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81.
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83.
Te-Hsien Lin Ching-Hua Lo Sun-Lin Chung Fang-Jui Hsu Meng-Wan Yeh Tung-Yi Lee Jian-Qing Ji Yi-Zhau Wang Dunyi Liu 《Journal of Asian Earth Sciences》2009,34(5):674-685
We conducted a comprehensive 40Ar/39Ar geochronological study of the Jiali and Gaoligong shear zones to obtain a better understanding of crustal deformation and tectonic evolution around the Eastern Himalayan Syntaxis (EHS). The new age data reveal that the main phase of deformation in the Jiali and Gaoligong shear zones occurred from 22 to 11 Ma and from 18 to 13 Ma, respectively. Structural data collected during this study indicate that the Jiali shear zone underwent a change in shear sense from sinistral to dextral during its movement history. Based on a comparison with the deformation histories of other major shear zones in the region, we argue that the initial sinistral motion recorded by the Jiali shear zone was coincident with that of the Ailao Shan–Red River shear zone, which marked the northern boundary of the southeastward extrusion of the Indochina block during the Early Miocene. From the Middle Miocene (~18 Ma), the Jiali shear zone changed to dextral displacement, becoming linked with the dextral Gaoligong shear zone that developed as a consequence of continued northward indentation of the Indian continent into Asia. Since this time, the Jiali and Gaoligong shear zones have been united, defining the southwestern boundary of the EHS during clockwise rotation of the eastward-extruding Tibetan block, as revealed by recent GPS data. The temporal change in regional deformation pattern from southeastward block extrusion to clockwise rotation of crustal fragments may have played an important role in the development of the eastern Himalayan drainage system around the EHS. 相似文献
84.
Landsat MSS images and SPOT HRV data were employed to map the changes in turbidity levels in the Zhujiang estuarine region, South China, during the dry season in the period 1973–1987 at low and high tides. Analysis of turbidity trends and changes in the spatial pattern of high turbidity class was carried out with a GIS software—IDRISI. It was concluded that with the use of OVERLAY and RECLASS functions in the GIS approach a large number of turbidity maps could be easily compared and the turbidity trend determined. The GIS approach further permitted evaluation of the importance of such factors as water depths, mean tidal differences, and water salinity to sedimentation in the study region. 相似文献
85.
Béatrice Allard Michaël Danger Loïc Ten-Hage Gérard Lacroix 《Aquatic Sciences - Research Across Boundaries》2011,73(1):113-126
The effects of food web structure on the quantity and biochemical composition of seston, zooplankton and recently deposited
sediment in experimental freshwater mesocosms were examined. Food web structure was manipulated by addition of zooplanktivorous
fish. Biochemical characterisations were carried out using lipid biomarkers (sterols, fatty acids, chlorophyll-derived compounds
and long-chain alkanediols). Fish addition decreased zooplankton biomass and increased seston biomass and deposited sediment
through a trophic cascade. Fish presence strongly influenced the biochemical characteristics of seston and sediment. In contrast,
food web structure had a minor impact on the lipid biomarker composition of zooplankton. Although the relative abundance of
sterols in the different compartments did not differ strongly between treatments, sterol profiles in seston and sediment depended
on food web structure. The predominance of Δ7-sterols in seston and sediment in the fish treatment indicated a major contribution of Chlorophyceae. In contrast, the distribution
of sterols in seston and sediment in the fishless treatment, dominated by cholesterol, indicated a major zooplanktonic input.
The distribution of fatty acids and the relative abundance of chlorophyll-derived compounds and long-chain alkanediols agreed
with the predominant contribution of phytoplankton or zooplankton to seston and sediment in the two treatments. The relative
abundance of bacterial biomarkers suggested that the contribution of bacteria was rather low. The high relative abundance
of polyunsaturated fatty acids (PUFAs) and the absence of stanols in sediments suggested low microbial reworking of organic
matter in the recently accumulated sediments. The trophic cascade, generated by the addition of fish, increased the relative
abundance of PUFAs in deposited organic matter, thus enhancing sediment quality and potential degradability. 相似文献
86.
