Stable carbon and nitrogen isotopes of sinking particles in the eastern bransfield strait (Antarctica)

A time-series sediment trap was deployed at 1,034 m water depth in the eastern Bransfield Strait for a complete year from December 25, 1998 to December 24, 1999. About 99% of total mass flux was trapped during an austral summer, showing distinct seasonal variation. Biogenic particles (biogenic opal, particulate organic carbon, and calcium carbonate) account for about two thirds of annual total mass flux (49.2 g m^-2), among which biogenic opal flux is the most dominant (42% of the total flux). A positive relationship (except January) between biogenic opal and total organic carbon fluxes suggests that these two variables were coupled, due to the surface-water production (mainly diatoms). The relatively low δ¹³C values of settling particles result from effects on C-fixation processes at low temperature and the high CO² availability to phytoplankton. The correspondingly low δ¹⁵N values are due to intense and steady input of nitrates into surface waters, reflecting an unlikely nitrate isotope fractionation by degree of surface-water production. The δ¹⁵N and δ¹³C values of sinking particles increased from the beginning to the end of a presumed phytoplankton bloom, except for anomalous δ¹⁵N values. Krill and the zooplankton fecal pellets, the most important carriers of sinking particles, may have contributed gradually to the increasing δ¹³C values towards the unproductive period through the biomodification of the δ¹³C values in the food web, respiring preferentially and selectively¹²C atoms. Correspondingly, the increasing δ¹⁵N values in the intermediate-water trap are likely associated with a switch in source from diatom aggregates to some remains of zooplankton, because organic matter dominated by diatom may be more liable and prone to remineralization, leading to greater isotopic alteration. In particular, the tendency for abnormally high δ¹⁵N values in February seems to be enigmatic. A specific species dominancy during the production may be suggested as a possible and speculative reason.     

Design of sediment detention basins: Scaled model experiments and application

Sediment detention basins are implemented on mountain rivers to trap solid material that may aggravate the flooding of downstream settlements.However,retention structures built in the past may unnecessarily retain sediment during non-hazardous flood events,resulting in high maintenance costs and sediment deficit downstream.In addition,the so-called spontaneous self-flushing of previously retained sediment during floods has occasionally been observed.Recent research suggests to design sediment detention basins for controlling sediment passage with a guiding channel across the deposition area upstream of a hybrid barrier.Such barriers consist of a check dam with a slot orifice and an upstream bar screen with a bottom clearance in order to benefit from a combined mechanical-hydraulic retention control.The present paper enhances this pioneering research with the help of new experimental data,including a wide range of sediment mixtures and large wood,as well as variable barrier heights.Improved design criteria are provided regarding the bar screen and the basin storage capacity.The functionality of the enhanced concept for sediment detention is illustrated by a case study on a physical model:the protection of the Villard-Bonnot village(France)against torrential hazards.     

Time-series sediment trap record of alkenones from the western Sea of Okhotsk

C₃₇–C₃₉ alkenones were measured in time-series sediment trap samples collected from August 1998 to June 2000 at two depths in the seasonal sea ice region of the western Sea of Okhotsk, off Sakhalin, in order to investigate alkenone production and water-column processes in the region. Measurable export fluxes of alkenones are ranged from < 0.1 to 5.8 μg/m²/day and clearly showed that the alkenone production was restricted to autumn. In 1998, maximum export flux of alkenones occurred in September when surface water column was well stratified with low nutrients in the surface mixing layer. In the next year, the maximum flux is observed in October. Comparison between alkenone temperature and satellite based sea surface temperature (SST) shows that the estimated alkenone temperatures in August 1998 were found to be  10 °C lower than the temporal satellite SST, suggesting that alkenones are produced in surface to subsurface thermocline layers during the period. Annual mean flux of alkenones is lower in the lower traps than that of the upper traps, suggesting rapid degradation of alkenones in water column, but the U^K₃₇′ value is not significantly altered. This study indicates that U^K₃₇′ values preserved in the surface sediments off Sakhalin reflect the seasonal temperature signal of near surface water, rather than annual mean surface temperature.     

