Geochemical Characteristics of Oil from Oligocene Lower Ganchaigou Formation Oil Sand in Northern Qaidam Basin,China

Oil from the Oligocene oil sands of the Lower Ganchaigou Formation in the Northern Qaidam Basin and the related asphaltenes was analyzed using bulk and organic geochemical methods to assess the organic matter source input, thermal maturity, paleo-environmental conditions, kerogen type, hydrocarbon quality, and the correlation between this oil and its potential source rock in the basin. The extracted oil samples are characterized by very high contents of saturated hydrocarbons (average 62.76%), low contents of aromatic hydrocarbons (average 16.11%), and moderate amounts of nitrogen–sulfur–oxygen or resin compounds (average 21.57%), suggesting that the fluid petroleum extracted from the Oligocene oil sands is of high quality. However, a variety of biomarker parameters obtained from the hydrocarbon fractions (saturated and aromatic) indicate that the extracted oil was generated from source rocks with a wide range of thermal maturity conditions, ranging from the early to peak oil window stages, which are generally consistent with the biomarker maturity parameters, vitrinite reflectance (approximately 0.6%), and T_max values of the Middle Jurassic carbonaceous mudstones and organic-rich mudstone source rocks of the Dameigou Formation, as reported in the literature. These findings suggest that the studied oil is derived from Dameigou Formation source rocks. Furthermore, the source- and environment-related biomarker parameters of the studied oil are characterized by relatively high pristane/phytane ratios, the presence of tricyclic terpanes, low abundances of C₂₇ regular steranes, low C₂₇/C₂₉ regular sterane ratios, and very low sterane/hopane ratios. These data suggest that the oil was generated from source rocks containing plankton/land plant matter that was mainly deposited in a lacustrine environment and preserved under sub-oxic to oxic conditions, and the data also indicate a potential relationship between the studied oil and the associated potential source rocks. The distribution of pristane, phytane, tricyclic terpanes, regular steranes and hopane shows an affinity with the studied Oligocene Lower Ganchaigou Formation oil to previously published Dameigou Formation source rocks. In support of this finding, the pyrolysis–gas chromatography results of the analyzed oil asphaltene indicate that the oil was primarily derived from type II organic matter, which is also consistent with the organic matter of the Middle Jurassic source rocks. Thus, the Middle Jurassic carbonaceous mudstones and organic rock mudstones of the Dameigou Formation could be significantly contributing source rocks to the Oligocene Lower Ganchaigou Formation oil sand and other oil reservoirs in the Northern Qaidam Basin.

     

Radial velocity measurements from LAMOST medium-resolution spectroscopic observations: a pointing towards the Kepler field

Radial velocity is one of the key measurements in understanding the fundamental properties of stars, stellar clusters and the Galaxy. A plate of stars in the Kepler field was observed in May of 2018 with the medium-resolution spectrographs of LAMOST, aiming to test the performance of this new system which is the upgraded equipment of LAMOST after the first five-year regular survey. We present our analysis on the radial velocity measurements(RVs) derived from these data. The results show that slight and significant systematic errors exist among the RVs obtained from the spectra collected by different spectrographs and exposures, respectively. After correcting the systematic errors with different techniques, the precision of RVs reaches ～1.3,～1.0,～0.5 and ～0.3 km s~(-1) at S/Nr = 10, 20, 50 and 100, respectively. Comparing with the RVs of standard stars from the APOGEE survey, our RVs are calibrated with a zero-point shift of～7 km s~(-1). The results indicate that the LAMOST medium-resolution spectroscopic system may provide RVs with a reasonable accuracy and precision for the selected targets.     

Morphological characteristics of the paleochannel of the Yihe River in the Last Glacial Maximum,Shandong Province,China

The paleochannel of the Wenhekou–Liudaokou reach of the Yihe River was investigated using electrical soundings along the Zhuyong and Chuanliujie cross sections and drilling at the Chuanliujie cross section. Drilling data from the Liuhang Rubber dam and the Jiefang, Taoran, Yihe, and Luocheng road bridges were also used. Seven stratigraphic cross sections of the Yihe River paleochannel were confirmed based on electrical sounding and drilling, and samples were collected for ¹⁴C and optically stimulated luminescence dating near Zhuyang village, Chuanliujie village, Liuhang Rubber dam, south bank of the Benghe River bridge, and the riverbed near the Yihe Road bridge. The dating results suggest that the channels below 76.0, 70.0, 69.5, 55.1, 52.4, 56.5, and 56.4 m near Zhuyang village, Chuanliujie village, Liuhang Rubber dam, Jiefang Road bridge, Taoran Road bridge, Yihe Road bridge, and Luocheng Road bridge are paleochannels of the Yihe River during the Last Glacial Maximum (LGM). Lithology of the riverbed is complex and characterized by fracture zones. This reach of the river was braided with high width–depth ratios and the deep, incised valley at the Jiefang and Taoran road bridges was formed by a regional deep cut during the LGM.     

Difference of planktonic ciliate communities of the tropical West Pacific,the Bering Sea and the Arctic Ocean

Ciliates are important components in planktonic food webs,but our understanding of their community structures in different oceanic water masses is limited.We report pelagic ciliate community characteristics in three seas:the tropical West Pacific,the Bering Sea and the Arctic Ocean.Planktonic ciliate abundance had"bimodal-peak","surface-peak"and"DCM(deep chlorophyll a maximum layer)-peak"vertical distribution patterns in the tropical West Pacific,the Bering Sea and the Arctic Ocean,respectively.The abundance proportion of tintinnid to total ciliate in the Bering Sea(42.6%)was higher than both the tropical West Pacific(7.8%)and the Arctic Ocean(2.0%).The abundance proportion of small aloricate ciliates(10–20μm size-fraction)in the tropical West Pacific was highest in these three seas.The Arctic Ocean had higher abundance proportion of tintinnids in larger LOD(lorica oral diameter)size-class.Proportion of redundant species increased from the Arctic Ocean to the tropical West Pacific.Our result provided useful data to further understand ecology roles of planktonic ciliates in different marine habitats.     

