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101.
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. 相似文献
102.
Anita Moldenhauer-Roth Guillaume Piton Sebastian Schwindt Mona Jafarnejad Anton JSchleiss 《国际泥沙研究》2021,36(1):136-150
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. 相似文献
103.
Osamu Seki Takeshi Nakatsuka Kimitaka Kawamura Sei-Ichi Saitoh Masaaki Wakatsuchi 《Marine Chemistry》2007,104(3-4):253-265
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 UK37′ value is not significantly altered. This study indicates that UK37′ values preserved in the surface sediments off Sakhalin reflect the seasonal temperature signal of near surface water, rather than annual mean surface temperature. 相似文献
104.
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。 相似文献
105.
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 总被引:3,自引:2,他引:1
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。 相似文献
106.
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。 相似文献
107.
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。 相似文献
108.
109.
川西浅层储层地震“低频、强振幅”形成机理及陷井分析 总被引:1,自引:0,他引:1
黎家盆 《物探化探计算技术》2003,25(3):193-196
在川西地区浅层油气勘探开发过程中,已总结出地震“低频、强振幅”油气预测模式,并早已应用于勘探中。随着该区勘探开发程度的提高,该模式作为已成熟的油气预测方法在一些地区出现了预测失误。这里经分析了地震“低频、强振幅”的形成机理后总结出了模式预测中典型的“陷井”,并提出了降低模式预测风险的附加条件。 相似文献
110.
岩性圈闭地质风险评价原则与方法探讨 总被引:2,自引:0,他引:2
依据对油气勘探理论和圈闭概念的理解和认识,认为在建立岩性圈闭地质模型时,对岩性圈闭的地质风险评价应分3个层次进行,即圈闭的成藏环境、圈闭自身的成藏条件和圈闭可靠性的评价,从而得到圈闭的含油气性系数或圈闭的地质风险系数.在分析圈闭自身的成藏条件时,应对传统的"生、储、盖、运、圈、保"进行分类和归纳,利用圈闭获得油气的能力、圈闭的储集能力、圈闭的后期保存条件"三要素"对岩性圈闭的含油气性进行评价.运用该评价系统对西部新区塔里木、准噶尔盆地中的储备圈闭进行了评价,其评价结果均较合理. 相似文献