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1.
河口港湾沉积物中的￣(137)Cs剖面及其沉积学意义 总被引：1，自引：0，他引：1
本文通过对采自海南岛洋浦港、福建厦门外港、浙江象山港三个河口港湾的六个沉积柱样的１３７Ｃｓ分析，分别用１３７Ｃｓ剖面的最大峰值层及１３７Ｃｓ剖面的起始值层位估算了该六个站位的现代沉积速率，结果表明：在河口港湾沉积环境条件下，用１３７Ｃｓ剖面来估算沉积物的平均沉积速率是可行的，由１３７Ｃｓ最大值法，这六个站位的平均沉积速率分别为１．１４ｃｍ／ａ、１．５６ｃｍ／ａ、０．８２ｃｍ／ａ、０．７５ｃｍ／ａ、１．２６ｃｍ／ａ、１．６６ｃｍ／ａ，由１３７Ｃｓ最大值法得出的平均沉积速率其精确度与可信度要好于１３７Ｃｓ起始值得出的平均沉积速率。与２１０Ｐｂ法所得的结果符合的很好。１３７Ｃｓ起始值层位与预期值偏离的大小可以为我们提供有关该站位沉积环境、扰动作用强弱的信息。在应用１３７Ｃｓ剖面估算沉积速率时，还要注意沉积结构变化的影响。 相似文献
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珠江口沉积柱样^210Pb法年龄测定结果及其环境地球化学意义 总被引：22，自引：3，他引：19
提供了珠江河口及河道１０个沉积柱＾２１０Ｐｂ法的ＣＦ模式（稳恒放射性通量模式）和ＣＡ模式（稳恒初始放射性模式）的年龄测定结果,并据此讨论珠江三角洲近百年来沉积环境的演化,研究结果表明,西江河道和珠江广州河道１９８０年以前沉积速率为０．５－１．０ｃｍ／ａ．１９８０年以后沉积速率增长加快,９０年代达到４－６ｃｍ／ａ,沉积通量为４－６ｇ／（ｃｍ＾２．ａ）河口沉积速率逐年增长趋势,但一般比河道柱样小得多, 相似文献
4.
作者对渭南黄土剖面连续采取的样品进行了系统的１４Ｃ和ＴＬ年龄测定，测得的１４Ｃ年龄做了δ１３Ｃ校正和日历年龄校正，并与ＳＰＥＣＭＡＰ比较，取得了很好的结果。根据测得的年龄，Ｓ０底部１４３ｃｍ处的１４Ｃ年龄为１０３００ａＢ．Ｐ，即全新世起始于１０３００ａＢ．Ｐ．；Ｌ１可划分五层，其中Ｌ(１－２)和Ｌ(１－４)为古土壤层，Ｌ(１－２)顶部１４Ｃ年龄为２２０００ａＢ．Ｐ．，深度为３６１ｃｍ，Ｌ(１－４)．底部有一层明显的碳酸盐结核，其ＴＬ年龄为５１９１０ａＢ．Ｐ．，深度为６４０Ｃｍ；Ｌ１底部的ＴＬ年龄为７３０００ａＢ．Ｐ．，深度为８５５ｃｍ，这便是马兰黄土的起始年龄；Ｓ１底部为１３４５００ａＢ．Ｐ．，深度为１２１６ｃｍ。与深海沉积物氧同位素阶段对比，马兰黄土相当于１—４阶段，Ｓ１相当于５阶段。 相似文献
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对采自河北省迁西县太平寨ＨＢＴ１麻粒岩中的辉石、角门石、斜长石进行了４０Ａｒ－３９Ａｒ年龄测定，并对上述三种矿物做了４０Ｋ－４０Ａｒ同位素封闭温度计算，进而根据封闭温度与年龄的关系，研究了该区麻粒岩体的冷却抬升历史。分别得到辉石坪年龄为２．１６Ｇａ，封闭温度为６２０℃；角闪石坪年龄为１．９７Ｇａ，封闭温度为５１７℃；斜长石坪年龄为１．６６Ｇａ，封闭温度为２６５℃。从２．５Ｇａ（麻粒岩相变质年龄）到２．１６Ｇａ，岩体抬升速率为１４．１ｍ／Ｍａ，冷却速率为０．３９℃／Ｍａ；从２．１６Ｇａ到１．９７Ｇａ岩体抬升速率为１８．５ｍ／Ｍａ，冷却速率为０．５５℃／Ｍａ，从１．９７Ｇａ至１．６６Ｇａ岩体抬升速率为２９．１ｍ／Ｍａ，冷却速率为０．８１℃／Ｍａ。Ａｒ－Ａｒ法给出的这些同位素证据，反映了冀东太古代麻粒岩体变质作用晚期多阶段冷却抬升的漫长历史。 相似文献
