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1.
《华北地质》2017,(4)
为天津市宁河区在俵口-罾口河间拟建的"七里海牡蛎礁博物馆"进行了详细的全取心钻探调查和高程测量等前期勘查工作。结果表明:1)在面积约80 000 m~2、地表起伏仅0.7 m的调查区内,全部36个钻孔均钻遇并穿透牡蛎礁体。礁体顶板和底板的平均埋深分别是3.1 m和8.1 m(相当于现代黄海85高程-2.737 m和-7.684 m),礁体平均厚度约5 m。调查区东部,尤其是东南部礁体顶板埋深浅、底板埋深大,礁体较厚。已有的年代学证据显示,俵口牡蛎礁体发育于全新世早期,约4 000 cal BP时结束建礁;罾口河礁体发育于7 120 cal BP,约4 210 cal BP时结束建礁。两处礁体的终结均因为被潮间带泥质沉积物掩埋。根据俵口-罾口河礁体的时空展布,将此处的大范围礁体归属于渤海湾西北岸牡蛎礁平原第VI礁群。2)全新世以来,该地区相继经历了海侵和海退过程,可辨识出因海水进退与深度变化造成的潮上带盐沼→潮间带→潮下带浅海至潮间带中下部→潮间带中上部→潮上带沼泽-盐沼环境的完整的沉积相演化过程。在这一过程的中期,发育了牡蛎礁体。 相似文献
2.
渤海湾西北岸划分出了第Ⅰ道—第Ⅵ道牡蛎礁的平面分布(图1);对牡蛎礁壳体的几何形态特征进行了描述(图2),并将牡蛎礁壳体进行了剖面切割(图3);对牡蛎礁壳体进行了X光衍射与激光拉曼(活—古)矿物晶型的对比分析(表1,图4);对俵口村BKP20-2剖面(-2.84m)牡蛎礁一个体右壳:在双目镜下对其内部结构与矿物组分进行了分析(图5);通过机械挖掘剖面及钻探获得:牡蛎礁体的空间堆积厚度与赋存的海拔高度及其各剖面垂直方向上的14C年代数据;并获得牡蛎礁体堆积的内部结构特征(图6);以及牡蛎礁体水平夹层与CaCO3含量变化(图7),其中水平夹层CaCO3含量往往偏高,初步分析可能与气候偏冷有关。对牡蛎礁壳体内充填物及壳外沉积物进行了粒度分析(表3),粒度组分及概率累积曲线等(图9)为分析牡蛎礁的生态环境提供了佐证:即牡蛎礁基本以潮下带生活环境为主。以俵口BKP20剖面为例分析了牡蛎礁体堆积物从埋深-2.14～-6.90m的生物组合特征(表4)。以上资料为获得牡蛎礁堆积体的生长-发育-消亡等演化模式提供了依据(图10)。 相似文献
3.
在福建深沪湾发现7000多年前的古油杉林遗迹的同一海滩的稍南部, 保存着与其生境截然不同的牡蛎礁。这种陆上古油杉林与海上古牡蛎礁出现于同一海滩部位的现象, 乃自然界的一大奇观, 对于研究该区的海岸演化、海面变化和地壳运动, 具有重大的科学意义。我们于1998年10月上旬对上述遗迹进行了12000的地形测量、采样和研究, 从而对该牡蛎礁取得了如下的新认识： (1) 不但海底林有3片, 牡蛎礁也有两片, 二者呈北东向相间排列。新发现的北片牡蛎礁面积小, 仅约100m2左右, 礁体已被侵蚀破坏, 支离破碎地出露在中－低潮带附近, 南片为牡蛎礁主要分布区, 礁体保存较好, 由三大块礁体组成, 也沿海岩岸露在中－代潮带附近． 相似文献
4.
