Macrobenthos relative to the oxygen minimum zone on the East Indian margin,Bay of Bengal          下载免费PDF全文

Akkur V. Raman  Rayaroth Damodaran  Lisa A. Levin  Thiruchitrambalam Ganesh  Yannamani K. V. Rao  Sateesh Nanduri  Rakhesh Madhusoodhanan 《Marine Ecology》2015,36(3):679-700

The Bay of Bengal remains one of the least studied of the world's oxygen minimum zones (OMZs). Here we offer a detailed investigation of the macrobenthos relative to oxygen minimum zone [OMZ – DO (dissolved oxygen), concentration <0.5 ml·1^?1] at 110 stations off the North East Indian margin (16⁰ and 20⁰ N) featuring coastal, shelf and slope settings (10–1004 m). Macrobenthos (>0.5 mm) composition, abundance and diversity were studied in relation to variations in depth, dissolved oxygen, sediment texture and organic carbon. Using multivariate procedures powered by SIMPROF analysis we identified distinct OMZ core sites (depth 150–280 m; DO 0.37 ml·1^?1) that exhibited dense populations of surface‐feeding polychaetes (mean 2188 ind. m^?2) represented by spionids and cossurids (96%). Molluscs and crustaceans were poorly represented except for ampeliscid amphipods. The lower OMZ sites (DO > 0.55 ml·l^?1) supported a different assemblage of polychaetes (cirratulids, amphinomids, eunicids, orbinids, paraonids), crustaceans and molluscs, albeit with low population densities (mean 343 ind. m^?2). Species richness [E(S₁₀₀)], diversity (Margalef d; H’) and evenness (J’) were lower and dominance was higher within the OMZ core region. Multiple regression analysis showed that a combination of sand, clay, organic carbon, and dissolved oxygen explained 62–78% of the observed variance in macrobenthos species richness and diversity: E(S₁₀₀) and H’. For polychaetes, clay and oxygen proved important. At low oxygen sites (DO <1 ml·l^?1), depth accounted for most variance. Residual analysis (after removing depth effects) revealed that dissolved oxygen and sediment organic matter influenced 50–62% of residual variation in E(S₁₀₀), H’ and d for total macrofauna. Of this, oxygen alone influenced up to ~50–62%. When only polychaetes were evaluated, oxygen and organic matter explained up to 58–63%. For low oxygen sites, organic matter alone had the explanatory power when dominance among polychaetes was considered. Overall, macrobenthic patterns in the Bay of Bengal were consistent with those reported for other upwelling margins. However, the compression of faunal gradients at shallower depths was most similar to the Chile/Peru margin, and different from the Arabian Sea, where the depth range of the OMZ is two times greater. The Bay of Bengal patterns may take on added significance as OMZs shoal globally.  相似文献   

Macrobenthic polychaete assemblages of the continental shelf and upper slope off the west coast of the South Island,New Zealand     

P. K. Probert  G. B. Read  S. L. Grove  A. A. Rowden 《新西兰海洋与淡水研究杂志》2013,47(5):971-984

Polychaete assemblages are described from replicate box‐core samples collected in summer 1983 at 18 stations on the continental shelf and upper slope (28–943 m) off the west coast of the South Island, New Zealand, south‐eastern Tasman Sea (c. 41–43°S, 169–172°E). Three main station groupings were identified by multivariate analysis: (1) inner shelf sandy stations characterised by Prionospio australiensis, Aricidea (Acesta) sp., Magelona cf. dakini, Paraprionospio aff. pinnata, Aglaophamus sp., Heteromastus filiformis, and Magelona sp.; (2) middle to outer shelf muddy stations characterised by Levinsenia cf. gracilis, Prionospio australiensis, Paraprionospio coora, Aglaophamus verrilli, and Auchenoplax mesos; and (3) upper slope sandy mud or mud stations characterised by Prionospio ehlersi. A combination of water depth and sediment clay content provided the best correlation with the biotic pattern. Spionidae was the most abundant family (49% of polychaete individuals), which may reflect the scope for opportunistic species in a shelf environment characterised by a high input of terrigenous sediment and episodic upwelling.  相似文献   

Effects of beach nourishment on sediments and benthic assemblages     

Colosio F  Abbiati M  Airoldi L 《Marine pollution bulletin》2007,54(8):1197-1206

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Sediment records as archives of the Late Pleistocene-Holocene hydrological change in the alluvial Narmada River basin, western India     

Alpa Sridhar  L.S. Chamyal 《Proceedings of the Geologists' Association. Geologists' Association》2010,121(2):195-202

