Geodynamics of the Amirante Ridge and Trench Complex,Western Indian Ocean

The formation and evolution of the ～600 km long arcuate Amirante Ridge and Trench Complex (ARTC) is a significant geomorphic–structural feature in the Western Indian Ocean (WIO). The WIO contains evidence of at least two major magmatic episodes followed by continental rifting within the span of a little more than 20 million years. This involved the splitting of Madagascar from India at around 85 Ma and then separation between India and the Seychelles at 64–63 Ma as a possible consequence of two powerful volcanic eruptions from the Marion and Reunion hot spots, respectively. Formation and evolution of the ARTC represents this tumultuous period in the Indian Ocean, approximately between 85 and 60 Ma (Late Cretaceous–Early Tertiary).

We integrated geophysical, palaeomagnetical, and petrological data to examine three existing models that attempt to explain the formation of ARTC. In contrast, our study hints at several stages of extension and compression responsible for its formation. Our integrated data also suggest that the Carlsberg Ridge may have played a prominent role in the evolution of the ARTC that seems to have formed through a ridge-jump process after the conjugate spreading centres – Mascarene and Palitana ridges formed earlier during the India–Madagascar separation – ceased spreading because of violent eruption of the Reunion hot spot at around 65 Ma. The eruption disturbed the plumbing system of magma ascent, resulting in cessation of spreading along the conjugate spreading centres, forcing a ridge jump.

A collage of seismic refraction and reflection, free-air gravity, magnetic anomaly data, and Ar dating of rocks indicates that as the Carlsberg Ridge swept the Seychelles towards south, the crust between Madagascar and the Seychelles was increasingly compressed, with the abandoned northern Mascarene spreading centre absorbing the maximum stress. With continued compression, the western limb of the abandoned spreading ridge was thrust below the eastern limb to a limited degree. This partial subduction agrees with the gravity and seismic results. Our new study also accounts for the anomalous presence of 14 km-thick oceanic crust beneath the ARTC and its characteristic difference in petrology with other established subduction zones in the world.     

台湾浅滩沉积物粒度特征及输运趋势

2007年7月,对台湾浅滩43个站位进行了表层底质采样,在室内用Mastersizer 2000型激光粒度仪获得了沉积物的粒径分布,并用矩法计算其粒径参数.研究区内沉积物类型多为砂和含砾砂,平均粒径集中于0Φ到3Φ之间.福建—广东沿岸海域一带沉积略细,沿岸带外侧的浅槽,以及台湾浅滩东北边坡与南边坡沉积略粗.用粒径趋势分析计算结果显示,台湾浅滩东北方向与偏西方向的沉积物均向浅滩核部汇聚;而浅滩核心区的粒度参数比较接近,沉积物输运趋势弱化.     

Nummulitic banks in the upper Lutetian ‘Buil level’, Ainsa Basin,South Central Pyrenean Zone: the impact of internal waves

Nummulites, a particularly abundant and diverse genus of larger benthonic foraminifera, formed huge accumulations (banks) during the Eocene, which are often good hydrocarbon reservoirs, especially in North Africa. Despite their economical interest, these accumulations are not well‐understood and their origin is still under discussion. Reasons for this debate are the absence of living Nummulites accumulations and the high‐variability of facies, including the size, shape and extension of the banks, which reflect the array of processes controlling sediment production and accumulation. The nummulitic banks near Santa María de Buil, in the Ainsa Basin (South Pyrenean Foreland Basin) are composed of recurrent facies associations within mappable bed units bounded by physical surfaces. The depositional processes that produced the Nummulites deshayesi accumulations are interpreted considering the shape of the banks, the type of bounding surfaces, the distribution of sedimentary textures, Nummulites test shapes and the associated skeletal components within the banks. This integrative analysis indicates that nummulitic banks accumulated from mass flows, with very poor sediment sorting. Textural and compositional differences among banks suggest that globose Nummulites thrived in the shallower part of the mesophotic zone with abundant nummulithoclasts, whereas flat nummulitic forms thrived in deeper mesophotic, clay‐dominated settings. Interbedded with nummulitic banks, coral biostromes and coral mounds bearing Operculina, Discocyclina and Asterocyclina, represent in situ accumulation near the base of the photic zone. Internal waves (waves that propagate along the pycnocline) are thought to be the triggering mechanism for the density flows. Internal waves and induced bottom currents are sporadic but strong enough to bring sediments into suspension. In contrast to surface waves (both fair‐weather and storm), whose impact is strongest near the sea surface and decreases with bathymetry, the impact of internal waves is usually strongest in the mid‐shelf region and weaker in shallow water. This explains the compositional character of the nummulitic banks.     

