comprises ancient crystalline shields and magmatic rocks enriched in LREEs with significant contribution from the coastal erosion of the ice complex from the Laptev Sea and western East Siberian Sea. The terrigenous flux with a specific REE composition is supplied to the Chukchi Sea through the Bering Strait.     

南海北部陆架中全新世沉积记录及古环境意义

 通过分析珠江口外陆架C069孔沉积柱样的粒度、黏土矿物、主量元素及底栖有孔虫,来研究南海北部中全新世晚期古环境演化。4.2 ka前为全新世大暖期后期,气候湿润,珠江口外陆架受大量的珠江淡水影响,导致C069孔位置的水动力条件较强,形成下段粒度较粗的碎屑沉积物,高岭石含量较高,低的MgO/Al2O3比值,以及受冲淡水影响形成的底栖有孔虫。由于受4.2 ka的极冷事件的影响,C069孔上段的沉积环境受珠江冲淡水影响减小,水动力条件减弱,沉积物粒度变细,高岭石含量降低,MgO/Al2O3比值增大,形成正常浅水环境的底栖有孔虫。4.2 ka以后,台湾来源物质的贡献增多,导致沉积物中伊利石和绿泥石的含量增多,伊利石结晶度和化学指数值都明显变小。     

杭州湾潮滩沉积物黏土矿物空间差异与物源指示

通过对杭州湾潮滩沉积物中主要黏土矿物成分及组合类型的研究,分析了杭州湾潮滩沉积物黏土矿物的空间分布特征。借助聚类分析等手段,同时结合杭州湾水动力特征,探讨了研究区黏土矿物的来源和成因。研究结果表明,杭州湾潮滩表层沉积物主要为黏土质粉砂,其余为砂质粉砂。本区沉积物黏土矿物成分复杂,主要为伊利石,其次是高岭石和绿泥石;还有少量蒙皂石和蛭石及1.4 nm过渡矿物。根据其相对含量可分为3种组合类型:Ⅰ型为伊利石-高岭石-绿泥石-蛭石类-蒙皂石型,Ⅱ型为伊利石-绿泥石-高岭石-蒙皂石-蛭石类型,Ⅲ型为伊利石-高岭石-绿泥石-蒙皂石-蛭石类型。在空间上,北岸的蒙皂石和绿泥石平均含量高于南岸,而伊利石、高岭石和蛭石(含1.4 nm过渡矿物)平均含量则低于南岸。高潮滩和中潮滩黏土矿物对比,除了蒙皂石含量高潮滩大于中潮滩外,其他矿物含量均无明显规律。表层沉积物黏土矿物的分布特征与水动力条件和物质来源密切相关,杭州湾北岸乍浦以东潮滩受潮流和长江沿岸流影响明显,沉积物主要为长江和东海源的;南岸由于曹娥江和甬江两条河流的注入,流域物质所占比例明显比北岸高。柱状岩芯样品中各黏土矿物含量自下而上的变化则反映了物源区风化强度的波动特征。     

中国大陆架海底沉积物中的稀土元素

选择渤海、黄海、东海和南海有代表性的大陆架沉积物样品,利用X射张荧光光谱法测定了15个稀土元素。中国大陆架沉积物稀土元素的丰度为156ppm,相对接近于中国黄土和花岗岩的丰度,而与太平洋沉积物的丰度相差较远,具有明显的“亲陆性”。稀土的配分模式旦显著的负斜率,属陆壳稀土的典型特征。稀土含量受沉积物粒度控制。实验表明稀土主要以类质同像存在于粘土矿物之晶体构造中。根据数理统计,稀土与亲陆源粘土矿物的元素为一类,彼此呈正相关;与亲海洋生物的元素为负相关。事实说明中国大陆岩石的风化和搬运,是中国海大陆架沉积物中稀土的主要物质来源。     

Distribution of clay minerals in surface sediments of the Aegean Sea: a compilation

Extensive published data sets and some new data on the clay mineral composition of surface sediments in the Aegean Sea, northeastern Mediterranean Sea, have been compiled in order to map the distribution patterns of clay mineral assemblages and to decipher source areas and transport paths. We distinguished six provinces, a Northwest Aegean Province, a Marmara-Dardanelles Province, a West Turkey Province, a Southeast Aegean Province, a Kithira Province and a Central Aegean Province. The clay mineral assemblages in the coastal and shelf areas carry the signature of the riverine sediment discharge from southeast Europe and Turkey, respectively. The southern Aegean Sea is probably influenced by the River Nile discharge and transport of clay minerals by surface currents. The clay minerals in the central Aegean Sea form a mixed assemblage comprising components of the other assemblages. A dispersion and dilution of clay minerals by surface currents is obvious.     