激光囚禁放射性氪同位素技术测量地下水年代

地下水年代测定对于了解地下水循环具有十分重要的意义。放射性氪同位素⁸⁵Kr（半衰期10.8a）、⁸¹Kr（半衰期0.23Ma）具有十分理想的地球物理化学特性,十分适于对溶解了大气的水或冰样品进行绝对年代测定。由于样品中的放射性氪原子量极少,利用⁸¹Kr含量进行地下水测年时需要数吨水样品才能完成(Earth and Planetary Science Letters,2000,182：103～113;Geophysical Research Letters,2004,31: L05503)。本文主要介绍我们在中国科学技术大学建立的激光冷却氪原子测量装置,该系统已经成功地对氪原子进行了激光冷却和囚禁,实现了单个放射性氪原子⁸¹Kr和⁸⁵Kr的计数测量。氪原子的冷却捕获速率被大幅提高,预计测年应用中所需样品量可减小一个量级以上,这将使得我们可以开展新的地下水年代测定应用。     

松辽盆地北部他拉哈-齐家地区姚一段沉积与成藏特征再认识

综合20口井岩心和496口井测井、录井及分析化验资料,对松辽盆地他拉哈-齐家地区姚一段葡萄花油层进行高分辨率层序地层研究,提出葡萄花油层北、西部为同沉积构造抬升控制的底部缺失的层序地层新格架。研究区最有利相带砂体为窄而细的末梢河道砂、薄层河口坝及席状砂体,而研究区北半部大量宽泛的厚层优质河道砂却不含油,为大面积含水区。研究总结发现,砂体发育与岩性油气藏分布均受控于一挠曲坡折带,坡折带以内为低水位体系域沉积质量中心,砂岩厚薄相间,可形成地层超覆圈闭;坡折带之下为3个层序低水位和水进体系域三角洲前缘砂体叠合区,发育的砂岩较薄且连通性差,是多层位岩性圈闭和上倾尖灭型圈闭发育区;坡折带之上以水进体系域平原相及前缘相的大量厚层河道砂体为主,但因连通性好,油气易散失,不易形成岩性圈闭,而成为大范围的含水区。坡折带"控层""控相""控砂""控藏"的理论在本研究区又一次得到极好的应用与验证。     

广西乐业林旺金矿床构造解析及构造成矿作用

详细的构造解析表明,矿床构造线主要分为南北向、北东东向和北西向三组,其中造山期间形成的南北向构造线(不对称褶皱和逆冲断层)控制了矿床的基本构造格架。后碰撞造山侧向挤压期间构造应力场发生近直交的改变,一方面使造山期形成的褶皱发生重褶,形成走向北东东的叠加褶皱;另一方面导致F1的左旋-正滑运动,矿液沿着断层拉张的空间沉淀就位。矿床构造演化至少经历了同生期裂陷、造山期挤压和后碰撞造山侧向挤压等三个阶段,成矿发生在后碰撞造山侧向挤压阶段。层状矿体主要赋存于背斜构造中,在空间上与赋存于断层中的脉状矿体相连。能干性和渗透性明显不同的地层组合是形成层状矿体的岩性基础,断裂构造则是主要控制因素。泥质不透水层分别与反冲断层、背斜构造组成的构造圈闭,以及两期非共轴背斜叠加形成的构造高点则是形成厚大矿体的主要原因。林旺金矿在烂泥沟金矿与水银洞金矿之间形成了一个从脉状型式→脉状和层状之复合型式→层状型式的完整矿床型式系列。这种复合矿床型式直观地表明了层状矿体是后生热液成因矿床。     

裂谷盆地的断层封闭类型

对油气运移和聚集而言，裂谷盆地的断层可分为断面封闭型和生封闭型两大类；断面封闭型以以断面（或断裂带）本身作为遮挡体或通道；岩性封闭型断层依靠对盘财层遮挡或提供通道，根据断层的封闭能力，每大类还可分为完全封闭型、不完全封闭型和开启型３亚类、磊断层以断面封闭型为主；小断层大断层在浅层的分支断层都为生封闭型，但者的油气分布特所不同，一盘为基岩的断层较在盖层内的断层能力低，断层活动有利于油气运移。     

反转构造与油气圈闭

反转构造作为伸展盆地中的重要构造类型以及它对油气的聚集作用己成为石油地质界广泛重视的研究课题之一。盆地从拉张→挤压的构造反转对油气生成、运移和聚集有明显的控制作用。本文在综述反转构造的研究进展基础上，重点对伸展盆地反转构造构造样式、圈闭条件及其与油气聚集的关系进行了论述，旨在为我国东部含油气盆地中寻找与反转构造有关的油气藏提供科学基础。     

齐Ⅰ金矿床石英热发光研究

通过对石英热发光特征研究,发现石英热发光曲线的复杂与否,与矿床的形成深度、多期次成矿作用和矿化的贫富有一定的关系。进而,为在该区进一步深入找矿及寻找其它内生矿床提供一项新的研究途径。