东营市东辛2-4井磁性地层划分对比研究

本文通过东辛2—4井岩心样品的古地磁学研究,整段岩心呈现以正极性为主的混合极性特征。自上而下划分的布容、松山、高斯和吉尔伯特极性时和布容极性时内清晰显示出的哥德堡和布莱克亚时的界限分别位于井深28.0m、161.0m、274.5m和452.0m。据黄河口南北5个钻孔磁性地层的划分对比,长江口、苏北盆地和东营地区,吉尔伯特、高斯和布容极性时的沉积速度较快,松山极性时较慢或近于缺失;黄河口以北至河北地区,高斯极性时地层不发育,吉尔伯特、松山和布容极性时则较厚,表明它们所处的构造单元、地质基础和沉积环境有较大的不同。     

南黄海中部隆起晚新近纪—第四纪沉积序列的地层划分与沉积演化

CSDP-2孔位于南黄海中部隆起,其孔深超过2 800 m。该孔中下部中—古生代的固结成岩地层已被深入研究,但其最上部592 m未固结成岩的沉积序列尚未有研究报道。为了确定这部分沉积序列的地层划分,揭示其沉积演化历史,我们对其开展了古地磁测试、光释光测年、底栖有孔虫鉴定和沉积相分析,并与南黄海及其邻近海岸地区以往钻孔岩心分析成果进行对比研究。结果表明,CSDP-2孔0～592.00 m沉积序列最初形成于约5.2 Ma,其第四系底界位于孔深约227.91 m(年龄为2.59 Ma),下/中更新统界线位于孔深约65.23 m(年龄为0.78 Ma),中/上更新统界线位于孔深47.34 m(年龄约128 ka);自晚更新世以来形成的地层又可划分出MIS 5、MIS 4、MIS 3和MIS 1的沉积层段,MIS 2沉积缺失。南黄海中部隆起区在新近纪的剥蚀止于约5.2 Ma,从约5.2 Ma至约1.7 Ma发育河流沉积;由于浙闽隆起的逐渐沉降,约1.7 Ma发生自新生代以来的首次海侵,直至约0.83 Ma,发育潮坪—滨岸沉积与河流沉积的互层;从约0.83 Ma开始至今,浙闽隆起进一步沉降使得南黄海中部隆起区在间冰期高海平面时期的海洋环境基本接近现今环境;南黄海西部陆架在MIS 5发育范围比现今更广的冷水团沉积,在MIS 4、MIS 3早期、MIS 3晚期至MIS 2和MIS1分别依次发育河流、三角洲、河流和滨岸—内陆架环境。该沉积序列主要受控于区域构造沉降和海平面变化,其全新统、更新统及整个地层序列的沉积速率呈现依次明显下降的趋势,主要归因于地层时代越老其连续性越差,特别是晚更新世之前的地层有显著侵蚀的现象。本文的研究成果为深入理解南黄海西部陆架区晚新近纪以来的沉积环境演化进程和沉积地层的形成机制提供了新证据。     

南黄海前陆盆地系统及沉积—构造特征

典型的前陆盆地一般位于造山带和稳定克拉通之间的狭长槽地,而南黄海盆地则主要为华北—扬子地块陆陆碰撞及后期太平洋系构造运动叠加形成的"再生"陆内前陆盆地,因此具有其"特殊性"。虽然南黄海前陆盆地经过多期构造运动叠加改造及破坏,但仍然保存了比较完整的楔顶、前渊、前隆及隆后各带,故划分了各带分布的位置,认为其楔顶沉积带位于千里岩隆起、前渊带位于北部坳陷东北凹、前隆带位于其乳山凸起、隆后沉积带位于乳山凸起与中部隆起间;并从地震、沉积、构造3方面分析了各带的结构构造和沉积特征。     

三门峡地区的红粘土磁性地层及环境记录

位于黄土高原东南缘的三门峡红粘土地层，以陕县指望剖面为其典型代表。厚度为74．3m的指望剖面由上部厚34m的黄土地层和下伏厚40.3m的红粘土沉积组成，黄土为L24－L33的连续风尘沉积，下部红粘土为RS1－RS5的沉积。磁性地层研究显示：M／Ga界线位于33.8m处，黄土与红粘土界线之上20cm，Ga/Gi界线位于56.25m处的RS3中下部。该区红粘土近5Ma至2.6Ma的风尘沉积夹河湖相沉积。指望剖面的红粘土地层磁化率较黄土高原内部偏高，总体特征一致，说明近5Ma来东亚季风在区域演化上的一致性。     

南海北部深水区盆地特征及其动力学背景

南海北部陆缘深水区指水深〉300m的陆缘盆地区，包括琼东南盆地中央坳陷带及其南部隆起区、神狐隆起南侧、珠江口盆地珠二坳陷及其南部的西沙-中沙隆起和一统暗沙隆起区（图1），总面积超过120000km^2。2006年，从南海北部陆缘珠江口盆地白云凹陷水深1480m的荔湾构造上钻探的LW3—1—1井获得天然气重大发现，     

西沙礁序列的磁性地层学研究

利用西沙群岛西琛一井３３０ｍ以上井段的１４９块岩心标本，用美国２－Ｇ型超导磁力仪进行了古地磁测定，获得了一个从更新世至中新世晚期包括布容，松山，高斯和吉尔伯特四个极性时及若干亚极性的磁性地层柱，为礁序列的划分对比，提供了新的依据。     