天津空港牡蛎礁:中全新世环境恶化与新构造控礁作用 总被引：1，自引：1，他引：0
新发现的天津空港埋藏牡蛎礁体和下伏、上覆泥层的沉积学、AMS14C年代学研究显示,厚2.3m的礁体分为3部分,起讫年龄是6170～3980cal BP。5900～4100cal BP的中部,是受全新世冷事件4环境恶化控制的缓慢发育期。礁体的结束,则与冷事件3在时间上大致吻合。根据新的年龄数据,将该礁体的归属重新厘定为Ⅲ-2礁群。探讨礁体主要发育区与新构造活动的关系,表明全新世牡蛎礁平原主要位于海河-宝坻-工部-蓟运河断裂圈闭的北西-南东向区域内。这一认识,进一步从实证角度证实了牡蛎礁形成于渤海湾"湾中之湾"的推测。 相似文献
5.
福建中南部全新世的森林-牡蛎礁遗迹 总被引：7，自引：0，他引：7
福建晋江县东南的深沪湾,南北长约7km,位于一地堑型断陷带上,西为龙湖断裂,东为金井-深沪断裂。湾的北部海岸是海蚀红土陡崖,崖高约5m;南部海岸为砂质海岸,潮间带滩面平缓,堆积现代的中-细砂和卵石,距岸300m处有牡蛎海滩岩和古森林遗址。前者分布在土地察村西长500m、宽100m的范围内(北段),呈北西-南东向展布(大致与海岸平行),最大出露厚度可达40cm。它是近江牡蛎(Ostrearivularis)和僧帽牡蛎(O.cucullata)组成的礁体,壳体较完整,双瓣常是闭合状,表明组成礁体的牡蛎壳为原生态。据国家海洋局第三海洋研究所的14C同位素测定结果,牡蛎壳形成年龄为9355±199aB 相似文献
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8.
渤海湾西北岸大吴庄牡蛎礁测年与古环境变化 总被引：11，自引：2，他引：9
对位于渤海湾牡蛎礁平原东部的大吴庄牡蛎礁一个完整剖面的系统^14C年代测定与校正表明,该礁体的持续时间约为1600年(7200～5600calBP)。以壳体生长纹层氧、碳同位素获得的礁体平均建造速率1cm／yr来计算礁体的持续时间,结果仅为^14C计年历时的三分之一。^14C测年与壳体同位素计年结果的对比表明,礁体的每一水平层平均占据了一定的时间(约200年),这一时间段是不适宜礁体正常建造的“缓变型地质环境恶化期”。礁体正常建礁层及水平夹层的时空分布与地区性气候变化曲线对比结果表明,水平夹层与正常建礁层的转换与地区性气温波动相对应。水平夹层代表的“缓变型地质环境恶化期”,对应着地区性气温偏冷时期。 相似文献
9.
琼东南盆地深水区梅山组一段层序内发育大量丘状反射体,目前共有油气钻井6口,二维地震测线约12 000km,测网密度大多为6km×8km。三维地震区两块面积共约1 700km~2。以国内外研究现状与进展及区域地质资料为基础,立足研究区钻井资料、二维地震与三维地震剖面资料,通过地震测线剖面追踪,刻画丘状反射体地震反射特征和几何形态,进而开展波阻抗反演、类比与对比分析,结合成礁古构造背景研究等,分类对丘状反射体给出合理地质解释。研究结果表明:琼东南盆地深水区梅山组一段发育4类丘状反射体,地质解释为生物礁、等深积岩丘和底辟构造3类地质体。生物礁为斑礁群和台地边缘礁,发育在古地貌高地的清水环境,跟周围地层相比具有同期地层厚度增大特点。斑礁群为中强震中频丘状地震相,分布在南部斜坡缓坡单斜型台地的高部位;台地边缘礁为强震中频扁平丘状地震相,主要发育在南部隆起碳酸岩台地边缘。单个生物礁外形呈丘状、凸透镜状,具有礁脊和礁沟,内部可见前积,翼间双向上超,顶、底强反射,轮廓清晰。垂直于古水深方向礁前比礁后陡,呈微不对称,平行于古水深方向礁体呈对称—微不对称。波阻抗反演显示礁顶底统一连续,斑礁群波阻抗值达到7kg/m3*m/s左右,台地边缘礁波阻抗值达到7.5kg/m3*m/s左右。等深积岩丘为中强震中连低频丘状地震相,分布在南部斜坡带单斜型台地台缘斜坡。等深积岩断面上呈丘状,丘与丘之间界线模糊不清,在平面上呈长条状,波阻抗值为5.8kg/m3*m/s左右,与生物礁显著区别。岩浆底辟显著特点是具有"根"。 相似文献
10.