The rivers of western India are monsoon dominated and have been so throughout the late Quaternary. Sediment accumulation in these river basins has been controlled by climatic and tectonic changes over a time span from the Late Pleistocene to the recent. The lithofacies assemblages associated with the various sediment archives in the Narmada basin range from the boulders of the alluvial fans to overbank fines on the alluvial plains. Estimates, based on clast size, of stream power and competence, bed shear stress and discharge reveal that hydrological conditions during the Late Pleistocene (∼90 ka) were comparable to the present day. The size of the transported clasts and the thickness of the accumulated sediment indicate the influence of basin subsidence rather than an increase in discharge. Discharge estimates based on sedimentary structures preserved in the alluvial-plain facies suggest that the channel had a persistent flow, with a low width-depth ratio and large meander wavelength. The hydrological changes during the Holocene are more pronounced where the early Holocene is marked by a high-intensity hydrological regime that induced erosion and incision of the earlier sediments. The mid-Holocene stream channel was less sinuous and had a higher width-depth ratio and a higher meander amplitude in comparison with the present-day channel. Palaeo-fluvial reconstructions based on the sediment archives in the alluvial reach of the river basin are important tools in understanding the long-term hydrological changes and the intricate fluvial architecture preserved in the Narmada River basin ensures scope for detailed studies to identify phases of weak and enhanced hydrological regimes.  相似文献   

川北若尔盖高原表土孢粉的特征及其与现代植被的关系   总被引：1，自引：0，他引：1  

蔡遥  王燕  蒋复初  李朝柱 《中国区域地质》2010,(5):707-712

通过对若尔盖高原不同植被带34个表土样的孢粉分析,研究了各植被带的表土孢粉组合与现代植被的关系。结果显示：表土孢粉组合基本上能够反映出现代植被的整体特征,与现代植被带在空间分布、建群种和优势种属方面基本相同,但不完全等于植被组成,影响其差异的原因可能是人类活动、孢粉保存、孢粉产量、外来孢粉和孢粉鉴定。表土花粉的代表性因种属的不同而各有差异。乔木花粉中,松属具有超代表性,云杉属代表性较好,而桦木属不具有超代表性;草本花粉中,菊科具较好的代表性,蒿属和藜科等具代表性,而禾本科和莎草科具低代表性;蕨类孢子具等代表性。  相似文献   

黔北务川—正安—道真地区下二叠统大竹园组和梁山组孢粉学研究          下载免费PDF全文

史骁  喻建新  陈斌  黄程  顾松竹  李慧  迟鸿飞 《古地理学报》2014,16(2):217-226

文中材料采自黔北务川—正安—道真地区下二叠统大竹园组和梁山组。大竹园组孢粉化石类型单调,保存较差;而梁山组孢粉化石丰富,保存良好。孢粉组合特征为:(1)大竹园组包含丰富的Calamospora和Florinites及少量Torispora verrucosa,Gulisporites,Alisporites,Hamiapollenites和Striatopodocarpites,这一孢粉组合主要出现在上石炭统至下二叠统。按照大竹园组层位和孢粉化石特征,其地质时代应为早二叠世Asselian期—Artinskian期(相当于紫松期—隆林期)。(2)梁山组中可建立孢粉组合Laevigatosporites vulgaris-Gulisporites-Florinites ovalis,共计发现孢粉化石34属49种,其中蕨类植物孢子含量为51.6％～56.1％,裸子植物花粉含量为43.9％～48.4％。与大竹园组沉积时期相比,这一时期植被极为繁盛。根据孢粉组合特征,梁山组地质时代可能为早二叠世隆林期,即Kungurian期。  相似文献   

晋冀低山丘陵区人工扰动植被花粉组合特征          下载免费PDF全文

李洁  许清海  曹现勇  田芳  丁伟  梁剑 《古地理学报》2014,16(2):227-238

54个晋冀低山丘陵区人工和人工扰动植被表土花粉样品分析表明:花粉组合以草本植物花粉(74.5％)为主,乔木花粉含量低于20％。人类活动较强的农田以谷物禾本科、蒿属和藜科花粉为主,人类活动较弱的荒地以蒿属、藜科和杂草禾本科花粉为主。人类活动强度不同,指示种不同,孢粉浓度亦不同;农田指示种为谷物禾本科、葡萄科和胡桃科,孢粉浓度约4380粒/g;而蒿属、蓼科和蔷薇科则为荒地指示种,孢粉浓度约10983粒/g。农作物种植方式不同,谷物禾本科花粉含量不同,单一禾本科作物种植区谷物禾本科花粉含量(40.2％)高于多种作物混作区(18.8％)和荒地(3.8％)的含量。谷物禾本科含量的变化可以为利用化石花粉提取和检测人类活动信息提供依据,也可为利用地层中谷物禾本科花粉判断古代农业活动提供依据。  相似文献   

Temporal and cross-shelf distribution of ichthyoplankton in the central Cantabrian Sea   总被引：1，自引：0，他引：1  

