Variability of organic δC and C/N in the Mersey Estuary, U.K. and its implications for sea-level reconstruction studies     

Graham P. Wilson  Angela L. Lamb  Melanie J. Leng  Silvia Gonzalez  David Huddart 《Estuarine, Coastal and Shelf Science》2005,64(4):685-698

Microfossil analysis (e.g. diatoms, foraminifera and pollen) represents the cornerstone of Holocene relative sea-level (RSL) reconstruction because their distribution in the contemporary inter-tidal zone is principally controlled by ground elevation within the tidal frame. A combination of poor microfossil preservation and a limited range in the sediment record may severely restrict the accuracy of resulting RSL reconstructions. Organic δ¹³C and C/N analysis of inter-tidal sediments have shown some potential as coastal palaeoenvironmental proxies. Here we assess their viability for reconstructing RSL change by examining patterns of organic δ¹³C and C/N values in a modern estuarine environment. δ¹³C and C/N analysis of bulk organic inter-tidal sediments and vegetation, as well as suspended and bedload organic sediments of the Mersey Estuary, U.K., demonstrate that the two main sources of organic carbon to surface saltmarsh sediments (terrestrial vegetation and tidal-derived particulate organic matter) have distinctive δ¹³C and C/N signatures. The resulting relationship between ground elevation within the tidal frame and surface sediment δ¹³C and C/N is unaffected by decompositional changes. The potential of this technique for RSL reconstruction is demonstrated by the analysis of part of an early Holocene sediment core from the Mersey Estuary. Organic δ¹³C and C/N analysis is less time consuming than microfossil analysis and is likely to provide continuous records of RSL change.  相似文献   

龙须菜和扁江篱多糖的组成及其抗肿瘤效果   总被引：22，自引：0，他引：22  

邓志峰  纪明侯 《海洋与湖沼》1995,26(6):575-581

于１９８５－１９８７年期间用冷水和热水对采集于青岛的龙须菜和扁江篱的琼胶型多糖进行提取。两海藻的热水提取多糖都通过ＤＥＡＥ－ＳｅｐｈａｄｅｘＡ５０色谱桩用热水和不同浓度ＮａＣｌ深液前后进行洗脱分级。龙须菜和扁江篱多糖的主要级分分别为０．５ｍｏｌ／Ｌ和１．０ｍｏｌ／ＬＮａＣｌ洗脱级分。对各级分做化学分析及ＩＲ和＾１３ＣＮＭＲ光谱分析。结果表明，龙须菜多糖由琼二糖、琼胶糖前体和６－ＯＣＨ３－琼二糖组成  相似文献   

运城盆地11 kaBP以来气候环境变迁与湖面波动   总被引：7，自引：0，他引：7  

吴艳宏  吴瑞金  王强  朱育新  潘红玺 《海洋地质与第四纪地质》2001,21(2):83-86

通过黄土区湖泊沉积研究来恢复古气候、古环境，是对黄土区古气候、古环境研究的补充和检验。通过山西运城盆地硝地湖泊沉积物的多环境代用指标分析，结合史料记载，探讨了该地区11kaBP以来古气候演化和湖面波动的历史。结果表明，该地区存在YD（Younger Dryas）事件，进入全新世后气候有显著的趋势，最高湿润度发生在7．88－5．15和5kaBP后，气候逐渐变干，湖面波动与气候波动相关，全新世早期湖面开始上升，湖泊扩张，5kaBP后湖泊萎缩，盐类结晶析出。  相似文献   

南海294站柱状沉积孢粉、藻类研究及古环境意义     

张玉兰  贾丽  孙煜华  郑玉龙 《海洋学研究》2003,21(1):5-12

通过对南海294站深海柱状剖面孢粉、藻类的研究,将294站从下至上划分为7个孢粉组合带: 带为Dacrydium-Pinus-Lithocarpus-Quercus(常绿)-Cyathea-Polypodiaceae; 带为Castanopsis-Lithocarpus-Dacrydium-Quercus(常绿)-Pinus-Polypodiaceae; 带为Quercus(常绿)-Castanopsis-Podocarpus-Cyathea-Polypodiaceae; 带为Polypodiaceae-Cyathea-Pteris-Pinus-Gramineae; 带为Quercus(常绿)-Podocarpus-Lithocarpus-Pinus-Cyathea-Polypodi-aceae; 带为Pinus-Quercus(常绿)-Palmae-Mangrovepollen-Gramineae; 带为Dacrydium-Palmae-Mangrovepollen-Pinus-Cyperaceae-Cyathea。相应恢复了南海东部地区12万年以来5个植被、气候演替阶段,依次为:炎热、湿润的热带季雨林—暖热而稍干的热带北缘半常绿季雨林—炎热、湿润的热带季雨林—暖热而稍干的热带北缘半常绿季雨林—炎热、湿润的热带季雨林。结合氧同位素测年资料,对南海294站柱状剖面地层时代划分进行了讨论。  相似文献   

