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31.
Paleomagnetic and palynologic analyses of Albian to Santonian strata at Bayn Shireh, Burkhant, and Khuren Dukh, eastern Gobi Desert, Mongolia 总被引:1,自引:0,他引:1
Cretaceous terrestrial sediments deposited in a series of intracratonic basins across the Gobi Desert region of southern Mongolia and northern China contain a unique and diverse vertebrate fauna. In 1996 an expedition jointly sponsored by the Mongolian Paleontological Center and the Hayashibara Museum of Natural Sciences revisited a number of famous vertebrate fossil localities in the eastern Gobi region of Mongolia and, as part of a broad geological and paleontological study, collected a series of paleomagnetic samples from measured sections at Bayn Shireh, Burkhant and Khuren Dukh, as well as from an unmeasured locality adjacent to Khuren Dukh. Expedition members also collected palynologic samples from Khuren Dukh and the adjacent locality. Paleomagnetic analysis shows that all the sites from which samples were collected display detrital remnant magnetization that is consistently normal in polarity. The measured Cretaceous magnetic directions are oriented to the east or northeast of the present day expected direction (declination 356.2°, inclination 65.2°), and they are wholly concordant with that expected for a mid-latitude Northern Hemisphere sampling locality, and with the directions for this period reported by other workers. These results, when considered in tandem with the known biostratigraphy, strongly suggest that the sedimentary deposits at all four localities in the eastern Gobi correlate to the normal polarity chron 34 (the Cretaceous Long Normal), which ranges in age from approximately 121 to 83.5 million years. Previous vertebrate, invertebrate and palynological data from Khuren Dukh suggest that the lower and middle parts of the stratigraphic interval exposed there (which have been assigned to the Shinekhudag Formation) are ‘Khukhtekian’ in age and correspond to the Aptian–Albian interval that can be broadly correlated to the older, Early Cretaceous part of the Cretaceous Long Normal, C34n. New palynologic data presented here indicate that these strata are no older than middle to late Albian. The rocks at Bayn Shireh (the Bayn Shireh Formation) have been assigned a ‘Baynshirenian’ biostratigraphic age that may range from Cenomanian to early Campanian. The magnetostratigraphy results presented here indicate that the strata at both the Bayn Shireh and Burkhant localities do not cross the Santonian/Campanian Stage boundary, however, as this is believed to lie at, or very near, the C34n/C33r reversal boundary. Thus, the Bayn Shireh Formation was most likely deposited near the end of the Cretaceous Long Normal Interval, no later than the latest Santonian. 相似文献
32.
Using a set of numerical experiments from 39 CMIP5 climate models, we project the emergence time for 4°C global warming with respect to pre-industrial levels and associated climate changes under the RCP8.5 greenhouse gas concentration scenario. Results show that, according to the 39 models, the median year in which 4°C global warming will occur is 2084. Based on the median results of models that project a 4°C global warming by 2100, land areas will generally exhibit stronger warming than the oceans annually and seasonally, and the strongest enhancement occurs in the Arctic, with the exception of the summer season. Change signals for temperature go outside its natural internal variabilities globally, and the signal-to-noise ratio averages 9.6 for the annual mean and ranges from 6.3 to 7.2 for the seasonal mean over the globe, with the greatest values appearing at low latitudes because of low noise. Decreased precipitation generally occurs in the subtropics, whilst increased precipitation mainly appears at high latitudes. The precipitation changes in most of the high latitudes are greater than the background variability, and the global mean signal-to-noise ratio is 0.5 and ranges from 0.2 to 0.4 for the annual and seasonal means, respectively. Attention should be paid to limiting global warming to 1.5°C, in which case temperature and precipitation will experience a far more moderate change than the natural internal variability. Large inter-model disagreement appears at high latitudes for temperature changes and at mid and low latitudes for precipitation changes. Overall, the inter-model consistency is better for temperature than for precipitation. 相似文献
33.
