Detrital provenance of the Grenvillian Oaxacan Complex,southern Mexico: a zircon perspective     

Luigi A. Solari  Fernando Ortega-Gutiérrez  Mariano Elías-Herrera  Carlos Ortega-Obregón  Consuelo Macías-Romo  Margarita Reyes-Salas 《International Journal of Earth Sciences》2014,103(5):1301-1315

The Oaxacan Complex is the largest exposure of Grenvillian-age rocks in Mexico, constituting the backbone of the Oaxaquia microcontinent. Whereas the main rock-forming events were previously established at 1,150–1,200 Ma (charnockite–syenite–gabbros), 1,020 Ma (AMCG suite), 990 Ma (granulite-facies metamorphism), and ca. 970 Ma post-tectonic pegmatites, no data are yet available to establish provenance links with other Grenville-age terranes. In this work, we studied detrital zircons belonging to 12 samples, all metamorphosed under granulite facies but variably affected by retrogression. Laser ablation inductively coupled plasma mass spectrometry U–Pb geochronology was employed on selected zircons to determine their crystallization age and geochemistry. The results of the analysis of about 100 crystals per sample show that the studied zircons range between ca. 940 and 1,400 Ma, with only three samples having zircons between 1,400 and 1,600 Ma, and only one showing older zircons up to ca. 1,775 Ma. Whereas some of the slightly discordant (1–5 %) zircons in several samples show ages younger than the granulite metamorphism (probably as a result of Pb loss), and thus a disturbed geochemical pattern (abnormal enrichment in LREE, decreasing HREE), a few metamorphic zircons show flat and depleted HREE patterns, contrasting with the igneous pattern of older zircons (positive Ce anomaly, negative Eu anomaly, enriched HREE pattern). The main distributions observed using the kernel density estimator diagrams fall in the range 975–995 Ma (six samples), 1,100 Ma (four samples) and 1,120–1,170 Ma (six samples). Only the southernmost sample shows a marked peak at ca. 1,400 Ma. The application of the Kolmogorov–Smirnov (K–S) statistical test to the studied samples and particularly the comparison of obtained P values yield interesting similarities. Overall, two sample groups show internal similarities, i.e., they may belong to the same source area, whereas only one sample is dissimilar, failing to pass the K–S test. Comparison of these data with the timing of comparable events in the Sveconorwegian orogens, the Sunsas and Rondonia-San Ignacio belts of Amazonia, and some of the Precambrian massifs cropping out in the Andes help to constrain possible Mesoproterozoic conjugate margins of Oaxaquia.  相似文献   

The Role of Acoustic Sounding in a High-Technology Era     

R. L. Coulter  M. A. Kallistratova 《Meteorology and Atmospheric Physics》1999,71(1-2):3-13

Summary This paper presents a brief synopsis of past, current and anticipated progress and problems in the use of acoustic remote sensing for basic and applied research of the lower atmosphere. The potential and reality of the sodar for determination of meteorological parameters and turbulence characteristics is discussed. Sodars’ place alongside other ground-based remote sensors, including radar wind profilers, radioacoustic sounding systems (RASS) and lidars, is elucidated. Areas of atmospheric research where Doppler sodar has certain advantages are described such as cost, sensitivity, spatial and temporal resolution and surface layer measurements. The use of sodar in networks of integrated radar/RASS systems designed to supply uninterrupted monitoring of atmospheric parameters for improvements in forecasts of weather and air quality is demonstrated. The special potential role of sodar in education and training of specialists is suggested to aid in developing and using new methods of atmospheric measurements and meeting the requirements of modern environmental science. A number of problems are formulated whose solution would favor further advancement of acoustic remote sensing in integrated systems for remote monitoring of the atmospheric boundary layer. Received November 23, 1998 Revised January 29, 1999  相似文献   

Assessment of runoff,water and sediment quality in the Selenga River basin aided by a web-based geoservice     

Daniel Karthe  Sergey Chalov  Vsevolod Moreido  Margarita Pashkina  Anna Romanchenko  Gunsmaa Batbayar  Andrei Kalugin  Katja Westphal  Marcus Malsy  Martina Flörke 《Water Resources》2017,44(3):399-416

The Selenga River is the main artery feeding Lake Baikal. It has a catchment of ~450000 km² in the boundary region between Northern Mongolia and Southern Siberia. Climate, land use and dynamic socioeconomic changes go along with rising water abstractions and contaminant loads originating from mining sites and urban wastewater. In the future, these pressures might have negative impacts on the ecosystems of Lake Baikal and the Selenga River Delta, which is an important wetland region in itself and forms the last geobiochemical barrier before the Selenga drains into Lake Baikal. The following study aims to assess current trends in hydrology and water quality in the Selenga-Baikal basin, identify their drivers and to set up models (WaterGAP3 framework and ECOMAG) for the prediction of future changes. Of particular relevance for hydrological and water quality changes in the recent past were climate and land use trends as well as contaminant influx from mining areas and urban settlements. In the near future, additional hydrological modifications due to the construction of dams and abstractions/water diversions from the Selenga’s Mongolian tributaries could lead to additional alterations.  相似文献   

Hybrid method to update the design flood shape for spillway operation in a dam: case study of the Huites Dam,Mexico     

