羌塘盆地双湖地区曲色组冷泉碳酸盐岩及其地质意义          下载免费PDF全文

夏国清  伊海生 《沉积与特提斯地质》2015,(1):68-75

羌塘盆地南部双湖地区曲色组地层发育大量碳酸盐岩结核,这些结核多呈丘状、椭球状、透镜状、似层状、脉状、树枝状产出。其物质组分主要为泥微晶碳酸盐矿物,少量粘土矿物、石英及草莓状、半自形黄铁矿等。草莓状黄铁矿平均粒径在5.0μm左右,内部可见葵花状构造。发育凝块状、气孔状和渗漏孔等特殊构造。产双壳类、菊石类、蠕虫状或树枝状生物及超微生物化石,生物密度极高。碳同位素明显负偏,硫同位素则明显正偏,其特征与现代海底天然气水合物的渗漏、释放所形成的冷泉碳酸盐岩机理一致,因而推测为古代海底天然气渗漏喷发形成。大量海底天然气泉口的存在,可能表明羌塘盆地双湖地区早侏罗世大洋缺氧事件与海底天然气水合物喷发存在极大关联。  相似文献   

珠江流域碳酸盐岩与硅酸盐岩风化对大气CO_2汇的效应   总被引：6，自引：0，他引：6  

覃小群  蒋忠诚  张连凯  黄奇波  刘朋雨 《地质通报》2015,34(9):1749-1757

对珠江流域11个测站的河水1个水文年4次取样进行水化学和同位素测试分析,揭示无论是碳酸盐岩区还是硅酸盐岩区,岩石风化均使河流的离子成分以HCO3-、Ca2+、Mg2+为主,碳酸盐岩风化溶蚀速率和由碳酸盐岩风化溶蚀引起的大气CO2消耗量分别为27.60 mm/ka和540.21x103mol/(km2·a-1),是硅酸盐岩风化速率和由硅酸盐岩风化引起的大气CO2消耗量的10.8倍和6.7倍,说明碳酸盐岩风化是流域碳汇过程及效应的主体。由于有利的水热条件和高的碳酸盐岩面积比例,珠江流域平均岩石风化速率和由岩石风化作用引起的大气CO2消耗量分别为30.15mm/ka和620.36×103mol/(km2·a-1),为全球60条河流平均值的2.6倍。  相似文献   

腕足壳体与碳酸盐岩全岩中碳、氧、锶同位素差异   总被引：1，自引：0，他引：1  

程红光  李心清  黄思静  王兵  程建中 《沉积学报》2015,33(1):60-66

利用碳酸盐岩中的地球化学信息反演是研究地质历史时期古环境、古气候变化的一种常用手段.上世纪八十年代前,学术界一直将碳酸盐岩全岩样品作为研究对象.近年来,腕足化石壳体引起了科学家的注意,认为相比碳酸盐岩全岩样品,腕足壳体能更为完好地保存原始的地球化学信息.研究通过对比四川龙门山泥盆纪腕足化石和碳酸盐岩全岩样品中碳、氧、锶同位素(黄思静、卢长武等人数据),发现腕足化石中氧同位素明显高于碳酸盐岩全岩;但碳、锶同位素基本一致.上述结果表明:相比腕足化石,碳酸盐岩全岩样品蕴含的地球化学信息虽有所差异,但在大多数情况下,尤其是缺乏腕足化石的时期,碳酸盐岩全岩蕴含的地球化学信息照样可以反演地质历史时期的古环境变化,尤其是碳、锶同位素.  相似文献   

桂林洞穴滴水与现代碳酸钙δ18O记录的环境意义--以桂林七星岩NO.15支洞为例     

张美良  朱晓燕  吴夏  张碧云  潘谋成 《沉积学报》2015,33(4):697-705

现代洞穴动态监测的一个先决条件就是为洞穴碳酸盐(CaCO₃)沉积物-石笋的各种替代指标的解译提供可靠的依据,充分利用现代碳酸盐(CaCO₃)沉积物的各种替代指标,并与现代器测气象资料进行相互对比、并用以校正,是精确或定量解释石笋气候替代指标的关键.
经对桂林七星岩15号支洞的5个滴水点进行了长达四个水文年(2008~2011年)的大气降水、洞穴滴水、现代碳酸盐沉积物的动态监测和研究,并探讨了洞穴滴水和现代碳酸盐(CaCO₃)的δ18O与降水δ18O的相关关系.研究表明,洞穴滴水和现代碳酸盐(CaCO₃)的年平均δ18O值非常接近降水的δ18O平均值,并具有与地表降水δ18O相同的变化趋势,反映了洞穴滴水和现代碳酸盐(CaCO₃)的δ18O主要来自大气降水的δ18O,即明显受控于降水的δ18O.在4个水文年中,现代洞穴次生化学碳酸盐(CaCO₃)沉积物的δ18O值与滴水的δ18O值记录的年内(或年际)变化或多年的变化趋势基本相同,表现出明显的四高峰(δ18O低值区)四低谷(δ18O高值区)的波动变化特征,具有明显的年际、季节性变化规律,显示具有雨热同季的特点.研究结果表明洞穴滴水和洞穴现代碳酸盐(CaCO₃)沉积物的δ18O可以记录当地或洞穴上方的气候变化信号,即现代碳酸盐(CaCO₃)沉积物的δ18O主要作为夏季风强度或降雨量的替代指标.  相似文献   

