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Charles W. Hoffman Andrew E. Grosz John G. Nickerson 《Marine Georesources & Geotechnology》2013,31(2-3):173-184
One hundred fourteen vibracores from the Atlantic continental shelf offshore of southeastern North Carolina were opened, described, and processed over several contract years (years 6-9) of the Minerals Management Service Association of American State Geologists Continental Margins program. Reports for years 9 and 10 of the program compiled the results of the work and assembled the data for release as an interactive CD-ROM report, respectively. The continental shelf of Onslow and Long Bays consists predominantly of outcropping Cretaceous through late Tertiary geologic units. Nearshore these units are covered and incised by late Tertiary and Quaternary units. From oldest to youngest, formally recognized geologic units mapped as part of this study are the Late Cretaceous Peedee Formation a muddy, fine-to medium-grained quartz sand with trace amounts of glauconite and phosphate; the Paleocene Beaufort Forma tion a muddy, fine-to medium-grained glauconitic quartz sand with locally occurring turritelid-mold biosparrudite; the middle Eocene Castle Hayne Forma tion a sandy bryozoan biomicrudite and biosparrudite; the Oligocene River Bend Formation a sandy molluscan-mold biosparrudite; and the Miocene Pungo River Formation a medium-grained, poorly sorted slightly shelly phosphatic sand. Infor mal units include a very widespread, unnamed fine-to very fine grained, well-sorted, dolomitic muddy quartz sand that is biostratigraphically equivalent to the Oligocene River Bend Formation; several large valley-fill lithosomes composed of biomicrudite, biomicrite, and biosparrudite of Plio Pleistocene age; muddy, shelly sands and silty clays of Pliocene, Pleistocene, or mixed Plio Pleistocene age; and loose, slightly shelly, medium- to coarse-grained sands assigned a Holocene age. Heavy minerals (SG>2.96) comprise an average of 0.54 wt % (on a bulk-sam ple basis) of the sediments in 306 samples derived from the 114 vibracores. Heavy-mineral content ranges from <0.01 to 3.69 wt %. The economic heavy mineral content (EHM ilmenite zircon rutile aluminosilicates leucoxene [altered ilmenite] monazite) of the bulk samples averages 0.26 wt % in a range of <0.01-1.70 wt %. As a percentage of the heavy-mineral concentrate, the average EHM value is 45.78 % in a range of 0.27-68.60 %. The distribution of heavy minerals offshore of southeastern North Carolina is controlled by the lithostratigraphic framework. The unnamed Oligocene sand unit has the highest heavy-mineral content, averaging 0.86 wt % on a bulk-sample basis. The remaining geologic units and their heavy-mineral content (in decreasing order of abundance) are Beaufort (0.64 %), Holocene sand (0.60 %), Plio-Pleistocene muddy sand and silty clay (0.59 %), Peedee (0.42 %), River Bend (0.34 %), Plio-Pleistocene carbonate (0.12 %), and Castle Hayne (0.08 %). The heavy-mineral assemblage is fairly consistent throughout the different units. Significantly smaller percentages of heavy minerals correlate with increased amounts of CaCO3 in the sediments. The sediments analyzed in this study have significantly lower overall heavymineral content, as well as lower EHM content than sediments that are known to host commercially important heavy-mineral deposits in the southeastern United States. The potential for economic deposits of heavy minerals in the area of this study, therefore, appears to be limited. 相似文献
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Changing shoreline positions along the Sinai coast of Egypt were determined by comparing aerial photographs and historical
charts with present-day conditions. The analyses identify longshore patterns wherein erosion along a protruding stretch of
the coast gives way to accretion in an adjacent major embayment. This pattern defines two coastal subcells consisting of source/sink
couplets. There is a general correspondence between the mineral variation, grain sizes of beach sand, and the patterns of
shoreline changes. Associated with erosion/ accretion shoreline change is a selective transport of different minerals according
to their densities and grain sizes. Two heavy-mineral groups were obtained by applying Q-mode factor analysis on the heavy-mineral
data. These two groups are influenced by transport processes, including sediment provenance from different sources: eroded
Nile delta west of Sinai, relict sediments from the former Nile distributaries, and sediment supply by land valleys and from
wind-blown sand.
