南沙海区中生界岩相分布及构造特征

为了了解南中国海南部南沙群岛陆架-陆坡区中生代地层发育情况,作者通过综合分析该海区钻井、拖网及1987年以来采集的20000多公里的多道反射地震勘探等资料,得到了对该区中生界基本特征的如下新认识:空间分布上,南沙的中生界具有从北部的郑和-礼乐隆起南缘向南增厚的趋势;沉积岩相方面,东部三叠纪时为深海相,侏罗纪为浅海与三角洲相,白垩纪为浅海-内浅海相,而往西南部中生代的海水深度有变深的趋势;中-新生代变形上,在南沙西部的曾母盆地,中生界褶皱为复式的、非协调性的,南沙中部多为舒缓褶皱,东部仅在近巴拉望海槽地带出现小幅度的褶皱。结合围区中生界及特提斯构造域的发育特征,作者提出南沙地块上的海相中生界在大地构造上归属于残留在中特提斯洋北部减薄陆缘地壳上的中特提斯期海相沉积地层,是该海域油气资源勘探不可忽视的对象。     

The continent-ocean transition at the southeastern margin of the South China Sea

The South China Sea formed by magma-poor, or intermediate volcanic rifting in the Paleogene. We investigate the structure of the continent-ocean transition (COT) at its southern margin, off NW Palawan between the continental blocks of Reed Bank and the islands of Palawan and Calamian. Several surveys, recorded by the BGR from 1979 to 2008, established a comprehensive database of regional seismic lines, accompanied with magnetic and gravity profiles.We interpret two major rifted basins, extending in the NE direction across the shelf and slope, separated by a structural high of non volcanic origin.The continent-ocean transition is interpreted at the seaward limit of the continental crust, when magnetic spreading anomalies terminate some 80-100 km farther north. The area in between displays extensive volcanism - as manifest by extrusions that occasionally reach and cut the seafloor, by dykes, and by presumed basaltic lava flows - occurring after break-up.The COT is highly variable along the NW Palawan slope: One type shows a distinct outer ridge at the COT with a steep modern seafloor relief. The other type is characterised by rotated fault blocks, bounded by listric normal faults ramping down to a common detachment surface. Half-grabens developed above a strongly eroded pre-rift basement. The seafloor relief is smooth across this other type of COT.We suggest the pre-rift lithospheric configuration had major influence on the formation of the COT, besides transfer zones. Volcanic domains, confined to the north of competent crustal blocks correlate with the style of the COT.Gravity modelling revealed an extremely thinned crust across the shelf. We propose a depth-dependent extension model with crust being decoupled from mantle lithosphere, explaining the discrepancy of subsidence observed across the South China Sea region.     

Gas hydrate saturation from acoustic impedance and resistivity logs in the Shenhu area, South China Sea

During the China’s first gas hydrate drilling expedition -1 (GMGS-1), gas hydrate was discovered in layers ranging from 10 to 25 m above the base of gas hydrate stability zone in the Shenhu area, South China Sea. Water chemistry, electrical resistivity logs, and acoustic impedance were used to estimate gas hydrate saturations. Gas hydrate saturations estimated from the chloride concentrations range from 0 to 43% of the pore space. The higher gas hydrate saturations were present in the depth from 152 to 177 m at site SH7 and from 190 to 225 m at site SH2, respectively. Gas hydrate saturations estimated from the resistivity using Archie equation have similar trends to those from chloride concentrations. To examine the variability of gas hydrate saturations away from the wells, acoustic impedances calculated from the 3 D seismic data using constrained sparse inversion method were used. Well logs acquired at site SH7 were incorporated into the inversion by establishing a relation between the water-filled porosity, calculated using gas hydrate saturations estimated from the resistivity logs, and the acoustic impedance, calculated from density and velocity logs. Gas hydrate saturations estimated from acoustic impedance of seismic data are ∼10-23% of the pore space and are comparable to those estimated from the well logs. The uncertainties in estimated gas hydrate saturations from seismic acoustic impedances were mainly from uncertainties associated with inverted acoustic impedance, the empirical relation between the water-filled porosities and acoustic impedances, and assumed background resistivity.     

The effect of the dominant polychaete Scolelepis squamata on nematode colonisation in sandy beach sediments: An experimental approach

The effect of an abundant sandy beach polychaete, Scolelepis squamata, on the colonisation of defaunated sediments by marine nematodes indicates that sandy beach fauna can be partially controlled by biological interactions within and across size groups. Experimental cores, equipped with windows allowing infaunal colonisation, were filled with defaunated sandy beach sediment containing two different treatments with and without S. squamata. These cores were inserted into microcosms filled with sediment with indigenous meiofauna collected from the field. The treatments were incubated in the laboratory at ambient temperature and salinity for 2, 7, 14 and 21 days, in order to follow the colonisation process of the defaunated sediments by the indigenous nematode fauna over time. Nematodes initially colonised both treatments, with abundances of up to 10% of the densities in the control; after 2 weeks, nematode densities in the cores without S. squamata surpassed the control densities. Nematode assemblages in both treatments were not species rich, and also differed in composition from the natural assemblages. The most successful colonising species, Enoplolaimus litoralis, was rare in the surrounding sediment, suggesting that colonisation was determined by species-specific characteristics such as body size, motility and feeding strategy. Initially the presence of macrofauna did not affect the nematode community composition, but after 2 weeks of the experiment, the presence of the polychaete seemed to facilitate the earlier establishment of non-opportunistic species.     

