STONE‐BANKED LOBES AS A PRODUCT OF MILD FREEZE–THAW ACTION: AN EXAMPLE FROM WESTERN TASMANIA,AUSTRALIA

This paper interprets a stone‐banked lobe on the upper western face of Mt Rufus, at an altitude of 1380 m in western Tasmania, Australia. The morphology of the deposit resembles that of a solifluction lobe. Field observations show vertical and downslope movement of pebbles, cobbles and small boulders over a single winter season. The movement is largely related to frost pull (10–15 cm) and shallow freeze–thaw processes promoting the downslope (up to 50 cm yr^–1) creep of material and the accumulation of coarse clasts at the lobe riser. The climate of Mt Rufus is strongly maritime and this is reflected in the limited duration and depth of penetration of frozen ground at this site during the 2013 winter. Despite the relatively mild climatic conditions, freeze–thaw processes are clearly the dominant geomorphic force operating at the site. These findings support observations of active stone‐banked lobes on sub‐Antarctic islands where intense freezing is absent. Both there and at Mt Rufus, movement is dominated by freeze–thaw processes operating in the upper c. 20 cm of the regolith. These are typical landforms of marginal freeze–thaw settings.     

南海北部亚热带滨珊瑚对低温的耐受能力

Marginal scleractinian corals growing at their latitudinal limits should be quite sensitive to variations in winter sea surface temperatures(SSTs). An extreme cold event occurring in early 2008 offered a unique opportunity to examine the effect of cold-water anomalies on Porites lutea corals and their physiological tolerance and acclimation in the subtropical northern South China Sea(NSCS). Besides in-situ observation, a subsequent aquarium-based experiment was designed for reproducing the chilling process and a 50-year-long Sr/Ca ratio profile from two P. lutea skeletal slabs was analyzed for reconstructed the historical annual minimum SSTs which ceased Porites calcification. The 2008 low-temperature anomaly caused the minimum daily mean SSTs dropped below 13°C in the Daya Bay. The stress symptoms displayed by local P. lutea colonies included polyp retraction, reduced coloration and pale, but none showed tissue sloughing. The ability of P. lutea to survive implied its tolerance of extreme low temperatures. Here we suggest a model on the tolerance of high-latitude Porites under low-temperature stresses, which is when SSTs drop below 18°C, Porites corals contract their tentacles(losing heterotrophic capability), then cease calcification(reducing energy consumption), and meanwhile maintain relatively high levels of zooxanthellae density(sustaining host's life via photosynthetic capacity of symbiotic zooxanthellae). This study revealed remarkable acclimatization of P. lutea corals to low temperature extremes. This acclimatization is beneficial for Porites corals in the NSCS to expand their living ranges towards the higher-latitude areas and have the potential to be the incipient reef former.     

Carbonate sediments of Elizabeth and Middleton Reefs close to the southern limits of reef growth in the southwest Pacific

Elizabeth and Middleton Reefs are atoll-like structures that have developed on top of volcanic edifices and are close to the southern environmental limit of reef development in the southwest Pacific. Reef morphology and vertical accretion rates during the Holocene appear similar to those on other more tropical reefs. Sediment samples were collected from the lagoon of both reefs and around the flanks of Middleton Reef. A distinctly chlorozoan assemblage was observed with coral, molluscs, Halimeda, coralline algae and foraminifers being the dominant sediment constituents. Lagoon sediment samples show little variation within or between reefs, lacking the concentric zonation characteristic of larger atolls. Samples collected from the flanks of Middleton Reef, and subsurface material from vibrocores, differ compositionally from the surficial lagoon sand and were typically more tropical in character. A comparison of the sediment constituents from these reefs with those of samples from within a fringing reef and from the shelf around Lord Howe Island, further south, indicated regional patterns in sediment composition. Halimeda rapidly decreased in abundance with increased latitude, and appeared confined to deeper water, whereas coralline red algae increased significantly. The rapid change in these major sediment contributors is coincident with the general decrease in coral growth rates with latitude. This reinforces the notion that the latitudinal limit of reef development is constrained by factors other than coral growth alone.     

南海典型珊瑚礁生态系统健康评价方法研究

本研究基于系统复杂性原理, 提出了南海典型珊瑚礁生态系统健康评价方法——组织力及系统功能评价法。该方法的评价框架包括珊瑚礁生态系统结构及功能、珊瑚礁生态系统与其他海洋生态系统间关系、与人类社会生态系统间关系、珊瑚礁生态系统发展制约因素等四大模块; 评价指标体系分为目标层、准则层、因素层、要素层等6个层级共计67个指标。同时, 本研究系统地提出了珊瑚礁生态系统健康评价的流程, 提高了珊瑚礁健康评价工作的规范性和时效性。应用组织力及系统功能评价法对2011—2018年西沙群岛珊瑚礁生态系统进行了健康评价, 结果显示自2011年起健康指数年均下降2.3%~2.4%, 除2012年、2015年健康指数稍有回升外, 其余年份均呈下降走势, 整体评价为亚健康状态。根据七连屿周边岛屿的实地考察和居民生活问卷调查结果, 2006—2008年的渔业发展、2012年的海星泛滥和2014—2015年的岛礁建设均对珊瑚礁生态系统造成了较大影响, 使10年内渔业产量下降了50%~80%。这与应用组织力及系统功能评价法的评价结果相吻合, 侧面验证了该评价方法的科学性和可行性。     

