山东半岛南部近岸海域碎屑矿物对中小河流的物源响应

对山东半岛南部近岸海域的106个表层沉积物样品及大沽河、五龙河和乳山河的94个表层沉积物样品进行碎屑矿物分析,系统地研究了碎屑矿物的分布特征及物源指示。研究区共鉴定出40种重矿物和13种轻矿物,重矿物以普通角闪石、绿帘石、黑云母和自生黄铁矿为主,轻矿物以石英、斜长石、钾长石和风化云母为主。根据碎屑矿物组合特征,将研究区分为4个矿物区:Ⅰ区为胶州湾口至崂山头的附近海域;Ⅱ_1亚区为丁字湾和鳌山湾附近水深约15m以浅的海域,Ⅱ_2亚区为研究区东南部水深20m的远岸区;Ⅲ区处于Ⅱ区和Ⅳ区的过渡带;Ⅳ区为乳山口西南部近岸海域。Ⅰ区和Ⅱ区的矿物组合均为普通角闪石-绿帘石-石英-长石,Ⅰ区和Ⅱ_1亚区受大沽河、五龙河和乳山河输入的物质及沿岸基岩、岛屿风化碎屑的影响较大,Ⅱ_2亚区主要为晚更新世低海平面时形成的陆架残留沉积。Ⅲ区矿物组合为普通角闪石-石英-长石-片状矿物,Ⅳ区矿物组合为云母类-自生黄铁矿-普通角闪石-石英,Ⅲ区、Ⅳ区物源多样,黄河物质对两区贡献显著。     

东海内陆架EC2005孔重矿物组合特征及其物源指示意义

为探讨东海内陆架17.3ka BP以来的重矿物含量变化及其物源指示意义,对东海内陆架南部泥质沉积中心EC2005孔的沉积重矿物进行了鉴定和分析。结果表明:(1)在0.063—0.25mm粒级沉积物中,重矿物含量平均值为27.3%,变化范围为3.7%—89.6%,重矿物含量较高的部分均出现在自生黄铁矿富集的层位;(2)片状矿物、含铁氧化物、角闪石族矿物、绿帘石族矿物、白云石、辉石族矿物、变质矿物、蚀变矿物和自生黄铁矿占重矿物颗粒总数的96.0%以上,但其含量变化很大;(3)以重矿物分布特征为依据将岩心划分为Ⅰ—Ⅴ五个沉积层段,各层段对应的特征矿物分别为片状矿物、白云石、片状矿物、自生黄铁矿和榍石。结合粒度、AMS14C年代及西太平洋海平面变化等数据对物源进行分析,结果表明:自17.3ka BP以来,EC2005孔沉积物源主要是长江,其次还可能受到瓯江等浙江沿岸河流所输运物质的一定影响。     

莱州浅滩表层沉积物重矿物分布特征及物源识别

对莱州浅滩80个表层沉积样品进行碎屑矿物分析,主要研究重矿物分布特征,并探讨其物质来源。研究表明:本区优势矿物组合为普通角闪石-绿帘石-黑云母-褐铁矿,可划分成5个矿物区。浅滩滩体(Ⅰ区和Ⅱ区)稳定矿物(以榍石、石榴子石为主)含量高。浅滩北部顶端(Ⅱ区)金属矿物类分布集中,褐铁矿含量近1/3;浅滩两侧(Ⅲ区和Ⅳ区)为云母类高值区。浅滩西侧海域(Ⅳ区)含大量自生黄铁矿,为还原性沉积环境;浅滩西北(Ⅴ区)重矿物含量最高,优势矿物组合为普通角闪石-绿帘石-石榴子石。依据重矿物种类和矿物组合特征,结合陆源近岸河道及黄河沉积物矿物特征,研究显示:浅滩滩体沉积物主要为近岸河流输送,而浅滩两侧沉积物是双重来源,既来自陆地近岸又来自黄河物质向东的输送。矿物区的变化反映了该区水动力的复杂性。重矿物分布特征对研究本区海洋动力环境和探讨浅滩物源都有重要意义。     

