嵊泗列岛潮间带群落生态学研究 Ⅲ.岩相潮间带底栖生物的种类分布

对嵊泗列岛岩相潮间带底栖生物种类分布进行的研究表明,种类的水平分布主要受盐度及海岸开敞度的影响,从近岸到外海,随着盐度及海岸开敞度的增加,潮间带底栖生物的种类数呈增加的趋势。不同海区的优势种不同,近岸较屏蔽区以软体动物及甲壳动物占优势,外海开敞区以甲壳动物及藻类占优势,近外海较开敞区为一过渡区;种类的垂直分布主要受潮区及海岸开敞度的影响,各海区不同潮区生物种类数均为中潮区多于低潮区多于高潮区,高潮区基本上为滨螺分布带,中潮区为日本笠藤壶－藻类带,低潮区为藻类带;外海区种类的季节变化明显,近岸区种类季节变化小。所有物种中,以底栖海藻的季节变化最为明显。     

利用远震接收函数方法研究南海西沙群岛下方地壳结构

利用西沙琛航岛流动地震台站和永兴岛固定地震台站的资料,提取了远震P波接收函数,结合正演和反演方法模拟了台站下方的地壳结构.模拟结果显示:西沙群岛地壳顶部存在2 km厚的新生代低速沉积层,横波速度只有2.0~2.2 km/s;上地壳为一速度梯度带,横波速度由2 km处的3.4 km/s逐渐增加到12 km深度时的3.8 km/s;下地壳存在明显低速层,厚度达到12 km,平均横波速度3.5 km/s;莫霍面埋深26~28 km,也表现为一速度梯度带,横波速度从3.8 km/s变化到4.6 km/s左右,并保持稳定;该地区的地壳泊松比值大于0.3,推测西沙群岛的壳内低速层和异常泊松比值与地幔热活动引起的韧性流变构造和岩石矿物的各向异性排列有关.     

Rock glaciers on the Faeroe Islands,the North Atlantic

Three sites with alleged relict rock glaciers are described from southern Faeroe Islands, in the North Atlantic Ocean. The rock glaciers represent both talus-derived and glacier-derived types and were most likely initiated during the late Weichselian. One of the rock glaciers apparently became unstable at some point during degradation of permafrost and was subsequently transformed by a landslide. The age of the rock glaciers are not known precisely, but a Younger Dryas age is suggested, partly by considering contemporary local equilibrium line altitudes. The climatic background for rock glacier initiation on the Faeroe Islands during the Younger Dryas is investigated, using various types of palaeoclimatic information. The potential of using relict rock glaciers in palaeoclimatic reconstructions is discussed, and their implications for estimates on air temperature, precipitation, permafrost, rock weathering and the contemporary extent of the Weichselian Faeroe Ice Cap is outlined. © 1998 John Wiley & Sons, Ltd.     

浙江舟山群岛首次发现二叠纪变质岩

浙江舟山群岛大衢岛及周边若干小岛出露少量变质岩系,包括斜长角闪岩、片麻岩、片岩、大理岩等,以往被归为陈蔡岩群。LAICP-MS锆石U-Pb测年结果表明,黑云斜长片麻岩变质新生锆石或岩浆锆石的变质边年龄在260~270Ma之间,大理岩的变质年龄为261.1±1.3Ma,侵入变质岩的未变形伟晶岩脉年龄为258.0±1.6Ma,表明该套变质岩系的变质时代约为260Ma,不能归入加里东期变质的陈蔡岩群。这是在华南东北缘地区首次发现二叠纪变质岩,为探讨华南东吴运动和全球海西运动,甚至泛大陆的重建提供了重要新信息。     

The 14 August 2003 Lefkada Island (Greece) earthquake: Focal mechanisms of the mainshock and of the aftershock sequence

The central area of the Ionian Sea is dominated by the Cephalonia Transform Fault Zone (CTFZ) with a pronounced dextral strike-slip component of motion. The CTFZ has two main segments: the Lefkada Segment (LS) in the north and the Cephalonia Segment (CS) in the south. On 14 August 2003 an M_w 6.2 earthquake ruptured the Lefkada Segment and produced extensive damage, especially to the western coast of the island. Teleseismic waveform modelling revealed the multiple source character of the mainshock, which occurred as three sub-events along a ∼N12^∘E line. The first sub-event occurred at a depth of about 15 km, followed 2.5 s later by the second and largest sub-event at a depth of 11 km and the third sub-event 14 s after the second at a depth of 15 km. The total moment from the body waves of this sequence is about 22.3×10¹⁷ Nt m (M_w 6.2) with a source duration of ∼15 s. The rupture started at the northern part of the Lefkada fault Segment and propagated southwards. The second and third sub-events are located at 7 and 40 km to the south-east in respect to the first sub-event. The focal mechanisms of the two strongest sources indicate strike-slip faulting along the NE–SW trending Lefkada segment (sub-event 2: Strike = 12^∘, Dip = 81^∘, Rake = 174^∘; sub-event 3: Strike = 20^∘, Dip = 63^∘, Rake = −179^∘). Moment tensor inversion applied to regional broad band waveforms obtained from the Greek National Seismographic Network provided focal mechanisms for 23 aftershocks with magnitudes ranging from M_w 3.6 to 5.4. The aftershock sequence presented spatial and temporal variation. The aftershocks were concentrated in two clusters one at the northern part of the activated area and another at the southern part. Most of them were of strike-slip character, following the major tectonic lines of the area, although low-angle thrust and reverse faulting mechanisms were also observed. Thrust and reverse type mechanisms are mainly concentrated in the northern and mainland part of the Lefkada Island which probably indicates the segmented character of the fault and probable activation of adjacent structures.     