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通过龙门山区和川西前陆盆地岩石样品的裂变径迹和镜质体反射率的测定和计算机模拟得出：１）松潘－甘孜褶皱带１０Ｍａ以来至少隆升了３－４ｋｍ，隆升速率最低为０．３－０．４ｍｍ／ａ；（２）龙门山逆冲推覆构造带１０Ｍａ以来至少隆升了５－６ｋｍ，隆升速率最低为０．０１６－０．０３２ｍｍ／ａ；（４）川西前陆盆地６０Ｍａ以来降升１－２ｋｍ，降升速率为０．０２８－０．０５ｍｍ／ａ；（５）１０Ｍａ以来北川－映秀－小关 相似文献
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北祁连奥陶纪洋脊扩张速率及古洋盆规模的岩石学约束 总被引：8，自引：0，他引：8
北祁连奥陶纪期间为一多岛洋，由中间微陆块分隔的三个相对独立的洋盆联合组成。火山岩可区分为洋脊型、洋岛（海山）型及岛弧型三种主要的构造岩石组合类型。根据火山岩化学成分计算获得三个洋盆的扩张速率分别为４．４５ｃｍ／ａ，０．７５ｃｍ／ａ和０．８ｃｍ／ａ；闭合速率分别为４．０５ｃｍ／ａ，３．１０ｃｍ／ａ和４．８７ｃｍ／ａ。奥陶纪末期，三个洋盆相继闭合，形成了下伏的中南祁连陆块—北祁连陆－陆碰撞构造混杂带—上叠的阿拉善陆块三个构造单元叠置的构造构局 相似文献
8.
中国第四纪地层 总被引：32，自引：0，他引：32
本文综述了中国第四纪沉积类型及第四系的划分,并与国际第四系划分进行了对比。指出中国第四纪沉积物分布广泛,种类繁多,以陆相沉积为主。按其成因主要有风成黄土堆积、河一湖相沉积、冲一洪积堆积、冰川沉积、洞穴堆积、风化壳残积（红土）、火山堆积和海相沉积等。各种沉积物都有很好的剖面,尤其是黄土和河一湖相沉积更为连续完整。按中国第四纪地层发育的实际情况,第四系的底界应置于松山一高斯极性转换界线（Ｍ／Ｇ,２．６ＭａＢ,Ｐ,）;第四系内部划分为更新统（Ｑｐ）和１４新统（Ｑｈ）,界线在１１０００ａＢ,Ｐ,。更新统进一步划分为下、中和上３个阶(Ｑｐ１, Ｑｐ２, Ｑｐ３), Ｑｐ２／Ｑｐ１的界线为布容一松山极性转换界线（Ｂ／Ｍ; ０．７８ＭａＢ,Ｐ,）;Ｑ(ｐ３／Ｑｐ２的界线为本次间冰期的起始时间（０．１２８ＭａＢ,Ｐ,）。 相似文献
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中国中、新生代板内变形速度研究 总被引：7，自引：0，他引：7
依据中国中、新生代１１８０３件岩浆岩常量元素化学全分析资料,采用Ｓｕｇｉｓａｋｉ的由岩石化学成分推算板块运动速度的方法,求得中国各构造时期板内缩短速度与扩张速度。印支、燕山与四川期板内平均缩短速度均在５４～５６ｃｍ／ａ,华北期稍小,为４５ｃｍ／ａ,喜马拉雅期在中国西部平均缩短速度又达５２ｃｍ／ａ,新构造期仅为２５～２８ｃｍ／ａ。在印支期—华北期,中国西南地区一直存在着扩张速度较低（０２～１６ｃｍ／ａ）的特提斯洋。喜马拉雅期以来中国西南部进一步碰撞,青藏高原隆升,地壳缩短;而东部地区则普遍表现为微弱的扩张（０１～０６ｃｍ／ａ）。 相似文献
10.