王亚明 《地质灾害与环境保护》2018,(1)
为有针对性对天津古海岸与湿地国家级自然保护区的古海岸、牡蛎礁进行保护,对天津古海岸带的牡蛎礁进行钻探勘察和地质调查,获取了古海岸牡蛎礁的平面分布特征,主要分布9道牡蛎礁,揭示了牡蛎礁以典型的二元结构为主,且牡蛎礁体层内含有部分夹层的结构特征,同时解释了牡蛎礁主要形成于水流相对静止状态的宽屏浅滩或堆积平原海岸,且有零散牡蛎逐渐聚集形成小群体牡蛎,形成牡蛎层,然后继续聚集附着、密集簇生,最后形成牡蛎礁。 相似文献
11.
渤海湾西北岸大吴庄牡蛎礁是近年来研究程度最高的礁体,天津空港物流中心牡蛎礁则是近年来新发现的礁体。该两处礁体上部的牡蛎个体内部充填的泥、个体之间的泥以及礁体上覆沉积泥层中的硅藻研究表明,礁顶上下（即礁体的上部-顶部和上覆沉积泥层的下部）均富含潮间带环境指示种的Auliscus caelatus,表明礁体发育后期和上覆沉积泥层的初期,均为潮间带环境。尽管如此,从礁顶向上覆沉积泥层转换方式在两处礁体却不相同:（1）大吴庄:Auliscus caelatus种向上逐渐减少,暗示着大吴庄剖面由礁体上部的潮间带中上部、直至上覆沉积泥层下部的潮间带上部、进一步向上覆沉积泥层上部的潮上带转化的趋势。（2）空港:牡蛎礁上覆沉积泥层出现了比例达6%~23%的河口咸水-半咸水种Achnanches brevipes,而下伏礁体内则未见该种,暗示此处泥层受河口作用显著影响。此种不同揭示了礁体停止发育的原因有所不同:在5 520cal BP时,大吴庄礁顶进入潮间带中上部,礁体经常脱离海水而发育停止;在约4 000 cal BP时,空港礁体所在位置因河流作用突然增强,在时间上看很可能是黄河改道在天津入海,古黄河携带大量泥砂入海,掩盖了潮间带的牡蛎礁而导致牡蛎礁发育停止。 相似文献
12.
珊瑚礁是发育于热带海洋环境中由生物作用和地质作用共同形成的地质体,具有独特的新构造运动意义。南海西北部珊瑚礁记录所反映的新构造运动主要有火山活动、地壳升降运动和地震活动等。珊瑚礁区第四纪火山活跃,到现代已停止活动,部分火山构成珊瑚礁的基座,个别出露海面为火山岛;地壳升降运动差异较大,雷州半岛西南部珊瑚礁呈上升趋势,上升率为0.02~0.05mm/a;西沙群岛等岛礁地壳运动则呈下降趋势,下降率为-0.07~-0.10mm/a,岛礁中的造礁石珊瑚生长率、礁顶和灰沙岛的堆积率均相当于或大于地壳下降率与现代海平面上升率的总和;南海西北部珊瑚礁区内地震活动较强,尤其是1994年12月31日和1995年1月10日在雷州半岛西南部海域发生了6.1级和6.2 级地震,这两次地震对该区珊瑚礁的发育有较大的影响。 相似文献
13.