青岛近岸海域表层沉积物重矿物分布及物源北大核心CSCD

对青岛近岸海域127个表层沉积物样品和周边入海河流22个表层沉积物样品重矿物分析,系统地研究了重矿物分布特征和物质来源。结果表明,研究区矿物组合为普通角闪石—绿帘石—黑云母—褐铁矿—自生黄铁矿,可划分为3个矿物分区。田横岛—千里岩岛矿物区(Ⅰ区)矿物组合为普通角闪石—绿帘石—褐铁矿—黑云母—阳起石,物源主要来自五龙河等沿岸河流,黄河物质也有贡献;崂山头东部矿物区(Ⅱ区)矿物组合为普通角闪石—绿帘石—褐铁矿—石榴子石,物源以残留沉积和沿岸侵蚀物为主;海阳—乳山近岸矿物区(Ⅲ区)矿物组合为普通角闪石—自生黄铁矿—黑云母—水黑云母—绿帘石—褐铁矿,沉积物受黄河影响显著,沿岸河流和岛屿侵蚀物也有影响。     

青岛近岸海域表层沉积物重矿物分布及物源

对青岛近岸海域127个表层沉积物样品和周边入海河流22个表层沉积物样品重矿物分析,系统地研究了重矿物分布特征和物质来源。结果表明,研究区矿物组合为普通角闪石—绿帘石—黑云母—褐铁矿—自生黄铁矿,可划分为3个矿物分区。田横岛—千里岩岛矿物区(Ⅰ区)矿物组合为普通角闪石—绿帘石—褐铁矿—黑云母—阳起石,物源主要来自五龙河等沿岸河流,黄河物质也有贡献;崂山头东部矿物区(Ⅱ区)矿物组合为普通角闪石—绿帘石—褐铁矿—石榴子石,物源以残留沉积和沿岸侵蚀物为主;海阳—乳山近岸矿物区(Ⅲ区)矿物组合为普通角闪石—自生黄铁矿—黑云母—水黑云母—绿帘石—褐铁矿,沉积物受黄河影响显著,沿岸河流和岛屿侵蚀物也有影响。     

龙口屺(山母)岛海区重矿物分布——泥砂运移趋势

通过本海区156个表层沉积样品和主要河流自然重砂的鉴定分析,掌握了本区重矿物的分布规律。主要矿物有角闪石、绿帘石、金属矿物;标志性矿物有屑石、石榴石、辉石和自生黄铁矿。根据主要矿物和标志诖矿物含量变化及分布特征,划分五个矿物组合区,各组合区矿物组合特征指明了海区物质来源及泥沙运移趋势。海区物质主要来源于河流,除此,少量的物质来源于岛岸海蚀物质和特殊海区的化学或生物化学沉积。     

黄海全新世泥质体表层沉积物重矿物特征及其指示意义

基于对黄海56个表层沉积物样品的碎屑重矿物和粒度分析,研究了黄海全新世泥质体底质表层沉积物的重矿物特征及其指示的物源和环境信息。结果表明:泥质体重矿物含量低且组成变化大,矿物组合主要为普通角闪石-不透明矿物-片状矿物-绿帘石-自生黄铁矿,泥质体可分为三个矿物区:泥质体北部矿物区(Ⅰ区)、山东半岛沿岸矿物区(Ⅱ区)和泥质体南部矿物区(Ⅲ区),泥质体之外西南侧分布着南黄海西部矿物区(Ⅳ区)和南黄海南部矿物区(Ⅴ区)。Ⅰ区和Ⅱ区明显受黄河物质控制,Ⅲ区物源较为复杂,除黄河物质外,东海北部陆架和长江物质也对其产生一定影响。自生黄铁矿的富集指示了冷水团的存在和弱还原的沉积环境;多种矿物的含量分布指示了切变锋的存在,其"水障"作用对泥质体的空间分布和矿物组成造成了很大影响,对沉积物的运移趋势也具有显著限制作用。     

