共查询到20条相似文献，搜索用时 718 毫秒
1.
全新世大暖期的最大海侵对沿海地区具有深刻影响,但是海南岛北部全新世的最大海侵范围研究较少。本研究利用高精度DEM数据解译以及野外钻探验证,发现海南岛北部全新世精确的最大海侵古岸线空间展布位置,其总面积约260 km2,其中约115 km2属于现今的江东新区规划建设范围内,占整个江东新区规划面积的38%。海南岛北部全新世最大海侵古海岸线的发现,不仅对理解南海全新世高海平面特征及规律提供琼北地区新证据,并且对海南自贸区（江东新区）应对未来海平面升高问题提供背景参照。 相似文献
2.
全新世大暖期的最大海侵对沿海地区具有深刻影响,但是海南岛北部全新世的最大海侵范围研究较少。本研究利用高精度DEM数据解译以及野外钻探验证,发现海南岛北部全新世精确的最大海侵古岸线空间展布位置,其总面积约260 km2,其中约115 km2属于现今的江东新区规划建设范围内,占整个江东新区规划面积的38%。海南岛北部全新世最大海侵古海岸线的发现,不仅对理解南海全新世高海平面特征及规律提供琼北地区新证据,并且对海南自贸区（江东新区）应对未来海平面升高问题提供背景参照。 相似文献
3.
本文讨论了广西北海现代海岸各种环境的自然地理分带、地质营力、沉积物以及生物生态等特征，指出环境能量直接决定了环境类型、沉积物类型以及生物组合类型。海岸环境据其能量划分为高能海滩、低能海湾、中能岩质潮坪和砂质潮坪、低能泥质红树林潮坪以及高能潮上沙丘等6种沉积类型；混合沉积作用主要发育于高能海滩和中能潮坪沉积环境内。涠洲岛现代地壳的上升活动控制着该区海蚀地貌的形成。 相似文献
4.
5.
南海北部湾全新世以来沉积物地球化学特征及物源分析 总被引：2，自引：0，他引：2
为探讨全新世以来南海北部湾沉积物的沉积环境变化,对北部湾海域的SO-31沉积物柱状样进行了元素地球化学分析。根据元素地球化学的垂向分布特征,将SO-31沉积柱划分为3个单元,反映了全新世不同时期的区域海平面波动以及沉积物物源的变化。SO-31沉积柱的稀土元素配分曲线和La/Co与La/Sc散点图分析表明:111 400~12 800 a BP(全新世前期),研究区海平面较低,红河、其他周边河流及海岸侵蚀物均为本区的主要物源;28 500~1 1400 a BP(全新世早期),随着海平面的逐渐上升,河口和岸线逐渐后退,各物源供给区对本区沉积物的贡献量也发生了相应变化,相对而言红河贡献率有所下降;30~8 500 a BP(中全新世至今),区域海平面持续上升导致了琼州海峡打开,北部湾水动力环境和物源供给发生了剧变,红河对本区的物源贡献逐渐变小,而来自北部湾东部的物质成为本区沉积物的主要物源。 相似文献
6.
泉州湾处于我国东南沿海构造活动带,具有发生地震的地质环境和同震海岸崩塌、海湾下沉的构造地貌条件。通过对泉州湾海滩岩产状、14 C测年、古生物化石及岩石学特征的研究分析,认为其物源为海岸崩塌的志留纪花岗岩和潮滩、河口堆积的陆源碎屑。搬运方向自南向北偏东,形成于泉州湾北部潮间带接近高潮位,在温暖和高蒸发的气候条件下有淡水参与,由钙质胶结发生的快速成岩作用。海滩岩形成的地质时代为全新世晚期,是突发性海洋强动力事件的记录,可能与距今2 000a在泉州湾以南发生的古地震造成深沪湾岩岸大规模崩塌和海湾快速下沉引发的海啸有关。 相似文献
7.
8.
9.
广东全新世海平面重建与冰川均衡调整模型结果的比较 总被引：2，自引：0，他引：2
中国广东沿岸作为一个冰川均衡调整(GIA)“远场”地区,按照水动型均衡理论,应存在全新世中期高海平面.本文通过海平面标志物重建了广东古海平面的历史,结果显示出在粤东、粤西与珠江三角洲的海平面历史存在明显的差异.若将海平面历史与GIA模型结果对比,可以看出广东沿岸在全新世以来具有微小的区域性地壳沉降.这种大区域的沉降可归因于华南陆块向南延伸所引起.此外,粤西雷州半岛因新构造运动,于全新世早中期有轻微抬升.珠江三角洲盆地则因断裂构造沉降和沉积物压实作用,重建的中全新世海平面明显低于GIA结果. 相似文献
10.
