尖吻兽（Akidolestes）的齿列和头后骨骼     

陈萌  罗哲西 《地质学报》2008,82(2):155-164

尖吻兽（Akidolestes）是新近在中国辽宁省下白垩统义县组地层发现的对齿兽动物,保存了非常完整的头后骨骼。其齿列特征表明它属于鼹兽超科（Spalacotheroidea）中的鼹兽科动物（Spalacotheriidae）,该科是以臼齿齿尖呈对称三角形排列、上下臼齿反转咬合为特征的单系类群,是现生兽类（有袋类和有胎盘类）的近亲,拥有许多兽类骨骼的原始特征。尖吻兽区别于张和兽科的特征是具有更宽大的下颌冠状突和臼齿齿尖呈更小的锐角排列。对尖吻兽的骨骼解剖学和比较形态特征的研究,表明尖吻兽演化模式是一种  相似文献   

Responses of a Mediterranean soft bottom community to short-term (1993-1996) hydrological changes in the Rhone river   总被引：1，自引：0，他引：1  

Salen-Picard C  Arlhac D  Alliot E 《Marine environmental research》2003,55(5):409-427

The polychaete fauna of muddy bottoms off the Rhone delta (NW Mediterranean) was seasonally sampled at two sites at 70 m depth, from 1993 to 1996. During this period, five severe flood events occurred. A clustering analysis (distance coefficient of Whittaker) and three way fixed factor ANOVAs (site x season x year) showed strong year-to-year changes in species density and community structure, changes that masked seasonal variations. Total density increased by a factor of 3 and density of most species significantly increased following the first flooding event. Changes in the community structure were due to the successive dominance of a few species. The opportunistic species, such as Cossura sp., Mediomastus sp. and Polycirrus sp., exhibited peaks in density 1-3 months after the flood. These peaks were followed by a drastic decline. For species with a long life span, such as Sternaspis scutata, a slower but continuous increase in density was observed which was maintained for several months. The density fluctuations of these species exhibited a good correlation with river flow with time lags of 1-2 years. The successional dynamics observed are explained according to the geographical origin of the floods and the biology and feeding ecology of species.  相似文献   

浅议煤系地层区地热资源开发     

张国建 《地下水》2008,30(3):20-23

开发地热资源是节约其它能源的一种方式,可以改变一个地区的投资环境,通过对山东滕州市煤系地层的区域地质情况进行勘察,并运用先进施工工艺及机械,开钻了鲁南地区第一眼煤系地层下的温泉井。并对之进行了经济效益分析。鲁南第一温泉井（滕温1号地热井）。  相似文献   

漳州热田的对流热流和传导热流的研究   总被引：5，自引：1，他引：4       下载免费PDF全文

熊亮萍  汪集YANG 《地球物理学报》1990,33(6):702-711

漳州地热系统属对流型地热系统.漳州热田是我国东南沿海地区目前所见热田中温度最高（121.5℃）的一个.地表热流值的研究表明,热田中心具有最大的实测热流值（359mw/m²）.本文根据热田内152个钻孔的测温资料和56块岩石样品的热导率数据,采用三种不同方法计算出漳州热田及其邻近地区的大地热流值,并讨论了热流值分布的特点.  相似文献   

遥感技术在腾冲西南地区地热资源研究预测中的应用   总被引：2，自引：1，他引：2  

杨波  吴德文  赖健清  唐攀科 《国土资源遥感》2003,14(2):23-26

利用TM数据,对滇西腾冲西南地区进行地质构造解译,阐明了该区多地热活动的原因.通过对TM6波段热红外异常信息的提取,经构造解译与地热异常分布区的叠加分析,发现了该区地热富集的规律性,提出了地热田的遥感影像模式.据此,预测出腾冲西南地区62处水热活动Ⅰ级异常区.  相似文献   

The GGOS as the backbone for global observing and local monitoring: A user driven perspective   总被引：1，自引：0，他引：1  

H.-P. Plag   《Journal of Geodynamics》2005,40(4-5):479

A key geodetic contribution to both the three Global Observing Systems and initiatives like the European Global Monitoring for Environment and Security is an accurate, long-term stable, and easily accessible reference frame as the backbone. Many emerging scientific as well as non-scientific high-accuracy applications require access to an unique, technique-independent reference frame decontaminated for short-term fluctuations due to global Earth system processes. Such a reference frame can only be maintained and made available through an observing system such as the Global Geodetic Observing System (GGOS), which is currently implemented and expected to provide sufficient information on changes in the Earth figure, its rotation and its gravity field. Based on a number of examples from monitoring of infrastructure, point positioning, maintenance of national references frames to global changes studies, likely future accuracy requirements for a global terrestrial reference frame are set up as function of time scales. Expected accuracy requirements for a large range of high-accuracy applications are less than 5 mm for diurnal and sub-diurnal time scales, 2–3 mm on monthly to seasonal time scales, better than 1 mm/year on decadal to 50 years time scales. Based on these requirements, specifications for a geodetic observing system meeting the accuracy requirements can be derived.  相似文献   

