The present geoecological situation within the territory of the city of Irkutsk

Presented are the results derived from studying the exogenous geological processes within urbanized territories. Specific areas are identified: local geosystems of urban territories with intense development of natural-technogenic exogenous geological processes which require analysis of the evolution of the geological environment and engineering technical work in order to minimize the negative technogenic load.     

西伯利亚板块旋转漂移运动刍议

西伯利亚板块是世界上古老的地质构造单元之一。根据板块构造理论，该板块当今的地表形态和地理位置，是其经过不断迁移，与其它板块不断发生碰撞的结果。本文试从展现板块的水平运动特点出发，着重揭示西伯利亚板块在各地质时期的运动状态，从而阐述该板块自寒武纪以来的旋转漂移的全过程。     

湖南境内沅水流域地质灾害形成因素分析

沅水流域流经湖南省的西部地区，由于地质环境和社会经济背景的特殊性，已成为湖南省地质灾害的主要分布区。通过对流域内地质灾害发育特征的归纳，着重从自然影响因素和人类活动两个方面来分析流域内地质灾害的形成。主要采用灰色关联理论来分析流域内大气降水、地形条件和人类活动等3个主要致灾因子的关联度，其结果分别为0．8332、0．6589和0．5654，从而来探求流域内地质灾害灾变机理的规律性，为流域内各个地区的防灾减灾提供依据，最大限度减少地质灾害所造成的经济损失，促进流域内社会、经济、生态环境的可持续发展。     

洪江市地质灾害经济损失评估

洪江市位于湖南省的西部,地形以山地为主,属于地质灾害多发区。由于自然和人类工程一经济活动的影响,以滑坡、崩塌为主的地质灾害时有发生。这些地质灾害严重危害了人民的生命财产,造成了重大的损失。通过调查与评估,到2008年底为止,全市发生各类大小的地质灾害共77处,其中滑坡66处、崩塌8处、地面塌陷1处、地面沉陷1处、泥石流1处,导致死亡5人,毁房234间,毁田26.4hm^2（396亩）,直接经济损失达到642.5万元,间接经济损失更是达到了8744.0万元。     

Relief formation in the littoral zone of the lake-like part of the Sayano-Shushenskoye reservoir

We examine the exogenous geological processes of a technogenic nature that were taking place in the littoral zone of the lake-like part of the Sayano-Shushenskoye reservoir after its impounding (1979-1980), and at the period of operation. We analyze the factors promoting the development of technogenic processes and the creation of an unfavorable ecological situation.     

Evolution of Anisotropic Coal Permeability Under the Effect of Heterogeneous Deformation of Fractures

Natural Resources Research - Permeability is one of the key parameters to better understand the processes of coalbed methane mining and carbon dioxide geological storage. As a unique porous medium,...     

Generalized Mathematical Morphological Method for 3D Shape Analysis of Geological Boundaries: Application in Identifying Mineralization-Associated Shape Features

The shapes of geological boundaries such as contacts and faults play a crucial role in the transportation, deposition and preservation of metals in magmatic and hydrothermal systems. Analyzing the shapes of geological boundaries, in particular those associated with mineralization, is an important step in 3D mineral prospectivity modeling. However, existing methods of shape analysis are limited in the adaptation of various shapes, scales and topologies of geological boundaries. This paper presents a general method of shape analysis based on mathematical morphology (MM), which is a generalization of the original MM method for shape analysis. The generalization extends the applicability of the original MM method from closed surfaces to general surfaces, while inheriting the real 3D and multi-scale analysis capabilities of the original method. This is achieved by regarding MM operations on 3D sphere structural elements as their equivalent operations, and redefining the operations to general surfaces. The generalized MM method enables us to handle complex 3D shapes such as overturned and/or recumbent geological boundaries as well as incomplete shapes due to weathering processes and data unavailability. The proposed method was applied to analyze the shape of an intrusive contact in the Fenghuangshan Cu ore field, Eastern China, whose shape was in the form of a non-closed surface. This analysis revealed a stronger spatial association between the large concave parts of the contact zone and the mineralization. Due to its enhanced adaptability to different shapes, the generalized MM method, compared with the original MM method, allows us to capture shape features that are more plausible for the geological setting.

