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1.
A group of methyltrimethyltridecyl chromans (MTTCs) was found in core samples of Member 1 (K2n1) and Member 2 (K2n2) of the Nenjiang Formation (Upper Cretaceous) from the SK-l southern borehole (Songliao Basin, China). They are assigned for the first time in sediments older than the Tertiary in China. Their composition and distribution are indicative mainly of the redox and salinity conditions in the depositional environment. The δ-MTTC isomer is in relatively higher abundance in samples from enhanced salinity and reducing conditions, but was not detected in samples from aerobic and low salinity environments, while α-MTTC appears to be present in samples from environments with a broad range of salinity and redox conditions. The α-MTTC/γ-MTTC (α/γ) ratio has a similar indication as that of the α/δ ratio and could be used as a corroborative ratio of paleosalinity. A combination of biomarker parameters suggests that the massive lacustrine petroleum-prone source rocks associated with the K2n1 interval were likely developed under a stratified water column with enhanced salinity and an anoxic bottom water layer, associated with a much less saline (fresh to brackish) upper water layer.  相似文献   

2.
松辽盆地嫩江组脱羟基维生素E的分布及其地球化学意义   总被引：1，自引：0，他引：1  
王丽  宋之光 《地球化学》2010,39(5):469-478
脱羟基维生素E是沉积物（岩）中一类具有水体盐度指示意义的生物标志化合物,在现代和古代沉积物及原油中均有检出。在松辽盆地松科1井晚白垩系嫩江组岩芯样品中检测发现的脱羟基维生素E系列化合物显示脱羟基维生素E的组成分布在剖面上的变化主要反应了沉积埋葬时的环境盐度、氧化还原状态的变化,而与母源组成、有机质成熟度等无明显相关性,其中,δ-MTTC在咸水还原性环境最为丰富,而在低盐的半咸水-淡水氧化性环境中基本缺失,Ⅱ一MTTC在所有盐度环境中都很丰富,γ-MTTC的丰度则在盐水-咸水环境中明显高于低盐半咸水环境,而且在盐水环境中γ-MTTC〉β-MTTC-咸水环境显示γ-MTTC〈β-MTTC。研究发现,α-MTTC／γ-MTTC（cur）可作为Ⅱ-MTTC／δ-MTTC（α/δ）比值的替代指标,当Ⅱ-MTTC／γ—MTTC比值小于2时为盐水环境,比值大于15时为半咸水-淡水环境,介于之间为咸水环境。相关参数及综合分析显示嫩江组一、二段沉积时期水体盐度及氧化还原条件显著不同,嫩一段主力烃源岩沉积时期以与海水盐度相当的咸水、存在水体分层的还原性湖泊环境为主,顶部出现短期戚化的盐水环境,而嫩二段主要为半咸水-淡水氧化性湖泊环境,盐度比较稳定。  相似文献   

3.
A series of branched alkylbenzene ranging from C15 to C19 with several isomers (2–5) at each carbon number were identified in sediments from the Dongsheng sedimentary uranium ore deposits, Ordos Basin, China. The distribution patterns of the branched alkylbenzenes show significant differences in the sample extracts. The branched alkylbenzenes from organic-rich argillites and coals range from C15 to C19 homologues, in which the C17 or C18 dominated. On the other hand, the C19 branched alkylbenzenes dominated in the sandstone/siltstone extracts. The obvious differences of the branched alkylbenzene distributions between the uranium-host sandstones/siltstones and the interbedded barren organic-rich mudstones/coals probably indicate their potential use as biological markers associated with particular depositional environments and/or maturity diagenetic processes. Possible origins for these branched alkylbenzenes include interaction of simple aromatic compounds with, or cyclization and aromatization reactions of, these linear lipid precursors such as fatty acids, methyl alkanoates, wax esters or alkanes/alkenes that occur naturally in carbonaceous sediments. The possible simple aromatic compounds may include substituted benzenes, functionalized compounds such as phenols that are bound to kerogen at the benzyl position, and phenols that are decomposition products derived from aquatic and terrestrial sources. The distributions of methyl alkanoates and n-alkanes were found to be different between organic-rich mudstone/coal and sandstone/siltstone. From this result, it can be concluded that such differences of the alkylbenzene distributions were mainly resulting from the differences of organic precursors, although maturity effect and radiolytic alteration cannot be completely excluded.  相似文献   

