Distributional Feature of Detrital Minerais in the Superficial Sediment of South Yellow Sea

The composition ofdetrital minerals with grades of 0.063 - 0.25 mm in the superficial sediment of South Yellow Sea is mainly studied in the paper. The research result shows that the minerals can be divided into more than fifty sorts. The light minerals are mainly feldspar, quartz, mica, etc. The heavy minerals are mainly composed of amphibole, epidote, mica. autogeny pyrite, magnetite, hematite, garnet,zircon and so on, which mainly distribute in the sediments of silty clay and lutaceous silt. According to the content and distribution of the main minerals, the research area is divided into five mineral combination provinces. The assembled types of minerals in every province have close relationship with its hydrodynamic conditions and sedimentary environment. And the sorts of detrital minerals also show that the detrital substances in the sedimentary areas mainly originate from the drainage areas of rivers,bedrock weathering, and transformed sediment, etc.     

北极王湾表层沉积物中的粘土矿物及其对物源与古环境变化的指示意义

Kongsfjorden is a typical fjord on the edge of the ice cap of the Arctic Svalbard-Barents Sea. Its inner bay is connected with a modern glacier front along the direction of the fjord axis with a significant gradient change in the parameters of hydrology, sedimentation, and biology. In summer, ice and snow melt-water and floating ice collapse continuously and thus transport the weathering products on the surrounding land into the sea. Thus Kongsfjorden is regards as a natural laboratory for the study of unique sedimentation in polar fjords under modern glacial-sea water conditions. In this study, fifty-two surface sediments were collected in Kongsfjorden for clay mineral analysis to study the sediment source and sediment-transport process. Our results indicate that clay minerals in the surface sediments from Kongsfjorden are mainly composed of illite, chlorite, and kaolinite, and no smectite is found. Rocks from different periods exposed extensively in the surrounding areas of Kongsfjorden provide an important material basis for clay minerals in the Kongsfjorden. Kaolinite may be mainly derived from the fluvial deposits, weathered from reddish sandstones and conglomerates during the Carboniferous Period.Illite is mainly derived from Proterozoic low-grade and medium-grade metamorphic phyllite, mica schist, and gneiss. While chlorite is mainly from Proterozoic low-grade metamorphic phyllite and mica schist. In the direction from the fluvio-glacial estuary to the sea of the glacier front of Kongsfjorden, illite increase gradually,and the content of kaolinite declines gradually. However, the change pattern of chlorite is insignificant, which may be related to the provenance. Kongsfjorden detritus is mainly transported by the fluvio-glacial streams and icebergs into the sea and deposited in the inner bay. Coarse sediments are rapidly deposited in the glacier front,estuary, and near-shore areas. Clay fraction begins to deposit significantly by 200–400 m after flowing into the sea,which due to the crystal behavior of clay minerals, hydrodynamic condition and flocculation. Kaolinite and chlorite on the south of the bay near the Blomstrandhalv?ya Island is mainly affected by ice-rafted detritus and thus can reveal the trajectory of transportation by the floating ice while entering the sea.     

Characteristics of silicon and oxygen isotopic compositions of basalts near East Pacific Rise 13°N

In this study, 13 groups of silicon and oxygen isotopes and major elements of the basalts near the East Pacific Rise 13°N are used to study the fractionation of silicon and oxygen isotopes. Among these data, δ30Si values of basalts vary from -0.4%o to 0.2%o with a mean value of δ30Si of （-0.18±0.22）%o. The δ180 values range from 4.1%o to 6.4%o with a mean δ180 value of （＋5.35±0.73） %0. Since the δ30Si values increase in the series of basalt-basaltic andesite- andesite, and δ180 values display a positive correlation with the SiO2 content, we propose that the fractionation of silicon and oxygen isotopes is influenced by the SiO2 content in igneous rocks. Compared with the igneous rocks from Manus Basin with clinopyroxene as their dominant mineral phase, MORBs in this study containing olivine and plagioclase as primary minerals have lower δ180 and δ30Si values, indicating that the fractionation of silicon and oxygen isotopes is also affected by different Si-O bridges in silicate minerals. Furthermore, our samples from the EPR are defined as E-MORB based on K/Ti ratios. Probably, the difference in δ30Si and δ30O between our samples and a normal MORB are cause by the enriched components in E-MORBs.     