Applications géodésiques du système DORIS à l'Institut géographique national     

Pascal Willis  Claude Boucher  Hervé Fagard  Zuheir Altamimi 《Comptes Rendus Geoscience》2005,337(7):653-662

IGN is in charge of the installation and maintenance of the DORIS orbit determination network. More recently, in collaboration with JPL, precise geodetic computations were performed. The goal of this paper is to recall the various historic contributions of IGN to the DORIS system in their international context and then to describe a new estimation technique developed for a multi-satellite mode, making full profit of a better modeling for satellites and ground clocks as well as tropospheric correction parameters. Derived geodetic results demonstrate a precision in the order of 1 cm for station positions. To cite this article: P. Willis et al., C. R. Geoscience 337 (2005).  相似文献   

Is Darwin's ‘Abominable Mystery’ still a mystery today?     

《Cretaceous Research》2016

Darwin described the Cretaceous diversification and subsequent rapid rise of flowering plants (angiosperms) as an “abominable mystery”: how could they have achieved worldwide ecological dominance by early Paleogene times when the oldest angiosperm fossils are only Cretaceous in age? However, recent phylogenetic and palaeobiogeographical analyses have suggested a much earlier, perhaps Triassic origin for the stem angiosperms. We suggest that the fossil record is accurately reflecting the rapid diversification of the crown angiosperms that molecular data suggests occurred in Cretaceous–early Palaeogene times, and which coincides with similar explosive diversifications that occurred in other parts of the terrestrial biota including insects, birds and mammals. Early, stem angiosperms are poorly represented in the fossil record for a combination of taphonomic and ecological reasons. We conclude that the reported evidence shows that the Darwin's “mystery” is in fact no mystery and confirms that it merely requires an appropriate reading of the fossil record.  相似文献   

Coevolution between Terrestrial Ecosystem and Earth Environment     

Zhou Zhekun  Zhou Zhonghe  Wang Yi 《地球科学进展》2016,31(7):682-688

Coevolution between terrestrial ecosystem and Earth environment is a hot research topic in both biology and geology. Last progresses in these field are reported from following research subjects: evolution of jawed vertebrates(gnathostomata) from Silurian; occurrence of earliest forests from Devonian of Xinjiang; biodiversity of insects in amber from Cretaceous of Myanmar; Evolution of primates and geochemistry studies from Eocene/Oligocene; studies of Longdan fauna from Lingxia basin, Gansu Province of earlier Pleistocene and endemic cloven-breast fishes from Pliocene Tibet; the correlations thick-boned fish,Hsianwenia wui, and the aridification of the Qaidam Basin; monsoon climate and its impact on biodiversity; study on the flora from Mankang, Tibet of Miocene and its palaeoclimate; depositional environment and its impact on the preservation of fossils; contraction of high resolution Stratigraphic series by using data of paleomagnetism and mammal fossils.  相似文献   

Characteristic and Geological Significance of Microbially Induced Sedimentary Structures(MISS) in Terrestrial P-T Boundary in Xingyang,Western He’nan Province     

Zheng Wei  Qi Yongan  Zhang Zhonghui  Xing Zhifeng 《地球科学进展》2016,31(7):737-750

Microbially Induced Sedimentary Structures (MISS) are primary sedimentary structures that arise syndepositionally from microbial community activity. Especially valuable are MISS for the analysis of early Archean (and extraterrestrial) deposits. However, most reports of MISS have focused on the Precambrian and Phanerozoic mass extinction marine sediments, and only a few and terrestrial MISS have been studied. The MISS presented in this paper, which mainly consists of mat growth feature, mat destruction feature and mat decay feature, are well preserved in terrestrial clastic rocks around the P-T boundary in Xiyang area, western Henan. Large U ridges, oriented sand quartz, mica grains and thin clayey laminae arranged parallel to bedding plane are the main features visible under the microscope. Several lines of evidence indicate that the Xingyang MISS are of biogenic origin. Abundant MISS in Xingyang may indicate the degradation of terrestrial ecosystems and proliferation of microbial mats immediately after the severe Permian-Triassic mass extinction. Study aiming at MISS helps to analyze their space distribution in the globe and to probe into links between microbial proliferation and environmental stresses following the end-Permian mass extinction in terrestrial ecosystems.  相似文献