浮游有孔虫标准化壳体重量测试方法及在西太平洋的应用          下载免费PDF全文

安佰正  李铁刚  孙晗杰  熊志方  常凤鸣 《地球科学》2015,40(5):881-889

使用标准化壳体重量法和传统壳体重量法分别对中国南海(South China Sea,简称SCS)站表层沉积物和MD06-3052岩心沉积物样品进行了测试,获得了浮游有孔虫种属Globigerinoides ruber(G. ruber)的标准化壳体重量和传统壳体重量.通过对SCS站表层沉积物中G. ruber标准化壳体重量与传统壳体重量的比较,认为在该海域使用标准化壳体重量替代性指标能够更好的排除壳体粒径的干扰.通过对MD06-3052岩心中G. ruber标准化壳体重量与南极Vostok冰心的CO₂浓度(pCO₂)曲线进行对比,认为标准化壳体重量方法能够较好的反映出表层海水[CO₃2-]的变化.标准化壳体重量方法快速简便,指示性好,在探讨晚更新世以来表层海水在全球碳循环的重要作用中,是一个很有潜力的指标.   相似文献   

使用纳米碳酸钙降低低孔低渗煤层气储层伤害          下载免费PDF全文

谷穗  蔡记华  常德武  维克多·费多罗维奇·契霍特金 《地球科学》2015,40(6):1093-1100

传统暂堵剂难以封堵低孔低渗煤层气储层中的大量纳米级别孔隙.通过煤岩显微观测、钻井液基本性能测试、泥饼清除实验、煤岩孔隙分布实验和气体渗透率实验,探讨了纳米碳酸钙降低低孔低渗煤层气储层伤害的效果.结果表明:纳米碳酸钙材料只有在水溶液中保持纳米级的分散状态,才可能对低渗煤岩起到暂堵作用;基于纳米碳酸钙的可降解钻井液既能封堵低孔低渗煤岩中微米级别孔隙,也能封堵其中的纳米级别孔隙;经过生物酶和稀盐酸双重解堵后,煤岩渗透率恢复值达77.17%~97.98%,储层保护效果好;煤岩孔隙分布实验可以在纳米尺度上研究纳米材料对低孔低渗储层的暂堵效果.研究成果可为纳米碳酸钙在低孔低渗煤层和页岩钻完井过程中的应用奠定良好技术基础.   相似文献   

Emerging coral diseases: a temperature‐driven process?          下载免费PDF全文

Aaron W. Miller  Laurie L. Richardson 《Marine Ecology》2015,36(3):278-291

In the last few decades there has been a surge in research focusing on coral disease. While climate change, specifically rising sea surface temperature, has been proposed as a major and growing driver of the emergence of marine diseases, to date a solid connection between disease epizootics and elevated sea surface temperature has not been established. However, a wealth of data now exists, compiled from many different perspectives, that may support such a connection. In this work we provide a comprehensive review targeting one coral disease, black band disease, that spans the infection process, pathobiology, and epizootiology, and links specific mechanisms of the disease process to increasing temperatures. This temperature‐driven pattern of infection can be expanded to include similar processes associated with other temperature‐related coral diseases. The conclusions presented here are based upon the results of many studies using a diverse suite of approaches that have been synthesized to argue that the emergence and continuing spread of black band disease is linked to warming sea surface temperatures. In summary, as global ocean temperatures increase seasonally and over decades, the environment shifts to become more favorable for the growth of potentially pathogenic microorganisms endemic to the immediate environment of the reef. The increase in the relative number of potential pathogens in the microbial community produces microenvironments conducive to the growth of other potential pathogens, leading to infection by a polymicrobial consortium. This consortium is easily perturbed by a (seasonal) temperature decrease, but remains associated with the coral host and can be reactivated with a subsequent seasonal increase in temperature, resulting in a cycle of temperature‐dependent disease emergence.  相似文献   

Low calcification rates and calcium carbonate production in Porites panamensis at its northernmost geographic distribution          下载免费PDF全文

Carlos Orión Norzagaray‐López  Luis Eduardo Calderon‐Aguilera  José Martín Hernández‐Ayón  Héctor Reyes‐Bonilla  Juan P. Carricart‐Ganivet  Rafael Andrés Cabral‐Tena  Eduardo Francisco Balart 《Marine Ecology》2015,36(4):1244-1255