Received: 2 June 1995 / Revision received: 29 May 1996 相似文献
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谢帕德和福克碎屑沉积物分类方法在南黄海表层沉积物编图中的应用与比较 总被引：7，自引：0，他引：7
谢帕德(Shepard,1954)和福克(Folk)等(1970)的沉积物结构分类是较为常用的两种分类方法。尽管都是基于沉积物粒度组成的三元分类,但分类的出发点和基本思路有很大的不同。Shepard分类是三端元等价的纯描述性分类,不反映沉积物粒度组成的水动力学属性,砾质沉积物未考虑在内。Folk分类虽然也是三端元分类,但三个端元是不等价,首先按砂/泥比划分基本类型,然后再按粉砂/黏土比进一步分类,砂/泥比反映动力强度的大小,粉砂/黏土比反映介质的混浊度,具有明显的动力学意义。鉴于粒度分异与搬运距离的成因联系,Folk分类也是分析物源区的工具。笔者用两种分类研究了南黄海的表层沉积物,发现按照Folk分类,南黄海的表层沉积物分布可以分为两个沉积系列。在南黄海西部,沉积物由西向东依次为砂-粉砂质砂-砂质粉砂-粉砂;而在东部,由东向西依次为砂-泥质砂-砂质泥-泥组成。由岸及海随着沉积水动力由强变弱,沉积物粒度变细,大致与由东西两侧的强潮流作用区到中部的静水涡流作用区的动力学格局相一致,在一定程度上反映了沉积环境的变化、沉积物的物源和输运方向。实践证明,Folk分类的应用效果明显优于Shepard分类,可以较好地满足海洋地质研究的需要,应当在我国海洋沉积物的研究中予以推广。 相似文献
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山东半岛东北部滨浅海区表层沉积物粒度及矿物成分 总被引：4，自引：3，他引：1
对山东半岛东北部滨浅海区海底表层沉积物的粒度和矿物组分进行了分析,探讨了其物源及其粒度分布特征与沉积动力条件的关系。结果表明,本区表层沉积物主要来源于现代黄河物质,底质类型主要有黏土质粉砂、砂质粉砂和粉砂质砂3种类型,其中黏土质粉砂约占该区沉积物分布面积的60%以上,呈“Y”形由西北向东南展布。研究区沉积作用的主控因素是黄海沿岸流,各粒级组分的分布和粒度参数特征与海流的方向和强弱有明显的相关性。 相似文献
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利用2010年1月与2010年8月采集的钱塘江中下游河床沉积物粒度和磁性测量数据以及2010年8月测量的流速数据,分析了沉积物粒度和磁性的时空分布特征,探讨了粒度和磁性参数对沉积动力环境的指示意义.结果表明:(1)冬季河床沉积物以粉砂和黏土为主,夏季以粉砂和砂为主,沉积物粒度呈现从中游到富春江水库逐渐变细、近口段到河口... 相似文献
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本文通过对黄河三角洲埕岛海域146个表层样的粒度分析,表明该区有5种沉积物类型,以砂质粉砂为主体,呈斑块状分布,极细砂与粗粉砂是沉积物的主要粒级,普遍分选差。运用"粒径趋势"分析的方法,分析探讨了埕岛海域表层沉积物净输运趋势。研究区的沉积物的净输运趋势大致以12 m水深为界,深水区沉积物的净输运趋势向岸,12 m以浅海域的沉积物具有离岸的净输运趋势,说明深水区沉积物受冬季风浪作用向岸运移作用显著,12 m以浅海域的沉积物受夏季风浪作用离岸运移作用显著,沉积物运移的季节变化已成为研究区海域沉积物净运移的主要控制因素。 相似文献
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长江口表层沉积物重矿物在不同粒级中的分布与研究意义 总被引：3，自引：0，他引：3
在粒度分析基础上,以0.5Φ为间距对长江口表层沉积物的不同粒级分样进行碎屑重矿物分析,并对各粒级重矿物特征与广粒级(1.5Φ～6Φ)进行相似度分析。结果表明,长江口沉积物粒度跨度大,从粗砂到泥(黏土)均有分布,粉砂含量高。样内不同粒级分样重矿物含量、种类和组合均有一定变化,样间表现出较一致的规律性。长江口出现碎屑重矿物30种左右,粗粒级分样中矿物种数为10余种,细粒级分样中重矿物种类增至20多种;3.5Φ～4.5Φ是重矿物种类多、矿物成分复杂的粒级区段。粗粒级(粒径大于3Φ)云母族富集,其重矿物组合为云母+角闪石,随粒级变细(粒径小于4Φ)云母急剧减少;闪石族分布粒级广泛,在3Φ～5Φ粒级含量相对较高;帘石族、稳定矿物尤其是金属矿物在粒径小于3.5Φ粒级逐渐增多。长江口重矿物整体组合为普通角闪石+绿帘石+褐铁矿,榍石为特征矿物。相似度分析表明,长江口沉积物样品中主要粒级与广粒级重矿物特征相近,能代表沉积物整体重矿物特征。长江口碎屑重矿物特征深受粒度分布的影响,其矿物种类、矿物组合和矿物指数及其所蕴含的水动力和物源意义都要结合粒度特征来综合分析。 相似文献