4.
The relationships between electrical conductivity, temperature, salinity, and density are studied for brackish Lake Issyk-Kul. These studies are based on a newly determined major ion composition, which for the open lake shows a mean absolute salinity of 6.06 g kg−1. The conductivity-temperature relationship of the lake water was determined experimentally showing that the lake water is about 1.25 times less conductive than seawater diluted to the same absolute salinity as that of the lake water. Based on these results, an algorithm is presented to calculate salinity from in-situ conductivity measurements. Applied to the field data, this shows small but important vertical salinity variations in the lake with a salinity maximum at 200 m and a freshening of the surface water with increasing proximity to the shores. The algorithm we adopt to calculate density agrees well with earlier measurements and shows that at 20°C and 1 atm Lake Issyk-Kul water is about 530 g m−3 denser than seawater at the same salinity. The temperature of maximum density at 1 atm is about 0.15°C lower than that for seawater diluted to the same salinity. Despite its small variations, salinity plays an important role, together with temperature changes, in the static stability and in the production of deep-water in this lake. Changes in salinity may have had important consequences on the mixing regime and the fate of inflowing river water over geological time. Uncharged silicic acid is negligible for the stability of the water column except near an ∼15 m thick nepheloid layer observed at the bottom of the deep basin.  相似文献   

5.
Early to late Holocene sediments from core F80, Fårö Deep, Baltic Sea, are investigated for their palynomorph composition and dinoflagellate cyst record to map variations in sea‐surface‐water salinity and palaeoproductivity during the past 6000 years. The F80 palynomorph assemblages are subdivided into four Assemblage Zones (AZs) named A to D. The transition from the stratigraphically oldest AZ A to B reflects a marked increase in palaeoproductivity and a gradual increase in surface‐water salinity over the ～1500 years between the Initial Littorina (former Mastogloia Sea Stage) and Littorina Sea Stage. A period with maximum sea‐surface salinity is recorded within the overlying AZ C from 7200 to 5200 cal. a BP, where the process length of Operculodinium centrocarpum indicates that average salinities were probably the highest (～15–17 versus 7.5 psu today) since the last glaciation. The change from AZ C to D correlates with a shift from laminated to non‐laminated sediments, and the dinoflagellate cyst assemblages suggest that the surface‐ and the deep‐water environment altered from c. 5250 cal. a BP, with less productivity in the surface water and more oxygenated conditions in the deep water. Here we demonstrate that past regional changes in surface salinity, primary productivity and deep‐water oxygenation status in the Baltic Sea can be traced by mapping overall palynomorph composition, dinoflagellate cyst assemblages and variations in the process length of O. centrocarpum in relation to periods of laminated/non‐laminated sedimentation and proportion of organic‐matter in the sediments. An understanding of past productivity changes is particularly important to better understand present‐day environmental changes within the Baltic Sea region.  相似文献   

6.
The alkenone unsaturation index UK′37 has been applied to reconstruct past temperature changes in both marine and lacustrine systems. However, few studies have addressed whether the relative abundance of the C37:4 alkenone to the total C37 production (%C37:4) can reflect surface salinity changes in lacustrine systems. Here we present long-chain C37 alkenone distribution patterns in surface sediments from Lake Qinghai, China. Surface sediments were sampled over a large range of surface salinity changes (1.7-25 g/l) within Lake Qinghai and its surrounding lakes, while temperature differences at these sampling locations should be relatively small. We have found that %C37:4 varies from 15% to 49% as surface salinity decreases. We tentatively describe this %C37:4-salinity link with a general linear regression: %C37:4 = 53.4 (±7.8) − 1.73 (±0.45) × S (n = 28, r2 = 0.62), although step-wise %C37:4 changes in response to salinity variation may exist. UK′37 values vary between 0.10 and 0.16 at these sites and the inferred range of lake water temperature changes is ∼2-3 °C, suggesting that UK′37 largely reflects temperature signal across a large salinity range, consistent with previous findings that UK′37 can indicate temperature changes over a large diversity of environmental settings. We have also found that UK′37 values are correlated with salinity changes (r2 = 0.4), and thus cannot exclude potential temperature effect on %C37:4 and salinity effect on UK′37 in this study. However, even extreme estimates of temperature differences within the lake are still unable to explain the observed %C37:4 changes. We therefore suggest that %C37:4 could be used to infer past lake salinity changes at a regional scale.  相似文献   

