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141.
Jong-Kuk Choi Hyun-Joo Oh Bon Joo Koo Joo-Hyung Ryu Saro Lee 《Estuarine, Coastal and Shelf Science》2011
The purpose of this study was to apply probabilistic models to the mapping of the potential polychaeta habitat area in the Hwangdo tidal flat, Korea. Remote sensing techniques were used to construct spatial datasets of ecological environments and field observations were carried out to determine the distribution of macrobenthos. Habitat potential mapping was achieved for two polychaeta species, Prionospio japonica and Prionospio pulchra, and eight control factors relating to the tidal macrobenthos distribution were selected. These included the intertidal digital elevation model (DEM), slope, aspect, tidal exposure duration, distance from tidal channels, tidal channel density, spectral reflectance of the near infrared (NIR) bands and surface sedimentary facies from satellite imagery. The spatial relationships between the polychaeta species and each control factor were calculated using a frequency ratio and weights-of-evidence combined with geographic information system (GIS) data. The species were randomly divided into a training set (70%) to analyze habitat potential using frequency ratio and weights-of-evidence, and a test set (30%) to verify the predicted habitat potential map. The relationships were overlaid to produce a habitat potential map with a polychaeta habitat potential (PHP) index value. These maps were verified by comparing them to surveyed habitat locations such as the verification data set. For the verification results, the frequency ratio model showed prediction accuracies of 77.71% and 74.87% for P. japonica and P. pulchra, respectively, while those for the weights-of-evidence model were 64.05% and 62.95%. Thus, the frequency ratio model provided a more accurate prediction than the weights-of-evidence model. Our data demonstrate that the frequency ratio and weights-of-evidence models based upon GIS analysis are effective for generating habitat potential maps of polychaeta species in a tidal flat. The results of this study can be applied towards conservation and management initiatives for the macrofauna of tidal flats. 相似文献
142.
Since the 1980s, the coastal wetlands in Korea have been rapidly degraded and destroyed mainly due to reclamation and landfills
for coastal development. In order to recover damaged coastal environments and to develop wetland restoration technologies,
a 4-year study on ecological the restoration of coastal vegetated ecosystems was started in 1998. As one of a series of studies,
a small-scale experiment on salt marsh restoration was carried out from April 2000 to August 2001. The experiment was designed
to find effective means of ecological restoration through a comparison of the changes in environmental components and species
structure between two different experimental plots created using sediment fences, one with and one without small canals. Temporal
variation in surface elevation, sedimentary facies, and benthic species were measured seasonally in each plot and in the adjacent
natural reference sites. Monthly exposure occurred from 330 cm to mean sea level, which represents the critical tidal level
(CTL) at which salt marsh plants colonize. Vegetation, especially Suaeda japonica, colonized the site the following spring and recovered to a similar extent in the natural marshes 16 months later. The sedimentary
results indicated that the sediment fences had effects on particle size and sediment accumulation, especially in the plot
with small canals. This experiment also showed that tidal height, especially that exceeding the CTL, is an important factor
in the recovery of the benthic fauna of salt marshes. From these results, we suggested that designs for the restoration of
salt marsh ecosystems must consider the inclusion of a tidal height exceeding CTL, as this may allow reconstruction of the
previous natural ecosystem without artificial transplanting. 相似文献
143.
Recent years have witnessed debates in the American South between traditional white Southerners and African American Southerners over whether and how symbols from the region's two defining historical events – the Civil War and the Civil Rights movement – are displayed on the region's landscape. This paper examines the most contentious of these debates, the conflict over government sanction for flying the various flags of the Confederate States of America. This article first discusses the concepts of iconography and public memory, and then the role of Confederate flags in traditional white Southern iconography. We then examine four recent attempts in the states of Georgia, Alabama and South Carolina, and within the chambers of the U.S. Senate to remove government sanction for flying Confederate flags. We conclude from these debates that while icons can act as centripetal forces binding a people together, they can also emerge as centrifugal forces, further splitting apart a region's population along major cultural and racial divisions. 相似文献
144.