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根据北仑河口3个钻孔柱状沉积物的粒度分析结果,结合14C测年和210Pb测年资料,分析了钻孔沉积物的粒度特征,结果表明：KL1柱样沉积物主要为粉砂质砂、砂质粉砂、中细砂、细中砂,沉积物由下到上由细到粗再变细,经历了2个沉积变化;KL2柱样沉积物单一,为细中砂;KL3柱样沉积物由下到上依次为砾石、砂砾、粗中砂、细中砂、砾砂、粉砂质砂、粘土质粉砂、砂-粉砂-粘土,沉积物粒度由下到上逐步细化,该孔早期离物源较近.3个孔的沉积物分选大多很差,反映当时水动力作用较强或者离物源较近.这些沉积物类型为晚更新世末次冰期以来的沉积,记录了晚更新世以来2个沉积变化. 相似文献
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山东龙口港口区表层沉积物的粒度分析 总被引：1，自引：0，他引：1
通过对龙口港航道附近小范围内表层沉积物的粒度分析,探讨该港口航道附近的表层沉积物的类型和分布特征。结果表明：1）研究海域的表层沉积物类型分为砂、粉砂质砂、砂质粉砂和粘土质粉砂4种。2）研究海域的表层沉积物主体是砂,其主要变化趋势是由岸到海砂的质量分数逐渐减小又逐渐增大。从它们平面分布来看,粉砂粒组与砂粒组含量的平面分布特征正好相反,粘土含量的平面分布特征与粉砂相似。3）研究海域表层沉积物的平均粒径为2．14～12．79Φ,平均为7．7Φ,沉积物颗粒的直径总体上为细砂粒径;分选系数为0．55～2．99,平均为1．82,分选差;偏态为一0．10～O．75,平均为o．20;峰态为0．63～2．76,平均为1．01。 相似文献
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The coast of the State of Kuwait is characterized by a relatively wide intertidal flat area. At the north, where it is close to Shatt-al-Arab estuary, the intertidal sediments are mainly fluviomarine, while open marine sediments dominate the southern intertidal flat area. Samples were examined from the intertidal zone of deposition from the fluviomarine and open marine environments.The sediments consist mainly of carbonate minerals (low-Mg calcite, high-Mg calcite, aragonite and dolomite), quartz, feldspars, clay minerals and heavy minerals. The mineralogy of the clay fractions of the sediments is dominated by illite, mixed-layer illite—montmorillonite, montmorillonite, chlorite, kaolinite and palygorskite with only minor amounts of quartz. Heavy minerals are concentrated in the very fine sand fraction and are dominated by opaque minerals, amphiboles, pyroxenes, epidotes, garnet, kyanite and sillimanite. Zircon, tourmaline, andalusite, staurolite and rutile are present in subordinate amounts.Three main sources are suggested for the intertidal sediments of Kuwait: (a) Shatt-al-Arab fluviatile deposits, (b) aeolian dust fallout, and (c) direct chemical and biogenic precipitation from the Gulf water. 相似文献
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对2007年采自越南红河水下三角洲北区24个表层沉积物样品进行了粒度分析和粒度参数计算,初步探讨了该区沉积物的主要类型及分布特征。结果表明,越南红河水下三角洲北区的表层沉积物主要由粉砂组成(体积平均含量为54.35%),平均粒径为6φ。按Link沉积物命名法,该区沉积物主要类型有砂、砂质粉砂和黏土质粉砂。水平分布上,由西部的砂向东逐渐变为黏土质粉砂,呈现出由近岸三角洲前缘相的粗粒级沉积物逐渐向前三角洲-浅海相的细粒级沉积物变化的趋势。与前人研究成果对比发现,红河水下三角洲北区沉积物黏土的比例较1996年的比例明显增大,可能与海岸线近10a来总体上呈向陆迁移、水下三角洲沉积向岸蚀退以及纵向上水动力逐渐变弱有关。 相似文献