The importance of intertidal estuarine habitats, like salt marsh and oyster reef, has been well established, as has their ubiquitous loss along our coasts with resultant forfeiture of the ecosystem services they provide. Furthering our understanding of how these habitats are evolving in the face of anthropogenic and climate driven changes will help improve management strategies. Previous work has shown that the growth and productivity of both oyster reefs and salt marshes are strongly linked to elevation in the intertidal zone (duration of aerial exposure). We build on that research by examining the growth of marsh-fringing oyster reefs at yearly to decadal time scales and examine movement of the boundary between oyster reef and salt marsh at decadal to centennial time scales. We show that the growth of marsh-fringing reefs is strongly associated to the duration of aerial exposure, with little growth occurring below mean low water and above mean sea level. Marsh-shoreline movement, in the presence or absence of fringing oyster reefs, was reconstructed using transects of sediment cores. Carbonaceous marsh sediments sampled below the modern fringing oyster reefs indicate that marsh shorelines within Back Sound, North Carolina are predominantly in a state of transgression (landward retreat), and modern oyster-reef locations were previously occupied by salt marsh within the past two centuries. Cores fronting transgressive marsh shorelines absent fringing reefs sampled thinner and less extensive carbonaceous marsh sediment than at sites with fringing reefs. This indicates that fringing reefs are preserving carbonaceous marsh sediment from total erosion as they transgress and colonize the exposed marsh shoreline making marsh sediments more resistant to erosion. The amount of marsh sediment preservation underneath the reef scales with the reef’s relief, as reefs with the greatest relief were level with the marsh platform, preserving a maximum amount of carbonaceous sediments during transgression by buffering the marsh from erosional processes. Thus, fringing oyster reefs not only have the capacity to shelter shorelines but, if located at the ideal tidal elevation, they also keep up with accelerating sea-level rise and cap carbonaceous sediments, protecting them from erosion, as reefs develop along the marsh. 相似文献
14.
Allison M. Colden Kelsey A. Fall Grace M. Cartwright Carl T. Friedrichs 《Estuaries and Coasts》2016,39(5):1435-1448
The eastern oyster, Crassostrea virginica, is a prominent ecosystem engineer, whose reefs exhibit strikingly consistent morphologies at multiple spatial scales throughout its North American range. These distinct morphologies are thought to form by interactions of nascent reef structures with hydrodynamics. We carried out two field studies to determine if historical reef configurations applied in a restoration context would improve reef persistence and restoration outcomes. We collected seabed and water column observations across constructed reefs of three orientations representative of those found historically throughout the oyster’s range: parallel or perpendicular to tidal currents or circular. Areas adjacent to reefs were sites of fine sediment trapping, with lower flow velocities, evidence of particle settling, and more fine sediments on the seabed relative to off-reef reference sites. The water column above the reef crest exhibited higher acoustic backscatter, higher flow velocities, and larger particles in suspension, consistent with local erosion of flocculated fine sediment from the reef crest. Perpendicular reefs produced conditions that were more conducive to reef persistence and improved oyster performance, including high flow velocities and enhanced resuspension of sediments from the reef, compared to parallel or circular reefs. Particle trapping in areas between reefs has the potential to inhibit reef growth between existing reef structures, providing support for hypotheses of landscape-scale reef pattern formation. Oyster reef restoration efforts can benefit from this improved understanding of biophysical interactions arising from reef orientation that contribute to sediment dynamics on constructed oyster reefs. 相似文献
15.
海南三亚鹿回头半岛珊瑚礁和连岛坝的发育 总被引：8，自引：1，他引：7
海南岛南端三亚市鹿回头半岛由鹿回头岭陆连岛、椰庄连岛坝和南边岭－火岭三部分组成。该地珊瑚岸礁发育良好。为揭示珊瑚礁发育历史,作者在椰庄连岛坝上打了一口深达２６．５ｍ穿透第四纪松散沉积物的钻孔,并对钻孔岩芯进行了微体古生物和孢粉分析以及１４Ｃ和热释光年龄测定,从而区分出晚更新世和全新世两套海相地层,其间隔以晚更新世末期的陆相沉积。研究表明,本区的珊瑚礁主要建造于标高－１３—－９ｍ左右的松散沉积物基底上,开始出现于８５００—８０００ａＢ．Ｐ,繁盛于６３００—４８００ａＢ．Ｐ．的全新世最高海面时期,当时海面高于现今２—３ｍ或更多。近五千年来,随海面波动和下降,珊瑚礁发育渐趋衰退,连岛坝随之开始形成。 相似文献
16.