     

Controls on basalt terrace formation in the eastern Lesotho highlands

The objective of this study is to ascertain the relative importance of lithological controls and geomorphological processes in the development of Drakensberg basalt terraces. Various hypotheses for terrace formation are considered, including geological controls, macroscale geomorphology, and climatic–geomorphological controls. The variations in strength and relative age differences for scarp surface exposures on two slopes of varying aspect are determined, so that a comparison can be made between various scarp outcrops and relative rates of weathering. Scarp outcrops were measured for their rock mass strength, rock surface roughness, and percentage lichen cover. The ethylene glycol test was performed on prepared rock samples to determine susceptibility to tensional breakup. A satellite image depicting the distribution of late-lying contemporary snow was used to assist in the construction of topo-climatic linkages with scarp terrace localities. Findings show that terraces are most common on southeast-facing aspects, and coincide with the major joint strike direction. Lithological factors are thus considered the primary control to such terrace development. It is suggested that a different set of geomorphological processes operates on various slope-altitudinal and slope-orientational positions at any given time.     

Spatial Analysis Techniques as Successful Mineral-Potential Mapping Tools for Orogenic Gold Deposits in the Northern Fennoscandian Shield,Finland

Geoscientific Information Systems (GIS) provide tools to quantitatively analyze and integrate spatially referenced information from geological, geophysical, and geochemical surveys for decision-making processes. Excellent coverage of well-documented, precise and good quality data enables testing of variable exploration models in an efficient and cost effective way with GIS tools. Digital geoscientific data from the Geological Survey of Finland (GTK) are being used widely as spatial evidence in exploration targeting, that is ranking areas based on their exploration importance. In the last few years, spatial analysis techniques including weights-of-evidence, logistic regression, and fuzzy logic, have been increasingly used in GTK’s mineral exploration and geological mapping projects. Special emphasis has been put into the exploration for gold because of the excellent data coverage within the prospective volcanic belts and because of the increased activity in gold exploration in Finland during recent years. In this paper, we describe some successful case histories of using the weights-of-evidence method for the Au-potential mapping. These projects have shown that, by using spatial modeling techniques, exploration targets can be generated by quantitatively analyzing extensive amounts of data from various sources and to rank these target areas based on their exploration potential.     

黄河流域甘肃段地质遗迹空间区划及可持续开发利用策略

地质遗迹是珍贵的且为不可再生的自然资源。对地质遗迹的保护性开发是其可持续开发利用的前提,也是生态文明建设、脱贫攻坚、乡村振兴战略不可或缺的组成部分。基于黄河流域甘肃段地质遗迹调查数据,采用最邻近点指数和GIS空间分析法,对该区域的地质遗迹空间分布特征进行评价,提出地质遗迹可持续开发利用建议。结果表明：（1） 黄河流域甘肃段地质遗迹调查共发现地质遗迹点1046处,其中具有重要价值的有153处。研究区地质遗迹空间分布广泛,类型多样,内涵独特,以碎屑岩地貌、地层剖面、古生物遗迹化石为主;其不均匀分布的特点,与当地气候分带、地貌分区、水系分布、地质构造发育等存在一定的相关性。（2） 根据赋存环境、发育特征等将研究区地质遗迹划分为2个地质遗迹区、6个分区和15个小区。（3） 以国家自然保护地整合优化为契机,建议通过地质公园、研学旅行基地、特色小镇、地质文化村建设等多层次、多样化的开发利用路径,推进黄河流域甘肃段地质遗迹的可持续开发利用。     

Contribution of a three-dimensional regional scale basin model to the study of the past fluid flow evolution and the present hydrology of the Paris basin, France