海南岛鹿回头造礁珊瑚的14C年代及珊瑚礁的发育演化

通过2002年7月沿鹿回头珊瑚礁坪断面方向,在原生滨珊瑚(Porites)礁表面进行系统采样,并进行C测年和年代校正,初步划分出全新世以来珊瑚礁演化的5个阶段珊瑚礁繁盛期(7 300-6000cal.aBP)、珊瑚礁发育停滞期Ⅰ(6 000-4 800cal.aBP)、珊瑚礁发展期(4 800-3000 cal.aBP)、珊瑚礁发育停滞期Ⅱ(3 000-1000 cal.aBP)和现代珊瑚礁发育期(1 000cal.aBP以来).鹿回头珊瑚礁在7 300-000cal.aBP处于发育的繁盛期,己基本上形成了现代珊瑚礁的地貌格局.后来不同时期珊瑚礁是在此时期形成的礁塘或礁坑等低洼地中形成,并在鹿回头半岛两侧向外发展,现代珊瑚礁则发育于全新世珊瑚礁的外礁坪或礁前斜坡带.     

辽东湾中部晚第四纪沉积物物源与沉积环境:来自碎屑矿物和自生黄铁矿的证据

对渤海辽东湾LDD7岩心的沉积物样品进行了碎屑矿物鉴定,分析了岩心轻重矿物组合、粗颗粒沉积物物质来源、碎屑矿物特征指数及氧同位素3期渤海相对海平面位置。结果表明,轻矿物是以石英和长石为主的组合,片状矿物和碳酸盐矿物次之;重矿物是以角闪石类、绿帘石类、云母类和自生黄铁矿为主的组合,其次为金属矿物、石榴子石和榍石等。岩心为多源沉积,物质主要来源于辽河、滦河和黄河等中大型河流的入海沉积物。碳酸盐矿物作为黄河的特征矿物,指示黄河对岩心低海平面时期的沉积层影响较大。石英/长石比值、极稳定矿物ZTR指数和磷灰石ATi指数之间具有一定的对应性,能够大致反映流域的风化程度,但在利用这些指数指示风化作用时不能忽视物源对它们的影响。与还原环境密切相关的自生黄铁矿在水动力较弱且富含有机质的河漫滩、湖泊相和潮滩相中含量高。渤海岩心中氧同位素3期沉积物的年代和距现代海平面深度投点整体位于全球海平面上方,考虑到沉积环境水深、构造沉降和沉积物压实等因素,渤海相对海平面位置高于全球平均海平面。     

长江水下三角洲沉积物的重矿物分布及组合

对2004年取自长江水下三角洲南部区域的145个表层样品进行了重矿物研究。结果表明,本区重矿物可划分为4个矿物组合区,即三角洲前缘南部矿物区(Ⅰ区)、三角洲前缘北部矿物区(Ⅱ区)、前三角洲主体矿物区(Ⅲ区)和前三角洲南部矿物区(Ⅳ区),它们代表了不同的沉积动力、沉积环境和风化作用条件;长江水下三角洲重矿物以普通角闪石-绿帘石为优势矿物组合,以低级变质来源的绢云母、白云母为特征矿物,局部富含普通辉石和氧化铁矿物;粉砂质砂和砂质粉砂中的重矿物组成比较稳定,基本可以代表长江物源。     

Microbial Biomass and Organic Nutrients in the Deep-Sea Sediments of the Central Indian Ocean Basin

In order to assess the impact of deep-sea mining on the in situ benthic life, we measured the microbial standing stock and concentration of organic nutrients in the deep-sea sediments of the Central Indian Ocean Basin in the Indian pioneer area. Sediments were collected using box core and grab samples during September 1996. The total bacterial numbers ranged from 10 10 -10 11 cells per g -1 dry weight sediment. There was a marginal decrease in the number of bacteria from surface to 30 cm depth, though the subsurface section registered a higher number than did the surface. The highest numbers were encountered at depths of 4-8 cm. The retrievable number of bacteria were two orders less in comparison with the direct total counts of bacteria. An almost homogeneous distribution of bacteria, total organic carbon, living biomass, and lipids throughout the depth of cores indicates active microbial and benthic processes in the deep sea sediments. On the other hand, a uniform distribution of total counts of bacteria, carbohydrates, and total organic carbon in all the cores indicates their stable nature and suggests that they can serve as useful parameters for long-term monitoring of the area after the benthic disturbance. Further studies on temporal variability in this region would not only verify the observed norms of distribution of these variables but would also help to understand restabilization processes after the simulated benthic disturbance.     

