黔南、湘中地区早二叠世四射珊瑚生态环境分异研究

本文通过对黔南、湘中下二叠统(包括链带:Sphoeruschwagerina 带,Panirina m带和misllr-na 带)各个岩相内四射珊瑚及其共生分子的数量统计,探讨了这两个地区本期内四射珊瑚的生态环境分异,并区分出了几个主要岩相中四射珊瑚动物群的典型面貌和特征性分子,为今后岩相古地理研究提供了重要证据。     

Stratigraphy of upper Viséan carbonate platform rocks in the Carlow area,southeast Ireland

The stratigraphy of the upper Viséan (Asbian to Brigantian) carbonate succession in southeast Ireland is revised on the basis of seven quarry and two borehole sections. Six lithological units have been distinguished, two units (units 1 and 2) in the upper Asbian Ballyadams Formation, and four units (units 4 to 6) in the Brigantian Clogrenan Formation (both formations are dated precisely using foraminiferans, calcareous algae and rugose corals). The boundary between the Ballyadams and Clogrenan formations is redefined 19 m below the horizon proposed by the Geological Survey of Ireland, and thus, lithological characteristics of both formations are redescribed. The upper part of the Ballyadams Formation is characterized by well‐developed large‐scale cyclicity, with common subaerial exposure surfaces. Fine‐ to medium‐grained thin‐bedded limestones with thin shales occur in the lower part of cycles, passing up into medium‐grained pale grey massive limestones in the upper part. The Clogrenan Formation is composed mainly of medium‐ to coarse‐grained thick limestone beds with variable presence of shales; but no large‐scale cyclicity. There is a decrease in the number of subaerial exposure surfaces towards the top of the formation and common chert nodules; macrofauna occurs mostly concentrated in bands. The six units recognized in the Carlow area are comparable with other units described for the same time interval (Asbian–Brigantian) from south and southwest Ireland, demonstrating the existence of a stable platform for most parts of southern Ireland, controlled principally by glacioeustatics. Copyright © 2004 John Wiley & Sons, Ltd.     

Population Density, Distribution and Consumption Rates of Three Corallivores at Cabo Pulmo Reef, Gulf of California, Mexico

Abstract. The influence of corallivores on coral community structure of eastern Pacific reefs has been considered less important then that of abiotic oceanographic factors. The data that support this assumption, however, are only available for Central American reefs. To assess the role of predation on hermatypic corals in a different regional reef environment, the abundance, spatial distribution and consumption rate of three corallivores: the echinoid Eucidaris thouarsii (Valenciennes), the asteroid Acanthaster planci (Linnaeus) and the teleostean fish Arothron meleagris (Bloch & Schneider), were estimated at Cabo Pulmo reef, Gulf of California, México (23°25' N, 109°25' W). Statistically, the abundances of the species did not change in any sections of the reef (mean values: E. thouarsii , 0.17 indiv. · m⁻²; A. planci , 1.9 indiv. · m⁻²; A. meleagris , 39 indiv. · ha⁻¹). The average daily individual consumption rates of coral were calculated at 1.83 g CaCO₃· m⁻² for E. thouarsii , 118.4 cm² for A. planci , and 16.38 g CaCO₃· m⁻² for A. meleagris , and were lower than those reported for Central American reefs. Considering the mean estimated carbonate production (7.9 kg CaCO₃· m⁻²· a⁻¹), corallivores eliminate less than 4% of the coral standing stock of Cabo Pulmo reef. The low corallivore population density and consumption rates, together with high local coral cover, indicate that corallivores are not key factors determining scleractinian abundance in this marginal reef.     

进化序列系统学——以二叠纪瓦岗珊瑚类为例

进化序列系统学是古生物学中研究物种间和类别间的系统发育关系为目的的学科, 包括研究物种或类别间的亲缘关系, 并确定它们形成的先后序列.表型-分支系统学是该系统学的基础.分支系统学的许多重要概念在该系统学中加入了时间的含义, 例如, 认为最亲近的姐妹种之间的时间间隔不会超过它们母种的生存期.姐妹群和性状镶嵌分析是进化序列研究的主要方法, 而理解性状镶嵌分布是关键.这些分析可由计算机程序实现.以二叠纪瓦岗珊瑚类作为研究进化序列系统学的实例, 该类在特提斯地区广泛分布.通过对瓦岗珊瑚类的特征分析确定了17个性状用于研究, 并且每一性状确定了几个变化状态.根据最广布的性状状态、化石记录和个体发生等原则分辨出近祖性状状态, 并根据性状在系统发育中的重要性确定性状分级.然后, 确定了姐妹群间的关系和物种间的进化序列.在姐妹群与进化序列分析相互检验中可发现性状退化、平行演化和多向分支等古生物学重要现象, 并分辨出物种的异常顺序.在检验生物地层学首次出现事件讨论中推测了一些化石首次出现的可能层位.      

热带与亚热带遥感：需求、挑战与机遇

热带与亚热带拥有大量丰富的自然资源,同时也正在经历着快速的城市化进程,其资源、生态、环境等都面临着前所未有的挑战。同时,热带与亚热带地区存在着大量的自然灾害(如台风、干旱、地震等),威胁着该地区人类经济社会的可持续发展。应用遥感技术对热带与亚热带区域进行全面的监测,对于热带与亚热带区域甚至全球的可持续发展具有重要的意义。然而,由于热带与亚热带特殊的地理条件(如多云多雨等),遥感监测需要克服特殊的技术挑战。本文通过Web of Science核心数据库的7594篇研究论文进行分析,综述了热带与亚热带遥感的研究现状,分别从热带与亚热带遥感的需求、现状、挑战和机遇,通过共被引文献分析和主题词频率分析,建立共被引文献网络和主题词网络,并通过非监督机器学习进行聚类,分别识别出22个共被引文献聚类和6个主题词聚类。通过对这些共被引文献类别和主题词类别的深入分析,本文总结了:(1)热带与亚热带遥感研究的主要监测对象,包括城市地表、热带雨林、红树林、珊瑚、热带草原、生物多样性和自然灾害;(2)热带与亚热带遥感主要采用的遥感技术,包括:遥感数据的选择和使用、遥感数据分析的方法、多云多雨的问题应对以及多源遥感技术。最后,从现代遥感技术的快速发展,本文从8个方面讨论热带与亚热带遥感面临的挑战和未来发展的机遇。     

