河北围场早中新世藓类化石的植物地理学意义

对河北省围场地区广发永剖面藓类植物薄网藓Leptodictyum riparium、似叶镰刀藓Drepanocladus trichophyllus和多姿柳叶藓Amblystegium varium的古地理及其对应的现代植物地理分布研究显示,这些植物最早出现于早中新世的围场地区,可能起源于该时期的古北大陆,东亚为起源中心。之后向东通过白令陆桥扩散到北美,向西沿欧亚大陆扩散至欧洲西部,至全新世时主要分布在北半球。全新世后,薄网藓与多姿柳叶藓进一步向南扩散,分别由北美及亚洲东部扩散到南美洲及澳大利亚地区,逐步形成现在的分布格局;毛叶镰刀藓则在更新世就已形成与现代相近的分布格局。该研究确立了3种藓类植物的地理起源、地史分布及迁移路线。     

High kinetic energy density jets in the Earth’s magnetosheath: A case study

We study several high kinetic energy density jets observed during a traversal of the dayside magnetosheath by the Cluster spacecraft on March 17, 2001, at various distances from the magnetopause, generally characterised by anomalously high values of the local magnetosonic Mach number. We concentrate on two jets observed just outside the magnetopause, the first almost parallel to the GSM x axis and the second directed northward-tailward along the nominal magnetopause surface. We present evidence that none of them can be ascribed to magnetic reconnection at the magnetopause and show that the magnetopause is severely deformed by the jets, so that its local normal forms an angle of 97° with the quiet time magnetopause normal. On these grounds, we suggest that the indentation of the magnetopause is caused by an anti-sunward jet ramming into the magnetopause slightly equatorward of the northern cusp and that the northward-tailward jet is the result of its reflection at the deformed magnetopause. Finally, we briefly discuss our results by comparing them with past studies of events which in some way recall the one analysed herein.     

GEOLOGY OF KENKOU ON THE HUNAN-KWANGTUNG BORDER AND ITS BEARING TO THE OROGENY OF THE NANLING RANGES

INTRODUCTION In the winter of 1932 and the spring of 1933, the Nanling Mountain ranges covering the borders of Hunan, Kwangtung, Kwangsi and Kueichou were studied by the members of the National Research Institute of Geology,     

Long-term evolution of the aerosol debris cloud produced by the 2009 impact on Jupiter

We present a study of the long-term evolution of the cloud of aerosols produced in the atmosphere of Jupiter by the impact of an object on 19 July 2009 (Sánchez-Lavega, A. et al. [2010]. Astrophys. J. 715, L155-L159). The work is based on images obtained during 5 months from the impact to 31 December 2009 taken in visible continuum wavelengths and from 20 July 2009 to 28 May 2010 taken in near-infrared deep hydrogen-methane absorption bands at 2.1-2.3 μm. The impact cloud expanded zonally from ∼5000 km (July 19) to 225,000 km (29 October, about 180° in longitude), remaining meridionally localized within a latitude band from 53.5°S to 61.5°S planetographic latitude. During the first two months after its formation the site showed heterogeneous structure with 500-1000 km sized embedded spots. Later the reflectivity of the debris field became more homogeneous due to clump mergers. The cloud was mainly dispersed in longitude by the dominant zonal winds and their meridional shear, during the initial stages, localized motions may have been induced by thermal perturbation caused by the impact’s energy deposition. The tracking of individual spots within the impact cloud shows that the westward jet at 56.5°S latitude increases its eastward velocity with altitude above the tropopause by 5-10 m s⁻¹. The corresponding vertical wind shear is low, about 1 m s⁻¹ per scale height in agreement with previous thermal wind estimations. We found evidence for discrete localized meridional motions with speeds of 1-2 m s⁻¹. Two numerical models are used to simulate the observed cloud dispersion. One is a pure advection of the aerosols by the winds and their shears. The other uses the EPIC code, a nonlinear calculation of the evolution of the potential vorticity field generated by a heat pulse that simulates the impact. Both models reproduce the observed global structure of the cloud and the dominant zonal dispersion of the aerosols, but not the details of the cloud morphology. The reflectivity of the impact cloud decreased exponentially with a characteristic timescale of 15 days; we can explain this behavior with a radiative transfer model of the cloud optical depth coupled to an advection model of the cloud dispersion by the wind shears. The expected sedimentation time in the stratosphere (altitude levels 5-100 mbar) for the small aerosol particles forming the cloud is 45-200 days, thus aerosols were removed vertically over the long term following their zonal dispersion. No evidence of the cloud was detected 10 months after the impact.     

Precipitable water vapor (PWV) estimations from the site of the Eastern Anatolia Observatory<Superscript>∗</Superscript> (DAG), a new astronomical observatory in Turkey

We present preliminary statistics on the precipitable water vapor (PWV) content over the Karakaya Hills in Erzurum city, where the largest optical and near-infrared astronomical telescope in Turkey will be operated. Since the observatory will observe in the near-infrared (NIR), it is intended to perform PWV measurements of the atmosphere above the site by using signal delays in Global Positioning System (GPS) communication. The analysis of the GPS data recorded on the summit for almost one year shows that the atmosphere over the site of the observatory, which has an altitude of 3170 m, has favorable conditions for NIR observations. From GPS measurements, we report that the site had an average PWV of 3.2 mm and a median PWV of 2.7 mm between October 6, 2016, and June 15, 2017. We also present the time dependency of the PWV content and the correlations between the amount of PWV and the other meteorological records gathered from radiosonde flights and ground-based measurements.     