A Review of Some Environmental Issues Affecting Marine Mining

This article reviews information recently available from existing marine and coastal mining for responses to environmental issues affecting marine mining at different depths. It is particularly but not exclusively concerned with those issues affecting seabed biodiversity impact and recovery. Much information has been gathered in the past 10 years from shallow mining operations for construction aggregate, diamonds, and gold, from coastal mines discharging tailings to shallow and deep water, and from experimental deep mining tests. The responses to issues identified are summarized in a series of eight tables intended to facilitate site-specific consideration. Since impacts can spread widely in the surface mixing layer SML, and can affect the biologically productive euphotic zone, the main issues considered arise from the depth of mining relative to the SML of the sea. Where mining is below the SML, the issue is whether it is environmentally better to bring the extraction products to the surface vessel for processing (and waste discharge), or to process the extraction products as much as possible on the seabed. Responses to the issues need to be sitespecific, and dependent on adequate preoperational environmental impact and recovery prediction. For deep tailings disposal from a surface vessel, there are four important environmental unknowns: (1) the possible growth of "marine snow" (bacterial flocs) utilizing the enormous quantities of fine tailings particles (hundreds or thousands of metric tons per day) as nuclei for growth, (2) the possibility that local keystone plankton and nekton species may migrate diurnally down to and beyond the depth of deep discharge and hence be subjected to tailings impact at depth, (3) the burrow-up capability of deep benthos and their ability to survive high rates of tailings deposition, and (4) the pattern and rate of dispersion of a tailings density current through the deep water column from discharge point to seabed. Actions to obtain relevant information in general and site-specifically are suggested.     

Increased Particle Fluxes at the INDEX Site Attributable to Simulated Benthic Disturbance

Particle fluxes were measured 7 m above the sea bottom during the predisturbance, disturbance, and postdisturbance periods by using time series sediment traps attached to seven deep-sea moorings deployed in the INDEX experiment site in the Central Indian Basin. The predisturbance particle fluxes varied between 22.3 to 55.1 mg m -2 day -1 . Increased and variable particle fluxes were recorded by the sediment traps during the disturbance period. The increase observed was 0.5 to 4 times more than the background predisturbance fluxes. The increases in particle fluxes (~4 times) recorded by the sediment trap located in the southwestern direction (DMS-1) were the greatest, which could be the result of preferential movement of resuspended particles generated during the deep-sea benthic disturbance along the general current direction prevailing in this area during the experimental period. Also, the traps located closer to the disturbance area recorded greater fluxes than did the traps far away, across the Deep Sea Sediment Resuspension System path. This variability in recorded particle fluxes by the traps around the disturbance area clearly indicates that physical characteristics such as grain size and density of the resuspended particles produced during the disturbance had an important effect on particle movement. The postdisturbance measurements during ~5 days showed a reduction in particle fluxes of ~50%, indicating rapid particle settlement.     

Assessing the Validity of Seismo-Acoustic Predictor Equations for Obtaining Seabed and Sub-Surface Sediment Physical Properties

