Dolomite in caves: Recent dolomite formation in oxic, non-sulfate environments. Castañar Cave, Spain

Dolomite is a common mineral in the rock record but rare in recent superficial environments. Where it does occur, it is related to anoxic, sulfate-rich environments and microbial activity. The occurrence of some dolomite deposits in caves, however, indicates that dolomite formation is also possible in oxic, non-sulfate settings. Dolomite is forming at 17 °C and in oxic-vadose conditions on the host rocks and aragonite speleothems of the Castañar Cave, Cáceres, Spain. It appears as spheroids and dumbbells 50–300 μm in diameter that internally consist of micron-sized rhombic to rounded crystals. Initially this dolomite is Ca-rich, non-stoichiometric and poorly ordered. Mg-rich solutions allow the precipitation of metastable Mg-rich carbonates, such as huntite. This soon transforms into this Ca-rich dolomite, which later “ages” to form a more stoichiometric dolomite. These dolomites show similarities to those grown under anoxic, sulfate-rich conditions and their presence in caves provides a different setting that may contribute to the understanding of the “dolomite problem”, including their initial formation and later recrystallization processes.     

Investigation of the deep structure of the Sivas Basin (innereast Anatolia, Turkey) with geophysical methods

Sivas Basin is the easternmost and third largest basin of the Central Anatolian Basins. In this study, gravity, aeromagnetic and seismic data are used to investigate the deep structure of the Sivas Basin, together with the well seismic velocity data, geological observations from the surface and the borehole data of the Celalli-1 well. Basement depth is modeled three-dimensionally (3D) using the gravity anomalies, and 2D gravity and magnetic models were constructed along with a N–S trending profile. Densities of the rock samples were obtained from the distinct parts of the basin surface and in-situ susceptibilities were also measured and evaluated in comparison with the other geophysical and geological data. Additionally, seismic sections, in spite of their low resolution, were used to define the velocity variation in the basin in order to compare depth values and geological cross-section obtained from the modeling studies. Deepest parts of the basin (12–13 km), determined from the 3D model, are located below the settlement of Hafik and to the south of Zara towns. Geometry, extension and wideness of the basin, together with the thickness and lithologies of the sedimentary units are reasonably appropriate for further hydrocarbon exploration in the Sivas Basin that is still an unexplored area with the limited number of seismic lines and only one borehole.     

Geometric and radiometric evaluation of Resouresat-1 sensors

Resourcesat-1, launched in October 2003, is the 10th in the series of Indian Remote Sensing satellites built by the Indian Space Research Organization. Resourcesat-1, also known as IRS-P6, provides continuity to applications developed using data from IRS-1C and IRS-1D satellites. It also offers newer applications owing to enhanced capabilities of the sensors. The satellite contains three different imaging sensors: LISS-IV, with a ground sampling distance (GSD) of 5.8 m; LISS-III, with a GSD of 23.5 m; and AWiFS, with a GSD of 56 m at nadir. This paper provides data quality evaluation of the Resourcesat-1 sensors in terms of geometric and radiometric qualities. It is found that the sensors onboard Resourcesat-1 spacecraft has met all the mission set specifications and will help to generate data products with the required image geolocation and radiometric quality.     

Evaluation and use of Resourcesat-I data for agricultural applications

Resourcesat-1 satellite offers a unique opportunity of simultaneous observations at three different spatial scales through LISS-IV, LISS-III^* (improved LISS-III) and AWiFS sensors from a common platform. The sensors have enhanced capabilities in terms of spectral, spatial and radiometric resolution as compared to earlier Indian Remote sensing Satellite sensors. This paper summarizes the results of various studies such as evaluation of sensor characteristics, inter-sensor comparison studies, derivation and validation of surface reflectance measurements, quantification of improvements due to Resourcesat-1 sensors, and their use for various agricultural applications. The studies presented in this paper demonstrate that suit of sensors onboard Resourcesat-1 satellite provides better prospects for several agricultural applications like crop identification, discrimination and crop inventory for some major Indian crops, than its predecessors on IRS satellites.     

