New pterosaurian remains from the Late Cretaceous (Santonian) of Hungary (Iharkút, Csehbánya Formation)     

Attila ?si  Eric Buffetaut 《Cretaceous Research》2011,32(4):456-463

The Late Cretaceous (Santonian) continental vertebrate locality of Iharkút, western Hungary has provided numerous azhdarchid pterosaur remains including the recently described, <em>Bakonydraco galaczi</em>. Since the first report of these fossils, additional remains have been discovered that improve considerably our knowledge of some aspects of the anatomy of azhdarchid pterosaurs. New cranial material described here indicates an edentulous, non-crested premaxillary rostrum in <em>Bakonydraco</em> similar to that of <em>Quetzalcoatlus</em> and reveals that this rostrum was considerably thinner and more lightly built than the relatively massive, pointed mandibular symphysis. In addition, the contact surface of the upper and lower jaws of <em>Bakonydraco</em> at least in the symphyseal region was more similar to <em>Tapejara wellnhoferi</em> than to other azdarchids: the contact is irregular and the premaxilla does not fit closely the rostral part of the mandible. Among the postcranial material the atlas-axis complex possessing lateral pneumatic foramina is of great importance because it further supports the notion of interspecific variability of vertebral pneumaticity among pterosaurs.  相似文献   

“井水不犯河水”水文地质学含义初步探讨   总被引：1，自引：0，他引：1  

刘元章  武强  刘久荣  林沛  邢立亭  刘守强 《地下水》2011,(6):122-127

利用水化学及同位素水文地质学的方法,对密云水库、潮白河及位于潮白河边的2个地下水分层专门监测井进行取样测试,并结合收集相关资料,从水位、水质及氚、氘、氧-18等同位素方面进行分析研究,对中国古语“井水不犯河水”的水文地质学方面的含义进行了一定的微观层次的分析探讨.得出研究点处潮白河水对50 m外的25 m深的浅井井水有...  相似文献   

Quantifying Barrovian metamorphism in the Danba Structural Culmination of eastern Tibet   总被引：3，自引：0，他引：3  

O. M. Weller  M. R. St‐Onge  D. J. Waters  N. Rayner  M. P. Searle  S.‐L. Chung  R. M. Palin  Y.‐H. Lee  X. Xu 《Journal of Metamorphic Geology》2013,31(9):909-935

The Danba Structural Culmination is a tectonic window into the late Triassic to early Jurassic Songpan‐Garzê Fold Belt of eastern Tibet, which exposes an oblique section through a complete Barrovian‐type metamorphic sequence. Systematic analysis of a suite of metapelites from this locality has enabled a general study of Barrovian metamorphism, and provided new insights into the early thermotectonic history of the Tibetan plateau. The suite was used to create a detailed petrographic framework, from which four samples ranging from staurolite to sillimanite grade were selected for thermobarometry and geochronology. Pseudosection analysis was applied to calculate <i>P</i>–<i>T</i> path segments and determine peak conditions between staurolite grade at ～5.2 kbar and 580 °C and sillimanite grade at ～6.0 kbar and 670 °C. <i>In situ</i> U–Pb monazite geochronology reveals that staurolite‐grade conditions were reached at 191.5 ± 2.4 Ma, kyanite‐grade conditions were attained at 184.2 ± 1.5 Ma, and sillimanite‐grade conditions continued until 179.4 ± 1.6 Ma. Integration of the results has provided constraints on the evolution of metamorphism in the region, including a partial reconstruction of the regional metamorphic field gradient. Several key features of Barrovian metamorphism are documented, including nested <i>P</i>–<i>T</i> paths and a polychronic field gradient. In addition, several atypical features are noted, such as <i>P</i>–<i>T</i> path segments having similar slopes to the metamorphic field gradient, and <i>T</i><sub>max</sub> and <i>P</i><sub>max</sub> being reached simultaneously in some samples. These features are attributed to the effects of slow tectonic burial, which allows for thermal relaxation during compression. While nested, clockwise <i>P</i>–<i>T</i>–<i>t</i> loops provide a useful framework for Barrovian metamorphism, this study shows that the effects of slow burial can telescope this model in <i>P</i>–<i>T</i> space. Finally, the study demonstrates that eastern Tibet experienced a significant phase of crustal thickening during the Mesozoic, reinforcing the notion that the plateau may have a long history of uplift and growth.  相似文献   

Temporal relationship between Holocene human occupation and vegetation change along the northwestern margin of the Central African rainforest     

Anne-Marie Lézine  Augustin F.-C. Holl  Judicaël Lebamba  Annie Vincens  Chimène Assi-Khaudjis  Louis Février  Émmanuelle Sultan 《Comptes Rendus Geoscience》2013,345(7-8):327-335

