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1.
The siliceous skeletal remains of diatoms are a primary component of sediments, covering vast areas of the sea floor. We used high performance liquid chromatography–electrospray ionization–tandem mass spectrometry (HPLC–ESI–MSn) under high resolution time-of-flight MS (TOF-MS) conditions, as well as nuclear magnetic resonance spectroscopy (NMR) and Fourier transform infrared spectroscopy (FTIR), to investigate the distribution and molecular diversity of long chain polyamines (LCPAs) entrapped in sedimentary diatom biosilica in sediments from the Indian sector of the Southern Ocean, the Bering Sea and the Northeast Pacific. This revealed the existence of complex polyamine populations with both known and unknown structural features, including the presence of ketone and carboxylic acid groups in the LCPA backbone, functional groups that likely modulate the silica precipitating properties of LCPAs in the environment and which may constitute points of initial silica deposition (Wallace, A.F., De Yoreso, J.J., Dove, P.M., 2009. Kinetics of silica nucleation on carboxy- and amine-terminated surfaces: insights for biomineralization. Journal of the American Chemical Society 131, 5244–5250). Although various LCPA species overlapped between samples (putrescine-based LCPAs with various degrees of methylation and N-methyl propylamine repeat units were ubiquitous in all samples), clear regional differences were shown in composition and structural characteristics, likely reflecting the various diatom species contributing to the total LCPA pool for each sedimentary environment. We further show, using scanning electron microscopy and energy dispersive X-ray analysis (SEM–EDX) that LCPAs purified from diatom skeletal remains rapidly re-direct the formation of silica nanospheres in vitro, and become embedded in the precipitated silicified matrix, forming an LCPA–silica composite material. The results show that aliphatic polyamines produced by diatoms for morphogenesis of their cell walls are widespread in sediments where the fossil frustules are preserved. These newly assigned components constitute useful biological markers of diatom input to sediments. 相似文献
2.
Frédéric Bouchard Reinhard Pienitz Joseph D. Ortiz Pierre Francus Isabelle Laurion 《Boreas: An International Journal of Quaternary Research》2013,42(3):575-595
Thermokarst ponds are widespread in arctic and subarctic regions, but little is known about their temporal evolution prior to human observations. This paper presents a pioneer biostratigraphic study conducted at a subarctic site with limnologically contrasted ponds located on the eastern shore of Hudson Bay, Canada. Fossil diatom and visible near infrared (VNIR) derivative spectral analyses were performed on short sediment cores, confirming the occurrence of three distinct stratigraphic facies as already inferred from an anterior sedimentological study: a lacustrine upper facies (UF) and a marine lower facies (LF), separated by an organic‐rich/peat transitional zone (TZ). Diatoms were almost absent from LF, but increased significantly in both TZ and UF. Identified diatom taxa were mainly benthic species (e.g. genera Fragilaria, Pinnularia), and their down‐core distribution appeared to be related to dissolved organic carbon (DOC) and possibly pH conditions. Diatom‐inferred DOC showed a decreasing trend towards the surface (potentially associated with an increase in pH), inverse to the general trend in this region, suggesting the action of other mechanisms on DOC, such as exhaustion of external inputs from limited catchments and the role of discontinuous peat layers (former surfaces of permafrost mounds) during the initial stages of pond formation. These bryophilous substrates in aerophilic habitats probably controlled diatom community composition. The combination of diatom and VNIR data revealed similar trends between (i) opal (amorphous silica) and diatom abundances; (ii) eukaryotic/prokaryotic algae ratio and anoxia or hypoxia in bottom waters; and (iii) limonite (iron oxide) and redox conditions in surface sediments. These findings indicate that diatom community changes and pond limnological evolution in the recent past were controlled mainly by autogenic processes (e.g. local vegetation/soil development, peat accumulation and erosion), rather than by allogenic forcing mechanisms (e.g. precipitation and temperature, geochemical leaching of the surrounding glaciomarine sediments). 相似文献
3.
The subtidal sediments of four coastal environments (beach, berm, surf zone and nearshore sea floor) of Kuala Terengganu have
been studied in terms of their textural characteristics and depositional process. Sampling and statistical analyses of the
grain size distributions of beach, surf zone and shallow sea-floor sediments at various locations along the coastline show
that they varied in their mean grain size as well as values of sorting and skewness. The statistical parameters of grain size
distributions thus allowed recognition of distinct sub-environments. The size distribution of such sediments suggests that
the various processes that are responsible for their transportation and deposition are wave, current and wind action. The
different energy conditions and the morphology of each coastal environment seem to be reflected in the characteristics of
the sediments in each environment. 相似文献
4.