The interdependence between the seismo-acoustic properties of a marine sediment and its geotechnical/physical parameters has been known for many years, and it has been postulated that this should allow the extraction of geotechnical information from seismic data. Though in the literature many correlations have been published for the surficial layer, there is a lack of information for greater sediment depths. In this article, a desktop study on a synthetic seafloor model illustrates how the application of published near-surface prediction equations to subsurface sediments (up to several tens of meters burial depth) can lead to spurious predictions. To test this further, acoustic and geotechnical properties were measured on a number of sediment core samples, some of which were subjected to loading in acoustically-equipped consolidation cells (oedometers) to simulate greater burial depth conditions. For low effective pressures (representing small burial depths extending to around 10 meters subsurface), the general applicability of established relationships was confirmed: the prediction of porosity, bulk density, and mean grain size from acoustic velocity and impedance appears generally possible for the investigated sedimentary environments. As effective pressure increases through, the observed relationships deviate more and more from the established ones for the near-surface area. For the samples tested in this study, in some instances increasing pressure even resulted in decreasing velocities. There are several possible explanations for this abnormal behavior, including the presence of gas, overconsolidation, or bimodal grain size distribution. The results indicate that an appropriate depth correction must be introduced into the published prediction equations in order to obtain reliable estimates of physical sediment properties for greater subsurface depths.     

Geoacoustic Inversion via Genetic Algorithm and Its Application to Manganese Sediment Identification

An acoustic inversion method using a wide-band signal and two near field receivers is proposed and applied to multiple layered seabed models including a manganese sediment. The inversion problem can be formulated into a probabilistic model comprised of signals, a forward model, and additive noise. The forward model simulates wide-band signals, such as chirp signals, and is chosen to be the source-waveletconvolution plane wave modeling method. The wavelet matching technique, using weighted least-squares fitting, estimates the sediment sound-speed and thickness on which determination of the possible numerical ranges for a priori uniform distribution is based. The genetic algorithm is applied to a global optimization problem to find a maximum a posteriori solution for determined a priori search space. Here the object function is defined by an L 2 norm of the difference between measured and modeled signals. Not only the marginal pdf but also its statistics are calculated by numerical evaluation of integrals using the samples selected during importance sampling process of the genetic algorithm.     

海上大直径钢管桩打桩过程中桩周土强度弱化研究

海上大直径钢管桩打桩过程中,桩周土体受到强烈扰动而发生强度弱化,掌握桩周土体强度弱化规律对于准确预测打桩过程、保证工程安全具有重要意义。为研究土体强度弱化规律,开展了环剪试验模拟打桩对桩周土体的扰动,测试土体强度随剪切速率的变化规律,建立了描述土体强度弱化规律的拟合公式,引入到打桩分析软件中。研究结果表明：土体的强度折减程度不仅与土体本身的性质有关还受到土体的埋深和剪切速率的影响,埋深越深土体强度折减程度越低,剪切速率越高土体强度折减越高,在打桩分析中可采用这里推荐的线性折减方法来模拟不同深度处土体强度的折减规律。     

Determination of In Situ Sediment Shear Strength from Advanced Piston Corer Pullout Forces

The advanced piston corer (APC) has been used by the Ocean Drilling Program since 1985 for recovering soft sediments from the ocean floor. The pullout force measured on extracting the core barrel from the sediment is shown to correlate with the average shear strength of the sediment core measured in the ship's laboratory. A simple rule of thumb is derived relating the shear strength of the sediment to the pullout force. Multiple APC holes at individual sites allow the consistency of the pullout measurements to be assessed. The effects of different operational procedures during APC coring are also explored. Although generally applicable, the correlation between pullout force and laboratory measurements of shear strength breaks down for some APC holes, possibly because of the disturbance of some sediment types during the APC coring process. A better understanding of the physical process of APC coring, and its effect on the properties of the sediment both inside and immediately outside the core barrel, would indicate what confidence can be put on the measurement of pullout force as a way of evaluating the in situ shear strength of deep sea sediments.     

Interannual Sea Level Variations and Annual Tides in the Northwestern Pacific

Specific properties of the interannual sea level variations and annual tides in the Northwestern Pacific were studied. Several tide stations were monitored. The monthly mean sea level for the year of 1995 was analyzed at each tide station. A seismic event in 1995, some tectonic activity around the subject area, and the Kuroshio (the oceanic western boundary current) may possibly contaminate results which would have occurred from the astronomical annual tide alone.     

《Acta Oceanologica Sinica》Vol. 33(2014) contents

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