Porites panamensis is a hermatypic coral present in the eastern Pacific Ocean. Skeletal growth parameters have been reported, but studies of the relationship between annual calcification rates and environmental controls are scarce. In this study, we investigated three aspects of the annual calcification rates of P. panamensis: growth parameters among three P. panamensis populations; the sea surface temperature as a calcification rate control spanning a latitudinal gradient; and calcium carbonate production among three sites. Growth parameters varied among the sites due to the colony growth form. Massive colonies in the north showed a higher calcification rate than encrusting colonies in the south (mean: 1.22–0.49 g CaCO₃ · cm^?2 · yr^?1), where variations in calcification rates were related to growth rate (0.91–0.38 cm · yr^?1) rather than to skeletal density differences (overall mean ± SD, 1.31 ± 0.04 g CaCO₃ · cm^?3). Our results showed a positive linear relationship between annual calcification rates and sea surface temperatures within these P. panamensis populations. Differences were related to distinct oceanographic environments (within and at the entrance of the Gulf of California) with different sea surface temperature regimes and other chemical properties. Different populations calcified under different environmental conditions. Calcium carbonate production was dependent upon the calcification rate and coral cover and so carbonate production was higher in the north (coral cover 12%) than in the south (coral cover 3.5). Thus, the studied sites showed low calcium carbonate production (0.25–0.43 kg CaCO₃ · m^?2 · yr^?1). Our results showed reduced calcification rates, regional temperature regime control over calcification rates, different growth forms, low coral cover and low calcium carbonate production rates in P. panamensis.  相似文献   

Microbial biomass response to different quantities and sources of organic matter in Brazilian coastal sediments          下载免费PDF全文

Cintia O. Quintana  Paula C. de Moraes  Marcos Y. Yoshinaga  Stuart G. Wakeham  Paulo Y. G. Sumida 《Marine Ecology》2015,36(3):766-779

This study investigates the benthic microbial responses to organic matter (OM) variations in quantity and sources in two shallow water bays (Fortaleza and Ubatuba Bays) on the SE coast of Brazil on six occasions during the year. The pelagic and benthic compartments of the bays were evaluated by: (i) nutrients and chlorophyll a (Chl a) in the water column; (ii) quantity and sources of OM in the sediment (Chl a, total organic carbon and total nitrogen and lipid biomarker composition); and (iii) microbial biomass in sediments as an indicator of active benthic response. Although there were changes in water‐column nutrients during the year, Chl a was fairly constant, suggesting a regular supply of microalgae‐derived OM to the sea bottom. Based on the composition of lipid biomarkers in sediments, OM sources were classified as mostly marine and with high contributions of labile (microalgae‐derived) OM. Labile OM composition varied from diatoms in the summer to phytoflagellates in the winter and tended to accumulate in areas protected by physical disturbances in one of the bays. Microbial biomass followed this trend and was 160% higher in protected than in exposed areas. This study suggests that the coupling between labile OM and benthic microbial biomass occurs primarily in protected areas, irrespective of the time of the year. Since meio‐ and macrofaunal assemblages depend upon secondary microbial production within the sediments, this coupling may have an important role for the benthic food‐web.  相似文献   

西沙群岛生物碳酸盐的成因和沉积:来自活体仙掌藻的证据   总被引：1，自引：0，他引：1  

许红  赵新伟  Gregor P. Eberli  LIU Xinyu  朱玉瑞  蔡瑛  LUO Wei  闫桂京  张柏林  魏凯  施剑 《海洋学报(英文版)》2015,34(4):62-73

A recent island survey reveals that the Xuande Atoll and the Yongle Atoll in the Xisha Islands can be classified into one of two systems: the depleted atoll system and growth atoll system; the survey also indicates that the decreased area of several shoals is an unbearable burden for the Xisha Islands, of which the largest island area is 2.13 km2 and the minimum elevation is 1.4 m. According to a survey on the ecological characteristics of Halimeda in the Laolongtou breaker zone of Shidao Island in the Xisha Islands, the green and white living Halimeda are collected,the isotopic ages of 14 C contained in the Halimeda are shown to be 27 years and 55 years, respectively, and carbonate mainly occurs in five types, i.e., luster, segment, sand, sand grain, and marl in the formation. The Halimeda segments mainly provide the carbonate sediments of long-term biogenic deposits in the reef environment and the annual productivity per area is 60–100 g/m2; the characteristics of the microstructure of the Halimeda are analyzed, the aragonite raphide carbonate is deposited and enriched in the cortexes, medullas and cysts, and the Halimeda generally contain major elements such as C, O, Ca, Cl, Mg, K, Na, S and Al, and are rich in trace elements such as tellurium(Te), rhodium(Rh) and strontium. It is believed that the Halimeda grow slowly,including the biotic community of reef corals in the reef areas, thus they possess an environmental remediation capacity, but it takes much time to remedy the environment, and it is necessary to make the law to protect the diversity and vulnerability of the Xisha marine ecology, the ecology of the reef community and the island environment in a scientific way. As indicated in the survey, under the background of global warming and sea-level rise, the discovery of large amounts of Halimeda in the Laolongtou sea area is significant for the natural increase of the depleted atoll system of the Xuande Atoll, while the Halimeda segments represent the primary form of the fossil Halimeda, of which the species can be identified and preserved in great numbers under geological conditions. The Miocene was discovered in large amounts in the Xichen-1 well, therefore the study on the characteristics and mechanism of Halimeda carbonate sediments plays a pivotal role in the formation and construction of organic reefs in the South China Sea as well as oil and gas exploration.  相似文献