科学家们调查研究引起美国西北部极地冰原融化的温度变化

科学家们调查研究引起美国西北部极地冰原融化的温度变化得克萨斯农机大学学院站报道，全球变暖已影响到美国西北部地区，生活在那里的人们应该感到庆幸，大约在１．３—１．４万年以前，半英里厚的极地冰原覆盖着现在的西雅图以及其北地区．大型淡水湖在犹他、内华达和加...     

冰盖崩塌和海平面变化

海平面记录包含着地球气候变化和海平面与海底地形之间相对运动的基础信息。这些记录提供了全球范围的尺度 ,衡量地球历史中不同时期有多少水被锁在了冰盖和冰川内。此外 ,Ｃｌａｒｋ等认为海平面变化的地理模式能够提供冰消期融水脉冲成因的线索。有许多现象导致了以往的海平面变化 ,这些现象的模拟模式越来越精细化 ,使我们能够弄清地球体系各部分 (水圈、冰冻圈、岩石圈和大气圈 )之间复杂的相互作用以及它们对气候和生物圈的影响。此外 ,还辅之有现有的和计划中的卫星空间数据以帮助我们提高探测现代海平面变化的能力。以弄清地球体系各…     

Does sedimentary organic delta 13C record variations in quaternary ocean [CO2(aq)]?

Ocean surface water [CO2(aq)] variations based on glacial/interglacial changes in sediment delta 13Corg are shown to compare favorably with reconstructions based on ice core [CO2]. In particular, an approximate 80 microatmospheres increase in atmospheric pCO2 during the last glacial-interglacial transition is calculated to correspond to a 3-4 micromolar increase in ocean surface water [CO2(aq)] at atmospheric equilibrium. A widespread marine delta 13Corg decrease of 1-2% accompanied this event and was not preceded by an equivalent isotopic change in surface water total dissolved inorganic carbon. These observations support the hypothesis that [CO2(aq)] influences photosynthetic isotope fractionation between marine inorganic and organic carbon pools, and therefore that plankton/sediment delta 13Corg may serve as a proxy for surface water [CO2(aq)].     

Hepatic metallothionein as a biomaker for metal contamination: age effects and seasonal variation in European flounders (Pleuronectes flesus) from the Severn Estuary and Bristol Channel

Hepatic concentrations of metallothionein [MT] and three metals (Cu, Zn, Cd) were determined in 242 European flounders (Pleuronectes flesus) collected from power stations at Oldbury-upon-Severn and Hinkley Point, located in Severn Estuary and Bristol Channel, UK, respectively, between March 1996 and February 1998. A model involving three-factor analysis of variance (ANOVA) was used to examine variation in MT and metal concentrations with respect to season, year and site; with age-class included as a covariate in the analysis. Hepatic concentrations of MT and Cd (and to some degree, Cu, but not Zn) increased significantly with age. The model explained 38, 25, 17 and 26% of the variation in MT, Cu, Zn and Cd, respectively, with significant effects due to season, and to a lesser extent, to year. Site was only a significant factor for Cd which was higher in fish from Hinkley. Correlation between the individual concentration of MT and each metal alone, or in combination, was poor, and explained only an additional 3.0% of the residual variation in MT, most of which was attributable to Cu (2.7%). Compared to other industrialised estuaries, Cd concentrations were high (>20 micro g-1 in some individuals). The study emphasises the importance of seasonal variation and other factors in biomonitoring programmes and highlights the limitations of using [MT] as a biomarker for metal contamination in flounders from the Severn Estuary.     