人类活动对砂坝泻湖海岸潮汐通道冲淤变化的影响--以香港大屿山岛银矿湾海岸为例 总被引：6，自引：0，他引：6
香港海岸岸线曲折,海湾小而深入,砂坝泻湖是其主要的一种海岸地貌类型。香港港湾砂坝海滩的沉积物主要来源于河流带来的物质。由于香港(岛区)为山地丘陵地貌,河流短小,集水盆面积不大,储流时间短,径流大小紧随降水量变化而变,加上沉积物数量有限,所以砂坝体积细小,对海岸环境变化反应甚为敏感。因此,香港砂坝泻湖海海岸的演化过程比较容易反应出人类活动的影响。香港又是近代城市化最快的地区之一,人类活动对海岸演化过程的作用明显。根据历年地图、航片的对比,以及实地的测量,可以反映出香港砂坝泻湖海岸潮汐通道的冲淤变化与人类活动的相关关系。图1香港银矿湾排洪道修建前后潮汐通道的冲淤变化香港地区大屿山岛南岸的银矿湾是 相似文献
11.
Submerged upper Holocene beachrock on San Salvador Island,Bahamas: implications for recent sea-level history 总被引：1，自引：0，他引：1
Sedimentological, petrographic and radiometric data from a submerged beachrock on San Salvador Island, Bahamas, provide new information about the Late Holocene sea-level history in this area.At French Bay, on the southern shore of the island, samples of beachrock collected at a depth of 1 m below low tide level yielded an average 14C age of 965 ± 60 years before present. These samples further display a well developed fenestral porosity and present an early generation of low Mg calcite meniscus cement. These features characterize intertidal and supratidal settings; they are not consistent with the present beachrock position and the reported Late Holocene sea-level history in the Bahamas. A 1.5–2m low stand of the sea about 1000 years ago would best explain the observed particularities of the French Bay beachrock.This example from San Salvador shows that the smooth trend of Late Holocene sea-level rise proposed by previous workers might be overprinted by high frequency, low amplitude fluctuations. Recognition of these fluctuations is fundamental when calculating rates of sea-level rise and evaluating the coastal response to a marine transgression.
Correspondence to: P. Kindler 相似文献
12.
山东乳山海滩岩及其重要科学意义 总被引：2，自引：0，他引：2
乳山海滩岩,经过室内对微体化石、大化石和沉积岩石学研究,查明该岩体具有典型的海滩岩特征:含有两种文石胶结物、滨海相微体古生物和热带大化石。该岩体形成在全新世最佳气侯期,至少有3次成岩期,对研究古环境变化规律具有重要的科学意义。 相似文献
13.
南黄海潮成辐射砂脊群的面积约为20000km2，以160° 的角度从弓京港向海展开。它与以弓京港为顶点的辐聚辐散潮流场相伴而生。60余个钻孔揭示，毗邻海区辐射砂脊体系的江苏沿岸平原上存在一个面积约3000 km2潮成砂区，其顶点位于东台，同样呈扇形以130°的角度向东展开。在潮成砂区内潮成砂质沉积单元位于冰后期海侵型砂坝-湖沉积层之上，二者之间具明显的冲刷面。砂坝-湖沉积层位于晚更新世基底硬粘土层之上，二者之间有较长的沉积间断。潮成砂沉积层上覆潮坪沉积层，二者呈渐变关系。以潮成砂层底部的侵蚀面为界，其下为海侵序列，其上为海退序列。古潮流的研究揭示，潮成砂区内同样存在辐聚辐散的古潮流场，其顶点位于东台附近。由此推断，沿海平原的潮成砂区内也是辐射状潮成砂脊体系，它形成于全新世海退时期。由于长江和黄河三角洲的前展，以东台为顶点的潮成砂脊体系逐渐暴露成陆。陆上和海域潮成辐射砂脊群形成于相同的潮汐动力环境，但处在不同的发育阶段，前者形成于全新世中期，后者发育于全新世晚期。矿物分析揭示，陆上和海区的潮成辐射砂脊体系主要由长江和黄河沉积物组成，其中长江沉积物由南向北运移，且时间较早；黄河沉积物由北向南运移，时间较迟，这种泥沙的运移趋势一直延续至今。随着海平面上升趋于减缓，长江三角洲增长，江苏海岸线向外推进，苏北潮成砂区逐渐出露成陆。1128年黄河由苏北入海，大量的黄河沉积物的加入，加快了本区海岸线的推进速度。潮成辐射砂脊体系与辐聚辐散的潮流场相伴而生，全新世最大海侵以来，辐聚辐散的潮流场的位置曾经历三次变化，第一次以长江古河口湾为顶点，第二次位于现今陆上潮成砂区，第三次位于以弓京港为顶点的现代海域，代表了潮成辐射砂脊体系发育的三个阶段。只是长江古河口湾的潮成辐射砂脊体系由于河流的巨大改造作用，可能未很好保存，至今未发现典型的辐射砂脊体系。 相似文献
14.
