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Science China Earth Sciences 2008年第3期51卷 339-348页

作者： David Dian department of geography and geology the University of Hong Kong

Contemporaneous with MIS3, the MGS3 segment of the Milanggouwan stratigraphic section in the Salawusu River Valley, Mu Us Desert, China contains fossil gastropods (terrestrial and freshwater snails) in strata 33LS, 35LS, 37FL and 39LS. Examination of these fossils revealed 11 species belonging to 8 families and 10 genera. They can be classified as: (1) assemblage of Gyraulus and Galba mainly consisting of Gyraulus convexiusculus, Gyraulus sibiricus, Galba pervia and Galba superegra Gredler, etc. (2) assemblage of Vallonia mainly consisting of terrestrial snails, such as Vallonia patens, Pupilla muscorum and Discus paupe, etc. Based on the dating results, and the living habits, living conditions, and geographic distribution of their extant species, we suggest that: the ages of 33LS, 35LS, 37FL, and 39LS are 26000, 29000, 33000 and 38000 a, respectively, corresponding well to the interstadial period in GRIP 4, 5, 6 and 10 in terms of chronology and climatic characters; 33LS, 35LS and 39LS represent very warm-humid periods, while 37FL represents a less warm-humid period; the four periods of climatic fluctuations recorded in MGS3 were related to the strong impact of the summer monsoon in East Asia in Mu Us Desert of China during the interstadial of MIS3 on a global climatic background.

关键词： Salawusu River Valley Milanggouwan Section MGS3 stratigraphic segment fossil gastropods climatic environment

Hillslope coupled stream morphology, flow conditions, and their effects on detrital sedimentology in Garnet Canyon, Teton Range,Wyoming

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Geoscience Frontiers 2018年第4期9卷 1193-1202页

作者： Lisa M.Tranel department of geography Geology and the Environment Illinois State University

Characterizing stream erosion in any steep mountain landscape is arduous, but the challenge level increases when the stream flows through a glaciated catchment frequently modified by hillslope *** landforms and stochastic mass wasting in alpine systems may interfere with sediment delivery to downstream sites where detrital sediments are often collected to represent upstream bedrock *** use detrital sediments as indicators of erosion, we need to understand potential sediment accumulation in flat glaciated reaches or behind rockfall barriers. This study investigates the stream channel in Garnet Canyon, a glaciated catchment located in the central Teton Range, to describe hillslope coupled channel morphology and the subsequent effects on sediment transport throughout the *** cross-section surveys and sediment size measurements of the surface bedload were collected in the field within a glacially flattened segment of Garnet Canyon. Calculations of shear stress conditions allowed evaluation of the importance of mineral densities on potential grain entrainment. The length of the Garnet Canyon stream observed in this study was coupled with hillslope deposits. Critical shear stresses were sufficient to move gravel-sized sediments through all sections when calculated with quartz mineral density and through most sections when applying apatite mineral density. These results verify the application of detrital sediments to evaluate erosion rates or spatial bedrock sources because snowmelt stream flow efficiently moves entrained sediment past glacially reduced slopes and potential talus barriers.

关键词： Stream Morphology Garnet Canyon Sediment Talus

Analysis on variety and characteristics of maghemite

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Science China Earth Sciences 2010年第8期53卷 1153-1162页

作者： SHAW John BLOEMENDAL Jan HESSE Paul ROLPH Tim department of Earth Sciences University of Liverpool department of geography University of Liverpool department of Environment and geography Macquarie University department of geology University of Newcastle

Maghemite (γ-Fe2O3) is a very common mineral at the earth’s surface and also an important material for making music and video tapes. Maghemite is usually synthesized from magnetite under oxidizing conditions after a few hours or a few days below a temperature of 300°C. The magnetic property of thermal instability and the chemical action after heating is an important character for maghemite. That is, it will become hematite in certain proportion after being heated above 250°C. Maghemite is therefore actually unable to have its Curie temperature measured. But late using synthetic sample, maghemite was further found partially thermal stable with a measurable Curie temperature ~645°C. During our thermally magnetic experiments for a set of synthetic magnetite, we found that extra fined grain size (pseudo single domain (PSD) and small multi-domain (MD), mainly 1-10 μm) magnetite was formed to a completely thermally stable maghemite. This maghemite can also be produced by heating the same powder up to 700°C in an oven and keeping this temperature for 10 min, then cooling it down. When the generated maghemite by these two ways is heated from room temperature to 700°C, it shows almost fully reversible, or thermally stable. We used X-ray powder diffraction and Mssbauer spectroscopy to confirm the identity of this maghemite and compared its magnetic hysteresis, high temperature magnetization, low temperature thermal demagnetization, and low temperature susceptibility with those of the original preheated magnetite. Such quickly oxidized maghemite by heating to high temperature implies some types of maghemite formed in certain natural condition can carry a thermal remnant magnetization (TRM). Four types of maghemite were characterized and discussed according to their thermal stability. Among them, partially stable and fully thermally stable maghemite after heating should possess capability of carrying TRM. There is possibly a compensation of synthetizing maghemite between heatin