A basin model was built to simulate in three dimensions the 248 Myr geological history of the Paris basin, France, i.e. sedimentation, erosion, compaction heat and fluid flow. This multidisciplinary study was based on a detailed stratigraphic database of more than 1100 well logs together with a hydrodynamic database of 1000 data (heads and permeabilities). The region covers a maximum surface area of 700 000 km². The NEWBAS code of the Ecole des Mines de Paris was used in order to simulate compaction and heat and fluid flow. Three examples of the use of this model are given to illustrate different features of the geological functioning of the basin. (i) By modelling processes such as sedimentation, compaction, fluid and heat flow, the model provides estimates of the hydraulic conductivity fields within one order of magnitude from observations at the regional scale. This permeability field can reproduce the present‐day observed pressures and fluxes in the basin. (ii) Observed excess pressures in the main aquitards are considered as possible consequences of the geological history of the basin. The calculated excess pressures are small and stay within the range of the measured values, between 0 and 2.75 MPa, close to the pressures in the aquifers. However, the weak excess pressures measured in the Callovo–Oxfordian sequence in the eastern part of the basin are not reproduced by the model. Mechanisms other than compaction disequilibrium must be invoked. (iii) This model also calculates regional‐scale palaeofluid flow whose value is currently arbitrarily assumed by geochemists when studying diagenetic processes. Hence, it provides a hydrologic background for diagenetic models. The cementation in the western Keuper reservoirs was investigated. Topographically driven flow during tectonic inversion periods, e.g. the Lower Cretaceous and Early Tertiary, is shown to be a plausible cause of brine migrations. This brine displacement would then explain the high salinities recorded in the fluid inclusions trapped in the Keuper cements. The conditions for the migration would have been most favourable at the time of the maximum burial, i.e. the Early Tertiary and not the Early Cretaceous as previously suggested.     

Map Scale Effects on Estimating the Number of Undiscovered Mineral Deposits

Estimates of numbers of undiscovered mineral deposits, fundamental to assessing mineral resources, are affected by map scale. Where consistently defined deposits of a particular type are estimated, spatial and frequency distributions of deposits are linked in that some frequency distributions can be generated by processes randomly in space whereas others are generated by processes suggesting clustering in space. Possible spatial distributions of mineral deposits and their related frequency distributions are affected by map scale and associated inclusions of non-permissive or covered geological settings. More generalized map scales are more likely to cause inclusion of geologic settings that are not really permissive for the deposit type, or that include unreported cover over permissive areas, resulting in the appearance of deposit clustering. Thus, overly generalized map scales can cause deposits to appear clustered. We propose a model that captures the effects of map scale and the related inclusion of non-permissive geologic settings on numbers of deposits estimates, the zero-inflated Poisson distribution. Effects of map scale as represented by the zero-inflated Poisson distribution suggest that the appearance of deposit clustering should diminish as mapping becomes more detailed because the number of inflated zeros would decrease with more detailed maps. Based on observed worldwide relationships between map scale and areas permissive for deposit types, mapping at a scale with twice the detail should cut permissive area size of a porphyry copper tract to 29% and a volcanic-hosted massive sulfide tract to 50% of their original sizes. Thus some direct benefits of mapping an area at a more detailed scale are indicated by significant reductions in areas permissive for deposit types, increased deposit density and, as a consequence, reduced uncertainty in the estimate of number of undiscovered deposits. Exploration enterprises benefit from reduced areas requiring detailed and expensive exploration, and land-use planners benefit from reduced areas of concern.     

Plate kinematics of the Western Mediterranean region during the Oligocene and Early Miocene

The tectonic history of the Western Mediterranean region during the Oligocene and Early Miocene is illustrated through a series of plate reconstructions, from chron C13n to chron C6n. The reconstructions are based on a new interpretation of published magnetic anomaly data and two-ships seismic data, and their integration with known geological constraints, in order to determine style and timing of the backarc extension processes in the Liguro-Provençal, Valencia and Algerian basins. In particular, a reinterpretation of the regional magnetic anomaly field allowed the calculation of the instantaneous Euler poles associated with the motion of 11 microplates relative to Eurasia and Iberia. Furthermore, a quantitative analysis of the acoustic basement morphology and the balancing of deep crustal profiles were used to estimate the closure and pre-rift rotation angles associated with the Euler poles of opening of the Ligurian, Provençal, Valencia and Algerian basins. This rigorous reconstruction of the geometry of the pre-rift continental margins of Iberia and Eurasia could furnish important insights into the study of Mediterranean tectonics for older times.     

Uncertainty analysis and the relative contributions of geological factors for the Qingshankou source rocks in the North Songliao Basin, northeastern China

Source rock evaluation is a critical factor in resource assessment of oil and gas. Models for evaluating source rocks are dependent on established geomathematical principles, the calculation of source-rock parameters, and geological data. The sensitivities and uncertainties associated with these models are a matter of concern. In this paper, the effects and relative contributions of 13 major geological factors, as well as their variations and distribution probabilities, have been analyzed for the source rocks in the North Songliao Basin in northeastern China. The geological factors include the time of formation of the regional caprock, composition of the regional caprock, the phases of hydrocarbons in migration, and those factors associated with the generation, retention, and expulsion of hydrocarbons and their effects on source-rock efficiency. Of the 13 factors analyzed, the most important are the source-rock depth, sedimentation rate, total organic content, and kerogen-type index; the relative contributions to the uncertainty of efficient gas/oil migration amounts for the most important factors are 37, 25, 19, and 1% for oil and 32, 17, 20, and 15% for gas, respectively. These most reflect the changes that have occurred in the Qingshankou source rocks.     