柴达木察尔汗盐湖贝壳堤剖面介形类组合及其环境意义   总被引：3，自引：0，他引：3       下载免费PDF全文

张虎才  王强  彭金兰  陈光杰 《第四纪研究》2008,28(1):103-111

柴达木盆地察尔汗贝壳堤剖面记录了约39.7～17.514CkaB.P.期间古湖泊高湖面扩张、收缩的演化历史。剖面中丰富的介形类,皆为我国东部山间盆地～平原区系与西部高原区系常见种。依据青海地区现代介形类分布调查,可知研究剖面高湖面发育期为淡水湖,其中高分异度介形类组合代表近静水的浅湖环境,单种或近单种土星介大量出现层位指示缓流水环境,大量原生双壳类共生可能指示静水、较深水环境。据地层中介形类分布,自下而上划分为7个组合-沉积环境带,分别为:①少量湖沼种出现（积水洼地形成带）——湖泊前期,②单种缓流水种连续出现（湖泊初始形成带）——高湖面初始形成期,③高分异度组合、介形类富集（浅水大湖带）——高湖面水深加大期,④中分异度组合、介形类少量出现（深湖带）——高湖面最盛期,⑤中分异度组合、介形类少量出现、双壳类连续富集（湖泊变浅带）——高湖面略下降期,⑥缓流水介形类繁盛、双壳类多少不等（湖泊水位下降带）——古湖泊退缩期和⑦介形类稀少带——古湖泊快速消亡期。贝壳堤剖面所见双壳类在现代介形类调查区域没有发现,它们在地层中的出现,进一步指示大体相当MIS3阶段时期柴达木盆地比现代更温暖的气候背景,降水条件好于现代。  相似文献   

The paleoclimatic records and the relevance with the formation of hydrocarbon source rocks:A case study of Huanghekou depression,Bohaiwan basin     

Zhanhong LIU  Sitian LI  Renchen XIN  Changgui XU  Jianchun CHENG 《Frontiers of Earth Science》2008,2(1):73-82

Bohaiwan basin, covering an area of 200 000 km², is one of the most important oil-bearing basins in Eastern China. Rifting processes formed the basin, and two evolution phases can be recognized. The rifting phase developed in Paleogene, and post-rifting phase occurred in Neogene. More than 200 oil fields have been found in the onshore and offshore area in Bohaiwan basin in recent years. The distribution of the oil fields is closely related to the rich hydrocarbon depressions, and the Huanghekou depression is one of these rich hydrocarbon depressions. A number of large and medium-sized oil and gas fields have been found in this area, such as BZ25-1, BZ34 etc., and the hydrocarbon was mainly from the Huanghekou depression. The formation of rich hydrocarbon source rocks depended on the tectonic setting of rapid subsidence, favorable paleoclimatic conditions and paleolimnology environments. The effects of paleoclimatic condition on hydrocarbon source rocks are the focus of this paper. __________ Translated from Geological Bulletin of China, 2007, 26(7): 830–840 [译自: 地质通报]  相似文献   

A preliminary study of the carbon-isotopic content of ambient formic acid and two selected sources: Automobile exhaust and formicine ants   总被引：2，自引：0，他引：2  

Bryan J. Johnson  George A. Dawson 《Journal of Atmospheric Chemistry》1993,17(2):123-140

Relatively large quantities (1 mg) of formic acid have been collected from the atmosphere and subjected to carbon-isotopic analysis, as a means of source discrimination. Ambient formic acid was captured on Ca(OH)₂-treated filters using a high-volume sampler. The collection method was not only efficient (>96%), but also appears to have low artifact production.Most of the samples (36 out of 52) were collected over a two-year period at the summit of Mount Lemmon, Arizona, where a strong seasonality in HCOOH mixing ratio was observed (0.2 ppb during winter months to 1.5 ppb in the summer). Other collection sites included the Oregon coast, Colorado Rockies, urban Tucson, and the North Dakota prairie. The carbon-13 content of atmospheric HCOOH was found to be have little variation (–18 to –25), regardless of location or season. This is consistent with a single dominant source of formic acid. The carbon-14 measurements of 6 Mount Lemmon samples showed high levels of modern carbon (93–113% modern).The emissions from formicine ants and automobile combustion were selected as two other potential sources for isotopic analysis. The HCOOH collected from auto exhaust was much more depleted in¹³C than the atmospheric samples, with a ¹³C of –28.0 and –48.6 from a leaded and unleaded automobile, respectively. Formicine ants, on the other hand, ranged from –17.2 to –20.6.  相似文献   