基于AHP-变异系数法的越占南沙岛礁战略价值评价

选取南沙海域被越南非法侵占的29个岛礁的法律地位、军事基地潜力、水域通达性、岛礁资源价值、陆地联系紧密度与区域战略潜力等主要因素构建指标体系,采用主客观综合赋权的方法——层次分析法(AHP,Analytic Hierarchy Process)-变异系数法,定量评价越南侵占的我国南沙岛礁战略价值。研究结果表明:(1)越占岛礁价值最高的为南子岛,其次是南威岛,目前越南对其开发程度均较高;(2)战略价值较高的鸿庥岛、景宏岛等岛礁离我国控制的部分南沙岛礁距离较近,对我国战略防御构成威胁。另外西礁战略价值较高,已成为南沙旅游开发景点之一;(3)战略价值较低的金盾暗沙、奥南暗沙等目前受自身开发条件限制较大,但蕴藏着极大的油气潜力。以上越占岛礁战略价值分析结果,将为维护我国固有领土完整,为解决中越南沙争端提供支持。     

南沙群岛海区有机碳沉积作用与古生产力估算

根据南沙群岛海区５个沉积柱样和大量表层样的分析资料讨论了有机碳的沉积作用。深海有机碳含量一般为０．２％－１．３％。水柱深度对其分布的控制作用不明显。分析结果发现冰期、间冰期，尤其是本次冰期有机碳含量变化明显，４个柱样晚第四纪的质量堆积速率在末次冰期时最大。有机碳保存的主要控制因素是溶解氧浓度、粘土矿物含量、水柱深度和底栖混合强度，其中溶解氧浓度是最重要因素。底栖有孔虫的相对丰度，如Ｕｖｉｇｅｒｉｎａ和Ｂｕｌｉｍｉ－ｎａ，可用来指示溶解氧和有机碳含量。有机碳含量与海洋生产力关系极为密切，它可用来重建海洋古生产力的长期变化。采用Ｍｌｌｅｒ和Ｓｕｅｓｓ方程以及Ｓａｒｎｔｈｅｉｎ方程的计算结果与目前生产力值结果比较表明，后一种方法因充分考虑了溶解氧浓度和水柱深度而更接近现代值。     

Impact of the brine from a desalination plant on a shallow seagrass (Posidonia oceanica) meadow

Although seawater desalination has increased significantly over recent decades, little attention has been paid to the impact of the main by-product (hypersaline water: brine) on ecosystems. In the Mediterranean, potentially the most affected ecosystems are meadows of the endemic seagrass Posidonia oceanica. We studied the effect of brine on a shallow P. oceanica meadow exposed to reverse osmosis brine discharge for more than 6 years. P. oceanica proved to be very sensitive to both eutrophication and high salinities derived from the brine discharge. Affected plants showed high epiphyte load and nitrogen content in the leaves, high frequencies of necrosis marks, low total non-structural carbohydrates and low glutamine synthetase activity, compared to control plants. However, there was no indication of extensive decline of the affected meadow. This is probably due to its very shallow situation, which results in high incident radiation as well as fast dilution and dispersion of the brine plume.     

An unusual ‘blood rain’ over the Canary Islands (Spain). The storm of January 1999

An intense storm, including strong winds, a dust storm, ‘blood rain’ and heavy rains affected the Canary Archipelago between 5 and 10 January 1999, producing damage valued at 156 million euros. The present paper analyses the weather conditions and sedimentological features of the dust. The resulting data provide a possible explanation of palaeoclimatic conditions essential for the stabilization of sand dunes in the eastern parts of the Canary Islands.     

西沙群岛和涠洲岛气候变化特征 及其与近岸陆地的对比

采用1959―2014年中国西沙站和涠洲岛站及其临近陆地台站的基本气象观测资料,分析了2个海岛的气候变化特征及其与近岸陆地的差异。结果表明：1）近56年西沙和涠洲岛及近岸陆地气温变化均呈上升趋势,西沙增暖速率（0.19℃/10 a）大于涠洲岛（0.104℃/10 a）。显著的差异出现在近10年,西沙持续增暖（0.38℃/10 a）,而涠洲岛气温却呈下降趋势（-0.48℃/10 a）。从季节变化上,2个海岛都有春季越来越暖、冬季越来越冷的趋势。与周围陆地的气温相比,2个海岛的气温均高于近海陆地,但增温速率却小于近岸陆地。2）分析近56年降水量的变化,发现海岛降水量、降水强度和降水天数均小于陆地。受冬、夏季风转换的控制,海岛及近岸陆地有旱季、雨季的划分,且近半个世纪以来降水量波动大、变化趋势不显著,但伴随降水天数的减少,降水强度呈显著增长趋势。对比2个海岛近10年的降水变化特征,发现西沙站的旱季有越来越旱的趋势,涠洲岛及近岸陆地无论旱季、雨季降水量都有增加的趋势,表现为湿润化的趋势。