Heavy metal contents in growth bands of Porites corals: record of anthropogenic and human developments from the Jordanian Gulf of Aqaba

In order to assess pollutants and impact of environmental changes in the coastal region of the Jordanian Gulf of Aqaba, concentrations of six metals were traced through variations in 5 years growth bands sections of recent Porties coral skeleton. X-radiography showed annual growth band patterns extending back to the year 1925. Baseline metal concentrations in Porites corals were established using 35 years-long metal record from late Holocene coral (deposited in pristine environment) and coral from reef that is least exposed to pollution in the marine reserve in the Gulf of Aqaba. The skeleton samples of the collected corals were acid digested and analyzed for their Cd, Cu, Fe, Mn, Pb and Zn content using Flame Atomic Absorption Spectrophotometer (FAAS). All metal profiles (except Fe and Zn) recorded the same metal signature from recent coral (1925–2005) in which low steady baseline levels were displayed in growth bands older than 1965, similar to those obtained from fossil and unpolluted corals. Most metals showed dramatic increase (ranging from 17% to 300%) in growth band sections younger than 1965 suggesting an extensive contamination of the coastal area since the mid sixties. This date represents the beginning of a period that witnessed increasing coastal activities, constructions and urbanization. This has produced a significant reduction in coral skeletal extension rates. Results from this study strongly suggest that Porites corals have a high tendency to accumulate heavy metals in their skeletons and therefore can serve as proxy tools to monitor and record environmental pollution (bioindicators) in the Gulf of Aqaba.     

Sediment dynamics of a sandy contourite: the sedimentary context of the Darwin cold-water coral mounds,Northern Rockall Trough

Grainsize, mineralogy and current-meter data from the Northern Rockall Trough are presented in order to characterise the sandy contourite that forms the sedimentary environment of the Darwin cold-water coral mounds, and to investigate the impact of this environment on the mound build-up. Large clusters of small cold-water coral mounds, 75 m across and 5 m high, have been found southwest of the Wyville Thomson Ridge, at 900–1,100 m water depth. Their present-day sedimentary environment consists of a subtly sorted sandy contourite, elongated NE–SW, roughly parallel to the contours. Critical erosional and depositional current speeds were calculated, and trends in both the quartz/feldspar and foraminifera fractions of the sands show a bi-directional fining from bedload/erosion-dominated sands in the NE to suspension/deposition-dominated sediments in the SW and towards the S (downslope). This is caused by a gradual reduction in governing current speed, linked to a reduction in slope gradient, and by the increasing distance from the current core in the downslope direction. No specific characteristics were found distinguishing the mound sediments from the surrounding sands: they fit in the overall spatial pattern. Some mound cores show hints of a fining-upward trend. Overall the mound build-up process is interpreted as a result of sediment baffling.     

叶绿素荧光技术在珊瑚礁研究中的应用

珊瑚礁生态系统最基本的生态特征是虫黄藻与珊瑚虫的共生,虫黄藻的光合作用在珊瑚礁生态系统中发挥着重要作用,因此用于测定植物光合作用的叶绿素荧光技术在认识珊瑚礁生态系统中得到越来越广泛的应用。应用方面主要包括:①揭示珊瑚共生藻光生理学原理;②探索珊瑚白化的机制;③监测及预警珊瑚白化事件;④研究珊瑚对污染的响应;⑤监测珊瑚对水体浑浊的响应;⑥探寻珊瑚礁生态模式。叶绿素荧光技术具有快速、灵敏和非破坏性测量等优点,在造礁珊瑚生理生态研究方面将有广阔的应用前景。     

The Corwen Outlier and its implications for the Mid Mississippian palaeogeography of North Wales,UK

The isolated outlier of Visean (Mid Mississippian) limestones and sandstones near Corwen, North Wales, UK, provides a critical constraint on regional tectonic and palaeogeographical models. The late Asbian to Brigantian succession comprises a series of shoaling‐upwards cycles (parasequences). These were the product of forced, glacioeustatic regressions and have boundaries that testify to emergence, karstic dissolution and soil formation on a low gradient carbonate platform prior to flooding and the resumption of marine deposition. The recognition of two of the main marker beds within the North Wales Visean succession (Main Shale and Coral Bed) together with a newly applied foraminiferal and algal biozonation allow the outlier succession to be correlated with other Visean outcrops in the region and more widely throughout the British Isles. In revealing regional thickness and facies variations, these comparisons show that the outlier succession was deposited landward of the early Asbian shoreline in a region of enhanced subsidence localized along the Bala Lineament. The Corwen Outlier suggests that, within narrow gulfs associated with the region's major tectonic lineaments, Mississippian carbonate facies extended farther south into the contemporary hinterland of older rocks and that, in response to Brigantian climate change, these topographic features likely also influenced fluvial catchments supplying siliciclastic sediment to the platform's landward margin and, subsequently, Namurian deltas. Contrary to earlier suggestions, Visean outcrop patterns, facies distributions and thicknesses in the vicinity of the Bala Lineament can be explained without the need to invoke extensive post‐depositional lateral displacements. BGS © NERC 2013. Geological Journal © John Wiley & Sons Ltd.