白垩纪期间极端温暖的深海古温度记录

白垩纪温室效应盛行 ,同位素记录、陆源和海洋生物的古生物地理学、树叶外形和对气候敏感的沉积物分布都表明了其温度比目前温暖 ,尤其是在高纬地区 ( Barron,1 983 ;Herman和 Spicer,1 997;Frakes,1 999)。虽然有变暖的证据 ,但是对高纬的环境还是有争议的。已引入南极大陆冰盖来解释白垩纪的短期全球海平面波动 ( Matthews和 Poore,1 980 ;Abreu 等 ,1 998)以及高古纬度地区沉积的上白垩统沉积物中的钙芒硝状方解石和混积岩的存在 ( Kem-per,1 986;Frakes等 ,1 992 )。此外 ,从箭石属和其他大型无脊椎动物的氧同位素数据至少可以看出…     

深海锤击取样管

深海锤击取样管Ｄ·Ｊ·Ｓｍｉｔｈ，Ｋ·Ｔｒｏｎｓｔａｄ１前言锤击取样管在海洋沉积取岩芯中是一种新的设计原理，能在大陆边缘、斜坡以及深海平原沉积区钻取沉积芯样，以满足考古海洋学的要求。取样管可在水深５０００ｍ处获得长达３０ｍ的未扰动岩芯。它使用了类似陆...     

Whiting events: biogenic origin due to the photosynthetic activity of cyanobacterial picoplankton

An annual whiting event occurs each year in late May to early June in Fayetteville Green Lake, New York. The initiation of this event correlates with exponential growth of the Synechococcus population within the lake. Synechococcus is the dominant (by approximately 4 orders of magnitude) autotrophic organism owing to the oligotrophic condition of the lake. The delta 13C values of the dissolved inorganic C range seasonally from -9.5% in winter to -6.2% in summer due to photosynthetic activity. Calcite precipitates principally in the microenvironment surrounding Synechococcus because of a photosynthetically driven alkalization process and the availability of the cells as nucleation sites. This calcite has a heavier delta 13C value (>4%) than does the dissolved inorganic C of the lake water owing to the cells' preferential uptake of 12C. A conceptual model suggests that photosynthetic activity and cell surface chemistry, together with the substantial surface area that arises from the great abundance of micron-sized cells, allow Synechococcus to dominate the annual whiting events in Fayetteville Green Lake.     

拉腊米构造运动对墨西哥湾西部深水盆地晚中生代-新生代沉降史的影响

墨西哥湾盆地被普遍认为是一个中生代被动边缘盆地的例子．它构成了泛大陆裂谷和拉伸作用(包括之后的解体、海底扩张和热冷却)的一部分．其西部与太平洋板块向北美板块下面俯冲有关的构造事件影响了北美西部内陆(包括墨西哥)的很大一部分地区．     

死海地堑梅察达（Masada）附近的史前地震变形

死海地堑梅察达（Ｍａｓａｄａ）附近的史前地震变形ＳｈｍｕｅｌＭａｒｃｏ和ＡｍｏｔｚＡｇｎｏｎ活动地区的古地震记录对于评价过去的地震活动及地震灾害是很有价值的．一个理想的地震记录要有跨时久远的可靠、清晰和可测年代的地震指示．我们认为Ｌｉｓａｎ湖（古死海...     

贫岩浆陆缘从裂谷到海底扩张的演化

伊比利亚西部—纽芬兰共轭陆缘大约于１３３Ｍａ前开始经历早白垩世最后的裂谷和海底扩张期。阿尔卑斯特提斯陆缘在晚三叠世／早侏罗世经历了最后的裂谷期 ,形成了利古里亚—皮埃蒙特海 ,该海区海底扩张导致的岩浆活动开始于１６０～１６５Ｍａ之前。伊比利亚西部和阿尔卑斯这两个贫岩浆陆缘的特征是深水带与陆缘平行分布 ,明显表示出了陆缘演化阶段的顺序为 :低角度挤离断层将薄陆壳切割成陆块 ,剥露出陆下的地幔 ,镁铁质熔融物向海洋方向增加最后与洋壳溶为一体。笔者在提出解释这种现象之前 ,先根据两个陆缘区的种种迹象对各个地带分别加…