7.
The effect of seasonally reversing monsoons in the northern Indian Ocean is to impart significant changes in surface salinity (SS). Here, we report SS changes during the last 32 kyr in the Lakshadweep Sea (southeastern Arabian Sea) estimated from paired measurements of d18O and sea surface temperature (SST) using Globigerinoides sacculifer, an upper mixed layer dwelling foraminifera. The heaviest d18OG.sacculifer (–0.07±0.08‰) is recorded between 23 and 15 ka, which could be defined as the last glacial maximum (LGM). The d18OG.sacculifer shift between the LGM and Holocene is 2.07‰. The SST shows an overall warming of 2°C from the LGM to Holocene (28°C to 30°C). However, coldest SSTs are observed prior to LGM, i.e., ~27 ka. The SS was higher (~38 psu) throughout most of the recorded last glacial period (32.5–15 ka). This high salinity together with generally lower SSTs suggests a period of sustained weaker summer or stronger winter monsoons. The deglacial warming is associated with rapid reorganization of monsoons and is reflected in decreased salinity to a modern level of ~ 36.5 psu, within a period of ~5 kyr. This indicates intensification of summer monsoons during cold to warm climate transition.  相似文献   

8.
陕西富平地区上奥陶统赵老峪组发育等深流沉积。以实测剖面、岩石光面、薄片资料以及地球化学资料为基础,结合前人研究成果,对赵老峪组等深积岩类型、层序以及等深流沉积发育的影响因素进行了分析。研究认为: (1)赵老峪组发育灰泥等深积岩和粉屑等深积岩2种类型,识别出由单一的灰泥等深积岩以及灰泥等深积岩与粉屑等深积岩组成的2种等深积岩层序;(2)等深流水团温度越低,盐度越高,则等深流强度越大;(3)等深流水团水温由高变低、再变高,盐度由低变高、再变低,可能造成了等深积岩层序由细变粗、再变细;(4)古水深变大、古气候变干热、古盐度变低有利于等深流和等深流沉积的发育。  相似文献   

9.
根据2007年7月23～28日厦门-泉州近岸海域表层温、盐度31个密集断面走航观测结果,结合同期卫星遥感海表温度(SST)数据和潮汐资料,分析该海域表层温、盐度的分布,并采用非等间隔数据的谱分析方法研究温、盐度的变化特征.结果表明:①九龙江冲淡水的影响可延伸到围头、深沪近岸海域,表现为明显的表层盐度锋存在;但晋江冲淡水对调查海域的影响较弱.②在该调查海域,潮汐对表层温、盐度的分布和变化有一定的影响,靠近厦门湾口一端的围头、深沪附近海域尤为突出.谱分析结果显示,该段的盐度变化与潮汐涨落在周期上比较一致.③调查期间,表层温度变化呈逐渐升高的趋势,而且具有明显的周日变化特征.④围头近岸表层存在一个低温高盐水区域,且位置随潮汐有所变动.  相似文献   

