生命起源、早期演化阶段与海洋环境演变

近年的研究表明,地球生命可能起源于距今39~36亿年之间。除了碳元素以外,水、氮、氢、磷等元素也是生命起源的必备条件,黏土矿物和金属硫化物是有机质合成的重要催化剂,有热液活动的碱性热水环境是最有利生命发生的孵化场。自原核生物在约3.5 Ga出现之后,生命就一直表现为与环境的协同进化关系。大气圈氧化是地球史上最重大的地质事件之一,它不仅改变了地球表层环境条件、加速了表生地质过程和新矿物的产生,而且改变了海洋化学条件和元素循环。大气圈氧化事件的根本在于产氧蓝细菌的出现,元古宙中期海洋化学性质的整体转换也与微生物过程密切相关。新元古代多细胞生物的繁盛和末期后生动物的出现及其在寒武纪初期的快速多样化是生物圈演化的重大飞跃。这个过程也与海洋氧化增强及其导致的海洋化学变化密切相关,其中硫化水域消失和减弱以及海水中微营养元素可得性增加可能是重要因素,这也与微生物过程直接相关。     

Spatiotemporal variations of benthic macrofaunal community in the Xiamen Amphioxus Nature Reserve, eastern South China Sea

In order to realize the spatiotemporal variations of benthic macrofaunal communities at the "Amphioxus Sand"habitat, six surveys including four seasons and three consecutive summers(i.e., 2014, 2015 and 2016) were conducted in two core sites, i.e., Huangcuo(HC) and Nanxian-Shibaxian(NX), in the Xiamen Amphioxus Nature Reserve in China. A total of 155 species of macrofauna were recorded, therein, polychaetes were dominant in terms of species number and density. Significant spatiotemporal variations of macrofaunal communities were observed. The density of polychaetes and the biomass of molluscs in the HC site were higher than those in the NX site. Macrofauna were more diverse and abundant in the cold seasons(winter and spring) than that in the warm seasons(summer and autumn). The annual variations of macrofaunal communities may be attributed to the changes in sediment texture among the three years of the survey. The variations in macrofaunal communities were mainly related to the proportion of polychaetes within the community. In addition, the density of amphioxus(include Branchiostoma japonicum and B. belcheri) was negatively correlated to that of polychaetes, bivalves, and crustaceans. Amphioxus was less likely to be found in the sediments with higher silt and clay content. Five biotic indices including Margaref's richness index(d), Peilou's evenness index(J′), Shannon-Wiener diversity index(H′),AMBI and M-AMBI were calculated in the present study. AMBI seems suitable in assessing benthic health at the"Amphioxus Sand" habitat, and a potential risk of ecological health in Xiamen Amphioxus Nature Reserve should be aware.     

Assessing benthic ecological status in coastal area near Changjiang River estuary using AMBI and M-AMBI

The Changjiang （Yangtze） River estuary has been subject to a variety of anthropogenic pressures in recent decades. To assess the ecological health of the coastal benthic ecosystem adjacent to the estuary, three surveys were conducted in 2005, 2009, and 2010. The AZTI＇s Marine Biotic Index （AMBI） and multivariate-AMBI （M-AMBI） were used to analyse the benthic ecological status of this coast. The AMBI indicate that the ecological status of the coast adjacent to the Changjiang River estuary was only slightly degraded in all 3 years. In contrast, the M-AMBI indicated that the ecological status was seriously degraded, a result that is most likely due to pollution and eutrophication induced by human activities. The assessment of the coast＇s ecological status by the AMBI was not in agreement with that of the M-AMBI at some stations because of lower biodiversity values at those sites. The analysis of the two indices integrated with abiotic parameters showed that the M-AMBI could be used as a suitable bio-indicator index to assess the benthic ecological status of the coast adjacent to the Changjiang River estuary. The reference conditions proposed for the coast of the Changjiang River estuary should be further evaluated in future studies. Designation of local species could also provide an important reference for Chinese waters. To improve the reliability of AMBI and M-AMBI, further research into the ecology of local species is required to understand their arrangement in ecological groups.     

A Marine Biotic Index to Establish the Ecological Quality of Soft-Bottom Benthos Within European Estuarine and Coastal Environments

In this paper, a marine Biotic Index (BI) for soft-bottom benthos of European estuarine and coastal environments is proposed. This is derived from the proportions of individual abundance in five ecological groups, which are related to the degree of sensitivity/tolerance to an environmental stress gradient. The main difference with previously published indices is the use of a simple formula that produces a continuous Biotic Coefficient (BC) – which makes it more suitable for statistical analysis, in opposition with previous discreet biotic indices – not affected by subjectivity. Relationships between this coefficient and a complementary BI with several environmental variables are discussed. Finally, a validation of the proposed index is made with data from systems affected by recent human disturbances, showing that different anthropogenic changes in the environment can be detected through the use of this BI.     

松辽盆地及周缘地区侏罗系/白垩系界线区域对比特征探讨

松辽盆地及周缘地区是白垩纪时期全球最大的陆地出露区,是开展陆相J/K界线研究的理想地区.但是,受制于盆内埋深大、盆缘露头出露不佳等原因,松辽盆地及周缘地区J/K界线发育区域及层段仍然存在较大争议.同时,对于陆相J/K界线划分与对比这样的重大疑难问题,其研究很难一步到位.总结一套影响广泛、区域对比性强的J/K界线区域对比...     