The distribution characteristics of clay minerals in the northern South China Sea

The clay minearals are composed of illite, chlorite, kaolinite, montmorillonite and mixed-layer minerals in the submarine sediments of the northern South China Sea. Three types of clay mineral zone can be recognized on the basis of the distributive regularity of clay minerals, submarine relief, hydrodynamic conditions and depositional characteristics in this region. Apart from the northern mainland source, kaolinites carried from the Philippines volcanic arc in the east and Malaysia in the south are also assumed to be one of the sources of the clay minerals in the deep sea. The increase of chlorites to the abyssal direction in the west of 116° E might be associated with the residual chlorites carried from the ancient Zhujiang River during the glacial period and the conversion of kaolinite into chlorite submarine volcanoes appear to be one of the sources of the increment of montmorillonite and chlorite around the Huangyan Island. From the distribution pattern of clay minerals in the whole area, it is kn     

南海神狐海域沉积物自生黄铁矿和石膏S同位素特征及对甲烷渗漏强度的示踪

The northern slope of the South China Sea is a gas-hydrate-bearing region related to a high deposition rate of organic-rich sediments co-occurring with intense methanogenesis in subseafloor environments.Anaerobic oxidation of methane(AOM) coupled with bacterial sulfate reduction results in the precipitation of solid phase minerals in seepage sediment,including pyrite and gypsum.Abundant aggregates of pyrites and gypsums are observed between the depth of 667 and 850 cm below the seafloor(cmbsf) in the entire core sediment of HS328 from the northern South China Sea.Most pyrites are tubes consisting of framboidal cores and outer crusts.Gypsum aggregates occur as rosettes and spheroids consisting of plates.Some of them grow over pyrite,indicating that gypsum precipitation postdates pyrite formation.The sulfur isotopic values(δ~(34) S) of pyrite vary greatly(from –46.6‰ to –12.3‰ V-CDT) and increase with depth.Thus,the pyrite in the shallow sediments resulted from organoclastic sulfate reduction(OSR) and is influenced by AOM with depth.The relative high abundance and δ~(34) S values of pyrite in sediments at depths from 580 to 810 cmbsf indicate that this interval is the location of a paleo-sulfate methane transition zone(SMTZ).The sulfur isotopic composition of gypsum(from–25‰ to –20.7‰) is much lower than that of the seawater sulfate,indicating the existence of a 34 S-depletion source of sulfur species that most likely are products of the oxidation of pyrites formed in OSR.Pyrite oxidation is controlled by ambient electron acceptors such as MnO_2,iron(Ⅲ) and oxygen driven by the SMTZ location shift to great depths.The δ~(34) S values of gypsum at greater depth are lower than those of the associated pyrite,revealing downward diffusion of 34 S-depleted sulfate from the mixture of oxidation of pyrite derived by OSR and the seawater sulfate.These sulfates also lead to an increase of calcium ions from the dissolution of calcium carbonate mineral,which will be favor to the formation of gypsum.Overall,the mineralogy and sulfur isotopic composition of the pyrite and gypsum suggest variable redox conditions caused by reduced seepage intensities,and the pyrite and gypsum can be a recorder of the intensity evolution of methane seepage.     

黄河口滨外区矿物分布特征及其控制因素探讨

In winter, 1983, forty surface sediment samples were collected from the area off the Huanghe River Estuary, Huanghe and Luanhe Rivers,and the rivers in Northwestern Shandong Peninsula. The sediments off the Huanghe River Estuary are composed of biotite, hornblende, epidote,actinolite, tremolite, garnet, zircon, sphene, diopside, magnetite, ilmenite, hematite, apatite, hypersthene, schorl, monazite, topaz, muscovite,leucoxene, rutile, zoisite, clinozoisite, vesuvianite, kynite, wollastoite,enstatite, bronzite, xenotime, anatase, pyrrhotine, glauconite, quartz,orthoclase, plagioclase, calcite and authigenic pyrite. On the basis of their mineral assemblages, the investigated area may be divided into three mineral provinces. Huanghe River, Luanhe River and Longkuo mineral provinces. The materials were derived from the Huanghe River, Luanhe Delta and Northwestern Shandong Coastal Region respectively. The sands from the Huanghe River are different from other sources, and are characterized by high contents of biotite, muscovite, plagioclase and calcite, and but low contents of pyroxene, epidote, Zircon, garnet and orthoclase. During the flood periods the materials from the Huanghe River fall into the Laichau Bay and are transported towards NE direction, which has been formed main outline of the distribution minerals in the sediment off the Huanghe River Estuary. However, Rmode cluster analysis shows that the sorting of the detrital minerals in this area is not strong. The data of the measurement current and nutrient salt in the water support the conclusions which are obtained from mineralogy study.     