Molecular and bulk isotopic analyses of organic matter in marls of the Mulhouse Basin (Tertiary, Alsace, France)     

Hollander DJ  Sinninghe Damste JS  Hayes JM  de Leeuw JW  Huc AY 《Organic Geochemistry》1993,20(8):1253-1263

Contents of 13C in kerogens and carbonates in 21 samples from a core of the MAX borehole, Mulhouse Evaporite Basin, range from -27.3 to -23.5 and -3.7 to -1.8% vs PDB, respectively. Organic nitrogen in the same samples is enriched in 15N relative to atmospheric N2 by 12.2-15.7%. Hydrogen indices and delta values for kerogens vary systematically with facies, averaging 493 mg HC/g Corg and -25.7% in the most saline facies (dominated by inputs from aquatic sources) and 267 mg HC/g Corg and -23.7% in the least saline facies (50/50 aquatic/terrigenous). Values of delta were measured for individual aliphatic hydrocarbons from three samples representing three different organic facies. For all samples, terrigenous inputs were unusually rich in 13C, the estimated delta value for bulk terrigenous debris, apparently derived partly from CAM plants, being -22.5%. In the most saline facies, isotopic evidence indicates the mixing of 13C-depleted products of photosynthetic bacteria with 13C-enriched products of halotolerant eukaryotic algae. At lower salinities, a change in the producer community is marked by a decrease in the 13C content of algal lipids. The content of 13C in algal lipids increases in the least saline facies, due either to succession of different organisms or to decreased concentrations of dissolved CO2.  相似文献   

Diagenesis of vascular plant organic matter components during burial in lake sediments   总被引：12，自引：0，他引：12  

Philip A. Meyers  Mary J. Leenheer  Richard A. Bourbonniere 《Aquatic Geochemistry》1995,1(1):35-52

Diagenetic changes are difficult to distinguish from variations in sources of organic matter to sediments. Organic geochemical comparisons of samples of wood, bark, and needles from a white spruce (Picea glauca) living today and one buried for 10,000 years in lake sediments have been used to identify the effects of diagenesis on vascular plant matter. Important biogeochemical changes are evident in the aged spruce components, even though the cellular structures of the samples are well preserved. Concentrations of total fatty acids dramatically diminish; unsaturated and shorter chainlength components are preferentially lost from the molecular distributions. Concentrations of total alcohols are similar in the modern and 10,000-year-old wood and bark but markedly lowered in the aged needles. Hydrocarbon concentrations and distributions show little diagenetic change in the 10,000-year-old plant materials. Cellulose components in the wood decrease relative to lignin components, although both types of materials remain in high concentration in comparison to other organic components. Aromatization of abietic acid proceeds more rapidly in buried spruce wood than in bark; retene is the dominant polyaromatic hydrocarbon in the aged wood. In contrast to the variety of changes evident in molecular compositions, neither ¹³C values nor C/N ratios differ significantly in the bulk organic matter of modern and aged spruce components.  相似文献   

Hydrogen isotope of individual n-alkanes from modern sediments and their application to environments     

Zhongping LI Liwu LI Li DU 《中国地球化学学报》2006,25(B08):207-207

Hydrogen isotopes are commonly fractionated to a much greater extent and as a result display larger variations in δ values, In terms of the hydrogen isotope ratios of individual n-alkanes of 16 samples of modern sediments selected from four different locations in the southern part of Gansu, China, the δD values for most of the n-alkanes varied from -150‰-300‰, Variations in δD also occurred between different ranges of n-alkanes, effects of environmental changes on the hydrogen isotopic compositions of individual n-alkanes have been detected. Besides the δD values of n-alkanes, the δD values of lipids including pristane （Pr）, phytane （Ph） were also examined, by the combination of D/H ratios with molecular fingerprinting, Our results further support the notion that hydrogen isotopes of n-alkanes from modern sediments can act as paleoclimatic and paleoenvironmental proxies and provide invaluable new sources of information in the research of paleoenvironment reconstruction.  相似文献