Compositional and geochemical characteristics of light hydrocarbons for typical marine oils and typical coal-generated oils in China

Different types of crude oils have different light hydrocarbon compositional and geochemical characteristics. Based on the light hydrocarbon data from two kinds of oils, i.e., coal-generated oils and marine oils in China, light hydrocarbons in marine oils in the Tazhong area are generally relatively enriched in n-heptane, and coal-generated oils from the Turpan Basin are enriched in methylcyclohexane. The K1 values, reported by Mango （1987）, range from 0.97 to 1.19 in marine oils, basically consistent with what was reported by Mango on light hydrocarbons in terms of the majority of the crude oil data. But the K1 values of coal-generated oils are particularly high （1.35-1.66） and far greater than those of marine oils; heptane values in marine oils, ranging from 32.3% to 45.4%, and isoheptane values, ranging from 1.9 to 3.7, are respectively higher than those of coal-generated oils, indicating that the oils are in the high-maturity stage. In addition, expulsion temperatures of coal-generated oils from the Turpan Basin are obviously lower than those of marine oils from the Tazhong area.     

珠江口盆地珠一坳陷古近系构造样式分析

研究分析了近年来构造样式的研究现状和新的进展,结合珠江口盆地珠一坳陷张性构造环境下构造发育的特点,建立了利用三维空间构造信息的构造样式划分方案。据此对珠一坳陷的各类构造样式进行了研究。根据盆地(坳陷)结构、断层组合及动力学机制,将珠一拗陷构造样式划分为断块与板式正断层组合构造,断块与铲式正断层组合构造,转换带构造,潜山披覆构造,底辟构造和重力背形构造等6大类13小类。研究还指出了基于构造样式的油气有利聚集部位及勘探方向。     

Sentinel-1 observations of the 2016 Menyuan earthquake: A buried reverse event linked to the left-lateral Haiyuan fault

Knowledge on the interaction of active structures is essential to understand mechanics of continental deformation and estimate the earthquake potential in complex tectonic settings. Here we use Sentinel-1A radar imagery to investigate coseismic deformation associated with the 2016 Menyuan (Qinghai) earthquake, which occurred in the vicinity of the left-lateral Haiyuan fault. The ascending and descending interferograms indicate thrust-dominated slip, with the maximum line-of-sight displacements of 58 and 68 mm, respectively. The InSAR observations fit well with the uniform-slip dislocation models except for a larger slip-to-width ratio than that predicted by the empirical scaling law. We suggest that geometric complexities near the Leng Long Ling restraining bend confine rupture propagation, resulting in high slip occurred within a small area and much higher stress drop than global estimates. Although InSAR observations cannot distinguish the primary plane, we prefer the west-dipping solution considering aftershocks distribution and the general tectonic context. Both InSAR modelling and aftershock locations indicate that the rupture plane linked to the Haiyuan fault at 10 km depth, a typical seismogenic depth in Tibet. We suggest that the earthquake more likely occurred on a secondary branch at a restraining bend of the Haiyuan fault, even though we cannot completely rule out the possibility of it being on a splay of the North Qilian Shan thrusts.     

基于高分一号用于植被信息提取的假彩色数字正射影像制作方案研究

对如何利用高分一号卫星数据制作假彩色数字正射彩色影像图进行了研究,基于高分一号利用432波段组合,可以突出地显示出植被信息,处理成果纹理细节清晰,无明显噪声,高分一号数据制作的标准假彩色数字正射影像图可以保证数据成果色彩分明,植被提取和解译精度高。     

地理国情监测与1∶50000地形数据库更新两者之间的作业模式相关性研究

结合地理国情监测与1∶50 000地形数据库更新的各作业工序,将可协同作业的部分提炼出来,以期为两个项目的顺利开展提供技术支撑。     

基于大气温度和水汽含量改进HJ-1B地表温度反演

为了提高地面气象站稀少地区地表温度遥感反演的精度,本文基于多源遥感数据的优势,首先利用MODIS影像获取研究区像元尺度上平均大气水汽含量;然后利用同时相的HJ-1B影像估算区域地表比辐射率,再采用温度-植被指数法获取近地表大气温度;最后将以上3个参数输入单窗体算法,改进其地表温度反演的精度。研究结果表明,改进单窗体算法反演地表温度与地面实测温度的偏差小于1 K,为地面气象站点稀少的植被覆盖区域提供了一种可行的精确遥感反演地表温度方法。