我国产出的砷铅矿族矿物的研究 总被引：3，自引：0，他引：3
砷铅矿族矿物是一族六方晶系的类质同象系列矿物，包括砷铅矿、钒铅矿和磷氯铅矿。砷铅矿呈淡黄色、浅黄绿色和灰白色六方柱状晶体产出，Ｈｍ＝３．５，Ｄ≥６．７５ｇ／ｃｍ３，一轴晶负光性，Ｎ＞２，晶胞参数为ａ０＝１．０２５１ｎｍ，Ｃ０＝０．７４４ｎｍ，Ｚ＝２。广西德保矿区产出的砷铅矿的化学成分为（ｗｔ．％）：ＰｂＯ７４．９４，Ａｓ２Ｏ５１９．５３，Ｐ２Ｏ５２．３１，ＣｕＯ０．３６，Ｃｌ２．４１，总量为９９．５５。云南个旧矿区产出的钒铅矿呈桔红色至红褐色，六方短柱状自形晶，Ｈｍ＝３．０，Ｄｘ＝６．９５ｇ／ｃｍ３，一轴晶负光性，Ｎ＞２，晶胞参数为ａ０＝１．０３１ｎｍ，Ｃ０＝０．７４３ｎｍ，Ｚ＝２，空间群为Ｐ６３／ｍ，其化学成分为（ｗｔ．％）：ＰｂＯ７９．９８，Ｖ２Ｏ５１８．９４，Ｃｌ２．６１，总量为１０１．５３。广西阳朔产出的磷氯铅矿，呈暗绿色六方柱状晶体产出，Ｈｍ＝３．５，Ｄ＝６．９８ｇ／ｃｍ３，一轴晶正光性，Ｎ＝２±，平均化学成分为（ｗｔ．％）：ＰｂＯ８１．６４，Ｐ２Ｏ５１５．０８，Ａｓ２Ｏ５０．１０，ＣｕＯ０．２０，Ｃｌ２．６７，总量为９９．６９。 相似文献
11.
Duncan M. Fitzgerald Mark Kulp† Shea Penland† James Flocks‡ Jack Kindinger‡ 《Sedimentology》2004,51(6):1157-1178
The Barataria barrier coast formed between two major distributaries of the Mississippi River delta: the Plaquemines deltaic headland to the east and the Lafourche deltaic headland to the west. Rapid relative sea‐level rise (1·03 cm year?1) and other erosional processes within Barataria Bay have led to substantial increases in the area of open water (> 775 km2 since 1956) and the attendant bay tidal prism. Historically, the increase in tidal discharge at inlets has produced larger channel cross‐sections and prograding ebb‐tidal deltas. For example, the ebb delta at Barataria Pass has built seaward > 2·2 km since the 1880s. Shoreline erosion and an increasing bay tidal prism also facilitated the formation of new inlets. Four major lithofacies characterize the Barataria coast ebb‐tidal deltas and associated sedimentary environments. These include a proximal delta facies composed of massive to laminated, fine grey‐brown to pale yellow sand and a distal delta facies consisting of thinly laminated, grey to pale yellow sand and silty sand with mud layers. The higher energy proximal delta deposits contain a greater percentage of sand (75–100%) compared with the distal delta sediments (60–80%). Associated sedimentary units include a nearshore facies consisting of horizontally laminated, fine to very fine grey sand with mud layers and an offshore facies that is composed of grey to dark grey, laminated sandy silt to silty clay. All facies coarsen upwards except the offshore facies, which fines upwards. An evolutionary model is presented for the stratigraphic development of the ebb‐tidal deltas in a regime of increasing tidal energy resulting from coastal land loss and tidal prism growth. Ebb‐tidal delta facies prograde over nearshore sediments, which interfinger with offshore facies. The seaward decrease in tidal current velocity of the ebb discharge produces a gradational contact between proximal and distal tidal delta facies. As the tidal discharge increases and the inlet grows in dimensions, the proximal and distal tidal delta facies prograde seawards. Owing to the relatively low gradient of the inner continental shelf, the ebb‐tidal delta lithosome is presently no more than 5 m thick and is generally only 2–3 m in thickness. The ebb delta sediment is sourced from deepening of the inlet and the associated channels and from the longshore sediment transport system. The final stage in the model envisages erosion and segmentation of the barrier chain, leading to a decrease in tidal discharge through the former major inlets. This process ultimately results in fine‐grained sedimentation seaward of the inlets and the encasement of the ebb‐tidal delta lithosome in mud. The ebb‐tidal deltas along the Barataria coast are distinguished from most other ebb deltas along sand‐rich coasts by their muddy content and lack of large‐scale stratification produced by channel cut‐and‐fills and bar migration. 相似文献