舟山海域陆源溶解有机质变化及其对近岸羽状流的响应

2007年夏季在东海舟山海域河口锋区开展了陆源溶解有机质的调查研究。测定了有色溶解有机质(CDOM)在激发波长370 nm/发射波长460 nm处的荧光强度和在λ=355 nm处的吸收系数,用于代表陆源CDOM浓度,并测定了荧光指数以指示CDOM来源。结果表明,CDOM的荧光值和紫外吸收系数之间呈显著正相关性,陆源CDOM浓度大体有向海方向降低的趋势,但是纵向上存在一些"突跃"现象。在舟山海域东北角不时观测到表层水体含有高浓度的CDOM,但变异性很大,推测可能该海区受到长江口羽状流的影响。在连续观测站发现陆源CDOM浓度在低平潮时往往比高平潮时要高。河海水在混合过程中CDOM浓度与盐度呈显著的线性负相关关系。在低盐度的悬沙锋区(S<24)CDOM浓度明显低于理论稀释值,而在较高盐度的羽状锋区,CDOM浓度接近于理论稀释值。在盐度为24~31范围内,大部分水样的荧光指数在1.50上下波动,表明其中CDOM来源以陆地来源为主;在较低盐度(S<24)的水样中荧光指数在1.70至1.90以上,表明CDOM以海洋来源为主,这与其陆源组分在高浊度的低盐度区存在显著的去除过程有关。研究表明,舟山海域水质存在着显著的变异性,与近岸羽状流密切相关,陆源溶解有机质的分布特征对此有较好的响应。     

中国第三次北极科学考察走航路线上空黑碳气溶胶的观测研究

2008年7月至9月,中国第3次北极科学考察期间,在走航路线上利用黑碳仪对黄海-日本海-鄂霍次克海-西北太平洋-白令海-楚科奇海-加拿大海盆等海区上的黑碳气溶胶浓度进行连续观测,最北观测位置达85°21.3′N.观测结果显示,北冰洋是全航线黑碳浓度最低的海区,平均浓度为(5.3±3.7)ng/m3;在70°N以北的海区...     

中国近海蒸发波导的数值模拟与预报研究

利用中尺度大气模式MM5对2007年中国近海大气蒸发波导进行了全年的高分辨的数值模拟。模拟结果统计表明,整个海域蒸发波导的平均出现概率约为90%。本文重点关注强度较大的蒸发波导,详细分析了其季节分布特征及其与海洋环流和海面气象条件的相关关系。研究发现,25°N以南的开阔海域的蒸发波导出现概率全年都较高,而以北的东海西北部、黄海与渤海,蒸发波导的出现概率呈现明显的季节特征;蒸发波导的空间分布受中国近海海洋环流的强烈影响,存在1个与黑潮区域相一致的带状波导高出现概率区域,台湾暖流、黄海暖流和对马暖流使得在某些季节相应海域蒸发波导出现概率高于其周围海域。此外,本文还基于WRF模式及其3DVAR系统构建了大气波导数值预报系统,尝试对中国东南海域的蒸发波导进行数值预报。     

1990s年代际转型前后南海季风系统的季节变化

利用多变量经验正交分解(MV-EOF)等方法,研究了在季节变化尺度上南海季风系统的时空分布特征。结果表明:南海夏季风的爆发时间在1993—1994年前后存在显著的年代际转型,由爆发偏晚转变成爆发偏早。第一模态表现为冬夏反位相的年周期变化,但爆发早年夏季风持续时间略长于爆发晚年,空间上都反映了南海中央海盆区的夏季强降水和850 hPa上南海北部的气旋性环流异常,但夏季风爆发早年中国华南沿海降水加强而南海南部降水偏少。相应的大范围环流场上主要反映了南海夏季风爆发后进入盛夏时节亚太地区大范围的环流特征,南海夏季风爆发偏早年索马里越赤道气流偏强,东亚季风槽位置偏北,爆发偏晚年则相反。第二模态反映了南海季风系统春秋反位相的季节变化,且秋季的振幅更强,空间降水场上对应着秋季华南沿海和南海北部与南海中南部北旱南涝的跷跷板式分布,850 hPa风场上则主要表现为异常的东北季风,该模态时空特征表明南海夏季风爆发偏早年的秋季,冬季风建立也偏早,越南及周边地区的降水偏多。相应的大范围环流场上则主要反映了冬季风的环流特征,在南海夏季风爆发偏早年的秋季,菲律宾以东的热带对流减弱,PJ波列增强,爆发晚年则相反。     

中国木叶鲽属鱼类一新纪录种

2008年8月,在浙江舟山附近海域(东海)采集到4尾木叶鲽属鱼类,经鉴定为中国鱼类新纪录种——长木叶鲽,其主要特征为:体棕褐色,有眼侧和无眼侧颞上枝前端有小分枝,鳞片小但不狭长,背鳍鳍条数72~74(73.3);臀鳍鳍条数56~59(57.5);有眼侧胸鳍鳍条数8~10(8.8),无眼侧胸鳍鳍条数为8;有眼侧与无眼侧腹鳍鳍条数均为6;尾鳍鳍条数19~20(19.5),脊椎骨数为36;鳃耙数为3+7。基于线粒体COI基因片段得到的长木叶鲽与角木叶鲽的K2P遗传距离为9.4%,2种间遗传分化达到了种间水平。     

用沿岸上升流指数分析中国东南沿岸风生上升流的特征

对1968年1月到2007年12月中国东南沿海(17°N～30°N,109°E～123°E)上升流指数月平均数据进行分析,结论如下:(1)风生沿岸上升流主要在4-8月间发生于海南岛东部、雷州半岛东部、汕头以北至浙江沿岸.(2)风生沿岸上升流的强度具有时空分布变化特征,其中海南岛东部沿岸上升流最强,浙江沿岸其次;整个中国...