Maritza Liliana Arganis-Juárez  Margarita Preciado-Jiménez  Óscar A. Fuentes-Mariles  Alejandro Mendoza-Reséndiz  Ramón Domínguez-Mora  Faustino De Luna-Cruz 《水文科学杂志》2019,64(8):934-947

To design and review the operation of spillways, it is necessary to estimate design hydrographs, considering their peak flow, shape and volume. A hybrid method is proposed that combines the shape of the design hydrograph obtained with the UNAM Institute of Engineering Method (UNAMIIM) with the peak flow and volume calculated from a bivariate method. This hybrid method is applied to historical data of the Huites Dam, Sinaloa, Mexico. The goal is to estimate return periods for the maximum discharge flows (that account for the damage caused downstream) and the maximum levels reached in the dam (measure of the hydrological dam safety) corresponding to a given spillway and its management policy. Therefore, to validate the method, the results obtained by the flood routing of the 50-year hydrograph are compared with those obtained by the flood routing of the three largest historical floods. Both maximum flow and elevation were in the range of values observed within 37.5–75 years corresponding to the length of the historical record.  相似文献   

Wide-field ultraviolet imager for astronomical transient studies     

Joice Mathew  S. Ambily  Ajin Prakash  Mayuresh Sarpotdar  K. Nirmal  A. G. Sreejith  Margarita Safonova  Jayant Murthy  Noah Brosch 《Experimental Astronomy》2018,45(2):201-218

Though the ultraviolet (UV) domain plays a vital role in the studies of astronomical transient events, the UV time-domain sky remains largely unexplored. We have designed a wide-field UV imager that can be flown on a range of available platforms, such as high-altitude balloons, CubeSats, and larger space missions. The major scientific goals are the variability of astronomical sources, detection of transients such as supernovae, novae, tidal disruption events, and characterizing active galactic nuclei variability. The instrument has a 80 mm aperture with a circular field of view of 10.8 degrees, an angular resolution of ～22 arcsec, and a 240 - 390 nm spectral observation window. The detector for the instrument is a Microchannel Plate (MCP)-based image intensifier with both photon counting and integration capabilities. An FPGA-based detector readout mechanism and real time data processing have been implemented. The imager is designed in such a way that its lightweight and compact nature are well fitted for the CubeSat dimensions. Here we present various design and developmental aspects of this UV wide-field transient explorer.  相似文献   

Sodar Sounding of the Atmospheric Boundary Layer: Review of Studies at the Obukhov Institute of Atmospheric Physics,Russian Academy of Sciences   总被引：1，自引：0，他引：1  

M. A. Kallistratova  I. V. Petenko  R. D. Kouznetsov  S. N. Kulichkov  O. G. Chkhetiani  I. P. Chunchusov  V. S. Lyulyukin  D. V. Zaitseva  N. V. Vazaeva  D. D. Kuznetsov  V. G. Perepelkin  G. A. Bush 《Izvestiya Atmospheric and Oceanic Physics》2018,54(3):242-256

Acoustic sounders (sodars) are the simplest and economically most effective devices for the ground-based remote sensing of the lower troposphere. Using sodars, a vast amount of knowledge about the structure and dynamics of the atmospheric boundary layer (ABL) has been obtained. The principal physics of sodar sounding was given by A.M. Obukhov in two short theoretical articles published in the Reports of the USSR Academy of Sciences in 1941: “On the Scattering of Sound in a Turbulent Flow” and “On the Distribution of Energy in the Spectrum of a Turbulent Flow.” In the late 1950s, Obukhov initiated the development of theoretical and experimental studies of sound scattering by turbulence, as well as a practical sodar sounding of the ABL at the Institute of Atmospheric Physics (IAPh). The present work is a short review of sodar applications in studies of the ABL based on results obtained at IAPh in the 1980s–2000s. The results of recent studies of low-level jets and Kelvin–Helmholtz billows in the stable stratified ABL are described in more detail.  相似文献   

A software package for evaluating the performance of a star sensor operation     

Mayuresh Sarpotdar  Joice Mathew  A. G. Sreejith  Nirmal K.  S. Ambily  Ajin Prakash  Margarita Safonova  Jayant Murthy 《Experimental Astronomy》2017,43(1):99-117

We have developed a low-cost off-the-shelf component star sensor (StarSense) for use in minisatellites and CubeSats to determine the attitude of a satellite in orbit. StarSense is an imaging camera with a limiting magnitude of 6.5, which extracts information from star patterns it records in the images. The star sensor implements a centroiding algorithm to find centroids of the stars in the image, a Geometric Voting algorithm for star pattern identification, and a QUEST algorithm for attitude quaternion calculation. Here, we describe the software package to evaluate the performance of these algorithms as a star sensor single operating system. We simulate the ideal case where sky background and instrument errors are omitted, and a more realistic case where noise and camera parameters are added to the simulated images. We evaluate such performance parameters of the algorithms as attitude accuracy, calculation time, required memory, star catalog size, sky coverage, etc., and estimate the errors introduced by each algorithm. This software package is written for use in MATLAB. The testing is parametrized for different hardware parameters, such as the focal length of the imaging setup, the field of view (FOV) of the camera, angle measurement accuracy, distortion effects, etc., and therefore, can be applied to evaluate the performance of such algorithms in any star sensor. For its hardware implementation on our StarSense, we are currently porting the codes in form of functions written in C. This is done keeping in view its easy implementation on any star sensor electronics hardware.  相似文献