共查询到20条相似文献，搜索用时 62 毫秒
1.
广东省深圳大鹏湾沿岸沙堤粗颗粒石英热释光测年 总被引：5，自引：0，他引：5
用粗粒(90-125μm)石英热释光技术对深圳大鹏湾沿岸沙堤和沙丘的10个砂样作年龄测定.初步结果表明,各小湾外缘白色拦湾沙堤形成于中全新世,约4.5ka-7.5ka B.P.;白色沙堤后侧和下伏的黄棕色老沙堤形成于晚更新世,约30ka-40ka B.P.;大鹏半岛南端西冲湾的沙丘形成于晚全新世,约1.5ka-2.7ka B.P.,沙丘后侧古潟湖前缘的洁白色石英砂层形成于60ka-70ka B.P.这些沙堤和沙丘除受波浪作用外,主要是风积成因的,其高程与海平面升降变化可能无大关系. 相似文献
2.
依据南海低纬地区SA09-040孔高分辨率的孢粉记录,自下至上划分了4个孢粉组合带。从孢粉成分的变化,重建了22.25ka B P以来的植被与气候变化历史。结果表明:孢粉主要来源于婆罗洲和周围岛屿,孢粉1带(22.25～16.6ka B P),低山雨林植被发育,为暖热气候,从测年时间看,当时为末次冰期晚期。孢粉2带(16.6～10.82ka B P,为末次冰消期),植被以热带低山雨林和低地雨林为主,针叶的松数量较多,当时的气温比现在低。孢粉3带(全新世早期,10.82～6.43ka B P),植被以热带低山雨林和低地雨林为主,针叶松属数量减少,气温比前期升高,海平面也上升。孢粉4带(全新世中晚期,6.43ka B P至今),全新世中期为炎热、湿润的气候环境,全新世晚期可能与婆罗洲现今的植被景观相近,为热、湿的气候环境。 相似文献
3.
本文根据作者多年的实地考察,并参考了有关文献,研究了莆田海岸近4 000年来的变迁与气候的关系。结果表明,4 000a,B.P.莆田岸线大约沿海拔5～6m一线分布,当时气温比现今高2℃;2 570a,B.P.莆田岸线约沿海拔4m 一线分布,当时气温比现今高1℃;1 400a,B.P.以来,莆田气候冷暖交替出现,海平面基本上也随之升降而升降。 相似文献
4.
5.
海平面变化速率可以从地质记录中识别 ,分为长期 ( <1 0 0 0ka)、冰后海侵期 ( 2 0～ 7ka)以及其后的对于现代海平面的调整期 ( >7ka)。另外 ,还有仪测的历史记录。1 <10 0 0ka长期海平面变化的地质记录提供了一幅海平面自然波动的景象 ,表明海平面的变化是颤动的。深海沉积物的浮游有孔虫氧同位素( 1 8O/ 1 6O)比给出了冰期 /间冰期循环的大量海平面波动的证据 ,Vostok冰心提供了更为详尽的至少 4个循环的记录。这些周期大约为 1 0 0ka的循环已在东南澳大利亚地质记录和相关的氧同位素记录中识别出 ,这里的一系列滨岸沙坝的时代可追溯… 相似文献
6.
对位于东海内陆架泥质区的MZ05孔浅钻岩芯进行粒度、常微量元素、AMS~(14)C测年分析,获得2.90-1.80ka B.P.期间粒度和常微量元素随时间变化的高分辨率曲线。综合分析MZ05孔地球化学元素比值(CIA,Rb/Sr)曲线发现沉积物源区的化学风化强度变化可以分为3个阶段:2.90-2.70ka B.P.的增强期,2.64-2.35ka B.P.的减弱期和2.35-1.80ka B.P.的较弱期,反映该段时间内东亚夏季风的强弱变化。MZ05孔的沉积物敏感粒级(1.2～22.1μm)平均粒径指示晚全新世东亚冬季风波动频繁,呈现出3个各具特点的阶段:2.90-2.65ka B.P.属于中等频率波动的冬季风强盛期;2.64ka B.P.左右东亚冬季风由强转弱,2.60-2.35ka B.P.冬季风先减弱后增强;2.35-1.82ka B.P.为相对稳定的冬季风弱期。东亚冬季风的演化趋势在其他气候记录中也发现相应的降温证据,揭示全球气候变化的区域性响应。研究同时发现晚全新世研究区东亚冬、夏季风在百年尺度上呈现反相位关系。 相似文献
7.