海南岛海砂资源丰富,质量较好,储量位居全国前列,其中钛铁矿、锆英石和独居石是海南岛的优势滨海砂矿资源。根据其用途主要分为3类: 锆钛砂矿、石英砂矿和建筑用砂矿。通过资料收集和整理,分别研究了海南岛不同类型海砂资源的分布范围、勘查程度、资源储量、形成环境和资源潜力等。研究结果表明: 锆钛砂矿开发程度最高,主要分布于琼东沿海及水下阶地一带的全新统,规模较大,品位较高,开发条件较好; 琼西则以建筑用砂矿和石英砂矿为主,海砂质量好,杂质含量较低; 位于浅海区的潮流沙脊和河口三角洲,工作程度不高,但其海砂分布广、厚度大、砂质好,是今后海砂勘查的重点区域,具有良好的资源开发前景。总结海南岛海砂资源的主要成矿特点为: ①分布广泛,规模巨大,开发条件好; ②主要产于全新世地层; ③沉积厚度较大,纵向连续性好; ④海砂质量较好,并富含重矿物。 相似文献
15.
16.
JOHN S. COMPTON 《Sedimentology》2007,54(1):55-70
Coastal sediment-filled depressions (pans) are one of the few areas that contain Quaternary records of sea-level and palaeoenvironmental change along the western margin of southern Africa. Anichab is a 128 km2 salt-encrusted pan on the hyper-arid southern coast of Namibia with an emergent, well-preserved and in-place mid-Holocene mollusc assemblage. The molluscs are typical of subtidal sands on the sheltered side of offshore islands but include several warm-water species no longer found living along this coast. The Holocene evolution of the pan was largely influenced by changes in sea level and supply of sand along the coast. Calibrated radiocarbon ages of mollusc shells indicate a maximum Holocene sea level of ca 2 m above mean sea level (msl) from 7·0 to 6·3 ka and a return to near present-day sea level by 5·3 ka. The pan surface is 2 m below msl and has been emergent since 4·9 ka from the build up of sandy beaches and coastal dunes. A thin (1–4 cm) halite crust occurs over much of the pan surface but a layer of halite-cemented sand up to 40 cm thick is restricted to the central pan. Gypsum occurs near the subsurface brine interface and is limited by calcium to the edges of the pan. Nodules of calcite-cemented sand are forming in brackish, relatively high alkalinity subsurface waters in the south-east corner of the pan and nodules of aragonite-cemented sand are forming in brines 1 m below the central pan surface. Although modern dolomite has been reported from coastal lagoons of Brazil and Australia, carbonate cements are a minor feature of Anichab Pan and dolomite was restricted to a single reworked nodule most likely of Late Pleistocene age. Therefore, Anichab Pan does not appear to be a modern analogue to extensive, mixed-water dolomite cements found in Upper Pleistocene sediment-filled depressions on the Namibian shelf. 相似文献
17.
MIS 3晚期以来江苏中部海岸的层序地层 总被引：6，自引：0，他引：6
通过对苏北岸外西洋潮流通道内钻孔和地震剖面的地层沉积学、年代地层学、地震地层学和层序地层学等多学科再研究,以及区域钻孔再对比,本文确定该海域约从35kaBP(14C惯用年龄)开始经历了滨岸砂坝、淡水湖沼、河流泛滥平原、滨岸沼泽、潮流沙脊和潮流通道一系列的环境演变,主要受控于MIS3晚期以来的海平面旋回以及古河流入海沉积物供给,而构造沉降是相对次要的,由此形成了五级层序地层中的末次冰期晚间冰阶准层序和冰后期准层序,以及前者的高水位体系域和强制海退楔体系域、后者的海侵体系域和高水位体系域。海域中潮流沙脊可能开始发育于冰后期海侵淹没本区(约9calkaBP)之后,但一直只是水下暗沙且处在不断调整之中,直到1128～1855AD间黄河夺淮从苏北入黄海,大量泥沙充填潮道,部分水下暗沙出露海面成为明沙。西洋潮流通道并非是晚全新世期间通过沙脊的蚀低而形成,而在全新世高海面前后就已具雏形并持续至1128AD,1128～1855AD和1855AD至今分别经历了充填淤浅与冲刷成型的过程,且今后具有进一步展宽刷深的趋势。 相似文献
18.