Surficial and Deep Earth Material Prediction from Geochemical Compositions

Prediction of true classes of surficial and deep earth materials using multivariate spatial data is a common challenge for geoscience modelers. Most geological processes leave a footprint that can be explored by geochemical data analysis. These footprints are normally complex statistical and spatial patterns buried deep in the high-dimensional compositional space. This paper proposes a spatial predictive model for classification of surficial and deep earth materials derived from the geochemical composition of surface regolith. The model is based on a combination of geostatistical simulation and machine learning approaches. A random forest predictive model is trained, and features are ranked based on their contribution to the predictive model. To generate potential and uncertainty maps, compositional data are simulated at unsampled locations via a chain of transformations (isometric log-ratio transformation followed by the flow anamorphosis) and geostatistical simulation. The simulated results are subsequently back-transformed to the original compositional space. The trained predictive model is used to estimate the probability of classes for simulated compositions. The proposed approach is illustrated through two case studies. In the first case study, the major crustal blocks of the Australian continent are predicted from the surface regolith geochemistry of the National Geochemical Survey of Australia project. The aim of the second case study is to discover the superficial deposits (peat) from the regional-scale soil geochemical data of the Tellus Project. The accuracy of the results in these two case studies confirms the usefulness of the proposed method for geological class prediction and geological process discovery.

     

区域地质灾害风险评估模型的初建--以广州市崩塌灾害为例

地质灾害的研究必须基于其自然和社会经济的双重属性特征,并把它作为一项系统工程来研究;风险评估是这系统工程中不可或缺的重中之重内容,也是新世纪地质灾害防灾减灾领域的前沿和热点.鉴于地质灾害风险评估研究现状,初步探讨了区域地质灾害风险评估模型的构建,即基于格网单元的地质灾害危险性评价、基于行政单元的社会经济易损性评价和基于危险度和易损度乘积的区域风险评估.同时以广州市崩塌灾害为例,采用该模型进行评估并取得了良好的效果.     

Identification of Quaternary subsurface glacial deposits using 3D databases and GIS

To solve the problem of handling numerous data from drillings and geophysical surveys for specific information of subsurface geological formations, the use of databases and geographic information systems (GIS) is demonstrated. Geological formations are in 3D and commercial GIS packages are normally in 2D. This problem is solved here by a 1D database of the layering of the drillings and export of query results from the database to a 2D GIS. The queries will ask for grain size and altitude for the actual sedimentary layers. To include point data from ground penetrating radar (GPR) data survey profiles in a 2D GIS, a stepwise technique of dynamic segmentation has been developed. The points are digitized along sedimentary boundaries from 2D GPR profiles. The concept was applied on a small area of glacial sediments in Telemark, Norway. Results from the processes were clustering of points with properties connected to specific geological formations. The clustering subsurface geological formations were moraine ridges, a diamict layer, gravel and coarse sand above and below the diamict layer, till above bedrock, and glaciomarine deposits of gravel and sand. Information about extension of these geological formations is useful and essential for modelling of sedimentary environments and for aquifer modelling.     

Geologically constrained changes to landforms caused by human activities in the 20th century: A case study from Fukuoka Prefecture,Japan