Rayees Ahmad Shah Hema Achyuthan Aasif Mohmad Lone R. Ramanibai 《Journal of the Geological Society of India》2017,90(2):159-168
Lakes and wetlands are dynamic geomorphic units of a landscape that hold geochemical signatures of sediment provenance and paleo-environmental shifts and are major sinks for organic matter accumulation. The source of organic matter is diverse in lake sediments and varies widely with the type and size of the lake and hence it is important to understand the source of organic carbon (terrestrial or in situ) in lake systems in order to monitor the health of the lake. Wular lake, located in north Kashmir, is one of the largest fresh water lake in India, situated at an average elevation of 1580m ASL. The lake is fed by a number of watersheds that bring a diverse type of sediments and organic matter and thus deposit them into the Wular lake basin. In order to understand sediment distribution pattern, content and source of organic matter, sediment provenance and the persisting environment in the Wular lake, 32 lake floor sediment samples covering the entire lake were collected and analyzed for organic element analysis, CaCO3, organic matter, sediment texture and diatom analysis. The results indicated that sediments in the lake are dominated by silt and silty clay. The organic carbon in the lake ranged from 0.83%-4.52% and nitrogen varied from 0.06%-0.5%. The Carbon to Nitrogen (C/N) ratios (9.04 to 22.03) indicate a mixed source of organic carbon but dominated by in situ lake sources from the vascular and lake biota accumulation. The diatom analysis revealed the occurrence of a diverse type of species along the sampling sites present within the lake. The wide distribution of the diatom species such as Cymbella, Cyclotella and Tabularia etc. in the lake indicate high organic pollution and alkaline fresh water environment prevailing in the lake. 相似文献
5.
6.
VENKATARATHNAM KOLLA JOHN A. KOSTECKI LAWRENCE HENDERSON LILLIAN HESS 《Sedimentology》1980,27(4):357-378
Most of the Quaternary sediments of the Mozambique Fan have been derived from Africa-Madagascar and deposited by turbidity currents in Pleistocene time. Currents caused by movement of the Antarctic Bottom Water also played a significant role in reworking and redepositing sediments along the marginal areas of the fan. The inner or upper Mozambique Fan is characterized by a single, leveed valley. Due to the effects of the Coriolis force, the natural levees to the east of the valley (left, looking downstream) are higher and contain more terrigenous sediments than those to the west of the valley. The sea floor to the west of the valley returns regular hyperbolic echoes as seen on 3·5 kHz echograms, whereas to the east of the valley, the sea floor is relatively smooth. The sediments on the valley floor are coarse-grained (with median grain up to 2 mm) and poorly sorted, and occur often as massive turbidites, interbedded with hemipelagic sediments. Away from the valley, both to the east and the west, the terrigenous sediments are relatively fine-grained and have been deposited as overbank turbidite sequences. We estimate the maximum velocities of the channelized turbidity currents in the upper fan to have been 8–32 ms?1. The middle fan has several distributary channels with no levees and has a relatively flat sea floor, characterized by lack of acoustic penetration. Thick, sheet-like, turbidite sand beds, deposited primarily by unchannelized turbidity currents, characterize the middle fan. The middle fan grades, towards the margins, into the outer (lower) fan which is relatively free of channels, has good acoustic penetration and contains hemipelagic and pelagic sediments, and thin, fine-sand turbidite and/or contourite beds. A wide zone of sediment waves, formed from the reworking of the turbidity current-fed sediments by the Antarctic Bottom Water, forms part of the outer fan. 相似文献
7.
