Paleoenvironments, organic petrology and Rock-Eval studies on source rock facies of the Lower Maastrichtian Patti Formation, southern Bida Basin, Nigeria

The southern Bida Basin in central Nigeria forms a part of the larger Bida or Middle Niger Basin, which is contiguous with the south east trending (petroliferous) Anambra Basin. These basins were major depocenters for Campanian–Maastrichtian sediments in southern and central Nigeria prior to the build up of the Tertiary Niger delta. The successions in the southern Bida Basin consist of the basal Lokoja Formation, overlain by the Patti Formation and capped by the Agbaja Formation. The Lokoja Formation is a sequence of matrix supported conglomerates and sandstones overlying the Pre-Cambrian to Lower Paleozoic basement. Depositional environments are predominantly within fluvial systems of a continental setting. The Patti Formation consists of dark grey carbonaceous shales; mudstone and siltstones representing flood plains to shallow marine deposits with likely organic rich intervals. The overlying Agbaja Formation is made up of ferruginised oolitic and kaolinitic mudstone of a marginal marine environment. Twenty samples of shales of the Patti Formation were studied by incident light microscopy and geochemical analysis to determine the maceral components, geochemical type and potential yield of the pyrolysate. Maceral analysis indicate a large abundance of vitrinite (50–85%; mean = 66%); moderate abundance of liptinites (10–33%; mean = 18%) and lesser amounts of inertinite (9–40%; mean = 16%). Total organic carbon (TOC) values vary from 0.17 to 3.8 wt.% (mean = 2.1 wt.%) with most samples having greater than 2 wt.% TOC. Three of the samples yield greater than 2 kg_(HC)/ton of rock suggesting a fair source rock potential. Most of the samples are thermally immature to marginally mature with vitrinite reflectance ranging from 0.4 to 0.6% R_om and T_max values of 407–426 °C. Given the prevalence of the humic Type III kerogen, maturity and hydrocarbon potential yields, we conclude that the Patti Formation source rock facies have moderate to fair potential for gaseous hydrocarbons which have not yet been generated at the present day outcrop levels but could be important gas source where buried down-dip.     

关于有限断层计算模型的研究——考虑位错时、空不均匀分布的滑动时间函数

断层面上某一点的滑动时间函数需要用三个参数来表达:断层的平均位错量、上升时间和破裂传播的时间延迟。本文基于有限断层模型,根据断层面上每个子源的位错量时、空不均匀分布特征,采用Brune模型系统确定了相应滑动时间函数的三个参数,构建了位错量呈时、空不均匀分布的有限断层滑动模型。该方法可以表现破裂面上断层位错量在时间和空间上分布的不均匀特征,既能够表现震源的复杂性同时又能够简化震源模型的构建过程,为考虑断层附近的强地震动数值模拟计算提供了有效的途径。     

南鄱阳坳陷乐探1井原油树皮煤成油的地球化学特征

南鄱阳坳陷二甲村凹陷乐探1井在上白垩统周家店组发现油气显示。其原油的地球化学特征与新疆非树皮煤成因的煤成油对比表明,它既具有煤成油的一般特征(如原油物性、族组分、姥植比、碳同位素特征),又有树皮煤的特殊性(如轻烃甲基环己烷指标、规则甾烷和萜烷的组成特征等),由此认为该井原油主要是由树皮煤形成的煤成油,它与本区广泛分布的海相二叠系龙潭组树皮煤有亲缘关系。     

长江源各拉丹冬地区上三叠统结扎群双壳类组合与古环境

在长江源各拉丹冬地区雀莫错一带上三叠统结扎群采获大量双壳类化石,根据产出层位,建立了Quemocuomegalodon orientus-Neomegalodon boeckhi、Halobia superbescens-Halobia disperseinsecta、Amonotis togtonheensis-Cardium(Tulongocardium)xizangensis3个组合.这一生物组合反映的地质时代为诺利期,依据双壳类化石的外部形态和内部构造特征及围岩岩石化学分析,说明垂向上双壳类生活的结扎群具浅—深—浅的古地理变化特征,为区域上地层对比及生物生存环境提供了基础资料.     