全新世以来山东半岛东北部沿岸的相对海面（基准面）变化控制了入海河流河谷内全新统的发育,并通过影响进入海岸带碎屑物质的类型与数量,深刻影响了海岸带全新统的发育。全新世早期（１０～６ｋａ Ｂ． Ｐ．）快速的相对海面上升导致河谷溯源堆积,河流输沙中的推移质均堆积于河谷中,仅有悬移质进入海岸带堆积,因而海岸全新统下部均为细粒的海湾、湖、沼泽相沉积。全新世中期（６～４ｋａ Ｂ．Ｐ．）时海面虽已相对稳定,但早期基准面上升导致的河谷堆积作用仍在进行,因而中全新统的粗碎屑海岸沉积均为源于基岩海岸侵蚀的含贝壳砂砾石。从全新世后期（４ｋａ Ｂ．Ｐ．以来）开始有较丰富的河流推移质输沙进入海岸带,但由于不同规模河流对相对海面变化的地貌响应有显著差别,不同河流对海岸全新统发育的影响各不相同。上述结论为精确地解释低序列、小尺度地层层序提供了理论依据 相似文献
19.
In the Bengal Delta Plain (BDP) the primary arsenic sourcing appears to be different from the global scenario. Here, the Terminal Pleistocene–Holocene depositional platform, the interactive early Holocene depositional morphology with fluvio-estuarine and marine incursions played a crucial role for arsenic sourcing and enrichment. The lenticular silt-fine sand layer between anoxic clay beds favoured entrapment of dissolved organic carbon with decayed phyto-planktons debris. The Terminal Pleistocene–Holocene transgression and regression processes may have acted as major events in the BDP. Interestingly, at the end of the last glacial maxima, the Pleistocene delta had undergone block movements, wherein some parts of the platform were raised above the level of Holocene deposition. Those blocks were found to be free from arsenic in the groundwater. The sea, during re-emerging inundation (10–7 ka BP), has witnessed a monsoon-induced environment in the BDP with the resultant oscillation of sea level leading to higher upsurge towards the north. This might have resulted in the marine incursion and inundation in pre-existing land depressions. Meanwhile arsenic entrapments through marine incursion as well as enrichment in the presence of organic carbon/DOC and/or Fe/Mn/Al catalytic agents could have developed into localised redox traps. It may be of relevance that due to the repetitive transgressive–regressive phases in Holocene, resulting in periodic exposure and weathering of iron-bearing minerals and consequent iron enrichment in the aquifer system. The iron, thus present, had free charge to host arsenic as a sink. It appears that arsenic, wherever found, would likely be of atypical localised exhaustible phenomenon, both in horizontal and vertical context. It also rationalises the cause of the absence of arsenic in the other nearby Pleistocene platform, which has not come across Holocene interaction and marine incursion, as to the likely limiting condition for the search for arsenic in the BDP or beyond. 相似文献
20.
Quaternary deposits are described from well‐exposed sections in cliffs at Plage de Mezpeurleuch, Finistère, Brittany (France). The general lithostratigraphic sequence comprises Holocene perched dune sand, calcrete and palaeosol overlying Weichselian head and coarse clastic palaeobeach units attributed to the last interglacial (Eemian–isotope substage 5e). A lower and an upper palaeobeach, separated by a thin head deposit, are reported resting on an irregular palaeorock platform eroded in Hercynian granite. From a comparison with modern coastal environments a palaeoenvironmental interpretation of the palaeobeach deposits is made. Erosionally bounded facies of the lower palaeobeach, are considered to be a transgressive sequence preserved by drowning associated with a rapid rise in relative sea‐level. Its subsequent abandonment is attributed to a relative sea‐level fall, which allowed a terrestrial environment to develop briefly. Facies of the upper palaeobeach however indicate a prograding shoreline developed during a prolonged period of relatively stable sea‐level. These sea‐level observations are in good agreement with other evidence for a brief widespread intra‐Eemian cold event. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献