DONG Weihua YIN Xiuqin 《中国地理科学(英文版)》2007,17(2):166-172
Earthworms are the important constituents in the decayed food web and the main ecological conditioners in the process of decomposition and nutrient mineralization. The transformation of organic carbon (C) and total nitrogen (N) in the broad-leaved litters ingested by earthworms was researched by means of a laboratory experiment. Experimental samples were collected from broad-leaved Korea Pine mixed forest in Liangshui National Natural Reserve (47°10′50″N, 128°53′20″E) in the northeastern Xiao Hinggan Mountains of Northeast China. The contents of organic C and total N in earthworms, leaf litters and earthworm faeces were analyzed. Results show that the organic C content was in the fol- lowing order: leaf litters>faeces>earthworms, while total N content was contrary to that of the organic C. The organic C contents in the different leaf litters were in the following order: Tilia amurensis>Betula costata>Acer mono, whereas the total N contents in the different leaf litters were: Betula costata>Tilia amurensis>Acer mono. The contents of organic C and total N in the faeces from the different leaf litters were almost consistent with the contents of the leaf litters. After the leaf litters were ingested by earthworms, the organic C, which was transformed to increase earthworms' weights, ac- counted for 3.90%-13.31% of the total ingestion by earthworms, while that in the earthworm faeces accounted for 6.14%-13.70%. The transformed organic C through the other metabolism (e.g., respiration) of earthworms accounted for 75.04%-89.92%. The ingested organic C by earthworms was mostly used for metabolic activities. The N ingested by earthworms was less than organic C. It is estimated that 37.08% of total N was transformed to increase the earthworm's weight, 19.97% into earthworm faeces and 47.86% for the consumption of the earthworm's activities. The earthworms not only increased the content of organic C and total N in the soil, but also decreased the values of C/N in the soil and leaf litters. Earthworms play a major role in the leaf litters' decomposition and transformation. 相似文献
34.
针对目前GPS软件接收机C/A码捕获信噪比门限高、捕获速度慢的问题,提出一种基于平均分组和叠加相关的GPS弱信号捕获方法。首先,基于平均相关处理技术降低C/A码捕获过程中的自相关损耗,提高对微弱信号的捕获能力;然后,利用叠加相关提高相干运算的运算效率,并采用线性插值提高自相关函数性能;最后,利用频偏校正和内插进一步提高C/A信号的捕获精度。理论分析和仿真实验均验证,该方法能够在较低的信噪比下实现GPS信号捕获,且精度较高、运算量较低。 相似文献
35.
结合现代餐饮业自动化服务的需求,以无线Soc芯片nRF9E5和点阵型LCD模块ST7920为硬件核心,结合C++Builder软件编程环境,构建了一种基于nRF9E5芯片的无线网络自动化服务管理系统,该系统具有人机界面友好、数据管理软件完善、无线数据传输与控制稳定、高效等特点。可以推广应用到区域水质、土壤等环境的自动监测等领域。 相似文献
36.
The gastric shield and underlying stomach epithelium of Chlymas ffarreri were examined at the light and ultrastructural levels.The results showed that the gastric shield consisted of two different size lobes joined together by a narrow middle piece,the thicker lobe was shaped like a funnel,but unclosed at the lateral side;the other lobe was irregularly triangular-shaped.The transverse section of the thicker lobe was obviously laminated and gradually decreased in thickness from the peak to the margins of the shield.The underlying epithelium bore numerous about 3μm diameter spherical processes formed by the apical plasmalemma of the epithelial cells becoming blunt pseudopodia.Microvilli and some interspersed cilia were present in the areas among the spherical processes regions where only microvilli existed.Rough endoplasmic reticulum,Golgi apparatus,different-sized electron-dense secretory granules and electron-lucent vacuoles as well las abundant mitochondria were present in the underlying epithelial cells.Fused droplets of the secretion from the underlying epithelial cells formed the gastric shield. 相似文献
37.
使用FY-3C气象卫星GNSS掩星数据反演得到2017-03-01~2018-02-28大气温度廓线,并估计对流层顶高度变化;然后利用探空气球数据和ERA5模型数据进行验证;最后以2°×2°的空间分辨率将中国区域划分为608个网格,针对每一个单元格,分别计算对流层顶参数,建立格网模型,分析中国区域对流层顶参数的时空分布... 相似文献
38.