12.
《China Geology》2019,2(4):522-529
In recent years, development activities have had a significant impact on the environment of the Jiaozhou Bay, China. To ensure the sustainable economic and social development of the Jiaozhou Bay area, it is necessary to strengthen corresponding control measures. The important prerequisite is to properly understand the environmental conditions laws of natural change, especially the dynamic processes of sediment and the characteristics of landform evolution. Based on the data of continuous observation at 6 stations in Jiaozhou Bay for 25 hours, the Hydrodynamic Eutrophication Model (HEM-3D) was used to simulate the sediment erosion and deposition. The results show that the maximum suspended sediment concentration in the sea area of Jiaozhou Bay is about 40 mg/L, which appears in the northwestern area of the bay top and the Cangkou watercourse area, and the low concentration is located in the area of the central Jiaozhou Bay towards the bay mouth. The suspended sediment is 6–10 mg/L. Affected by a decrease in seawater material, the direction of the prevailing current in the Jiaozhou Bay area is different from that of the sediment transport. The velocity of the flood current is higher than that of the ebb current. However, during flood tide, the flux of resuspended seafloor sediment outside and at the mouth of the bay is limited and cannot contribute significantly to the suspended sediment in the bay. During ebb tide, the resuspended sediment at the shallow-water bay head and the east and west sides spreads toward the bay mouth with the ebb current, although it extends beyond the bay through the bay mouth. The research results can provide scientific support for the Jiaozhou Bay project construction and environmental protection. 相似文献
13.
This study reconstructed environmental changes to the seafloor associated with reclamation in Mishou Bay, Bungo Channel, Japan, based on measurements of sediment grain size, organic matter and sulfur contents of surface sediments and data from sediment cores. Grain size within sediment cores from the middle of Mishou Bay decreased from the beginning of the 1800s to the 1900s. In contrast, a grain size profile from the river mouth shows a gradual increase in grain size up through the sediment core. These changes in grain size indicate a decrease in tidal current velocity within the middle of the bay and that the delta system is gradually prograding from the river mouth. Records of organic matter composition and sulfur contents indicate that the effect of the river on seafloor sedimentation became stronger during the nineteenth century. These changes are related to reclamation during the late 1700s and 1800s. The decrease in sea area resulting from reclamation probably led to a decrease in tidal prism and current velocity. It is likely that the increasing effect of river water on sedimentation is associated with reclamation-related progradation of the river delta system. 相似文献
14.