The formation of the magnesium silicate minerals forsterite, enstatite, and roedderite by heating of amorphous “protosilicate” gels precipitated from aqueous solution has been studied by 29Si MAS nmr. Gentle drying of the hydrogels at 110° C gives materials with broad nmr signals that do not differ appreciably with preparation conditions, but the minerals formed by heating at 750° C or higher are greatly dependent on the precipitation and washing conditions of the original gel. The rare mineral roedderite, best known from studies of unequilibrated enstatite chondrite meteorites, becomes a major species along with forsterite when the hydrogels are washed with sodium hydroxide solution before drying and heating to 750° C. 相似文献
145.
Yujie Liu Wenqiang Yang Chao Zhang Zhian Bao Shitou Wu Renat R. Almeev Filippo Ridolfi Roberta Oberti 《Geostandards and Geoanalytical Research》2023,47(3):595-608
The amphiboles from Kakanui and Arenal are two natural minerals that have been used worldwide as microanalytical reference materials, but their compositions and crystal structures are still poorly constrained. In this paper, we report new data on H2O and trace element mass fractions and single-crystal structural refinement of these two amphiboles. H2O mass fractions of the Kakanui and Arenal amphiboles determined via Karl-Fischer titration are 0.92 ± 0.18 (2s) and 1.56 ± 0.22% m/m (2s), respectively; these values estimated based on crystal-structure refinement are 0.86 and 1.46% m/m, respectively. Trace element mass fractions measured via LA-ICP-MS in two laboratories are in good agreement, and spots from five fragments for both Kakanui and Arenal amphiboles are generally consistent within reproducibility precision (2s). Our measurements indicate a better homogeneity for the amphiboles from Kakanui than that from Arenal. According to the latest scheme for amphibole classification and nomenclature (Hawthorne et al. 2012), the sample from Arenal is a (partially dehydrogenated) pargasite, and that from Kakanui is a kaersutite. The significant amount of oxo-component and that CTi4+ content is strongly ordered at the M(1) site for both amphiboles indicate crystallisation under high fO2 conditions. 相似文献
146.
A. Díaz-Moreno G. Barberi O. Cocina I. Koulakov L. Scarfì L. Zuccarello J. Prudencio A. García-Yeguas I. Álvarez L. García J. M. Ibáñez 《Surveys in Geophysics》2018,39(1):57-97
In the Central Mediterranean region, the production of chemically diverse volcanic products (e.g., those from Mt. Etna and the Aeolian Islands archipelago) testifies to the complexity of the tectonic and geodynamic setting. Despite the large number of studies that have focused on this area, the relationships among volcanism, tectonics, magma ascent, and geodynamic processes remain poorly understood. We present a tomographic inversion of P-wave velocity using active and passive sources. Seismic signals were recorded using both temporary on-land and ocean bottom seismometers and data from a permanent local seismic network consisting of 267 seismic stations. Active seismic signals were generated using air gun shots mounted on the Spanish Oceanographic Vessel ‘Sarmiento de Gamboa’. Passive seismic sources were obtained from 452 local earthquakes recorded over a 4-month period. In total, 184,797 active P-phase and 11,802 passive P-phase first arrivals were inverted to provide three different velocity models. Our results include the first crustal seismic active tomography for the northern Sicily area, including the Peloritan–southern Calabria region and both the Mt. Etna and Aeolian volcanic environments. The tomographic images provide a detailed and complete regional seismotectonic framework and highlight a spatially heterogeneous tectonic regime, which is consistent with and extends the findings of previous models. One of our most significant results was a tomographic map extending to 14 km depth showing a discontinuity striking roughly NW–SE, extending from the Gulf of Patti to the Ionian Sea, south-east of Capo Taormina, corresponding to the Aeolian–Tindari–Letojanni fault system, a regional deformation belt. Moreover, for the first time, we observed a high-velocity anomaly located in the south-eastern sector of the Mt. Etna region, offshore of the Timpe area, which is compatible with the plumbing system of an ancient shield volcano located offshore of Mt. Etna. 相似文献
147.
Riegel Roberta Plangg Alves Darlan Daniel Schmidt Bruna Caroline de Oliveira Guilherme Garcia Haetinger Claus Osório Daniela Montanari Migliavacca Rodrigues Marco Antônio Siqueira de Quevedo Daniela Muller 《Natural Hazards》2020,103(1):497-511
Natural Hazards - The increase in the frequency of natural disasters in recent years and its consequent social, economic and environmental impacts make it possible to prioritize areas of risk as an... 相似文献
148.