低层大气烃类检测预测南黄海盆地油气远景

为了预测南黄海盆地油气远景,利用最新采集的383个站位的低层大气烃类检测数据进行评价。烃类检测结果为:高值甲烷异常区主要分布在南黄海北部坳陷西南,次高值甲烷异常区主要分布在中部隆起带西部和南部坳陷中部,而南北向带状分布的甲烷异常带位于南黄海的东部。结合南黄海盆地航磁异常和部分浅地层剖面资料,认为中部隆起带东侧及紧邻的北部坳陷西南具有较好的油气远景。     

渭南阎村W7孔岩心样品的古地磁学研究

对渭南阎村W7孔岩心地层样品的磁性地层学研究,确定了黄土组、三门组地层的时代。这一地区的黄土/古土壤层形成始于松山反极性时晚期,约为1.1MaB.P.。按照地层样品的剩磁特征和岩性特征对黄土/古土壤层作更精细地划分,这一地区的黄土/古土壤层相当于马兰黄土、离石黄土层,缺失午城黄土。地层的剩磁极性资料表明,三门组地层形成于高斯极性时晚期—松山极性时中期,按照奥尔都维正极性亚时为第四纪下限的年代准则,确定三门组地层的时代为晚上新世。 W7孔岩心的地层样品的剩磁极性序列与已有的地磁极性年代表的磁极性序列大体相当,本项研究也揭示了二个短周期极性事件的存在,位于第5黄土层的安比拉事件(Emperor)发生的年代约为0.445—0.458Ma B.P.。位于第9黄土层的后期哈拉米洛事件(Post-Jaramillo)发生的年代约为0.77—0.81MaB.P.。 磁性地层学研究表明这一地区在松山反极性时中晚期出现过沉积间断,持续时约0.5Ma。 根据W7孔的地层学研究认为,选择以奥尔都维正极性亚时末期的年代(1.60MaB.P.)作为第四纪下限是有利于第四纪地层的划分和对比的。     

东海西湖凹陷碎屑岩物源聚类分析

重矿物聚类分析是研究沉积物源的重要手段。通过对东海陆架西湖凹陷古近系宝石组至新近系龙井组32口钻井900多个砂岩样品的重矿物Q型、R型聚类和ZTR趋势线等分析认为:西湖凹陷碎屑岩主要具有2种不同性质的物源,其沉积区分别位于凹陷北部和中南部。凹陷中南部可以进一步划分出5个次级母岩分区,分别位于西斜坡带中部、西次凹北部和南部、中央反转构造带北部和南部。西湖凹陷北部碎屑岩母岩主要为酸性岩浆岩和变质岩,中南部碎屑岩母岩主要为变质岩,岩浆岩次之。西湖凹陷北部沉积物源主要为虎皮礁隆起带;而中南部沉积物源主要为海礁隆起和钓鱼岛隆褶带,这2个物源区母岩岩性类似。     

南海海域新生代沉积盆地的油气资源

南海新生代经历过大陆张裂与分离、海底扩张和地块碰撞等构造演化历史,南海北部为被动大陆边缘,南部是碰撞挤压边缘,东部为俯冲聚敛边缘,西部是走滑边缘。在这种构造体制下,形成了许多沉积盆地。北部和西部边缘上发育着张性沉积盆地和走滑拉张盆地;在南部边缘上,其北部发育着张性盆地,南部为挤压环境下形成的盆地,如前陆盆地、前孤盆地;东部边缘上发育着前孤盆地。目前油气勘探实践证明,南海南部的油气资源比北部丰富。究其原因,南海北部为被动大陆边缘,张性沉积盆地的烃源岩体积较小,而南部挤压环境下形成的沉积盆地的烃源岩体积大;北部的地热流较南部小,因此地温梯度也较小,故南部边缘烃源岩的成熟度比北部高;由于南部边缘处于挤压构造环境,在沉积盆地中形成了许多挤压构造,而北部边缘一直处于张性构造环境,形成的构造较少且较小;同时,南部边缘沉积盆地中,烃源岩生烃与构造形成在时间上搭配较好。因此,在南海南部边缘沉积盆地中形成了许多大型油气田,而南海北部边缘沉积盆地中,大型油气田较少,中小型油气田较多。     

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.     

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.     

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.     

Flow Cytometric Analysis of Coastal Lagoon Bacterioplankton and Picophytoplankton: Fixation and Storage Effects

The effect of different fixation and storage protocols on the flow cytometric (FCM) simultaneous analysis of bacterioplankton and phytoplankton in coastal seawater samples (Mediterranean coastal lagoons) was investigated. FCM measurements (cell number, fluorescence and scatter characteristics) were obtained through DAPI staining. Three fixatives [glutaraldehyde (GA), formaldehyde (FA) and paraformaldehyde (PFA)] and two storage (3 months duration) methods (5 °C and −196 °C) were tested. Two dominant populations were detected in studied samples: bacteria and eukaryotic picophytoplankton. Adding fixatives (2% final concentration) appears necessary to obtain FCM exhaustive counts of all the bacteria and phytoplanktonic cells. This was related to the permeation effect of fixatives which allowed a better DAPI staining of the cells. Maximum fluorescence, i.e. optimal staining of the cells was obtained with FA or PFA, and significant lower fluorescences with GA. Fixed samples stored at 5 °C induced rapid cell loss. Only storage in liquid nitrogen of samples fixed with FA or PFA, allows mid-term (≥4 months) preservation of bacteria or picophytoplankton cell numbers, and limited evolution of DAPI-induced fluorescence and scatter characteristics.     

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

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INFORMATION FOR AUTHORS

<正>Acta Oceanologica Sinica(AOS)is a comprehensive academic journal edited by the Editorial Committee of Acta Oceanologica Sinica and is designed to provide a forum for important research papers of the marine scientific community which reflect the information on a worldwide basis.The journal publishes scholarly papers on marine science and technology,including physics,chemistry,biology,