胶州湾沉积物中有机碳、三氧化硫和矿物学的初步研究

The present paper deals with the mineralogy and some chemical composition such as Organic Carbon、Carbonate and Sulphate of surficial sediments in Jiaozhou Bay using the data obtained from X-Ray diffraction,chemical analysis and microscopic observation. Quartz、plagioclase、patassium feldspars and clay minerals are the main terrigenous minerals, and calcite is the predominant authigenic mineral in the sediments. Relatively high content of organic carbon and So3 are drainged from industrial waste water from some river running into the Bay. Some X-Ray diffraction data and ratio of integrated intensity of mineral special peaks indicate the distribution tendency of these minerals.     

Characteristics of heavy minerals composition and distribution in surface sediment from the Xinghua Bay of Fujian, China

The composition, assemblage and distribution characteristics of heavy minerals from 63 to 125 μm grain sizes in surface sediment from the Xinghua Bay (17 stations) are studied. The matter source of silt and the relationship between heavy minerals and sedimentary environment are also discussed. The results show that there are 37 kinds of heavy minerals and the average content of them is 12.08%,which exceeds 6% compared with the Meizhou Bay (5.67%). The dominant minerals are magnetite, hornblende, epidote, ilmenite,hematite, limonite, zircon and so on. Mineral kinds reveal that the sources of silt in this bay are the fluvial input and eroded products of bedrock in circnmjacent land and islands of the Xinghua Bay. However, the matter source from outside this bay is less. Four mineral assemblage zones can be divided based on heavy mineral contents and distribution characteristics in the Xinghua Bay, which are not only influenced by matter source, but also controlled by hydrodynamic condition and sedimentary environment in the Xinghua Bay.     

Distribution and composition characteristics of heavy minerals in surficial sediment of Minjiang Estuary

Heavy minerals with a size range of 0.125～49.250 mm in the surficial sediment of Minjiang Estuary are studied. Thirty-four heavy minerals have been identified, with an average content of 1.92%. Major minerals include magnetite, epidote, hematite, hornblende, ilmenite, and zircon mica. These types are the same as those in the 0.063～0. 125 mm range; however, the average content is lower, which reveals that the heavy minerals in Minjiang Estuary are mainly enriched in the very-fine sand fraction. According to the content and distribution characteristics of the major heavy minerals, Minjiang Estuary can be divided into 4 mineral assemblage zones. In each zone the assemblage of heavy minerals is greatly affected by the hydrodynamic condition and the sedimentary environment. Heavy mineral types also show that detrital matters in Minjiang Estuary are originated from the weathering and erosion of the bedrock in the Minjiang River drainage area.     

A STUDY OF DETRITAL MINERALS IN THE SEDIMENTS FROM THE WESTERN CENTRAL PACIFIC OCEAN

No Jess than 90 species of detrital minerals have been identified from the fine and very fine sand grains in the sediments from the Western Central Pacific. It is demonstrated that the volcanic minerals were originated from the eruption of oceanic tholeiitic magma since the Early Pleistocene according to the mineralogical indications and the rare-earth element distribution pattern. The mineral assemblage indicates that the detrital minerals are principally of pelagic origin. But the Melanesia Basin has more terrigenous constituents of minerals, of which, the quartz content increased generally during the interglacial periods. The area of Wallis Islands, especially of the Northern Fiji Basin has relatively typical pelagic substances and less terrigenous components. The genesis of the authigenic manganese nodules is closely related to the brown clay and can also be found in the calcium carbonate sediments in form of fine grain, but not in the relatively loose calciferous volcanic ash bed in the Northern Fi     

Clay diagenesis in recent marine fecal pellets

Fecal pellets are ubiquitous in sediment collected from deep ocean ridge, continental shelf and fjord-type estuarine environments off the Canadian West Coast. Fecal pellets of the immature diagenetic stage are composed generally of the same mineral suite as the bulk sea-bottom sample; except that degraded biotite and/or illite has absorbed Fe and K to regrade into glauconite. These fecal pellets (<10 years old) contain 10 to 15% glauconite. Highly evolved monomineralic fecal pellets (e.g. glauconite, smectite) of such modern age show that diagenetic minerals commonly associated with burial can be produced by sediment-organism interactions.     