Franco Tassi Orlando Vaselli Elena Lognoli Fabrizio Cuccoli Barbara Nisi Elena Ramaldi Sandro Moretti Luca Lombardi Bruno Capaccioni 《中国地球化学学报》2006,25(B08):70-71
Mt. Amiata (Southern Tuscany, Central Italy) is an extinct Quaternary volcano located in an area still marked by high heat-flow that is caused by deep seated (6-10 km) hot masses related to Pliocene magmatic activity. The anomalous geothermal gradient gives rise, within the Mesozoic limestone formation (Tuscan series), to geothermal systems that fed the Ca-SO4 thermal springs characterizing this area. Besides of thermal fluids, several cold, dry CO2-rich gas emissions seep out on the NE flank of the volcano. These gas vents mostly consist of large sub-circular craters at variable depth and diameter (5-15 m and 10-50 m, respectively), and represent a serious hazard for the local population, as testified by the several asphyxia casualties that have been repeatedly occurred within these morphological depressions. In this work, the chemical and isotopic compositions of the Mt. Amiata "CO2-rich gas vents" and the estimation of both the CO2 flux from the soil and the CO2 distribution in air of their surroundings, has been carried out in order to: (1) assess the origin of gases, (2) recognize the mechanism of formation for these gas emissions and their relationship with local tectonics, and (3) to evaluate the CO2 hazard in the high flux emanations. The chemical composition of the gases is largely dominated by CO2 (up to 98 % by vol) and shows relatively high concentrations of N2, CH4 and H2S (up to 1.1%, 0.9% and 3.9 % by vol, respectively). These features, coupled with the carbon and nitrogen isotopic signatures, suggest that the origin of the main gas compounds may be related to the contribution of deep (i.e., thermometamorphic processes on carbonate formations for CO2) and shallow (i.e. thermal decomposition of organic material for CH4, N2 and H2S) sources. 相似文献
39.
S.
zdemir 《Astronomische Nachrichten》2010,331(3):300-303
Long term behaviours of a few selected X‐ray binaries are studied on the basis of RXTE/ASM archive covering a period of ∼13 years of continuous X‐ray data. Two new superorbital periods seem to be revealed for the GX354‐0 and X Persei systems as 8.7 years and 345 days, respectively. Although the X Persei system has two strongest peaks in its power density spectrum at 15.7 years and at 345 days, the latter is much more plausible. The GX354‐0 system also has few additional periodicities appeared in different time intervals (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
40.
M. Henze W. Pietsch F. Haberl G. Sala M. Hernanz D. Hatzidimitriou A. Rau D.H. Hartmann J. Greiner M. Orio H. Stiele M.J. Freyberg 《Astronomische Nachrichten》2010,331(2):193-196
Classical novae (CNe) have recently been reported to represent the major class of supersoft X‐ray sources (SSSs) in the central area of our neighbouring galaxy M 31. This paper presents a review of results from recent X‐ray observations of M 31 with XMM‐Newton and Chandra. We carried out a dedicated optical and X‐ray monitoring program of CNe and SSSs in the central area ofM 31. We discovered the first SSSs in M 31 globular clusters (GCs) and their connection to the very first discovered CN in a M 31 GC. This result may have an impact on the CN rate in GCs. Furthermore, in our optical and X‐ray monitoring data we discovered the CN M3 1N 2007‐11a, which shows a very short SSS phase of 29–52 days. Short SSS states (durations ≤ 100 days) of CNe indicate massive white dwarfs (WDs) that are candidate progenitors of supernovae type Ia. In the case of M31N 2007‐11a, the optical and X‐ray light curves suggest a binary containing a WD with MWD > 1.0 M⊙. Finally, we present the discovery of the SSS counterpart of the CN M31N 2006‐04a. The X‐ray light curve of M31N 2006‐04a shows short‐time variability, which might indicate an orbital period of about 2 hours (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献