委内瑞拉盆地奥里诺科重油带MPE-3区块Oficina组辫状河三角洲沉积相定量刻画难度大,是制约该区块水平井高效开发的关键地质因素。在区域沉积背景研究的基础上,利用岩芯描述和分析化验资料,确定该地区为辫状河三角洲沉积,区内主要发育辫状河三角洲平原和三角洲前缘亚相,心滩、复合心滩坝、辫状河道、决口扇/溢岸、泛滥平原、水下分流河道、分流间湾、席状砂和潮汐砂坝等微相。综合利用地震和测井资料、现代沉积测量类比和经验公式等三种方法,实现了研究区主要沉积微相的定量刻画,认为辫状河河道带宽度介于1~5 km,水下分流河道宽度在1 km左右,建立了心滩宽与心滩长、心滩宽与辫状河道宽度、水下分流河道单河道宽度与深度之间关系的经验公式,进一步阐明了Oficina组沉积时期辫状河三角洲沉积演化规律,为提高研究区超重油油藏采出程度提供了重要地质依据。 相似文献
15.
On the linkages among density, flow, and bathymetry gradients at the entrance to the Chesapeake Bay 总被引：1，自引：0，他引：1
Arnoldo Valle-Levinson William C. Boicourt Michael R. Roman 《Estuaries and Coasts》2003,26(6):1437-1449
Linkages among density, flow, and bathymetry gradients were explored at the entrance to the Chesapeake Bay with underway measurements of density and flow profiles. Four tidal cycles were sampled along a transect that crossed the bay entrance during cruises in April–May of 1997 and in July of 1997. The April–May cruise coincided with neap tides, while the July cruise occurred during spring tides. The bathymetry of the bay entrance transect featured a broad Chesapeake Channel, 8 km wide and 17 m deep, and a narrow North Channel, 2 km wide and 14 m deep. The two channels were separated by an area with typical depths of 7 m. Linkages among flows, bathymetry, and water density were best established over the North Channel during both cruises. Over this channel, greatest convergence rates alternated from the left (looking into the estuary) slope of the channel during ebb to the right slope during flood as a result of the coupling between bathymetry and tidal flow through bottom friction. These convergences were linked to the strongest transverse shears in the along-estuary tidal flow and to the appearance of salinity fronts, most markedly during ebb periods. In the wide channel, the Chesapeake Channel, frontogenesis mechanisms over the northern slope of the channel were similar to those in the North Channel only in July, when buoyancy was relatively weak and tidal forcing was relatively strong. In April–May, when buoyancy was relatively large and tidal forcing was relatively weak, the recurrence of fronts over the same northern slope of the Chesapeake Channel was independent of the tidal phase. The distinct frontogenesis in the Chesapeake Channel during the increased buoyancy period was attributed to a strong pycnocline that insulated the surface tidal flow from the effects of bottom friction, which tends to decrease the strength of the tidal flow over relatively shallow areas. 相似文献
16.
辽东湾北部浅海区泥沙输送及其沉积特征 总被引：16，自引：1，他引：16
根据实测资料，本文定量分析了辽东湾北部泥沙输送及其分布，并对辽河三角洲沉积区划作了初步讨论。研究表明本区泥沙以纵向搬运为特征。双台子河以西来沙和辽河西水道入海泥沙是区域东部拦门沙体和浅滩发育的主导因素。汛季大潮期，泥沙自西向东运移落淤在河口及毗邻浅水域；小潮期，泥沙除向东扩散外，大部泥沙向海方搬运。调查区可划分六个现代沉积作用区，即潮坪沉积区、辽河水下三角洲细粒沉积区、河口沙洲沉积区、波浪潮流冲蚀沉积区、河口冲积沉积区以及潮汐水道沉积区。 相似文献
17.