中国南海软珊瑚附生真菌Acremonium sp. SCSIO41216的次级代谢产物研究

采用硅胶柱层析色谱法、中压正相柱层析色谱法、中压反相柱层析色谱法以及半制备高效液相色谱法对中国南海软珊瑚来源真菌Acremonium sp. SCSIO41216的大米发酵产物进行分离纯化, 并使用核磁共振、质谱等波谱学方法, 结合其理化性质及文献数据鉴定了7个单体化合物结构: fischexanthone(1)、sydowinin A (2)、(22E)-5α,8α-epidioxyergosta-6,22-dien-3β-ol (3)、16-O-去乙酰基夫西地酸内酯(4)、环-(S)-脯氨酸-(R)-亮氨酸(5)、环-(S)-脯氨酸-8-羟基-(R)-异亮氨酸(6)和环(L)-脯氨酸-(L)-苯丙氨酸(7)。化合物1—7均首次从海洋软珊瑚来源的枝顶孢属真菌(Acremonium sp.)中分离获得。     

泥岩、砂岩石方开挖施工工法的创新与研究

通过新疆小山口水电站基础石方开挖工程实践,对当地泥岩和砂岩地质物理特性进行了深入研究,对其石方开挖工法进行了大胆创新,提出了纯机械法施工工法,分别从工程施工质量、进度、安全和成本等多个方面与传统的钻爆法进行比较,结果表明：新施工工法县有技术先进性和经济合理性,可以在今后的施工中使用和椎广。     

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南海北部滨珊瑚生长序列的X光数字图像分析和环境参数的相关分析表明，表层海温是滨珊瑚生长的首要气候因子，表层海温的季节性变化决定着滨珊瑚骨骼密度的季节性变化和年生长层的形成，高密度带形成于夏季而低密度带形成于冬季。年生长带的结构特征分析表明，季风环流控制的表层海流的性质和成分决定着年生长层的结构特征，微生长层的形成可能与潮汐和月光的周期性变化有关。     

邯郸石龙群的成因与年代研究

在野外调查的基础上,从地质学的角度对河北省南部邯郸县姜窑村出土的石龙群的成因及其形成年代进行了分析。结果表明,由1条大龙和9条小龙组成的石龙群是钙质胶结的洺河古河道沙体,形成于距今4万年前的晚更新世晚期,对应于玉木早冰期华北平原第Ⅲ古河道发育期。石龙沙体上的横切V形裂口是古河道沙体在干缩过程中形成的横切裂隙,沿古河道沙体下泄的富含碳酸钙的地下水在此渗出是形成裂隙两侧脊状突起和"龙爪"的直接原因,新构造运动可能是造成紫山断块隆升并迫使洺河改道和石龙群整体向北东方向翘首的直接原因。     

Further planktonic algae of Auckland sewage treatment ponds and other waters

Seventeen species of algae, newly recorded between 1965 and 1968 from sewage treatment ponds around Auckland City, are described together with another 11 species found in eutrophic waters of the area. These latter natural waters are often of a transient nature and usually heavily polluted in some way.

The genera recorded, with number of species (in brackets), are: Flagellata: Euglena (5); Lepocinclis (1); Phacus (3); Trachelomonas (1). Chlorophyceae (Volvocales): Chlamydomonas (1); Pteromonas (1); Pyrobotrys (1); Chloro‐gonium (1) (Chlorocoecales): Coelastrum (1); Tetrallantos (1); Closteriopsis (1) Scenedesmus (5). (Conjugates) : Closterium (3). Myxophyceae: Anabaena (1); Arthrospira (1); Oscillatoria (1).     

Shaking table study on liquefaction behaviour of different saturated sands reinforced by stone columns

Abstract

Liquefaction is a phenomenon developed in loose and saturated layers of sands subjected to dynamic or seismic loading, and often leads to excessive settlement and subsequent failures in structures. Several methods have been proposed to improve soil resistance against liquefaction, among which use of stone columns is one of the most applicable methods. In this research, the effect of stone columns with different geometries and arrangements on the liquefaction behaviour of loose and very loose saturated sands subjected to vibration is investigated using shaking table. Results of the experiments show that when using stone columns in sand layers, the level of maximum settlement is significantly reduced. Further, the presence of stone columns significantly reduces pore water pressure ratio. This further indicates that stone columns have a positive effect and reasonable performance, even in relatively strong earthquakes, provided that the number and cross-section of the columns are sufficient. In addition, stone columns reduce the pore water pressure dissipation time. Moreover, by increasing cross-sectional area and the number of columns, both pore water pressure and settlement decrease. Stone columns in loose sand have a greater effect on the reduction of pore water pressure compared to that of very loose sand.