I. F. Gablina I. G. Dobretsova E. V. Narkevskii A. N. Gustaitis T. A. Sadchikova N. V. Gor’kova A. T. Savichev A. D. Lyutkevich O. M. Dara 《Lithology and Mineral Resources》2017,52(5):335-357
Based on materials obtained in Cruises 33 and 34 of the R/V Professor Logachev, the paper addresses formation conditions, morphology, structures, mineral composition of the present-day oceanic sulfide ores, and their relationships with the host (biogenic carbonate) bottom sediments in the 19°–20° N MAR (Zenith-Victoria and Petersburg hydrothermal fields) region. The grain size distribution, mineral composition of the carbonate (background) and ore-hosting sediments, as well as physicochemical parameters of their interstitial waters, are examined. The results suggest a significant role of hydrothermal-metasomatic processes in the formation of ores and ore-bearing sediments. A model is proposed for the formation of sulfide mineralization in oceanic sediments at the geochemical barrier in the zone of their interaction with the acid hydrothermal (diffuse-type) ore-bearing solutions delivered from rocks of the ocean floor. 相似文献
8.
V. N. Sval’nov O. B. Dmitrenko G. Kh. Kazarina E. D. Berezhnaya 《Lithology and Mineral Resources》2014,49(4):281-291
Reference cores of sediments from the Angola and Cape basins were subjected to lithological, geochemical, and micropaleontological investigations. Based on nannofossil and diatom assemblages, the examined sediments represented by oxidized miopelagic clays, calcareous (nannofossil-foraminiferal, foraminiferal-nannofossil), calcareous-clayey, and clayey-calcareous mud are estimated to be the Pleistocene-Holocene in age. The Cape Basin section includes surface and buried ferromanganese nodules. There are indications of sedimentary material redeposition by the Antarctic Bottom Water and turbidity currents. The South Polar Front zone changed repeatedly its geographic position and migrated northward from the presentday one. As a whole, the Pleistocene-Holocene sedimentation in the Angola and Cape basins corresponds to the incomplete pelagic (miopelagic) type of oceanic lithogenesis. 相似文献
9.
Distinctive diatom assemblages may be associated with tsunami sediments and may often contrast with the assemblages found within sediments underlying the tsunami deposit as well as those associated with the modern coastal environment. Sediments associated with the 1998 tsunami that destroyed much of the Sissano lagoon area in northern Papua New Guinea have been investigated. Surface sediments from three transects across the sediment spit near Warapu have been examined for diatom content and preservation. The preservation is variable, and the data show an, often chaotic, assemblage that can be attributed to the tsunami waves incorporating and depositing diatoms from distinctive habitat zones during their runup and subsequent backwash. The diatoms identified within the Warapu sediments indicate an origin from within the inter-tidal and offshore area rather than from the beach–sand spit complex. The sand deposits disclose a high percentage, in excess of 75%, of broken diatom valves, and a predominance of centric (circular) species due to preferential preservation. The study demonstrates that the application of diatom biostratigraphy to modern tsunami deposits can be used in conjunction with other stratigraphical lines of evidence to interpret the source and provenance of historical and palaeo-tsunami deposits. 相似文献
10.
《Russian Geology and Geophysics》2016,57(9):1321-1333
We studied the upper 0-1000 mm of the bottom sediment core from the underwater Sofia Lepneva Ridge of Lake Teletskoye. The core sediments accumulated with a rate of 0.3 mm/year (with regard to their humidity, with a rate of 0.45 mm/year) and have an age of about 2000 years. A total of 194 species (212 varieties and forms) of diatoms have been revealed. Analysis of diatom composition in tanatocoenoses showed prevalence of species inhabiting the bottom and periphyton, widely distributed geographically, indifferent to salinity, and preferring a weakly alkaline environment, as well as beta-mesosaprobionts. The number of diatom valves ranged from 0.86 to 64.4 mln valves/g, with an average of 22.90 ± 0.78 mln valves/g. Over the last millennium, the peaks of the abundance of diatoms, especially representatives of the cold-water assemblage, including the main dominant Aulacoseira subarctica (O. Mull.) Haw., are referred to the periods with low water temperature. The pH value for the period from 172 BC to 2006 AD has been reconstructed from the proportion of the numbers of valves of pH-indicating diatom species, which varied from 7.51 to 7.69, with an average of 7.580 ± 0.003. The pH value predicted up to 2259 AD was estimated by spectral (Fourier) analysis at 7.53-7.63, with a similar average of 7.580 ± 0.001. Analysis of reconstructed and predicted pH values showed their insignificant changes and correspondence to a weakly alkaline environment (7.0-8.5). These pH values suggest stability of the lake environment both in the past periods and in the nearest future. 相似文献
11.