海南岛洋浦港现代沉积速率 总被引：17，自引：6，他引：11
通过对海南岛洋浦港4个沉积柱样沉积结构?Pb-210?Cs-137放射性强度的分析,研究该区的现代沉积速率?洋浦港海域为一潮汐叉道,沉积物的分布主要受潮流分布的影响,近代沉积过程具有阶段性的特点,在港口的许多地方正持续着侵蚀与堆积的循环?洋浦深槽的沉积物主要为粉砂?粘土,砂质物主要由河流?落潮流带入,而大部分的粘土颗粒物质由涨潮流带入深槽,在高平潮水动力能量减小的条件下沉降下来,由于这种沉积物传输的双向性导致了极易变化的沉积结构?粗砂粉砂的交替沉积反映了风暴潮事件对该区域的影响?根据Pb-210?Cs-137测年法,洋浦港深槽的现代沉积速率为0.5~2cm/a,本世纪初以来,拦门沙处于稳定增长的状态,其平均增长率为1~2cm/a?该方法应用于地质年代学具有实际的意义? 相似文献
18.
In October of 2004, a 3-d observational program to measure flow and sediment resuspension within a coastal intertidal salt
marsh was conducted in the North Inlet/Winyah Bay National Estuarine Research Reserve located near Georgetown, South Carolina.
Current and acoustic backscatter profiles were obtained from a moored acoustic Doppler current profiler (ADCP) deployed in
a shallow tidal channel during the spring phase of the tidal cycle under high discharge conditions. The channel serves as
a conduit between Winyah Bay, a large brackish estuary, and North Inlet, a saline intertidal coastal salt marsh with little
freshwater input. Salinity measurements indicate that the water column is vertically well mixed during flood, but becomes
vertically stratified during early ebb. The stratification results from brackish (15 psu) Winyah Bay water entering North
Inlet via the tidal channel, suggesting an exchange mechanism that permits North Inlet to receive a fraction of the poor water
quality and high discharge flow from upland rivers. Although maximum flood currents exceed maximum ebb currents by 0.2 m s−1, suspended sediment concentrations are highest during the latter ebb phase and persist for a longer fraction of the ebb cycle.
Even though the channel is flood-dominated, the higher concentrations occurring over a longer fraction of the ebb phase indicate
net particulate transport from Winyah Bay to North Inlet during spring tide accompanied by high discharge. Our evidence suggests
that the higher concentrations during ebb result from increased bed friction caused by flow asymmetries and variations in
water depth in which the highest stresses occur near the end of ebb near low water despite stronger maximum currents during
flood. 相似文献
19.
黄河三角洲滨海区沉积物的分异特征与规律 总被引：7，自引：0，他引：7
根据2000年79月黄河三角洲滨海区表层沉积物的分析结果,运用F lem ing的三角图式对沉积环境进行划分,并在此基础上结合沉积物结构、地形和水动力条件,探讨了沉积物的分布规律及其作用机制。结果表明:研究区域可划分为废弃三角洲滨海区、现行河口区和莱州湾滨海区三个沉积环境。对于废弃三角洲沉积区,在早期废弃的湾湾沟海区风浪作用为主,沉积物普遍较粗,抗冲能力较强;废弃不久的飞雁滩海区在波流联合作用下,沉积物粒径由岸向海变细,大致在-5-6m水深处存在一明显的界限,该水深以浅砂含量较高;而该水深以深以粉砂和粘土为主,砂含量较低。现行河口区,由于沙嘴前方强潮流带的作用,沉积物粒径由岸向海表现为粗—细—粗的演变趋势。在莱州湾海区,由于潮流场的影响,以广利河河口为界,以北粒径较细,而以南则较粗。 相似文献
20.
采用大凌河实测长系列河道径流及水下地形等数据, 通过建立水动力数值模型, 综合考虑潮流和河道径流的影响, 对大凌河口的潮流进行模拟, 探讨大凌河口及辽东湾北部海域水动力过程的主要特征. 结果表明: 大凌河口附近海域的海流以潮流为主, 具有明显的往复性质. 潮流总的运动趋势是, 涨潮主流向为北东, 落潮主流向为南西. 大潮流速大于小潮流速, 涨潮流历时与落潮流历时几乎相当. 最大涨潮流速约为0.52 m/s, 最大落潮流速约为0.4 m/s, 潮流涨落平均潮流强度的分布大体和该海域等深线相适应. 相似文献