Remarks on dynamical ellipticity at the Earth's

In this paper, two factors — the redistribution of the density and the variation in the angular velocity of the Earth rotation, that affect the adopted value of the flattening for equidensity surface within the Earth, are discussed. The computational results show that the contribution of the redistribution of the density in the Earth interior (especially in the core) on the change of the flattening at the core-mantle boundary (CMB) is marginal, and that the calculated value of the flattening at the CMB can be in good agreement with the VLBI observed value so long as the fact that the angular velocity of the Earth rotation has undergone the tidal evolution is taken into account. As a result, this paper presents a set of recommended values of the dynamical parameters of the Earth (see Table III) for computing Earth's forced nutation series.     

Comparison of 2D versus 3D modeling approaches for the analysis of the concrete faced rock‐fill Cokal Dam

This paper's primary purpose is to compare the 2D and 3D analysis methodologies in investigating the performance of a concrete faced rock‐fill dams under dynamic loading conditions. The state of stress on the face plate was obtained in both cases using a total strain based crack model to predict the spreading of cracks on the plate and the corresponding crack widths. Results of the 2D and 3D analyses agree well. Although significantly more demanding, 3D analyses have the advantage of predicting the following: (i) the opening of the vertical construction joints; (ii) the cracking at the valley sides; and (iii) the crushing of the plate during the seismic action. During the earthquake loading, the cracking predicted at the base of the face plate after the impounding spread significantly towards the crest of the dam; however, the crack widths are obtained relatively small. Crushing of the face plates at the construction joints is the primary cause of the large scale cracking predicted on the face plate for high intensity earthquakes. Earthquake induced permanent deformation of the fill increases the compressive stresses on the face plate, thereby reducing the minute cracking on the plate. However, this effect also leads to significant increases in the residual openings at the construction joints and at the plinth level. Copyright © 2013 John Wiley & Sons, Ltd.     

Isotope Constraints on the Aquatic Carbon Budget: Langat Watershed,Malaysia

Langat River drains a tropical watershed in the southwest of the Malaysian Peninsula. The watershed is heavily urbanized in its downstream portion. Water samples were collected from May 2010 to December 2011, at three localities along the main stem river, 1 location at its Semenyih tributary and from an upstream groundwater source. Concentration and δ¹³C data of riverine DIC and DOC indicate the dominance of C3 plant-derived material as the primary source of carbon, with δ¹³C_DIC values enriched in ¹³C relative to that of the C3 source. This enrichment is likely due to CO₂ outgassing, as calculated concentrations of riverine CO₂ are significantly higher than ambient atmospheric values, with methanogenic activity a theoretically possible contributing factor, particularly at the upstream location. The Langat River therefore acts as a net source of CO₂, with a total sub-basin flux of 19.7 × 10³ t C year^?1. This is comparable to the sum of riverine DOC, DIC and POC loss rates from the sub-basin, calculated as 24.5 × 10³ t C year^?1, and highlights the significance of CO₂ evasion from water bodies to the atmosphere for balancing the budget of the terrestrial carbon cycle. The DIC and DOC concentration and δ¹³C data also suggests that in the more urbanized downriver areas, much of the organic carbon input may be anthropogenicaly derived due to ubiquity of sewage treatment plants and landfill sites. Such human-induced perturbations to riverine carbon cycling should be taken into account in future studies of urbanized watersheds.     

The timing of ultrahigh-temperature metamorphism in Southern India: U–Th–Pb electron microprobe ages from zircon and monazite in sapphirine-bearing granulites

We report here U–Pb electron microprobe ages from zircon and monazite associated with corundum- and sapphirine-bearing granulite facies rocks of Lachmanapatti, Sengal, Sakkarakkottai and Mettanganam in the Palghat–Cauvery shear zone system and Ganguvarpatti in the northern Madurai Block of southern India. Mineral assemblages and petrologic characteristics of granulite facies assemblages in all these localities indicate extreme crustal metamorphism under ultrahigh-temperature (UHT) conditions. Zircon cores from Lachmanapatti range from 3200 to 2300 Ma with a peak at 2420 Ma, while those from Mettanganam show 2300 Ma peak. Younger zircons with peak ages of 2100 and 830 Ma are displayed by the UHT granulites of Sengal and Ganguvarpatti, although detrital grains with 2000 Ma ages are also present. The Late Archaean-aged cores are mantled by variable rims of Palaeo- to Mesoproterozoic ages in most cases. Zircon cores from Ganguvarpatti range from 2279 to 749 Ma and are interpreted to reflect multiple age sources. The oldest cores are surrounded by Palaeoproterozoic and Mesoproterozoic rims, and finally mantled by Neoproterozoic overgrowths. In contrast, monazites from these localities define peak ages of between 550 and 520 Ma, with an exception of a peak at 590 Ma for the Lachmanapatti rocks. The outermost rims of monazite grains show spot ages in the range of 510–450 Ma.While the zircon populations in these rocks suggest multiple sources of Archaean and Palaeoproterozoic age, the monazite data are interpreted to date the timing of ultrahigh-temperature metamorphism in southern India as latest Neoproterozoic to Cambrian in both the Palghat–Cauvery shear zone system and the northern Madurai Block. The data illustrate the extent of Neoproterozoic/Cambrian metamorphism as India joined the Gondwana amalgam at the dawn of the Cambrian.