基于Chirp数据和Biot-Stoll模型反演南海北部陆坡海底表层沉积物物理性质

浅地层剖面是基于声学信号(频率在几百至几千赫兹)在沉积物中的传播得到可反映沉积地层结构的数据，海底反射系数与沉积物物理性质密切相关。Biot-Stoll声波传播理论模型可以预测海底沉积物的物理性质，构建反射系数等声学参数与物理参数之间的关系，但在不同的海域采用不同的参数所获得的效果不同。为此，本文基于南海北部陆坡海底表层沉积物的实测物理参数，利用Biot-Stoll模型建立研究区海底反射系数和沉积物物理性质之间的关系，结果表明模型计算值与样品实测值吻合度总体较好，偏差在0.1%～4.9%之间，并建立了频率3.5 kHz时海底反射系数与沉积物孔隙度、密度、平均粒径之间的关系方程，且方程拟合度较高，可决系数R2均大于0.99。在对典型Chirp剖面数据计算其海底反射系数的基础上，反演了海底表层沉积物的孔隙度、密度、颗粒平均粒径等物理性质，其中反演孔隙度、密度、平均粒径与实测孔隙度、密度、平均粒径相对误差均小于5%，结果与实测值基本相符，表明该反演方法在南海北部陆坡区的应用是可行的。     

三分量磁传感器定位模型建立及可观测性分析

针对单个三分量磁传感器的定位理论问题进行了研究，建立了单个三分量磁传感器的定位理论模型，并对系统可观测性进行了详细的理论分析。基于磁性目标的点源磁偶极子等效性，将定位过程中的目标视为匀速运动，推导得到了单个三分量磁传感器的定位理论模型。基于该定位模型，利用批量的观测数据对目标运动状态参数进行估计。对于系统可观测性问题，通过考察 Fisher 信息矩阵的奇异性，严格证明了单矢量磁传感器的定位系统的不可观测性。根据现实应用情景，推导了在部分先验条件已知下的可观测性，得到以下结论：1)单个三分量传感器定位模型是不可观测的；2)在部分先验已知的条件下，系统是可观测的。 最后，通过仿真试验验证了本文结论的正确性，为接下来采用单个三分量传感器对汽车、水面舰艇等一些低动态运动目标的跟踪提供了重要的理论依据。     

基于预报钟差的轨道快速恢复

我国北斗卫星导航系统由GEO/IGSO/MEO混合星座构成,基本每7~10 d就会有一颗GEO卫星或IGSO卫星进行轨控操作。从卫星轨控开始,卫星存在5~6 h的不健康时期。造成机动卫星长期不健康的关键因素之一在于卫星和测站钟差数据的积累周期较长。本文提出了一种基于预报钟差的轨道快速恢复算法,通过结合星钟和站钟预报压缩机动卫星定轨观测数据积累的时间,从而缩短卫星恢复所需时间。6组机动试验结果表明:采用预报钟差策略在快速恢复初期的前几个小时对轨道预报的贡献尤为显著,对第1组定轨URE预报贡献最大可达84.82%。从3~8 h期间6组定轨平均情况来看,采用优化策略的预报URE,C01平均降低了26.06%,C04平均降低了31.58%,C03降低了9.95%。经测试该方法至少能将卫星不可用时间压缩1 h,对北斗系统建设具有重要工程应用价值。     

Effects of different land use types on potential evapotranspiration in the Beijing-Tianjin-Hebei region,North China

Journal of Geographical Sciences - Potential evapotranspiration (ET0) is vital for hydrologic cycle and water resource assessments as well as crop water requirement and irrigation demand...     

Multi-parameter Analysis of Local Singularity Mapping and Its Application to Identify Geochemical Anomalies in the Xishan Gold Deposit,North China

Natural Resources Research - Identification of geochemical anomalies from geological background is of great significance in the exploration of complex mineralization systems. For a 2D problem, the...     

Cropland physical disturbance intensity: plot-scale measurement and its application for soil erosion reduction in mountainous areas

Various kinds of human disturbances on cropland are the main reasons for soil erosion and land degradation. Farming practices in mountainous areas vary greatly among cropland plots because of the heterogeneity of biophysical conditions and differences in farmers’ management behavior. The main purpose of this paper is to develop a composite index of cropland physical disturbance intensity (CLDI) to reflect the plot-scale discrepancy of potential soil erosion in mountainous areas. The study was based on both plot survey and household interview data, collected from six typical catchments in mountainous areas of southwestern China. Four kinds of physical disturbance practices and two kinds of conservation practices during one crop rotation period were synthesized to develop the CLDI index. The rough set theory was referenced to avoid subjectivity during weight allocation. The results show that conventional tillage, deep fertilization, and manual weeding are the main causes of cropland soil erosion, whereas manure application in combination with seasonal fallow reduces soil erosion. Different crop types as well as cropland location factors determine the spatial pattern of CLDI. Crop rotation modes with major crops of tobacco and maize resulted in a maximal CLDI, and cropland plots with a distance radius of 150 meters away from households received the most intensive physical disturbance. These results are critical to help better protect rural environments in mountainous areas. Based on the results, methods to reduce cropland soil erosion are suggested.