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根据莱州湾西南部207个表层沉积物样品的粒度分析结果,对莱州湾西南部沉积物粒度分布特征进行了研究,在此基础上应用系统聚类分析方法并结合物源及水动力条件探讨了其现代沉积环境分区。结果表明,研究区表层沉积物类型以粉砂质砂、砂质粉砂和粉砂为主,分布范围最广的粉砂主要位于淄脉沟以北;沉积物平均粒径由近岸向莱州湾中部逐渐变细,从南向北呈现粗—细—粗的变化趋势;研究区现代沉积环境分为高能粉砂质砂粗粒沉积区、砂质粉砂过渡沉积区以及低能粉砂细粒沉积区,其水动力环境表现为波浪作用逐渐减弱,潮流作用逐渐增强,沉积物物源由近岸河流、岸滩侵蚀来沙为主变为以黄河悬浮—再悬浮物质为主。 相似文献
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青岛海岸带及邻近海域地形和沉积物类型研究 总被引：2，自引：0，他引：2
研究了青岛海岸带及邻近海域的地形特征、沉积物类型及分布特征。总体看来,沿海岸粒度较粗,为砂、粉砂质砂等,向海深处粒度有逐渐变细的趋势,海深处的沉积物主要为砂—粉砂—黏土,局部为粉砂质黏土、黏土质粉砂和黏土质砂。灵山岛周围,沉积物粒度较粗。胶州湾口内外为一海底深槽,水深流急,冲刷强烈,沉积物粒度非常粗,主要为粗砂、中砂,局部有基岩出露。深槽南北两侧各有一条突出海底的砂脊,平行于深槽延伸方向砂脊由中砂组成,混有少量黏土,北侧砂脊表面呈不规则起伏,南侧砂脊表面则较为平整。胶州湾内沉积物粒度总体较细,主要为粉砂质黏土、黏土质粉砂及砂—粉砂—黏土等。根据沉积物类型及分布特征,可把青岛海岸带及邻近海域的沉积划分为4个沉积区:胶州湾口及滨岸现代沉积区、北部浅海沉积区、南部浅海沉积区和残留—残余沉积区。 相似文献
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西南印度洋龙旂、断桥热液区沉积物中重矿物空间分布特征及其意义 总被引：1，自引：0，他引：1
以中国大洋第34航次在西南印度洋龙旂与断桥热液区采集的洋底表层沉积物样品为研究对象,为洋中脊热液硫化物勘查重砂找矿工作提供一定的理论与工作基础,开展了沉积物自然重砂矿物的相关研究。绘制了研究区重砂矿物分布图,并根据研究区已探明热液矿体(喷口)的位置,对沉积物重分散晕的形成与分布规律进行了分析;从研究区沉积物的34种矿物中,筛选出3种沉积物重砂找矿的指示性矿物(重砂总量、黄铜矿、黄铁矿)及5种参考性矿物指标(帘石类矿物、透闪石、磁铁矿、铬铁矿、钛铁矿);运用统计学方法,建立了沉积物中指标矿物含量与矿源距离之间的线性方程,提出了根据测站沉积物中指标矿物含量,初步推算矿源距离的方法。 相似文献
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The southeastern beaches and inner shelf of the Buenos Aires coastline are dominated by storms coming from the south and southeast. Erosion is dominant at the coastal cliffs and abrasion platforms, while deposition is extended below the 9-m contour depth. In relation to sand abundance on the inner shelf, there is a northward transition between shelly sand sheets, a fine-sand ribbon field, and sand ridges with oblique megaripples. Side-scan records indicate the selective sorting processes that lead to grain size diminishing to the north, and heavy-mineral enrichment, either at the beach or on the shelf. These storm-induced effects should be considered when evaluating placers on the inner shelf or monitoring the heavy-metal content in sediments. Two-way analyses of variance (ANOVA) tests were used to establish the grain-size effects on heavy-metal analysis. 相似文献
