Soil erosion along a long slope in the gentle hilly areas of black soil region in Northeast China

Characteristics of soil erosion change along a long slope in the gentle hilly areas in black soil region in Northeast China are discussed. A simplified slope model based on segments was used to analyze the runoff data and soil erosion data observed between 2003 and 2004 over 10 field plots with different slope length in Heshan Farm, Heilongjiang Province. We found that soil erosion rate over long slopes in the black soil region changed alternatively along the slope and creates alternative zones of intensive erosion and week erosion.The exact place of each zone is different for different rainfall conditions. In a year with less and mild precipitation, rill cannot happen within the top 50 m, while in a year with large and intensive precipitation, rill can be formed starting even at 15 m from the top of the slope.

斜坡带低位扇砂岩体岩性油气藏勘探方法——以埕岛潜山披覆构造东部斜坡带为例

针对隐蔽油气藏成因和分布规律复杂、勘探技术要求高的特点 ,把层序地层学方法应用于陆相湖盆隐蔽油气藏的勘探。在高分辨率层序地层研究的基础上 ,对沉积体系进行精细的解剖分析 ,研究沉积作用发生和演化的机制 ,探讨隐蔽油藏 (圈闭 )分布的边界条件 ,进而形成了关于斜坡带低位扇砂岩体隐蔽油藏 (圈闭 )分布与预测的地质方法和技术 ,初步提出了湖相盆地“低位扇”和“坡折带”的理论。以埕岛地区东部斜坡带为例 ,介绍了斜坡带低位扇砂体岩性油气藏的勘探思路和方法 ,使该类砂体油藏预测的成因类型和分布规律更加清楚 ,有效地指导了对该类油气藏的勘探。

Palaeogeomorphology and its control on the development of sequence stratigraphy and depositional systems of the Early Silurian in the Tarim Basin

The Silurian in the Tarim Basin was deposited on the basement deformed by the Caledonian tectonic movements at the end of the Late Ordovician. The development and distribution of sedimentary sequences of the Early Silurian have been clearly controlled by the palaeogeomorphology of the Late Ordovician. Based on unconformity characteristics and distribution of erosion, several zones can be differentiated including a high uplifted erosion zone, a transitional slope zone and a depression zone. The central and west Tabei Uplift zones show high angular unconformity and intense erosion. The Tarim Basin in the late Ordovician shows characteristics of higher in the west, lower in the east while higher in the south, lower in the north. The Early Silurian mainly developed transgressive and highstand systems tracts on the whole, while the lowstand systems tract only developed partly below the slope break. The palaeogeomorphology controlled the elastic source supply and deposit distribution. Braided delta system and tidal flat-estuary system were deposited. The duration of uplifting of the Tazhong paleo- uplift was longer than that of the Tabei paleo-uplift, and deposition was later. This led to the lower and middle members of the Kepingtage Formation missing in that area. As a large-scale transgression occurred during the deposition period of the upper member of the Kepingtage Formation, sediment from the west of the basin was transported and deposited by tides and waves, forming tidal-marine debris systems above the uplift. Proximal alluvial fan and fan delta coarse elastic deposits developed in proximal uplift zone in the east and southeast of the basin, and braided delta put forward to the transitional zone between the edge of uplift and the sea. Large-scale tidal channel, sub-distributary channel and mouth bar of the delta front can form favorable reservoirs, and they are primary targets for oil and gas exploration. This research on sequence-depositional systems development and distribution controlled by palaeogeomorphology is significant in guiding the prediction of reservoir sandstones.

Quantitative Estimation of Coastal Changes Along Selected Locations of Karnataka, India: A GIS and Remote Sensing Approach

Qualitative and quantitative studies on changes of coastal geomorphology and shoreline of Karnataka, India have been carried out using toposheets of Survey of India and satellite imageries (IRS-P6 and IRS-1D). Changes during 30 years period are studied at each station. Significant morphological changes in landforms like spit, channel Island, coastal plain, tidal flat, lateritic plain, alluvial plain and sand bar within and adjcent to estuarine river mouths of Kali, Sharavathi, Kollur-Chakkara - Haladi and Udyavara Rivers are observed. The study indicates that gradual erosion is observed at i) Karwar spit along the northern side of the Kali river mouth, ii) the spit at the southern side of the Sharavathi river mouth and iii) at some regions of Kundapur.