10.
Sharm Obhur is a narrow coastal inlet about 10 km long. The maximum depth at the entrance is about 35 m, which decreases gradually towards the head. Nine field trips were conducted for hydrographic survey in the Sharm during April 2015–January 2016 covering pre-summer transition, summer, pre-winter transition and winter seasons. In each trip, eight stations along the central axis of the Sharm were occupied for the measurement of temperature and salinity. In addition, an Acoustic Doppler Current Profiler (ADCP) mooring was deployed near the entrance (at station 2) during 18 February–26April 2015. The vertical structures of temperature and salinity show two distinct layers—a relatively low saline surface layer and a high saline bottom layer. The thermohaline properties increase from the entrance towards the head in all the seasons except for a slight decrease in temperature during December. Near the head, the observed maximum temperature and salinity are 33.22 °C (August) and 40.36 psu (April), respectively, while the observed minimum temperature and salinity are 25.05 °C and 38.97 psu, respectively, during January. The water exchange between the Sharm and the Red Sea shows two-layer structure, with a surface inflow and a deep outflow which is typical of basins where evaporation exceeds precipitation. The pressure gradient generated by the increasing density towards the head pushes the relatively low saline surface water from the Red Sea to the Sharm with a gradient in surface salinity influenced by the evapouration and heat exchange. Near the head, it sinks and returns as a deep water flow. The estimated flushing time of the Sharm varies between 7 and 12 days with an average of 9.5 days.  相似文献   

11.
The salinity of interstitial water (i.e., the salinity of the free soil water) was examined at 11 equidistant stations along a transect on a Mississippi tidal marsh dominated byJuncus roemerianus andSpartina cynosuroides. Changes in the nearby surface water (e.g., bay water) were reflected in the changes in interstitial water salinity. The salinity of interstitial water was usually higher, varying between 2.5 and 15.8‰ from February 1975 through January 1976, than the salinity of the nearby surface water which ranged from 0.0 to 11.5‰. Following a long period of high salinity in the bay and sound (exceeding 14‰), the salinity of the interstitial water increased to a maximum of 16.8‰ in October. The salinity increased as the distance of the sampling station from the source of the flood water increased. Mean interstitial wate salinity across the marsh studied was within 10‰ which did not seem to influence the marsh plant zonation occurring on the marsh.  相似文献   

12.
土体含盐特征是研究环境演化、工程地基基础设计和农业开发的重要参考指标。通过采集长江河口地区土样907件并对土体盐分进行测试,得到土体易溶盐8大离子含量和pH值。根据测试结果对研究区100 m以浅土层含盐特征进行系统分析。研究结果表明:各土层含盐量介于0.028%~1.226%之间。全新世土体随着深度的增加,土体含盐量呈增加趋势。含盐量最大值出现在如东组下段4-1层(埋深约26 m)淤泥质粉质黏土,盐分主要为NaCl。含盐量最小值出现在滆湖组下段的7~2砂层(埋深约81 m),其中HC03-离子含量最高,其次为Cl-与Na+。深部土层(滆湖组)含盐量有所降低,黏性土含盐量一般大于砂土。各土层ESR(交换性钠)值均大于当地地表淡水SAR(钠吸附比)值,ESR最大值为当地地表淡水SAR值的47.7倍,最低值也为当地地表淡水SAR值的2.7倍,说明土体中可交换Na含量高。100 m以浅地层含盐特征受晚更新世晚期海侵和全新世海侵控制,土体盐分主要为NaCl,其主要来源为海水浸渍或浸染。更新世土层为陆相沉积,但受晚更新世晚期海侵与全新世海侵浸染,土体含盐量较高。如东组下段和中段地层为三角洲相沉积,受长江和海侵共同作用,盐渍土广泛分布;如东组上段土层为陆相沉积,土体已普遍脱盐,HC03-离子含量最高。土体中Cl-含量对混凝土结构中的钢筋腐蚀性较大,特别是4-1淤泥质粉质黏土层,具有弱腐蚀性等级以上的土体占比高达99%,要做好基础防腐蚀工作。如东组上段的2-1和2-2土层(浅表土层)碱性较大,对农业和工程建设影响最大,需添加改良剂进行土体改良。  相似文献   