湖南桃源郝坪奥陶系五峰组顶部斑脱岩LA-ICP-MS锆石U-Pb年龄

为了认识奥陶纪-志留纪之交的火山活动及事件年龄,对湖南桃源郝坪剖面的斑脱岩进行了LA-ICP-MS锆石U-Pb定年。结果表明,五峰组顶部斑脱岩LA-ICP-MS锆石U-Pb年龄为442.2±8.1Ma,该年龄反映了扬子地区奥陶纪-志留纪之交火山活动的时代,与国际地层委员会公布的奥陶系-志留系界线年龄(443.7±1.5Ma)相一致,同属晚奥陶世。奥陶纪-志留纪之交的火山活动对于探讨晚奥陶世生物绝灭、沉积环境变化与年代地层对比具有重要的意义。     

腾格里沙漠固定沙丘结皮层藓类植物的生态功能及与土壤环境因子的关系

通过1998-2001年的野外调查,沙坡头地区固定沙丘结皮层藓类植物共3科、11属、24种,新发现 8 个本地区新记录种。人工固定沙丘仅分布有7种藓类,而自然固定沙丘包括了所有的 24 种藓类,具有较高的物种多样性,构成了复杂的苔藓植物群落。沿坡向随高度的上升,藓类植物的盖度减少,而藻类植物的盖度却有上升的趋势。自然固定沙丘藓类植物盖度明显小于围封的人工固定沙丘。人工固定沙丘随着固定年限的增加,藓类植物的生物量明显增高,不同种类藓类植物的生物量明显不同,综合盖度因素,真藓拥有该地区最大的生物量。不同类型、不同种类的藓类植物结皮厚度和株高之间都存在显著的相关性(P < 0.01)。不同固定沙丘藓类结皮土壤的总盐量、阴、阳离子总量都明显高于藻结皮和流沙,苔藓结皮中苔藓植物体内Mg/Ca率在0.50~0.98之间,结皮土壤Ca²⁺含量明显高于其他3种离子,Na⁺、K⁺离子含量较少。苔藓植物生物量与土壤磷、土壤有机质呈明显正相关(P < 0.05),土壤pH值与土壤磷含量和苔藓植物生物量呈显著负相关(P 分别为 < 0.01 和 < 0.05),表明高的 pH值显著影响土壤磷含量和植物生物量。藓类结皮土壤中的有机质、全磷、全氮、速磷、速氮含量显著高于藻结皮的含量,尤其是有机质含量,藓类结皮都超过了1%的水平,在有机质含量普遍低于1%的沙区,对维持沙丘的稳定,促进维管植物的定居和繁殖起着极其重要的作用。     

Geological Characteristics and Manifestations of Geological Processes of Sequence Boundaries and Their Vicinities

This paper discusses the geological characteristics and architectures of sequence boundaries and their vicinities and has proposed a classification scheme for the sequence boundaries, which can thus be grouped into three types and eight categories: type I includes exposed truncated surface, palaeosol surface, palaeokarst surface and exposed surface; type Ⅱ boundaries include structural transitional surface during sea-level fall and transgressive onlap surface; and type Ⅲ includes submarine erosional diagenetic diastem and event surface. A study has been made for the three major boundaries lying between the Permian and pre-Permian, the Permian and Triassic, and the Middle and Lower Triassic respectively in terms of multiple disciplines such as lithostratigraphy, biostratigraphy, magnetostratigraphy and carbon and oxygen isotopic geology. These three boundaries are ascribed to type I , typeⅡ and typeⅢ, respectively.     

应用底栖动物完整性指数评价太湖生态健康

依据2010年春季至2012年秋季,太湖32个样点的底栖动物和环境变量共11次的季节性调查结果,采用干扰程度最小系统法定义构建底栖动物生物完整性指数的参照系统,提出了确定参照系统的4个基本条件,进而按非湖心区和湖心区两个生态区分别构建太湖底栖动物完整性指数(LTB-IBI).通过对候选生物参数的分布范围筛选、判别能力分析、与理化因子的相关性和参数间的冗余分析,获得了非湖心区LTB-IBI的4个构成指数:总分类单元数、Simpson多样性指数、前3位优势单元%和BMWP指数,以及湖心区LTB-IBI的5个构成指数:总分类单元数、Simpson多样性指数、甲壳+软体分类单元数、前3位优势单元%和BMWP指数.采用比值法统一构成指数量纲,分别构建了非湖心区和湖心区LTBIBI指数,评价太湖水生态健康的等级.2010-2012年,太湖生态健康总体上呈现逐步提升的趋势.影响太湖底栖动物完整性的重要环境变量是水体中的氮含量.研究表明,连续观察数据可较大程度上提高太湖LTB-IBI指数的可靠性和评价结果的合理性.     

西秦岭三叠纪沉积盆地演化

笔者在概要介绍了西秦岭三叠系的分布与建造特征、沉积环境、生物区系特征，三叠系的构造形变特征以及与相邻地质体的形变差异性的基础上，论述了该区在中三叠世短暂的地质发展演化过程中，由扬子型稳定浅海碳酸盐岩沉积快速演变为特提斯型深海巨厚复理石沉积的演化历史，讨论了特提斯型裂陷槽由裂开接受沉积—关闭结束沉积。快速关闭并褶皱形变这一完整演化过程中的构造特征，总结了三叠系的盆地演化规律。