关键词： maghemite paleomagnetism environmental magnetism magnetic mineral thermal stability TRM

Theory and practice of runoff space-time distribution

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Science China(Technological Sciences) 2004年第z1期47卷 90-105页

作者： Thomas M. Over department of geology/geography Eastern Illinois University Charleston IL 61920 USA

Based on the domestic and foreign concerning researches, this paper submits the runoff space-time distribution theory which shows evident scientific significances and powerful practical functions. On the basis of digital basin unit cell deriving from the digital elevation model (DEM) and assumption of linear confluence, this theory has been applied successfully to the runoff correlation researches in humid regions. In order to prove the adaptability of the theory in arid and semi-drought regions, this paper is used to the runoff correlation analysis in Wuding River basin——a tributary of Yellow River Basin, and has gained preliminary effective verification.

关键词： runoff space-time distribution, theory, the Wuding River, correlation coefficient, practice.

Investigations　of　the　seismomagnetic　effect　in　the　geomagnetic　diurnal　variations

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Acta Seismologica Sinica(English Edition) 1994年第3期7卷 457-464页

作者：陈伯舫 1. department of Physics and department of geography and geology University of Hong Kong Hong Kong

In this paper we attempt to Abstract seismomagnetic signals from geomagnetic diurnal variations of three components in quiet days before and after great earthquakes. The method employed here is to examine the ratio of apparent depths between two geomagnetic observatories using the single-station Z/H method. We first estimate the apparent depth for the period of 24 h for two observatories which are located at almost the same latitude. Then we analyse the time changes of the apparent-depth-ratio between these stations. In the interval of 1962 1988, the time variation of apparent-depth-ratio between the Beijing and Lanzhou observatories seems to be related to the three great earthquakes occurred near Beijing. Roughly speaking, the anomalous change in apparentdepth-ratio appears to be positive before earthquake, and appears to be negative after earthquake.

关键词： geomagnetic S_q field single-station Z/H method deep conductivily seismomagnetic effect

An investigation on the wind profiles and gravity wave dynamics in MLT region based on the meteor radars from the Meridian Project

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Earth and Planetary Physics 2025年第1期9卷 29-38页

作者： Tai Liu Zhe Wang MengXi Shi Willie Soon ShiCan Qiu department of Geophysics College of the Geology Engineering and GeomaticsChang’an UniversityXi’an 710054China Center for Environmental Research and Earth Sciences(CERES) SalemMA 01970USA Institute of Earth Physics and Space Science(ELKH EPSS) 9400SopronHungary

The meteor radar can detect the zenith angle,azimuth,radial velocity,and altitude of meteor trails so that one can invert the wind profiles in the mesosphere and low thermosphere(MLT)region,based on the Interferometric and Doppler *** this paper,the horizontal wind field,gravity wave(GW)disturbance variance,and GW fluxes are analyzed through the meteor radar observation from 2012−2022,at Mohe(53.5°N,122.4°E)and Zuoling(30.5°N,114.6°E)stations of the(Chinese)Meridian *** Lomb−Scargle periodogram method has been utilized to analyze the periodic variations for time series with observational data *** results show that the zonal winds at both stations are eastward dominated,while the meridional winds are southward *** variance of GW disturbances in the zonal and meridional directions increases gradually with height,and there is a strong pattern of annual *** zonal momentum flux of GW changes little with height,showing weak annual *** meridional GW flux varies gradually from northward to southward with height,and the annual periodicity is *** both stations,the maximum values of zonal and meridional wind occur close to the peak heights of GW flux,with opposite *** observational evidence is consistent with the filtering *** horizontal wind velocity,GW flux,and disturbance variance of the GW at Mohe are overall smaller than those at Zuoling,indicating weaker activities in the MLT at *** power spectral density(PSD)calculated by the Lomb−Scargle periodogram shows that there are 12-month period and 6-month period in horizontal wind field,GW disturbance variance and GW flux at both stations,and especially there is also a 4-month cycle in the disturbance *** PSD of the 12-month and 6-month cycles exhibits maximum values below 88 km and above 94 km.

关键词： meteor radar wind field gravity wave Lomb−Scargle method

Seasonal comparison of moss bag technique against vertical snow samples for monitoring atmospheric pollution

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Journal of Environmental Sciences 2016年第3期28卷 128-137页

作者： Hanna Salo Anna-Kaisa Berisha Joni M?kinen department of geography and geology University of Turku Centre for Research of Lifelong Learning and Education(CELE) University of Turku

This is the first study seasonally applying Sphagnum papillosum moss bags and vertical snow samples for monitoring atmospheric *** bags,exposed in January,were collected together with snow samples by early March 2012 near the Harjavalta Industrial Park in southwest ***,chemical,scanning electron microscopy-energy dispersive X-ray spectroscopy（SEM-EDX）,K-means clustering,and Tomlinson pollution load index（PLI）data showed parallel spatial trends of pollution dispersal for both *** strengthen previous findings that concentrate and slag handling activities were important（dust）emission sources while the impact from Cu–Ni smelter＇s pipe remained secondary at closer *** significant correlations existed between the variables of snow and moss *** a summary,both methods work well for sampling and are efficient pollutant *** bags can be used also in winter conditions and they provide more homogeneous and better controlled sampling method than snow samples.