The distinctive compositional evolution of glauconite in the Cretaceous Ukra Hill Member (Kutch basin,India) and its implications

An integrated study involving sedimentology, mineral chemistry and spectroscopy highlights a distinctive compositional evolution of Cretaceous glauconite within the Ukra Hill Member. Glauconite occurs at the top part of transgressive systems tract deposits built on a marine shelf. The concentration of glauconite steadily increases towards the maximum flooding surface, maximizing around 50%, and sharply falls at the onset of progradation. Unlike most Phanerozoic examples, Ukra glauconite forms by the variable degree of replacement of quartz, feldspar and mica grains. XRD, FEG-SEM and spectroscopy of glauconite pellets indicate an ‘evolved’ stage of maturation. Mossbauer spectroscopy reflects a minor substitution of Al^3+-Fe³⁺ (total) in tetrahedral sites and significant substitution of the same in octahedral sites. A consistently high value of K₂O as well as Fe₂O₃ contradicts the two popular theories, ‘layer lattice’ and ‘verdissement’, and support replacement origin of glauconite in a high a_Si+ and high a_K+ pore water environment. Incipiently formed glauconite records a marginal increase in K₂O content accompanied by release of Al₂O₃ and SiO₂ to form evolved glauconite pellets; those forming within quartz grains involve an addition of Fe₂O₃ (total) content during maturation. The minimal increase in K₂O content of incipiently formed glauconite, best exhibited by those formed within quartz grains is possibly related to stratigraphic condensation. Compositional evolution like this is exhibited by Precambrian glauconites involving abiotic substrates, but is unusual for the Phanerozoic. Original K₂O and Fe₂O₃ (total) content of glauconites is reduced around peripheries and fractures during diagenesis, adding to compositional variability.     

The use of diagenetic signatures to distinguish marine from continental deposits in Triassic-Jurassic sandstone reservoirs from the UK Central Graben

Poor biostratigraphic control for some Triassic-Jurassic successions in the North Sea Basin and sub-basins necessitates the use of alternative correlation methods. This study examines the use of diagenetic signatures to distinguish continenetal from marine sandstone successions (Triassic-Jurassic) in the UK Central Graben. The key diagenetic alterations encountered in these successions include kaolinitization of the framework grains and the development of sphaerosiderite and pyrite. The δ ¹³C_V-PDB values of siderite (−8.1 to −8.5‰) and of ankerite (−10.8 to −9.2‰), indicate a strong contribution of dissolved carbon from the decay of plant material in soil. However, marine water likely influenced diagenesis during periods of relative sea level rise by providing the dissolved sulfate (SO₄²⁻) required for the precipitation of pyrite. The presence of diagenetic alterations such as kaolinitization of framework grains and cementation by sphaerosiderite could indicate that the sediments were deposited in an overall continental setting. However, the occurrence of pyrite and scattered grains of deep-green colored glauconite suggests occasional marine influence. Such information on the changes of the diagenetic realm provides important clues for establishing a framework for stratigraphic correlations. Caution should be exercised when interpreting petrographic data as subsequent episodes of telodiagenesis can complicate petrographic interpretations.     

Glauconite grains in continental shelf sediments around the Korean Peninsula and their depositional implications

Glauconite grains are an important component of the surficial sediments on the Korean continental shelf. Relatively high glauconite contents (>20%) occur near Huksan Island in the Yellow Sea and on the outer shelf of the southern East Sea where they are associated with relict, sandy sediments. By contrast, glauconite grains are rare (<1%) in clay-dominated sediments. The grains can be classified into four major categories: (1) very abundant, green to dark green, spheroidal and lobate grains displaying bulbous and honeycomb exteriors with well-developed surface cracks; (2) dark green, discoidal grains with poorly defined cracks; (3) scarce, moderately dark green, accordion-shaped grains characterized by series of closely spaced, parallel surface ridges; (4) scarce, green to dark green, foraminifer-shaped grains. Microprobe analyses as well as optical microscopy and SEM observations show that most grains are composed of mineral mixtures (e.g., quartz, mica, feldspar) rather than a single mineral species. The mineralogy, morphology, and textural properties suggest that the grains may have formed mainly by replacement of fecal pellets, and the alteration of mica and clays which have filled foraminifera tests. The high potassium contents, rosette-shaped clay structures, and bulbous shapes reflect an “evolved” (mature) stage of glauconitization. Glauconite grains in Korean shelf sediments are presumably relict, and have been produced by the reworking of older glauconitic sediments during the Holocene sea-level transgression. Received: 4 October 1999 / Revision accepted: 18 May 2000     