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大河河口的动力沉积过程一直是陆海相互作用研究的核心内容,其中水体泥沙的垂向交换是河口动力-沉积机制分析中的关键环节。基于2011年12月对长江河口及其邻近海湾采集的大范围、高密度的近底层悬沙、海床表层1~2cm(表层沉积物)和垂向向下约2~10cm的沉积物(次表层沉积物)同步3组303个样品,利用经验正交函数方法,对河口地区的悬沙和沉积物交换过程进行研究。结果表明:近底层水体悬沙的空间分布模式主要以粉砂粒级为主,空间分布差异性不大;表层及次表层沉积物的空间分布模式相似,但较近底层水体悬沙的分布复杂,存在明显的区域性特征,其中南汇边滩水域中部辐散区的沉积物表现为粗粉砂-细砂模式,其他区域由粉砂组分模式组成。近底层水体悬沙、表层和次表层沉积物的第一模态主要反映了粒径较细的泥沙运动,第二模态主要反映了粒径较粗的泥沙运动。在近底层水体悬沙与表层沉积物的垂向交换中,主要交换粒级为粉砂组分粒级。在表层沉积物与次表层沉积物的垂向交换中,南汇边滩中部辐散区的主要交换粒级为粗粉砂-细砂组分粒级,其他区域主要为粉砂组分粒级。 相似文献
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Manoj Datta G. Venkatappa Rao Shashi K. Gulhati 《Marine Georesources & Geotechnology》2013,31(4):307-341
Abstract This paper presents the results of a laboratory investigation undertaken to study the nature of two submarine carbonate soils from Bombay High off the west coast of India, as well as to study the shear and plasticity behavior of their sand and silt‐clay fractions, respectively. Scanning electron micrographs reveal that the carbonate content in both soils is comprised primarily of nonskeletal particles of various types. X‐ray diffraction and infrared absorption analyses indicate that in one soil the carbonate fraction consists of calcite and aragonite minerals, whereas in the other soil dolomite is also present. The non‐carbonate fraction of both soils is comprised primarily of quartz and feldspar, and also some clay minerals. The nature of the carbonate fraction of the two soils indicates that they were formed by different depositional processes. During drained triaxial shear the nonskeletal sand grains of both soils exhibit a lower degree of crushing when compared with that of the skeletal carbonate sands, and thus appear to be stronger foundation material. Although the carbonate contents of the silt‐clay fractions of the two soils are similar, they exhibit markedly different plasticity characteristics . This is probably because of the microlevel cementation produced by carbonate material in one soil. This study leads one to the conclusion that carbonate content alone should not be treated as a parameter which controls the engineering behavior of submarine soils; the nature and form of carbonate material must also be identified. 相似文献