关键词： Biomonitoring Industrial pollution Heavy metal Magnetic susceptibility Scanning electron microscopy-energy dispersive X-ray spectroscopy

Thermal history of a Late Mesoproterozoic paired metamorphic belt(?)during Rodinia assembly:New insight from medium-pressure granulites from the Aravalli-Delhi Mobile Belt, Northwestern India

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Geoscience Frontiers 2018年第2期9卷 335-354页

作者： Santanu Kumar Bhowmik Somnath Dasgupta Sudipta Baruah Deepika Kalita department of geology and Geophysics Indian Institute of Technology Kharagpur department of geography Faculty of Natural SciencesJamia Millia Islamia

In this study, we investigate the possible record of a Late Mesoproterozoic paired metamorphic belt in the Aravalli-Delhi Mobile Belt(ADMB), NW India using a suite of supracrustal and metaigneous granulites from the Pilwa-Chinwali granulite terrain at the north-western margin of the ADMB. Using metamorphic reaction textures, mineral chemistry, metamorphic reaction history, geothermobarometric computations and electron microprobe dating of monazite in 5 samples of pelitic granulite, leptynite gneiss, enderbite and charnockite, we have deduced a medium-pressure granulite facies metamorphism(P between 4.9 and 6.8 kbar, T> 760-815℃) along a heating-cooling, counterclockwise P-T path between 1.09 and 1.01 Ga. When collated with published metamorphic and chronological constraints and geological settings of the adjoining crustal domains of the ADMB, these findings provide new insights into the developments of two tectonic domains of contrasting thermal gradients at ca. 1.0 Ga, consistent with metamorphic transformations in tectonically thickened middle-lower crustal sections during continental collision to continental subduction and in the root zones of spatially adjacent island arc, as part of the Rodinia supercontinent assembly event.

关键词： ADMB Granulites CCW-P-T path Monazite chemical dating ca. 1.0 Ga metamorphism Paired metamorphic belt

Spatiotemporal variability of channel and bar morphodynamics in the Gorai-Madhumati River,Bangladesh using remote sensing and GIS techniques

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Frontiers of Earth Science 2020年第4期14卷 828-841页

作者： Md.Yousuf Gazi Farhad Hossain Sumiya Sadeak Md.Mahin Uddin department of geology University of DhakaDhaka1000Bangladesh department of geography and Environment University of DhakaDhaka1000Bangladesh

Bangladesh is a riparian country that is criss-crossed by the many tributaries and distributaries of the mighty Ganges,Brahmaputra,and Meghna river ***-Madhumati,a distributary of the Ganges River is an example where morphological development of the river is associated with frequent channel shifting within the catchment *** main objective of this research is to quantify the extent of channel migration,erosion-accretion,river width,sinuosity,and charland morpho-dynamics from 1972 to 2018 using geospatial techniques combined with satellite images and hydrological *** study also addressed the impacts of Farakka Barrage construction in India on the shifting,flow behavior,and siltation of Gorai-Madhumati *** study shows that bar surface areas have abnormally increased in both segments after 1975 due to the construction of Farakka *** flow in the Gorai-Madhumati has dropped remarkably in the downstream and instigated huge sedimentation in this *** of the time series satellite images revealed that the morphology of the river channel experienced huge changes simultaneously with the changes in the seasonal flow and sedimentation all over the study *** trend has frequently shifted and taken place in the NW and NE direction in the observed sections of the *** the study period,total amount of accretion was greater than the net percentage of erosion on both banks of the *** discharge,bar accretion,and erosion history show that the Gorai-Madhumati River will no longer exist with the present flowing condition without attention and proper river management.

关键词： channel migration erosion-accretion morphodynamics geospatial techniques Gorai-Madhumati Bangladesh

Were Late Cretaceous extinctions of gastropods selective by generic longevity?

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Geoscience Frontiers 2013年第1期4卷 87-93页

作者： Dmitry A.Ruban Division of Mineralogy and Petrography Geology and Geography FacultySouthern Federal University

Many gastropod taxa went extinct during the Late Cretaceous. The stratigraphic ranges of 268 genera permit to establish the longevity of extinction victims for each stage of this epoch. ＂Young＂ taxa （originated within B epochs before the extinction） prevailed among victims of the extinctions in all stages. The proportion of ＂old＂ taxa （originated before the Cretaceous） that went extinct was the highest in the Cenomanian, and it was the lowest in the Coniacian and the Maastrichtian. It appears that the end-Cretaceous mass extinction affected chiefly ＂young＂ taxa. However, the comparison with the earlier time intervals suggests that this pattern of selectivity by generic longevity was not specific for the noted catastrophe, but, in contrast, it was typical for the entire Late Cretaceous. The latest Cenomanian environmental perturbation （OAE2） caused a stronger extinction of＂old＂ taxa, and thus, this biotic crisis was less selective by generic longevity. This hypothesis, however, is not proven by the statistical test.

关键词： Gastropods Extinction Longevity Selectivity Late Cretaceous