Alfonso Mucci Louis-Filip Richard Marc Lucotte Constance Guignard 《Aquatic Geochemistry》2000,6(3):293-324
The distribution and partitioning of dissolved andparticulate arsenic and phosphorus in the water columnand sediments of the Saguenay Fjord in Quebec, Canada,are compared. In addition, selective and/or sequentialextractions were carried out on the suspendedparticulate matter (SPM) and solid sediments tocontrast their geochemical behaviors in this naturalaquatic system.Results of our analyses show that both arsenic andsoluble reactive phosphate are actively scavenged fromthe water column by settling particles. Upon theiraccumulation at the sediment-water interface some Asand P may be released to porewaters following thedegradation of organic matter to which they areassociated. The porewater concentrations are, however,limited by their strong affinity for authigenic,amorphous iron oxyhydroxides which accumulate in theoxic sediments near the sediment-water interface.The geochemical behavior of arsenic and phosphorusdiverge most strikingly upon the development of anoxicconditions in the sediments. Following their burial inthe anoxic zone, amorphous iron oxyhydroxides arereduced and dissolved, releasing phosphate and arsenicto the porewaters. We observed, however, thatporewater arsenic concentrations increase at shallowerdepths than phosphate in the sediments. The reductionof arsenate, As(V), to arsenite, As(III), and itsdesorption prior to the reductive dissolution of thecarrier phase(s) may explain this observation.Driven by the strong concentration gradientestablished in the suboxic zone, phosphate diffuses uptowards the oxic layer where it is readsorbed byauthigenic iron oxyhydroxides. In the organic-rich andrapidly accumulating sediments at the head of theFjord, porewater sulfate depletion and the resultingabsence of a sulfide sink for Fe(II), may lead to theformation of vivianite in the fermentation zone, apotential sink for phosphate. Arsenite released to theporewaters in the suboxic and anoxic zones of thesediments diffuses either down, where it is adsorbedto or incorporated with authigenic iron sulfides, orup towards the oxic boundary. Arsenite appears tomigrate well into the oxic zone where it may beoxidized by authigenic manganese oxides before beingadsorbed by iron oxyhydroxides present at the samedepth. Whereas, in the absence of authigenic carbonatefluorapatite precipitation, the ability of oxicsediments to retain mineralized phosphate is afunction of their amorphous iron oxyhydroxide content,arsenic retention may depend on the availability ofmanganese oxides, the thickness of the oxic layer and,its co-precipitation with iron sulfides at depth. 相似文献
12.
陕西宁强禅家岩天坑群是汉中天坑群中 4 个相对独立的喀斯特系统之一,位于扬子陆块北缘,发育有多样的地质遗迹。文章通过大量野外勘测,总结出陕西宁强禅家岩天坑群地质遗迹的分布特点,并分析了主要地质遗迹的基本特征及形成原因,以揭示南北过渡带峡谷地貌下喀斯特的形成及演化机理。结果表明:（1）研究区形成了以天坑、台原、溶洞、峡谷以及次生化学沉积物为特色的2大类4类5亚类的地质遗迹;（2）区内喀斯特地貌典型,天坑和溶洞最为发育;（3）受峡谷深切影响,研究区内形成有4个地表喀斯特台原,其均具有相对独立的喀斯特水文地质特征,而天坑和竖井均已进入退化期;（4）在地层、岩性和构造多因素作用下,区内天坑孕育于新构造运动时期。 相似文献
13.