Preface: Proceedings of the 5th International Symposium on Lithographic Limestone and Plattenkalk 总被引:1,自引:0,他引:1
Daniel Marty Jean-Paul Billon-Bruyat Christian A. Meyer Loïc Costeur Basil Thüring 《Swiss Journal of Geoscience》2011,104(1):1-29
Magmatic rocks from the pre-Mesozoic basements of the Sambuco and Maggia nappes have been dated by U–Pb zircon ages with the LA-ICPMS technique. Several magmatic events have been identified in the Sambuco nappe. The mafic banded calc-alkaline suite of Scheggia is dated at 540 Ma, an age comparable to that of mafic rocks in the Austroalpine Silvretta nappe. The Sasso Nero peraluminous augengneiss has an age of 480–470 Ma, like many other “older orthogneisses” in Alpine basement units. It hosts a large proportion of inherited zircons, which were dated around 630 Ma, a Panafrican age indicating the Gondwanan affiliation of the Sambuco basement. The calc-alkaline Matorello pluton yielded ages around 300 Ma, similar to numerous Late Carboniferous intrusions in other basement units of the Lower Penninic (Monte Leone, Antigorio, Verampio) and Helvetic domains (Gotthard and other External Crystalline Massifs). Associated lamprophyric dykes are slightly younger (300–290 Ma), like similar dykes sampled in gneiss blocks included in the sedimentary cover of the underlying Antigorio nappe (290–285 Ma). The Cocco granodiorite and Rüscada leucogranite, both intruding the basement of the neighbouring Maggia nappe, yielded ages of ca. 300–310 Ma, identical within errors to the age of the Matorello pluton. They are significantly older than former age determinations. This age coincidence, coupled with remarkable petrologic similarities between the Cocco and Matorello granodiorites, strongly suggests paleogeographic proximity of the Sambuco and Maggia nappes in Late Carboniferous times. In recent publications these two nappes have been interpreted as belonging to distinct Mesozoic paleogeographic domains: “European” for Sambuco and “Briançonnais” for Maggia, separated by the “Valais” oceanic basin. In this case, the similarity of the Matorello and Cocco intrusions would demonstrate the absence of any significant transcurrent movement between these two continental domains. Alternatively, according to a more traditional view, Sambuco and Maggia might belong to a single large Alpine tectonic unit. 相似文献
87.
Guor-Cheng Fang Chaur-Tsuen Lo Winn-Jung Huang Jyh-Cherng Chen Yuh-Shen Wu Jun-Han Huang Yi-Liang Huang 《Environmental Earth Sciences》2011,64(5):1237-1247
The main purpose of this study was to monitor ambient air particles and particulate-bound mercury Hg(p) in total suspended
particulates (TSP) concentration, dry deposition at five characteristic-sampling sites. In addition, the calculated/measured
dry deposition flux ratios of ambient air particles and particulate-bound mercury Hg(p) using three dry deposition models
during the years of 2009–2010 were also studied. The results showed that the order of seasonal variations for mean particulate-bound
mercury Hg(p) concentrations in TSP at Bei-shi (suburban/coastal), Chang-hua (downtown) and He-mei (residential) were all
shown as spring > fall, winter > summer, respectively. However, the order of seasonal variations mean particulate-bound mercury
Hg(p) concentrations in TSP that occurred at Gao-mei (wetland) were shown as spring > fall > winter > summer, respectively.
Finally, the results of this study also indicated that using the Noll and Fang model exhibited batten prediction results for
ambient air particles and particulate-bound mercury Hg(p) dry deposition when compared with the other depositions models at
any of the characteristic-sampling sites for this study. 相似文献
88.
Obligatory interactions between species are fundamental to ecosystem functioning and are expected to be particularly sensitive to climate change. Although the effect of past and current climate changes on individual species has been thoroughly investigated, their effect on obligatory interactions has been overlooked. In this review, we present predictions about the effects of climate change on obligatory interactions and illustrate these predictions with examples from the literature. We focus on abrupt past climate change, especially during the Quaternary, because knowing past responses is useful for understanding and predicting the response of organisms and ecosystems to the current climate change. We also pinpoint the need for better time calibration of demographic events from genetic data, and for more studies focused on particularly suitable biological models. We hope that this review will stimulate interaction between the earth sciences and the life sciences on this timely topic. 相似文献
89.
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
90.