Oysters can create reefs that provide habitat for associated species resulting in elevated resident abundances, lower mortality
rates, and increased growth and survivorship compared to other estuarine habitats. However, there is a need to quantify trophic
relationships and transfer at created oyster reefs to provide a better understanding of their potential in creating suitable
nekton habitat. Stable isotope analyses (δ13C and δ15N) were conducted to examine the organic matter sources and potential energy flow pathways at a created intertidal oyster
(Crassostrea ariakensis; hereinafter, oyster) reef and adjacent salt marsh in the Yangtze River estuary, China. The δ13C values of most reef-associated species (22 of 37) were intermediate between those of suspended particle organic matter (POM)
and benthic microalgae (BMI), indicating that both POM and BMI are the major organic matter sources at the created oyster
reef. The sessile and motile macrofauna colonizing the reef make up the main prey of transient nekton (e.g., spotted sea bass,
Asian paddle crab, and green mud crab), thus suggesting that the associated community was most important in supporting higher
trophic levels as opposed to the direct dietary subsidy of oysters. The created oyster reef consistently supported higher
trophic levels than the adjacent salt marsh habitat due to the dominance of secondary consumers. These results indicate that
through the provision of habitat for associated species, created oyster reefs provide suitable habitat and support a higher
average trophic level than adjacent salt marsh in the Yangtze River estuary. 相似文献
17.
Joseph T. DeAlteris 《Estuaries and Coasts》1988,11(4):240-249
Wreck Shoal is a subtidal oyster reef located in the James River estuary, Virginia. This estuary has moved upstream and landward in response to rising sea level. The recent geomorphic history of Wreck Shoal is analyzed based on bathymetric records from the 1850’s to the 1980’s. The data indicate that the shallow oyster reef areas have lost elevation in the last 130 yr. This is attributed to intense harvesting activity during the last century. The late Holocene evolution of Wreck Shoal is developed based on the results of sub-bottom profiles and coring data. These suggest that the Wreck Shoal oyster reef has developed on the ridge and swale topography of a point-bar formed during the late Pleistocene epoch. Contemporary biodeposition processes on Wreck Shoal are evaluated. The results indicate that sediments of biogenic origin (fecal and shell material) potentially accumulate at rates in excess of 50 cm 100 years?1. A model for subtidal oyster reef development is proposed that accounts for sea level rise, biodeposition, and the harvesting activity of man. The model is verified with field observations of reef elevation and radiocarbon dates of oyster shell material. The implications of these results are that oyster reefs should be considered a renewable natural resource, and therefore managed accordingly in concert with the oysters. 相似文献
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渤海湾西北岸埋藏牡蛎礁体中的 壳体形态与沉积环境* 总被引：1，自引：0，他引：1
渤海湾西北岸沿岸平原分布的众多埋藏牡蛎礁体中的壳体形态和泥沙沉积物特征是不尽相同的。不同礁体中的壳体形态有明显的区别,有些礁体中的壳体细窄,有些礁体中的壳体较宽厚; 与此相对应,具有不同壳体形态的礁体中的沉积物颗粒和粘土含量也有明显的差别。文章分别对组成大吴庄和岭头两个礁体剖面的牡蛎壳体和泥质沉积物进行测量和分析,结果表明大吴庄礁体中壳体的重量随高度增长的速率大于岭头礁体中的壳体,而两个礁体中壳体的壳重随体积增长的速率大致相同; 组成礁体的壳体形态与礁体的沉积环境有关,沉积物较细、粘土含量高时发育细窄的壳体,沉积物较粗、粘土含量低时发育宽厚的壳体。渤海湾西北岸地区埋藏牡蛎礁体中的壳体本身记录了其生长时的环境信息,可以通过分析礁体中的壳体形态来恢复礁体建礁过程中的沉积环境。 相似文献