长江粘土矿物示踪标记稳定性的初步研究

选择物质来源相对单一、区域较广的浙江沿岸东海内陆架区，以4种主要粘土矿物(伊利石、蒙皂石、高岭石、绿泥石)为研究对象，以探讨长江粘土矿物作为示踪标记的稳定性问题。研究区5组沉积物样品中粘土矿物的X射线衍射实验及含量分析结果表明，伊利石、蒙皂石和高岭石的相对含量较稳定，具有作为长江物源示踪标记的价值．而各区域的绿泥石含量之间不具有显著的统计相似性。现有资料还不能完全解释长江口及邻近东海内陆架区内粘土矿物组合的相对稳定状态，今后应对絮凝作用、沉积分异作用、海底生物地球化学作用等因素的效府做进一步的研究。     

Petrology and major element geochemistry of Peru margin phosphorites and associated diagenetic minerals: Authigenesis in modern organic-rich sediments

New petrographic and major element geochemical data from modern Peru margin upper slope-outer shelf phosphorites are presented, which provide insight into their origin and paragenetic relationship with other authigenic minerals (glauconite, pyrite and dolomite) occurring in organic-rich sediments. Glauconites are precipitated relatively early following the partial reduction of ferric iron and, following this process, phosphate, pyrite, and then dolomite precipitation take place at progressively deeper levels in the sediment in association with microbial reduction of sulfate. As in many ancient economic phosphorite deposits, the phosphatic facies here consist of nodules, crusts, coatings and strata composed of phosphatic pelletal grains (ooids, structureless grains, intraclasts, clumps and biogenic grains) in association with organic-rich biosiliceous sediments. All are considered to have formed within a few centimeters or within a few tens of centimeters below the sediment-water interface. Important factors that influence which morphology will tend to develop include the amount of available pore space, the presence of suitable nucleation sites, the amount and size of siliciclastic detritus incorporated as inclusions and the relative solution chemistries of the precipitating solutions. Bacterial mediation may play an important, but as yet unspecified role in the precipitation process. Textural data and factor analysis of chemical data suggest that structureless pellets are relatively inclusion-free Na-F-Mg-CO₃-substituted pore-water precipitates whereas ooids are inclusion-rich pore-water precipitates poor in lattice-substituted components. Variations in nodular cement birefringence and crystallinity are suggested to have been produced by similar lattice substitutions that directly reflect pore-water carbonate ion concentrations and thus relative degrees of organic-matter degradation. Phosphate and dolomite are intimately mixed, yet mineralogically distinct phases in phosphatized dolomicrites.

Depth-stratified threshold carbonate ion concentrations may control the lower limit at which phosphatic minerals may precipitate. Below depths of a few centimeters, excessive carbonate ion concentrations and diminished reactive iron and sulfate concentrations favor the development of dolomite while precluding further development of phosphatic minerals and pyrite. Periodic sediment reorganization (bioturbation, current winnowing and erosion, mass wasting, etc.) plays an important role in both concentrating pelletal grains and maintaining nodules and crusts at critical depth levels in the sediment, as well as mixing ordered mineral parageneses into complicated sequences.     

南海北部西侧海域粘土矿物的含量分布特征及来源分析

应用X射线衍射(XRD)方法对南海北部西侧海域315个表层沉积物<2μm的粘土组分进行分析.结果表明,本研究区粘土矿物有伊利石、绿泥石、蒙脱石和高岭石,其组合特征在不同区域表现出明显的差异.根据粘土矿物的空间分布特征以及研究区的海底地形特征,研究区大致可以分为3个不同区块:A区是珠江口外的大陆架区域;B区是海南岛以东陆架陆坡区域;C区为西沙海槽至西沙群岛附近区域.根据研究区表层粘土矿物分布特征、周围河流供给的主要粘土成分以及洋流搬运作用,发现A区高岭石(平均含量为19%)主要来自珠江,伊利石与绿泥石(平均含量分别为53%和18%)主要由台湾的河流提供,有珠江物质的混合,蒙脱石含量较低(平均含量为10%).B区的高岭石(平均含量为13%)主要由海南岛的河流提供,蒙脱石(平均含量为16%)主要由吕宋岛的河流提供,B区东部的伊利石和绿泥石来自台湾的河流,B区西部伊利石和绿泥石主要来自红河、越南中部河流,海南岛物源亦有贡献.C区高岭石含量较低(平均含量为12%),越南中部河流和红河为C区蒙脱石(平均含量为14%)的主要物源区,C区东部伊利石和绿泥石来自台湾的河流,C区西部伊利石和绿泥石主要来自红河、越南中部河流.     