福建深沪湾古森林遗迹和牡蛎礁发现的古地理意义 总被引：2，自引：0，他引：2
本文研究了分布于福建深沪湾南岸潮间带的古森林遗迹和牡蛎礁。结果表明,古森林属陆相裸子植物,距今约8ka;牡蛎礁主要由近江牡蛎ostrea rivularis化石组成,其形成年代约距今3k—4ka,从而为研究该区的地壳运动、海平面升降和古地理环境演变提供佐证。 相似文献
8.
《海洋地质与第四纪地质》2021,41(3)
西湖凹陷平湖斜坡带平湖组是西湖凹陷重要的油气勘探开发层系之一,明确其沉积背景、演化规律、探讨深层储层保存机制是提高地质油藏预测准确率的关键。综合利用岩心、测井(△GR)等资料对A气田沉积体系进行定量表征,并基于米兰科维奇旋回理论,通过小波变换、频谱分析等手段,结合全球海平面变化规律,对A气田平湖组海平面变化周期性进行探讨分析。结果表明,A气田平湖组沉积体系自下而上可分为潮控三角洲沉积体系、潮-河联控三角洲沉积体系及河控三角洲沉积体系。同时在潮控三角洲沉积体系及潮河联控三角洲沉积体系中共识别7次大规模海平面升降事件,其中以P7海平面升降规模最大,每次海平面升降周期约405ka。最后基于7次海平面升降事件指导气田内高频层序划分,且重点对P7—P6层砂体发育规律、展布特征进行分析,结合储层物性纵向变化规律认为,潮汐作用对研究区内砂体具有一定的改造作用,有利于纯净砂岩的发育,预测A气田潮下带潮汐改造砂体是未来有利勘探开发方向。 相似文献
9.
本文根据3个钻孔岩芯的~(14)C测年数据和微体古生物硅藻的分析结果,对福建沿岸晚更新世末次海侵及其海平面的变化进行了讨论。结果表明,福建沿岸晚更新。世的末次海侵约发生于44000—22000年B.P.间,海水表现为间歇性侵进形式,其中约在39000—34000年B.P.间曾发生一次海水退却。海平面的升降变化与这种海水入侵趋势基本上是一致的,当时的最高海面约出现在30000年B.P.,高度约达—15m。 相似文献
10.
对南海南部MD05-2897孔沉积物的分析显示,该孔涵盖氧同位素1~12期,底界年龄约为50万年。碳酸钙含量曲线形态基本与底栖有孔虫氧同位素曲线平行,即碳酸钙高值对应氧同位素轻值,呈现典型的大西洋型碳酸钙分布模式。碳酸钙含量在冰消期的高值出现及含量变化均领先于氧同位素,证明低纬海区"碳酸钙泵"对大气二氧化碳浓度和温度的作用。粒度分析显示,3~5μm组分含量曲线的变化与氧同位素曲线基本平行,说明它主要受海平面升降变化控制,可作为海平面变化的间接指标。而1.5~2.5μm粒级颗粒主要通过河流的悬浮搬运,直接受亚洲夏季风及其所带来降雨的影响,可间接反映夏季风的强弱变化。南海南部深海沉积中的季风记录具有0.1 Ma偏心率周期,40 ka斜率周期,20 ka岁差和10 ka半岁差周期等丰富的频谱,显示出低纬度海区气候变化对轨道周期的良好响应。 相似文献
11.
Derek V. Ellis 《Marine Georesources & Geotechnology》2001,19(1):51-63
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. 相似文献
12.
G. Parthiban 《Marine Georesources & Geotechnology》2000,18(3):223-235
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. 相似文献
13.
Arne Schnack-Friedrichsen Angela M. Davis Jim D. Bennell Dei G. Huws 《Marine Georesources & Geotechnology》2001,19(4):221-243
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. 相似文献
14.
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。 相似文献
15.
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. 相似文献
16.
Shigehisa Nakamura 《Marine Geodesy》2000,23(1):55-61
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. 相似文献
17.
18.
19.
《海洋学报(英文版)》2014,(11):161-F0003
<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, 相似文献