Depositional and diagenetic history of Pleistocene and Holocene oolitic sediments and sabkhas in Kuwait, Persian Gulf 总被引：1，自引：0，他引：1
FRANTISEK PICHA 《Sedimentology》1978,25(3):427-450
The Pleistocene and Holocene oolitic sediments of southern Kuwait appear as parallel ridges—ancient and recent barrier beaches and coastal dunes. They are underlain by Tertiary clastic deposits and interfingered with sabkhas. Considering the superposition, primary composition and diagenetic alterations five lithostratigraphic units were distinguished within the oolitic complex. Their formation and preservation were related principally to eustatic oscillations of sea level during Quaternary times, although post-Pliocene tectonics also played an important role both in physiographic and sedimentary developments of the region. The large accumulation of oolites in southern Kuwait might be related, at least partly, to the existence of two tidal channels, khors, discharging waters over-saturated with respect to calcium carbonate over broad tidal flats. The formation of oolites culminated in late Pleistocene probably due to an extreme aridity of the climate. The subaerial diagenesis of the oolitic ridges led to gradual cementation and recrystallization of oolites. The four stages of progressive diagenesis distinguished in the area are compared with schemes suggested by Land, Mackenzie & Gould (1967) for Quaternary sediments in Bermuda and by Gavish & Friedman (1969) for aeolianite ridges in Israel. On the sea floor the cementation has produced widespread beach rocks and hard layers. Aragonite encrustations and dripstones occur within the intertidal zone of channels and lagoons. The shallow, occasionally flooded depresssions in sabkhas are occupied by algal mats. The amount of dolomite in sabkha sediments is rather low in comparison with similar environments of the southern Persian Gulf. This might be at least partly explained by the absence of dolomitic rocks in the Tertiary substratum in Kuwait. The complex of Quaternary sediments in southern Kuwait represents a petroleum setting in which the organic rich source sediments of lagoons and sabkhas are closely associated with highly porous reservoir rocks of the oolitic coastal ridges. 相似文献
14.
To describe and analyse the role of sediments in the matter cycling in large shallow transboundary Lake Peipsi (L. Peipsi)
in north-eastern Europe, detailed surface-sediment mapping was conducted. On the basis of grain size the surface sediments
fall into three groups: coarse-grained sediments (prevailingly sands in the lake’s southern part), fine-grained sediments
(mainly silts) and silty sands, both in the central deeper part within the 8-m depth contour. The groups of deposits have
a distinct spatial distribution, determined mainly by the current system in the lake. The main source of bottom sediments
is the erosion of the lake floor and shores, the role of the river input seems to be limited. Fine-grained organic-rich sediments
are very cohesive, playing the main role in the circulation of various inorganic and organic pollutants like nutrients and
xenobiotics. Due to the cohesive character of the sediments their physical and chemical properties are extremely diverse and
if the near-bottom shear stress increases (extreme meteorological events, changes in the water level, etc.), the lake floor
may be subjected to episodic erosion and resuspension, which may cause remobilisation of impurities in muddy sediments and
their return to the food chain. 相似文献
15.
LLOYD H. BURCKLE DAVIDA E. KELLOGG THOMAS B. KELLOGG JAMES L. FASTOOK 《Boreas: An International Journal of Quaternary Research》1997,26(1):55-60
The occurrence of diatoms (both marine and freshwater) in sediments beneath the West Antarctic Ice Sheet (WAIS) is suggestive of past ice-sheet collapse. However, it is not the only model explaining such occurrences. We propose another mechanism for introducing diatoms beneath ice sheets by considering the fate of a diatom placed (by eolian processes) on top of an ice sheet. Mathematical modeling indicates that the route the diatom will take through the ice sheet is dictated by the basal melting rate. If no basal melting takes place, flowlines will crop out at the ice-sheet margin. However, if basal melting is as low as 0.01 m/yr the trajectories of all Howlines except for those nearest the margin will intersect the bed, with those diatoms deposited near the dome reaching the bed about halfway down the Howband. Larger values of basal melting lead to the diatoms reaching the bed even faster and closer to the point of origin. In light of these results, the presence of diatoms in sediments beneath the WAIS does not lead to a unique solution; it is not necessary to invoke past ice-sheet collapse to account for their presence. 相似文献
16.
湖泊是全球生态系统的重要组成部分。尽管湖泊初级生产力的生物多样性在湖泊生态系统中发挥着非常重要的作用,但对其如何在千年时间尺度上对气候变化做出响应却知之甚少,而千年时间尺度与预测未来变化最为相关。本文以云南云龙天池湖泊为研究对象,以湖泊重要的初级生产力硅藻为研究手段,分析了末次冰消期期间硅藻生物多样性对千年尺度上气候变化的响应。云龙天池硅藻生物多样性表现为暖期高、冷期低。随着全球温度的快速变化,硅藻生物多样性亦对应的快速响应:在转暖时(Bolling/Allerod暖期)快速增加,在转冷时(Herinrich 1和Younger Dryas)快速降低。这些变化主要与温度变化驱动的湖泊环境条件的变化(比如冰封期长短、边岸带水生植被的变化等)有关。研究结果还表明,在末次冰消期期间,云龙天池湖泊硅藻生物多样性与千年尺度的气候变化同步,而且在长时间尺度上,气候变暖对高山湖泊生物多样性可能是有利的。 相似文献
17.