白令海和西北冰洋表层沉积物磁化率特征初步研究

为了准确解释环境磁学参数记录的极地古气候环境变化信息,本研究对白令海和西北冰洋61个站位的表层沉积物进行了高、低频质量磁化率(χ)、非磁滞磁化率(χARM)和磁化率-温度(k-T)分析,以探明该区沉积物中磁性矿物的种类、来源与搬运路径。结果显示,样品的χ具有明显的地域分布特征。白令海的χ值整体高于楚科奇海,并在育空河口外侧和圣劳伦斯岛南侧较高,向北和向西南方向逐渐减小。楚科奇海中东部陆架上表层沉积χ值高于阿拉斯加沿岸,而西北冰洋深海平原和洋脊区的χ值最低。χARM的变化趋势与质量磁化率相似,但频率磁化率的变化趋势与质量磁化率正好相反。k-T分析结果显示阿留申海盆沉积物中的铁磁性矿物以磁赤铁矿占主导,白令海陆架育空河口外侧和圣劳伦斯岛南北两侧为磁铁矿,白令海陆架西部和楚科奇海陆架中东部为磁赤铁矿和磁铁矿,楚科奇海阿拉斯加沿岸为黄铁矿,而西北冰洋陆坡、深海平原和洋脊区为胶黄铁矿和黄铁矿,但高纬度区沉积物中的胶黄铁矿含量更高。沉积物中磁性矿物的区域性分布受沉积物来源、洋流和底质环境等因素的控制。白令海和楚科奇海陆架磁赤铁矿来源于亚洲大陆,白令海陆架东部的磁铁矿来自育空河流域,阿拉斯加沿岸沉积物中的黄铁矿,应为阿拉斯加西北部陆源侵蚀来源的或早期成岩作用形成的,西北冰洋深海盆区的胶黄铁矿,为自生成因的。     

Sea-floor sediment distribution in the Gulf of Mexico

Carbonate content, smear-slide analysis and diffuse reflectance spectrophotometry were utilized to determine modern sediment composition and distribution throughout the Gulf of Mexico. In all, 186 core top and grab samples distributed throughout the Gulf were analyzed. Reflectance spectra were taken from thick smear slides from the near ultraviolet, through the visible, and into the near infrared. The first derivatives of the percent reflectance data were subjected to factor analysis producing factors that grouped covarying first-derivative wavelengths. Factors were interpreted by comparison to first-derivative curves for known sediment components and minerals. Interpretation was aided by the mapping of both calcium carbonate content and smear-slide sediment classes. The most easily interpreted factor solution was produced by analyzing only the visible region of the spectrum and extracting seven factors which explained 98% of the cumulative variance. These factors, in order of their relative importance, are interpreted as (1) marl and calcareous clay, (2) glauconite, (3) kaolinite, (4) organic matter, (5) phosphorite, (6) hematite, and (7) goethite. Some factor maps are consistent with known sources of fluvial sediment input; for example, kaolinite is deposited off rivers draining the southeastern US. Other factor maps are related to the origin of the material in the factor, glauconite, for example, being confined to low sedimentation regions of the outer shelf. The most unusual observation concerns the distribution of hematite, which appears to be transported from the rivers of south Texas, primarily the Rio Grande, across the shelf then eastward downslope along the base of the Sigsbee Escarpment. This eastward transport seems to be explainable only by transport in bottom currents flowing along the base of the Sigsbee Escarpment.     

北部湾VI钻孔岩芯的重矿物组合研究

本文对北部湾XI钻孔岩芯中各种沉积相中的重矿物组合分别作了研究,结果表明,在湖相沉积物中自生黄铁矿物含量高,滨海相沉积物中稳定矿物(钛铁矿、电气石、锆石)特别富集,浅海相沉积物中则出现大量的自生海绿石,由此说明,重矿物组合的研究对阐明沉积相是有其重要意义的。