滇东岩溶区表层岩溶水源地特征及其开发利用

表层岩溶水源地是解决分散农村生活用水困难的重要水源，而且分布广泛，水质较好。但水源地含水介质的富水性不均匀，岩溶水动态变幅大，脆弱性突出，易受污染和生态环境变化的影响。由此，表层岩溶水源地生态环境建设及保护尤为重要。表层泉以池、管调蓄系统开发最为有效。表层富水块段适宜打浅井开发，建设庭院式供水工程。采用地质雷达验证地质认识，确定井位，是经济有效的技术手段。     

The impact of radio source structure on European geodetic VLBI measurements

European geodetic very long baseline interferometry (VLBI) sessions (also known as EUROPE sessions) have been carried out on a regular basis for the past 15 years to study relative crustal motions within Europe. These sessions are based on observations of extragalactic radio sources, which serve as distant fiducial marks to establish an accurate and stable celestial reference frame for long-term geodetic measurements. The radio sources, however, are not always point-like on milliarcsecond scales, as VLBI imaging has revealed. In this work, we quantify the magnitude of the expected effect of intrinsic source structure on geodetic bandwidth synthesis delay VLBI measurements for a subset of 14 sources regularly observed during the EUROPE sessions. These sources have been imaged at both X-band (8.4 GHz) and S-band (2.3 GHz) based on dedicated observations acquired with the European VLBI Network (EVN) in November 1996. The results of this calculation indicate that the reference source 0457+024 causes significant structural effects in measurements obtained on European VLBI baselines (about 10 picoseconds on average), whereas most of the other sources produce effects that are only occasionally larger than a few picoseconds. Applying the derived source structure models to the data of the EUROPE5-96 session carried out at the same epoch as the EVN experiment shows no noticeable changes in the estimated VLBI station locations.     

伽师强震群震源特征及震源机制力学成因分析

应用改进的主地震相对定位法对17年伽师强震群3级以上地震进行了精确定位,根据较强地震的空间分布和震源机制解推断出伽师震群的发震构造为北北西向的雁行断裂.根据伽师震群地震的2177个P波初动方向记录,计算了伽师震群的平均震源机制解.基于Silver的震源模型,由震源谱推断了伽师震群主要地震的破裂方向,破裂尺度及应力降.文中最后用右阶雁行断裂的数值模型计算了伽师震群的发震构造所产生的扰动应力场的空间分布图像,用其解释了序列地震震源机制的多样性和低应力降现象,并认为特定的雁行发震构造与强震的多发性有关.     

Analytical representation of phase characteristics for source time function modeled by stochastic impulse train

In order to discuss the relationship between the lower and higher frequency components of earthquake source spectra, we deal with impulse train model as source time function of earthquake, because spectral characteristics of source time function depend on occurrence times of impulse function which corresponds to small extent on the fault. Then, the spectral characteristics of source time function are obtained analytically and numerically from the stochastic viewpoints: namely, on one hand, the trend of impulse train dominates the frequency characteristics in low frequency range, and on the other hand, the fluctuation from the trend settles high frequency range. Furthermore, it is shown that the spectral properties of source time function can be determined using only two parameters which are number of impulses n and the probability density function of occurrence time of impulses f_T(t).     

Analysis of the effect of Water Diversion and Source Supplement Project on groundwater recharge in Daixi River Basin

The South-to-North Water Diversion Project is a major national water conservancy project, but the effect of the water transfer depends on the utilization of water in the receiving areas. Water Diversion and Source Supplement Project is a specific utilization of the South-to-North Water Diversion Project in Zouping City. In order to analyze the effect of Water Diversion and Source Supplement Project on groundwater recharge in Daixi River Basin, the authors adopted the water balance method to calculate the groundwater recharge and total recharge of water diversion sources, based on the analysis of the groundwater recharge items in Daixi River Basin after carrying out this project. The total recharge is regarded as the amount of exploitable groundwater resources. The exploitable potential of groundwater resources in this area is evaluated by the comparison of the amount of exploitable groundwater resources and the actual amount of groundwater exploitation, and the effect of Water Diversion and Source Supplement Project on the over-exploitation of groundwater on the remission area was also demonstrated. Besides, the effective replenishment effect of this project on the groundwater in the study area was also revealed based on the annual groundwater and multi-year groundwater level dynamic monitoring data, which provides some reference for the rational development and utilization of groundwater resources in this region.