Roberta L. Rudnick Lewis D. Ashwal Darrell J. Henry 《Contributions to Mineralogy and Petrology》1984,87(4):399-406
Fluid inclusions in quartz grains from five samples of high-grade rocks (two paragneisses, an amphibolite, a mafic gneiss and a tonalite dike) from the 2.7 Ga Kapuskasing structural zone (KSZ), Ontario, were examined with petrographic, microthermometric and laser Raman techniques. Three types of fluid inclusions were observed: CO2-rich, H2O-rich and mixed CO2-H2O. CO2-rich fluid inclusions are pseudosecondary or secondary in nature and are generally pure CO2; a few contain varying amounts of CH4·H2O-rich fluid inclusions are secondary in nature, contain variable amounts of dissolved salts, and generally contain daughter crystals. Mixed CO2-H2O fluid inclusions occur where trails of H2O-rich inclusions intersect trails of CO2-rich inclusions. Isochores for high density (p=1.03 g/cm3) pseudosecondary, pure CO2 inclusions intersect the lower pressure portion of the estimated P-T field for high-grade metamorphism, implying that pure CO2 was the peak metamorphic fluid. The variable CH4 content of CO2 inclusions within graphite-bearing samples suggests that CH4 was introduced locally after the formation of the CO2 inclusions; however the origin of the CH4 remains problematic. An aqueous fluid clearly penetrated the gneisses after the peak metamorphism (during uplift/erosion), forming secondary inclusions and contributing to the minor retrogressive hydration observed in these rocks. The presence of the pseudosecondary, high-density CO2 inclusions in quartz crystals in the KSZ rocks constrains the uplift/ erosion path for the KSZ to one of simultaneous decrease in pressure and temperature. 相似文献
149.
Ion microprobe UThPb ages of zircons from granulite facies lower crustal xenoliths from north Queensland, Australia, correlate well with the ages of major orogenic episodes manifest at the earth's surface. About half of the xenoliths contain Proterozoic zircons which are similar in age to the episodes of high-grade metamorphism of the older surface rocks. All the xenoliths contain late Paleozoic zircons which show a real 100 Ma range in206Pb238/U ages (from 320 to 220 Ma), which is attributed to granulite facies metamorphism followed by slow cooling in the deep crust. The Paleozoic zircon ages coincide in time with the prolonged episode of eruption of voluminous felsic ash-flows and intrusion of high-level granites in this region (320-270 Ma). Mineral and melt inclusions in the zircons provide clues to the origin of some of the xenoliths, and coupled with the age information, can be used to infer the geological processes operating in the lower crust. The zircons from two mafic xenoliths contain felsic and intermediate melt inclusions implying at least a two-stage history for these rocks, involving either partial melting of a more felsic protolith or crystal accumulation from an evolved melt. Some of the zircons from the felsic xenoliths contain CO2-rich fluid inclusions, indicating that those zircons grew during high-grade metamorphism. The isotopic and chemical data for the whole rock xenoliths show that they originate from a segment of the lower crust which is a heterogeneous mixture of supracrustal and mafic, mantle-derived, lithologies. The major orogenic event responsible for the formation of that crust occurred in the late Paleozoic, when Proterozoic supracrustal rocks were emplaced into the lower crust, possibly along thin-skinned thrust slices. This was accompanied by intrusion of high-temperature, mantle-derived melts which caused partial melting of pre-existing crust. The most likely setting for such tectonism is a continental margin subduction zone. 相似文献
150.
The effect of a magnetic field on a thermal instability has been studied in a radiatively cooling region behind an interstellar shock of moderate propagation velocity ( 10 km s–1). It is shown that the presence of a magnetic field of a few microgauss is very effective in preventing the thermal instability from building-up density concentrations. In the absence of the magnetic field, the shock-induced thermal instability will amplify a pre-shock density inhomogeneity by more than an order of magnitude. However, in the field's presence, the amplified density contrast is shown to be only a factor 2. Implications for the trace of a sweeping broom in the Pleiades nebula are discussed.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984. 相似文献