This paper discusses the relationship between patterns of human settlements and environmental change during the Holocene along the northwestern margins of the equatorial rain forest of central Africa. Palaeoenvironmental data from high-resolution sediment cores from lacustrine deposits, plant macro-remains from forest soils, and archaeological data are harnessed to discuss the differential impact of climate and/or humans on the central African rain forest. It is shown that climate change impacted the rain forest well before the widespread expansion of human settlements all over the study area.  相似文献   

Comparative phylogeography of African rain forest trees: A review of genetic signatures of vegetation history in the Guineo-Congolian region     

Olivier J. Hardy  Céline Born  Katarina Budde  Kasso Daïnou  Gilles Dauby  Jérôme Duminil  Eben-Ezer B.K. Ewédjé  Céline Gomez  Myriam Heuertz  Guillaume K. Koffi  Andrew J. Lowe  Claire Micheneau  Dyana Ndiade-Bourobou  Rosalía Piñeiro  Valérie Poncet 《Comptes Rendus Geoscience》2013,345(7-8):284-296

The biogeographic history of the African rain forests has been contentious. Phylogeography, the study of the geographic distribution of genetic lineages within species, can highlight the signatures of historical events affecting the demography and distribution of species (i.e. population fragmentation or size changes, range expansion/contraction) and, thereby, the ecosystems they belong to. The accumulation of recent data for African rain forests now enables a first biogeographic synthesis for the region. In this review, we explain which phylogeographic patterns are expected under different scenarios of past demographic change, and we give an overview of the patterns detected in African rain forest trees to discuss whether they support alternative hypotheses regarding the history of the African rain forest cover. The major genetic discontinuities in the region support the role of refugia during climatic oscillations, though not necessarily following the classically proposed scenarios. We identify in particular a genetic split between the North and the South of the Lower Guinean region. Finally we provide some perspectives for future study.  相似文献   

非饱和带水-气二相流数值模拟研究进展   总被引：3，自引：1，他引：2       下载免费PDF全文

陈家军  奚成刚  王金生 《水科学进展》2000,11(2):208-214

通过对近年来水-气二相流数值模拟情况的分析,总结了在水-气二相流模拟过程中,各个主要参数或物理过程的数学概化方法,以及近年来求解水-气二相流方程和污染物运移方程的各种方法,论述了各种方法的优点和不足.并提出了需进一步研究解决的问题.  相似文献   

The Recognition of the Chuxiong Foreland Basin System in Yunnan, China     

Tan Fuwen  Yin Fuguang  Xu Xiaosong  Wan Fang WT  ”BX 《地学前缘》2000,(Z1)

THE RECOGNITION OF THE CHUXIONG FORELAND BASIN SYSTEM IN YUNNAN,CHINA  相似文献   

张家口南部地区温泉形成的氢氧稳定同位素及气体组成证据   总被引：5，自引：0，他引：5  

王基华  林元武  刘成龙  刘五洲 《水文地质工程地质》2000,27(4):30-33

本文研究了张家口南部地区温泉（井）水的氢氧稳定同位素组成及溶解气体组分特征。结果表明,大气降水是该区温泉（井）水的补给来源。大气降水在深循环过程中,受地热增温,岩浆残余热的影响,使水温增高并在适当的构造部位涌出地表形成温泉．  相似文献   

垃圾夯扩短桩在邯郸市的工程实践   总被引：3，自引：0，他引：3  

叶洪东  段万喜  许佳尧  王遂正 《水文地质工程地质》2000,27(1):57-60

本文阐述垃圾夯扩短桩在邯郸新近堆积软土场地上的工程尝试,分析了其加固地基的机理,结合工程实例论述了夯扩短桩在邯郸的适应性及其推广应用前景。  相似文献   

Metamorphism and tectonic evolution of the Shangdan fault zone, Shaanxi, China     

HU NENGGAO  YANG JIAXI  AN SANYUAN  HU JIANMIN 《Journal of Metamorphic Geology》1993,11(4):537-548

Abstract The Shangdan fault in the Qinling Orogenic Belt of China is an important boundary between the Caledonian North Qinling Fold Belt and the Hercynian South Qinling Fold Belt. In the Danfeng area, the fault zone strikes WNW–ESE and comprises four strongly deformed zones and three weakly deformed domains parallel to each other. The fault zone has a complex history of multiple deformation and each domain has a different tectonic style that was formed at different stages of the deformation.
The rocks exposed in the weakly deformed domains belong to the Qinling, Danfeng and Liuling Groups. In this paper, the mineral chemistry and mineral assemblages are used to infer the metamorphic conditions and the P–T paths of these units. The metamorphic units in and near the fault zone have different metamorphic conditions and histories that are correlated with the tectonic evolution of the fault zone. Caledonian–Hercynian uplift and southward thrusting of the Proterozoic Qinling Group, over the Danfeng and the Liuling Groups, produced the main metamorphic and tectonic features of the fault zone. Folding of both the Liuling Group and the thrust faults during the Hercynian–Indosinian was accompanied by northward thrusting.  相似文献