13.
靳潇  杨文  孟宪红  雷乐乐 《岩土力学》2019,40(4):1449-1456
根据冻土中未冻水成因的本质——带负电黏土颗粒表面的扩散层中阳离子溶液特殊分布,依据基于静电场泊松方程与静电荷玻尔兹曼分布的双电层理论,推演出了未冻水含量理论公式,比较分析未冻水含量观测值拟合的经验公式,发现两者形式非常一致,经验公式实质为理论公式的简化。依据此理论,清晰地描述了冻土颗粒表面未冻水的结构特征及成因,定量分析了土壤类型、含盐度、温度对未冻水含量的影响;得出当土壤盐溶液浓度小于某一阈值时,盐渍度变化对未冻水含量的影响可以忽略,即不同类型常规（低含盐度）冻土,双电层结构几近相同,指数形式公式适用于所有常规冻土的未冻水含量;土壤类型通过比表面积影响着未冻水含量,在同等温度下,土壤中黏土颗粒越多,比表面积越大,未冻水含量越多;结合实测资料给出适用于不同类型冻土未冻水含量理论计算的参数值,随后通过两种已有的经验公式对计算结果进行了验证,证实了该理论公式的可行性。  相似文献   

14.
The studied area is in the Algerian Northeast. A number of interacting factors at the site are able to modify salinity. The main influences are: (1) The lithology, (2) Fedzara Lake, (3) marine waters, and (4) a prolonged drought. (1) The lithology is very clearly delineated by the outcrop of metamorphic formations (gneiss, marbles, micaschists, and quartzites) and sedimentary formations (limestones, clay, sandstones, and sands). All these formations can influence the chemical composition of waters. (2) Fedzara Lake evacuates its salted waters via the Wadi Meboudja, which connects with the Wadi Seybouse and the phreatic surface. These lake waters might induce changes in salinity. (3) The marine waters represent the third source of salinity change. Over-pumping of water from wells and drillings can cause an imbalance to the fresh–salted water interface. (4) The effects of a local prolonged drought of more than 10 years may increase water salinity. Over-pumping to augment water supply generates a fall in water levels and the drier atmosphere increases evapotranspiration. Both may contribute to increased salinity. Results of water analysis were used to observe the evolution of these various factors.  相似文献   

15.
Significantly high abundant methyl-MethylTrimethylTridecylChromans (MTTCs) have been detected in aromatic hydrocarbon fractions in crude oils from the Jizhong Depression and Jianghan Basin. The distribution of these compounds is dominated by methyl-MTTC and dimethyl-MTTC series, which indicate diagenetic products of a hypersaline depositional environment in the early stage and show a low degree of methylation. The occurrence of significantly high abundant methyl-MTTC depends mainly on good preservation conditions with a strongly reductive, hypersaline and water-columned depositional environment and subsequent non-intensive diagenetic transformations. The stable carbon isotopic compositions of the methyl-MTTCs and dimethyl-MTTCs in two samples are far different from the stable carbon isotopic composition of C30 hopane of apparent bacteria biogenesis (up to 4.11‰ and 5.75‰, respectively). This obviously demonstrates that the methyl-MTTC and dimethyl-MTTCs cannot be of bacteria origin, which is different from the previous point of view about non-photosynthetic bacteria products or possible bacteria-reworked products. On the contrary, the stable carbon isotopic compositions of methyl-MTTC and dimethyl-MTTCs in the two samples were similar to that of the same carbon-numbered n-alkanes (nC27-nC28-nC29), which indicates that they share the same source origin. Especially in the crude oil from the Zhao61 well, stable carbon isotopic compositions are also similar to that of the same carbon-numbered steranes with ααα-20R isomer (mostly less than 0.4‰). In consideration of the results of previous studies on saline lake ecological sedimentation, the authors hold that the methyl-MTTC and dimethyl-MTTCs in the saline lake sediments should be of algal biogenesis origin.  相似文献   

16.
贾国东  谢宏琴 《地学前缘》2006,13(1):199-204
氧同位素剩余值(Δδ)是指从浮游有孔虫氧同位素中扣除温度和全球冰量效应后得到的剩余值,它一般被用作海水古盐度变化的代用指标。文中给出了南海北部三个柱状样在氧同位素6期至5期(MIS6-5)和MIS2-1期间Δδ的变化曲线。末次冰期与全新世和倒数第二次冰期与末次间冰期的对比表明,Δδ在冰期比随之而来的间冰期低。冰期海平面下降和海岸线前移可能是冰期Δδ及盐度相对降低的原因。但在定量了解海平面下降、珠江口前移及现代盐度的分布情况后,笔者否定了海平面下降对Δδ变化的主要影响。因此,冰期南海地区降水相对增大和气候变湿可能是导致冰期Δδ偏低的主要原因。末次间冰期与全新世相比,Δδ明显增大,表明海水盐度增加。这可能与末次间冰期期间由于表层海水温度较高,厄尔尼诺事件频繁和海水蒸发量较大有关。  相似文献   