Human activity has been recognized to be an important geomorphic agent, and the resulting changes to landforms and land cover are regarded as a global problem. Although there has been much research into the relationships between geomorphic processes and types of land use such as agriculture, mining, and urbanization, it is important to clarify spatiotemporal human impacts on topography on a regional scale when predicting future changes in land cover.This study examined changes in land use to clarify the distribution and impact of anthropogenic changes to landforms, as well as the influence of geology on the extent of these changes. In a case study from Fukuoka Prefecture, Japan, changes in land use over the last century were analyzed using a geographic information system (GIS). The study area, which covers approximately 4930 km², has experienced urban development since 1950 and has a current population of over 5 million. Land use data were prepared using paper-based early editions of topographic maps. Subsequently, the distribution of anthropogenic landforms was evaluated by comparing landforms with regional geological data.GIS analysis using our prepared land use data, landform data, and regional geological data has clarified the following characteristics of the study area. (1) Land uses prior to 1950 were constrained by topographic relief. After 1950, land use was characterized by urban sprawl. Urban areas expanded and contained both higher elevations and steeper slopes at their margins. The relationships between land uses and landforms during this urbanization are unclear. (2) The area of urban land increased in the geological regions with Paleogene sedimentary rocks (PSD) and Mesozoic granitic rocks (GR) during the 20th century. The largest coal mining area in Japan was located in the PSD geological regions, and ancient iron working was common in the GR geological regions, particularly during the 7th century. This result indicates that the land use distribution, especially urban areas in sloping terrain, is related to the regional geology. (3) Deforestation related to land use resulted in steeper terrain in forest land in the PSD and GR geological regions. These changes to landforms in forest areas occurred as a result of rapid urban sprawl and have created many new boundaries between forest areas with steeper slopes and urban areas with gentler slopes. This phenomenon may have caused an increase in the frequency of sediment-related disasters.This case study indicates that predictions of anthropogenic changes to landform, which are important for the assessment of global climate change and natural hazards, must clarify the relationships between land uses, landforms, and regional geology.     

The geological heritages in Xinjiang, China: Its features and protection

The geological heritage protection and its development at home and abroad reflect the progress in the aspect from the single protection to the coordination between protection and exploitation. The geopark established by UNESCO has closely combined the protection of geological heritages with the promotion of sustainable development of local economy, which has become the best way to protect geological heritages. The geological heritages in Xinjiang, China, are characterized by their large quantity, rich variety and high grade. The complicated geologic-geomorphic environment in Xinjiang contributes to the creation of various geological heritage types and their spatial distribution, and at the same time makes them under control. The main types of the geological heritages in Xinjiang are the geologic- geomorphic landscapes and the water landscapes. The spatial distribution can be divided into five geological heritage districts: Altay, Junggar, Tianshan, Tarim and Kunlun-Altun, among which Tianshan and Kunlun-Altun are most important. Based on the first systematic investigation of the geological heritages in Xinjiang, it is confirmed that the insufficient coordination between protection and exploitation is the primary cause for the backward situation in the geological heritage protection. To solve the problem, this paper proposes 6 major protection steps—from determining the protection types, the protection forms, the protection modes, the protection grades, the protection sequences to determining the protection zones, brings forward the idea of optimal-selection which integrates geoparks with geological heritage protection areas and other protection areas as well as 5 corresponding modes, and makes a protection and exploitation reserve list for 209 important geological heritages in Xinjiang.     

青藏高原及横断山区地质灾害易发区空间格局及驱动因子

青藏高原及横断山区位中国西南部,地貌类型复杂,地质灾害频发,严重威胁到西南地区人民生命财产安全,尤其影响进藏交通线的通达度。系统研究该区地质灾害易发区空间格局及驱动因子,可为青藏高原及横断山区地质灾害风险防范及地质灾害的防灾减灾救灾提供重要理论支撑。研究结果表明,基于随机森林构建的判识模型对于灾害点的判识精度均高于80%,甚至达到91%,可准确模拟与预测研究区各分区的地质灾害点。研究区地质灾害易发点主要分布在横断山区南部与东北部以及青藏高原中南部地区,且以小型及中型规模地质灾害为主（占比为87%）。综合分区Ⅰ~Ⅲ的地质灾害易发区面积分别为17.5万km²、17.4万km²与27.5万km²。各综合分区地质灾害驱动因子研究表明,横断山区南部区域（综合分区Ⅰ内）小型及中型地质灾害的主要驱动力为道路建设导致的沿途坡面稳定性变化（贡献率为20.2%）;横断山区东北部区域及青藏高原地区（综合分区Ⅱ~Ⅲ）小型及中型地质灾害的主要驱动力为植被覆盖状况的变化对于坡面稳定性的影响（贡献率分别为23.6%与27.3%）。此外,综合分区Ⅱ~Ⅲ内影响小型及中型地质灾害空间格局的第二个驱动因子为道路建设导致的沿途坡面稳定性的变化（贡献率为15.7%）与河流对于周边坡面的侵蚀作用（贡献率为17%）。