Responding to Deforestation: Productive Conservation,the World Bank,and Beekeeping in Rondonia,Brazil

Productive conservation, a sustainable development concept for the Amazon, ideally leads to economic development in rural areas with conservation of rain forest ecosystems. This study evaluates the human and environmental dynamics of productive conservation in Rondonia, Brazil, using as a case study beekeeping, which has been promoted by the World Bank‐funded Rondonia Natural Resources Development Project. Promoters of beekeeping have given little attention to basic ecological or political economic issues that determine whether the practice contributes to ideals of productive conservation. While beekeeping can generate significant increases in household income, beekeeping cooperatives may become overdependent on donor funds. Once the flow of productive conservation donor funds stops, organizations may fail, making it too difficult for beekeepers to maintain their operations. Beekeeping does not lead directly toward rain forest conservation. Moreover, beekeeping almost exclusively employs introduced Africanized “killer” bees, commercially exploitable in the Amazon only because deforestation has temporarily created suitable habitats for them. Given the human and environmental configuration of beekeeping in Rondonia, the paper suggests ways to direct beekeeping toward accomplishing the goals of productive conservation.     

How “Water for All!” policy became hegemonic: The power of the World Bank and its transnational policy networks

As recently as 1990, few people in the global South received their water from US or European water firms. But just 10 years later, more than 400 million people did, with that number predicted to increase to 1.2 billion people by 2015, transforming water in Africa, Asia, and Latin America into capitalized markets as precious, and war-provoking, as oil. This article explains how this new global water policy became constituted so quickly, dispersed so widely, with such profound institutional effects. It highlights the prominent role of transnational policy networks in linking environment and development NGOs and the so-called global water policy experts with Northern high-end service sectors, and the ways in which the World Bank facilitates their growth, authority, and efficacy. This phenomenon reflects the World Bank’s latest and perhaps most vulnerable development regime, which I call “green neoliberalism.”     

闽南-台湾浅滩渔场海表温度对鲐鲹鱼类群聚资源年际变动的影响初探

利用闽南-台湾浅滩渔场1986-1997年遥感海表温度资料与同期灯光围网渔业信息船的渔捞日志,对该渔场海表温度与鲐鲹鱼类群聚资源年际变动之间的关系进行了初步的探讨.结果表明,沿着25.5℃等温线形成一个中心渔场,空间位置的年际摆动范围在纬向上小于0.5°;海表温度距平(SSTA)与鲐鲹鱼类资源指数的变动在年际尺度上没有关联,但在年代际尺度上存在一定关联,1988年起SSTA摆动的频度和幅度在正值态大于负值态,而资源指数则呈现逐步上升的趋势.     

秋初台湾浅滩水体浊度和荧光叶绿素分布特征研究

阐述了台湾浅滩邻近海域秋初的水体浊度、荧光叶绿素a的分布变化特征,指出荧光叶绿素a的分布除与营养盐的限制相关外,温盐等水文动力条件对其分布特征也起着重要控制作用,尤其在控制荧光叶绿素a极值分布下界方面可能起着关键作用.而在上升流涌升强烈的地区往往出现了浊度最大值,这可能与底层物质的再悬浮有关.     

Carbon input, production and turnover in the interstices of a Lake Tegel bank filtration site, Berlin, Germany

The sandy littoral zone of Lake Tegel (Berlin, Germany) was investigated during 2004–2006 down to sediment depths ≥26 cm to derive a scheme of seasonal carbon turnover under induced bank filtration conditions. Carbon turnover processes were quantified regarding external and internal sources of dissolved and particulate organic matter (DOM and POM), primary production, community respiration, redox potential as well as specific loads of soluble chemical compounds such as nitrogen, iron, manganese and DOC.Over the course of the year, infiltrating DOC decreased by about 13–20% within the upper 26 cm sediment of the infiltration stretch. Gradients of all observed soluble compounds that are highly cross-linked to biological activities were highest in the topmost centimetre. In this depth mass balances (output–input) were negative concerning NO₃-N (−1 mg dm⁻² d⁻¹, summer mean) and DOC (−2 mg dm⁻² d⁻¹, winter mean), respectively, while specific loads of cations such as manganese reached up to 0.2 mg dm⁻² d⁻¹ during summer. Carbon mineralization ranged between 3 and 7 mg C dm⁻² d⁻¹ and was nearly twice as high in summer as in winter. The turnover of the infiltrating DOC contributed maximally 25% in summer to 50% in winter to the entire organic carbon mineralization. Gross and net primary production differed up to a factor of >10, indicating very fast turnover reactions and the predominance of community respiration and mineralization, respectively. The POC in the upper sediment layer (10 cm) temporally varied around 1% sediment d.w.; benthic algae, organic seston input and autumnal leaf fall contributed similar percentages to the POC pool.