东海陆缘(闽北段)晚第四纪沉积的硅藻学研究 总被引：10，自引：1，他引：10
对东海陆缘 (闽北段 )晚第四纪沉积 4口钻井岩心进行系统的硅藻分析研究,获得丰富的硅藻化石,共发现硅藻 117种和变种,分属于 33个属。根据剖面硅藻组合特征变化,结合最优分割法和对应序分法的计算机运算结果,可以详细划分为 12个硅藻带,自下而上为 :1.Cascinodiscusargus-Cos.wittiomus-Cyclotellastriata硅藻带,2.Cos.blandus-Cyclotellastriata硅藻带,3.Cos.excentricus-Trbliepteychuscocconiformis硅藻带,4.Gomphonema-Cos.blandus-Actnolychusralfsii硅藻带,5.Cos.-Cyclotellastriata-Actinocyclusralfsii硅藻带,6.Cos.-Actinolychusralfsii硅藻带,7.贫乏硅藻带,8.Cos.lineatus-Cos.rothii-Actinolyclusralfsii硅藻带,9.Gomphonema-Cyclotellastriata-Cocconeisplacentulavareuglypta硅藻带,10.Cos.rothii-Cyclotellastriata-Actinolychusralfsi,11.Cymbel laaffinis-Cyclotellastriata-Gomphonema硅藻带,12.Coscinodiscuswittinus-Cyclotellastriata-Epithemiahynd manii硅藻带,建立了该区晚第四纪硅藻组合序列,并探讨其相应的古环境演变。 相似文献
18.
~(40)Ar-~(39)Ar GEOCHRONOLOGY OF THE SUTURE ZONE, LADAKH, INDIA1 TalatAhmedetal.GeochemicalJournal,1999.
2 HoneggerK ,etal.EarthandPlanetaryScienceLetters,1982 ,6 0 :2 53.
3 SearleMP ,etal.GeologicalSocietyofAmericaBulletin ,1987,98:6 78.
4 SharmaK ,K .PhysicsandChemistryoftheEarth ,1990 ,17( 2 ) :133.
5 Venkatesan ,etal.EarthandPlanetSciLett,1993,119:181.… 相似文献
19.
马桥遗址经多次发掘,取得了很多成果。本次采集了2005年发掘的05MMT4探方样品,进行孢粉、藻类研究。根据孢粉、藻类成分特征,划分出了3个孢粉组合带,它们分别是:1带是以Quercus(evergreen)-Gramineae-Typha-Pi-nus-Polypodiaceae-Concentricystes为主孢粉带;2带是以Concentricystes-Quercus(evergreen)-Salvinia-Polypodiace-ae-Typha-Gramineae为主孢粉带;3带是以Pinus-Salix-Quercus(evergreen)-Chenopodiaceae-Pteridium-Polyp-odiaceae-Concentricystes为主孢粉带,并以此恢复了当时古植被和古地理环境。且对马桥先人的生活环境、农耕发展作了探讨,为上海地区文化发展及文明化进程提供了新资料。 相似文献
20.
Aleksandra AJNOVI~ 《《地质学报》英文版》2008,(6)
Sediments of the western part of the Valjevo-Mionica basin(Serbia)were examined both geochemically and mineralogically to explain,on the basis of their sedimentologicai characteristics,the causes of changes in their qualitative and quantitative composition.A total of 62 samples obtained from the drilihole at depths up to 400 m was investigated.Using correlation of the obtained data,six geochemical zones were defined,two of which being specially distinguished by their mineralogical, geochemical and sedimentological characteristics.The first one,upper zone A,consists of banded marlstones interbedded with clay and oil shales and is characterized by presence of analcite and searlesite.These minerals and very high contents of Na_2O indicate sedimentation in alkaline conditions with increased salinity in arid climate.That provided pronounced water stratification,as well as higher bioproductivity in the basin and sedimentary organic matter preservation.Therefore,the zone A sediments are characterized by high organic matter contents of the type which provides good potential for production of liquid hydrocarbons.Another specific zone,zone F,contains sediments with very high MgO,K_2O and Li concentrations.Their geochemical correlation,as well as almost complete absence of illite in this zone,indicates the presence of interstratified clay mineral type illite-saponite (lithium-bearing Mg-smectite). 相似文献