新疆和田杜瓦二叠—三叠纪动物化石研究

在原定为侏罗系的剖面中发现丰富的叶肢介、介形虫及鱼化石,本文对所发现的化石进行了描述.其中叶肢介化石有7属18种(有8个新种).其时代为早三叠世,与吉木萨尔县大龙口剖面的锅底坑组上部相当.介形虫化石有4属5种,其时代为晚二叠世晚期.鱼化石为1新属种,其时代意见偏新,所以,产这些化石的地层不是侏罗纪,而应是二叠一三叠纪的.     

鄱阳湖流域饶河鱼类稳定同位素比值和营养级的空间变化

由于水文特征的变化和栖息生境的异质性,河流食物网结构存在着一定的空间变化.认识人类活动对河流食物网结构空间变化的影响能够为河流生态系统的科学管理提供有效指导.利用稳定同位素分析技术,测定枯水季节饶河不同地区初级生产者和鱼类的碳、氮稳定同位素比值(δ13C和δ15N),比较饶河下游鄱阳和中游海口河段4种常见鱼类的δ13C、δ15N值和营养级,并分析导致不同河段食物网结构差异的原因.结果表明,鄱阳与海口两个地区鱼类的δ13C值无显著差异,但δ15N值差异显著.鱼类的δ13C值变化范围在鄱阳河段大于海口河段,鳜(Siniperca chuatsi)和贝氏(Hemiculter bleekeri)在鄱阳河段的δ15N值要显著高于海口河段,而黄颡鱼(Pelteobagrus fulvidraco)和鲫(Carassius auratus)的δ15N值在鄱阳河段却表现更低.另一方面,除黄颡鱼外,鳜、贝氏和鲫在鄱阳河段的营养级均显著高于其在海口河段的营养级.研究认为,由于颗粒有机物和附着藻类的δ13C值在鄱阳与海口河段没有显著差异,因而导致鱼类的δ13C值也没有明显变化.不同生境下初级食物源δ15N值的差异及人为扰动的程度可能是影响饶河不同河段鱼类的δ15N值存在明显差异的主要原因.     

A Vegetated Urban Canopy Model for Meteorological and Environmental Modelling

An urban canopy model is developed for use in mesoscale meteorological and environmental modelling. The urban geometry is composed of simple homogeneous buildings characterized by the canyon aspect ratio (h/w) as well as the canyon vegetation characterized by the leaf aspect ratio (σ _l ) and leaf area density profile. Five energy exchanging surfaces (roof, wall, road, leaf, soil) are considered in the model, and energy conservation relations are applied to each component. In addition, the temperature and specific humidity of canopy air are predicted without the assumption of thermal equilibrium. For radiative transfer within the canyon, multiple reflections for shortwave radiation and one reflection for longwave radiation are considered, while the shadowing and absorption of radiation due to the canyon vegetation are computed by using the transmissivity and the leaf area density profile function. The model is evaluated using field measurements in Vancouver, British Columbia and Marseille, France. Results show that the model quite well simulates the observations of surface temperatures, canopy air temperature and specific humidity, momentum flux, net radiation, and energy partitioning into turbulent fluxes and storage heat flux. Sensitivity tests show that the canyon vegetation has a large influence not only on surface temperatures but also on the partitioning of sensible and latent heat fluxes. In addition, the surface energy balance can be affected by soil moisture content and leaf area index as well as the fraction of vegetation. These results suggest that a proper parameterization of the canyon vegetation is prerequisite for urban modelling.     

中建海底峡谷地貌及沉积特征的分段性

中建海底峡谷具有分段性,但分段的关键地貌特征、各段沉积充填及其控制因素缺乏精细描述和系统论证.综合利用高分辨率二维和三维地震资料,结合水深地貌数据,对中建海底峡谷地貌及沉积特征进行了详细分析,总结了其南北段沉积过程的主控因素.中建海底峡谷呈NW向顺直展布于广乐隆起与西沙隆起之间,以华光礁附近的地貌高点为拐点被分为南北两...     

The Early–Middle Triassic Supervolcano in the Yangtze Block,South China and associated obstacles to biotic recovery

The end–Permian mass extinction was one of the major global crises spanning the entire Early Triassic or longer. Eruptions of volcanos were one of the factors that delayed the biotic recovery after this event. Supervolcano eruptions can cause catastrophic effects on global environment, climate, and life. Here we investigate the tuff layers from Early–Middle Triassic boundary in the Yangtze Block and identify a supervolcano eruption event. The zircon U–Pb ages of the section–Langdai, section–Daijiagou and section–Longmendong tuff samples are 247.1 ± 1.9 Ma, 247.6 ± 2.0 Ma and 247.7 ± 1.7 Ma, respectively. These ages mark the Olenekian–Anisian boundary. The zircon grains from the tuff layers have negative ε_Hf(t) (−15.3 to −0.8), two–stage Hf model (T_DM2) ages (1.7 to 2.2 Ga) and display high–δ¹⁸O values (mostly > 10‰). Clay minerals and quartz dominate the rock composition. The whole rock compositions show that the tuff layers were derived from magma of intermediate to felsic composition, which formed by the remelting of Paleoproterozoic materials of continental crust. The volcanic eruption site is located in the Jinshajiang–Ailaoshan–Song Ma suture zone in the southwestern margin of the Yangtze Block. A combination of the closure of the Paleo–Tethys Ocean Basin and the collision of the Indochina Block and South China contributed to the eruption, which was a supervolcano eruption under the active continental margin arc settings. We speculate that this supervolcano eruption might have contributed to the delayed biotic recovery after the end–Permian mass extinction.     

皖南姚村岩体花岗岩风化壳稀土元素赋存特征

皖南地区花岗岩风化壳中稀土元素普遍富集，局部已成为矿床，其中，郎溪县姚村岩体风化壳富集程度较高。LA- ICP- MS锆石U- Pb定年表明，姚村花岗岩体的形成年龄为127. 9±1. 4 Ma，属于皖南地区燕山期晚期岩浆作用的产物。风化壳可细分为残坡积层（A）、强半风化层（C1）、过渡层（C2）、弱半风化层（C3）和基岩（D） 5层。稀土总量在纵向剖面上呈“波浪式”分布，各层稀土分布型式表现出对原岩的继承性。风化壳稀土配分型式与基岩一致， 富集LREE，轻重稀土分馏明显\[(La/Yb)N=15. 6\]，但总含量明显更高。基岩∑REE为338×10-6，半风化层∑REE最高达642×10-6，富集约两倍。风化壳物质由风化残余主矿物（石英、钾长石、斜长石、黑云母）、黏土矿物（高岭石、埃洛石、伊利石、三水铝石等）和副矿物（锆石、磷灰石、榍石等）等组成。黏土矿物以伊利石含量最高，指示风化壳发育不成熟。REE与埃洛石含量明显正相关，与其他黏土矿物关系不明显。（含）稀土矿物（尤其是榍石）对风化壳中稀土元素的贡献量超过 50%，其次为斜长石，是风化壳中REE的重要来源。