J.M. Rodriguez   《Estuarine, Coastal and Shelf Science》2008,79(3):496-506

Environmental variables have been measured and sampling for ichthyoplankton has been conducted monthly, since April 2001, at three stations, located at the inner (1), middle (2) and outer (3) shelf of the central Cantabrian Sea. This paper presents the results of the study of the ichthyoplankton collected from July 2001 to June 2004. Fish larvae from 99 species, belonging to 37 families, were identified. Families with higher number of species were Gadidae, Sparidae and Labridae. The larval fish assemblage was dominated by pelagic fish species, with Sardina pilchardus, as the most abundant. There was a pronounced spring peak in larval abundance, dominated by S. pilchardus. A smaller peak, dominated by S. pilchardus and Micromesistius poutassou, was recorded in late winter at Stns 2 and 3. This pattern was evident for the three-year study. Results also indicate that this study was limited to the coastal larval fish assemblage inhabiting the central Cantabrian Sea shelf. This assemblage was temporally structured into other three assemblages: winter, late winter–spring and summer–autumn. Temperature was apparently a key factor in larval fish assemblage succession. In a scenario of global warming, this study constitutes a basis to evaluating the ongoing changes in the pelagic coastal ecosystem of the central Cantabrian Sea.  相似文献   

湘南铜山岭矽卡岩铜铅锌矿床矿物组合分带特征及温压条件研究     

黄旭栋  陆建军  高剑峰  章荣清  SIZARET Stanislas  马东升  王汝成 《矿床地质》2023,42(3):506-530

湘南铜山岭矽卡岩铜铅锌矿床产于铜山岭岩体北东缘隐伏接触带及其外围地层中,在成因上与铜山岭花岗闪长斑岩密切相关。铜山岭铜铅锌矿床具有独特的成矿分带,从岩体向外依次发育近端内矽卡岩、近端外矽卡岩、硫化物-石英脉和远端矽卡岩矿体。根据穿切关系、交代结构和矿物组合等地质特征可以把铜山岭铜铅锌矿床划分为4个矿化蚀变阶段,从早到晚依次为进变质矽卡岩、退变质矽卡岩、石英-硫化物和碳酸盐阶段,其中石英-硫化物阶段为主成矿阶段。闪锌矿成分压力计研究表明,近端内矽卡岩型团块状硫化物矿石中闪锌矿的形成压力为(3.1±1.0)×108Pa,对应的成矿深度为6～12 km,相当于中—上地壳水平,说明铜山岭铜铅锌矿床形成于较大深度。近端内矽卡岩、近端外矽卡岩和远端矽卡岩中都存在两阶段绿泥石。绿泥石成分温度计研究表明,3类矽卡岩中退变质矽卡岩阶段绿泥石的形成温度分别为345～388℃、296～376℃和296～338℃,代表各类矽卡岩形成温度的下限;石英-硫化物阶段绿泥石的形成温度分别为270～318℃、209～238℃和200～223℃,代表各类矽卡岩矿体的成矿温度。3类矽卡岩的绿泥石温度表现出逐步降低的趋势,指...  相似文献   

羌塘南缘多龙矿集区荣那斑岩-高硫型浅成低温热液Cu-(Au)套合成矿:综合地质、热液蚀变及金属矿物组合证据   总被引：16，自引：12，他引：4  

李光明  张夏楠  秦克章  孙兴国  赵俊兴  印贤波  李金祥  袁华山 《岩石学报》2015,31(8):2307-2324

位于羌塘南缘多龙矿集区内的荣那斑岩-高硫型浅成低温热液Cu-(Au)矿床系近年来中铝西藏与西藏地质五队合作勘查取得重大找矿突破的铜矿床,控制资源量已达超大型规模,但对该矿床的成因类型仍存在争议。本文根据详细的钻孔岩芯、结合光学显微镜、扫描电镜观察、硫化物的电子探针分析,认为该矿床成矿与早白垩世花岗闪长斑岩有关。矿体主要产于下中侏罗统色哇组长石石英砂岩和成矿斑岩体中,矿体呈东西走向、南倾的隐伏状,延深巨大,金属矿化以铜为主,伴有金、银矿化,偶见钼矿化。热液蚀变具有两阶段蚀变:与斑岩型矿化有关的黑云母化、角岩化、硅化-绢云母化及硅化-伊利石-绿泥石化以上部叠加的高级泥化,蚀变分带明显。相应的该矿床具有斑岩型细脉浸染状矿化和以硫砷铜矿为特征的高硫型矿化,含铜矿物主要分为4个带,大致与蚀变分带相对应,下部主要为斑铜矿-黄铜矿;过渡带以斑铜矿-铜蓝组合为特征;中上部为蓝辉铜矿-砷黝铜矿-硫砷铜矿组合;顶部主要由为辉铜矿-蓝辉铜矿组成。总体上,矿床中上部为Cu-S体系、向下转变Cu-Fe-S体系。与其它类似矿床相比,该矿床硫化物中以富Zn、贫金为特征。综上认为该矿床为斑岩-高硫型浅成低温热液Cu-(Au)套合成矿的典型实例,其勘查突破为羌塘南缘火山岩区及覆盖区的找矿打开了一扇窗口。  相似文献