中全新世以来琼东南陆架粘土矿物特征及物质来源

以往针对南海北部陆架沉积物物质来源的诸多研究, 在一定程度上忽略了海南岛物质的影响.基于柱状沉积物样品的岩性、粒度、粘土矿物和AMS14C年代分析, 探讨了琼东南陆架沉积区X2站沉积物的物质来源.结果表明, X2站沉积物可划分为上、下两段, 下段(Ⅰ, 240~120 cm)主要为粘土质粉砂, 上段(Ⅱ, 120~0 cm)主要为粉砂质砂.粘土矿物主要由伊利石和高岭石组成, 含有少量绿泥石和蒙脱石.对比分析显示, 伊利石和绿泥石可能主要来自于珠江和台湾岛; 高岭石可能主要来源于海南岛和珠江, 蒙脱石主要来自于近源的雷琼地区, 即海南岛物源对南海北部陆架西段具有一定的影响.近4 ka以来, X2站沉积物的明显变粗和高岭石含量逐渐增高, 说明海南物质的输入增强, 这可能是由于近4 ka以来的气候变化或者人类活动增强所致.      

The paleoclimatic interpretation of clay minerals in sediments — a review

The application of paleoclimatic interpretation to clay minerals from continental and marine sediments is reviewed and the advantages of this method are indicated. Levels relatively rich in chlorite, illite, palygorskite and quartz are interpreted as corresponding to relatively dry periods, while more humid periods lead to more intensive weathering and consequently to the dominance of clay minerals more advanced in the relative stability scale, such as kaolinite. Smectite is taken to indicate a climate with contrasting seasons and a pronounced dry season.Using this and similar schemes, the paleoclimates of areas adjoining the Mediterranean Basin, North Sea, North Atlantic, Southern Arctic, Equatorial and North-West Pacific, and North Phillipine Sea are reconstructed.Clay minerals in sediments, particularly marine sediments, can be useful indicators of paleoclimatic conditions. While they do not produce direct indications of climatic parameters, they provide integrated records of overall climatic impact. Occasionally, they may be superior to the more conventional paleoclimatic methods, such as pollen or oxygen-isotope analysis.The limitations imposed on the paleoclimatic interpretation of clay minerals in sediments are discussed on the basis of examples. The distinction between authigenic and detrital clay minerals is shown to be problematic, particularly with regard to smectite. The relationship between climatic parameters and clay-mineral formation is complicated by the intervention of extra-climatic factors such as topography, geomorphology, lithology and time. Post-depositional diagenetic changes may not be recognized. Differentiation during transport, due to size sorting or differential flocculation may overlap climate-induced differentiation. The association of clay-mineral assemblages with specific source areas presents difficulties due to dispersal pathways that are affected by type of transport agency, i.e., water, ice or wind. Transport agencies are not constant with time. By an interdisciplinary approach, with the paleoclimatic information derived from clay minerals being correlated with that obtained from the analysis of microfossils and oxygen isotope data, many of these limitations can be overcome.     

Freshwater chlorophycean algae in recent marine sediments of the Beaufort, Laptev and Kara Seas (Arctic Ocean) as indicators of river runoff

Freshwater chlorophycean algae are characteristic organic-walled microfossils in recent coastal and shelf sediments from the Beaufort, Laptev and Kara seas (Arctic Ocean). The persistent occurrence of the chlorophycean algae Pediastrum spp. and Botryococcus cf. braunii in marine palynomorph assemblages is related to the discharge of freshwater and suspended matter from the large Siberian and North American rivers into the Arctic shelf seas. The distribution patterns of these algae in the marine environments reflect the predominant deposition of riverine sediments and organic matter along the salinity gradient from the outer estuaries and prodeltas to the shelf break. Sedimentary processes overprint the primary distribution of these algae. Resuspension of sediments by waves and bottom currents may transport sediments in the bottom nepheloid layer along the submarine channels to the shelf break. Bottom sediments and microfossils may be incorporated into sea ice during freeze-up in autumn and winter leading to an export from the shelves into the deep sea. The presence of these freshwater algae in sea-ice and bottom sediments in the central Arctic Ocean confirm that transport in sea ice is an important process which leads to a redistribution of shallow water microfossils.     

Clay minerals in SW Indian continental shelf sediment cores as indicators of provenance and palaeomonsoonal conditions: a statistical approach

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.