17.
Changes in the dentition of Mactra species from the Sarmatian of the Borisphenian Gulf are related to changes in the salinity of the waters. With increasing fresh water, the upper lateral teeth on the right valve become weaker and the lower more pronounced, and the dental plates of Tooth 2 on the left valve become closer and intergrade. With increased salinity, the opposite morphologic changes occur. The variability of hinge characteristics increases with an increase of fresh water, and decreases with increasing salinity. The entire molluscan fauna changes in the section, reflecting changes in the salinity. The salinity changes are related to climatic changes, documented by paleobotanical evidence from surrounding areas.—T. G. Gibson  相似文献   

18.
松辽盆地嫩江组一段和二段发育的油页岩是极其优质烃源岩, 生物标志化合物参数指示油页岩母质生源主要来自于水生生物其繁盛受温湿气候和湖泊富营养化控制.岩石学、元素地球化学、生物标志化合物等参数表明, 高盐和缺氧条件下的稳定水体分层是嫩一段油页岩沉积时期有机质保存的主控因素, 而嫩二段油页岩沉积时期水体盐度分层明显减弱, 此时藻类个体增大和孤立藻数量增多条件下的高生物生产力有利于有机质富集.为揭示嫩江组不同沉积环境下油页岩发育的控制因素, 建立了嫩一段油页岩沉积时期保存条件控制和嫩二段油页岩沉积时期生物生产力控制的两种有机质富集模式, 这对含氧淡水大型陆相湖泊的有机质富集成因探讨具有重要借鉴意义.   相似文献   

19.
This study focused on the warm pool-cold tongue confluence region (WCCR) in the central tropical Pacific Ocean where the warm and fresh water from the warm pool encounters with cold and saline water from the cold tongue. The WCCR is characterized by strong surface salinity front, shallow mixed layer and thick barrier layer. The WCCR is the key area for the development of different types of El Ni?o, and also the area with significant systematic bias in climate models. In order to reveal what role the structure and variability of salinity will play in the ocean dynamic and thermal conditions, and the cycle of the ENSO, a key project was approved by the National Natural Science Foundation of China (NSFC) in July, 2017. The key scientific issues that will be addressed in the project are as follows: ①to depict the three-dimensional structure and variability of salinity in the WCCR; ②to reveal the mechanism for the variability of salinity front and barrier layer; and ③to illustrate the main processes that control the impact of salinity on the upper-ocean variation in the tropical Pacific and the cycle of the ENSO. The present study will improve our understanding of the tropical ocean dynamics and ENSO dynamics, and will enhance the prediction skill of the ENSO.  相似文献   

20.
Estimates of water quality variables such as chlorophylla concentration (Chl), colored dissolved organic matter (CDOM), or salinity from satellite sensors are of great interest to resource managers monitoring coastal regions such as the Florida Bay and the Florida Shelf. However, accurate estimates of these variables using standard ocean color algorithms have been difficult due to the complex nature of the light field in these environments. In this study, we process SeaWiFS satellite data using two recently developed algorithms; one for atmospheric correction and the other a semianalytic bio-optical algorithm and compare the results with standard SeaWiFS algorithms. Overall, the two algorithms produced more realistic estimates of Chl and CDOM distributions in Florida Shelf and Bay waters. Estimates of surface salinity were obtained from the CDOM absorption field assuming a conservative mixing behavior of these waters. A comparison of SeaWiFS-derived Chl and CDOM absorption with field measurements in the Florida Bay indicated that although well correlated, CDOM was underestimated, while Chl was overestimated. Bottom reflectance appeared to affect these estimates at the shallow central Bay stations during the winter. These results demonstrate the need for new bio-optical algorithms or tuning of the parameters used in the bio-optical algorithm for local conditions encountered in the Bay.  相似文献   

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