Comparison between Paleozoic and CenozoicLithospheric Mantle in Eastern Part of North China Block: With a Discussion of Mantle Evolution

Paleozoic diamond- and xenolith-bearing kimberlites and Cenozoic xenolith-bearing basalts,erupted in the eastern part of the North China block (NCB), provide excellent mantle probes for the research of intra-plate processes and the Phanerozoic evolution of the subcontinental lithosphere mantle (SCLM ). In this study, the mineral inclusions in diamond and xenoliths from Mengyin (Shandong Province) and Fuxian (Liaoning Province) kimberlites were chosen for constraining the nature of the Paleozoic SCLM. while xenoliths from the Shanwang and Qixia basalt (both in Shandong Province) were chosen for constraining the nature of the Cenozoic SCLM.Shanwang lies astride the Tancheng-Lujiang (Taulu) fault zone, a major lithospheric fault in Eastern China as well as in Eastern Asia, and Qixia lies east of the rault zone. Based on the research of the petrography of mantle xenoliths, petrochemistry, major and the trace element of mantle minerals, lithospheric thermal state, combiued with tbe modern geophysical data, it is concluded that the attenuation and replacement of Paleozoic SCLM by upwelling asthenospheric materials through thermal erosion and possibly delamination resulted in the rormation of irregular-shaPed hot bodies, mainly along weak zones within the mantle- The Tanlu fault zone played an importont role in the Mesozoic-Cenozoic replacemeni or the pre-existing lithospheric mantle.

Creation Conditions and Development Model for Lithologic and Stratigraphic Traps in the West Sag of the Beach Area,Liaohe Depression

At present the Eocene reservoir is the focus of exploration in the west sag of the beach area,Liaohe Depression,and lithologic and stratigraphic traps are the most important in the future work.The regional geological background indicated that lithologic and stratigraphic traps might be created in the study area. Studies on creation conditions and distribution pattern of lithologic and stratigraphic traps are

Geo-Hazard Susceptibility Assessment and Its Impacts on Livelihoods in Kerio Valley, Kenya

Geohazards are a recurrent issue in the Kerio River catchment of Kenya, which usually results in life and property loss. This research focuses on mapping geo-hazard risk zones of the region. The risk zones were developed from a combination of land use land cover maps, agroecological zones maps and soil erosion maps using the Analytical Hierarchy Process method of multi-criteria analysis. The final results depict the geohazard risk maps which show the susceptibility of different areas in the catchment (classified as risk zones) to hazards. The zones range from no risk zones to very high-risk zones. The results showed that the lowlands are most susceptible to hazards as they were classified as high-risk zones. These risk zone areas have impacts on the socio-economic development hence negatively impacting livelihoods in the area.

A Case Study on Climate Change Response and Adaptation: Fictional Aysese Islands in the South Pacific

The Intergovernmental Panel on Climate Change (IPCC), established by the United Nations and World Meteorological Organization, has determined that humans have very likely influenced a net warming to the Earth from the increase of greenhouse gases, aerosols and land use changes. This warming has caused the amount of ice on the Earth to continue to decrease and sea levels to rise. In addition, extreme precipitation events are happening more often in selected regions of the world. A case study that assesses the impacts of, and adaptations to, these changes in climate is presented here. Two modeling programs, Sim CLIM and Train CLIM, (CLIM Systems, Hamilton, New Zealand) were used to support assessments for water supply, coastal zones and tropical cyclones in a fictitious island group in the South Pacific region. In the case study, a consulting group was “hired” to carry out these assessments. A final analysis and synthesis report were created to help the Ministry of the Environment of the made-up nation decide how to improve the governmental actions to address the real concerns posed by changing climate and sea level. Although a simulated island group is used in this article, there are sincere concerns about climate change and extreme weather events in this part of the world. It is important to address the real and dangerous threat that these islands and people face in the wake of a changing climate and a growing global society.

准噶尔盆地玛湖凹陷P-T转换期层序结构、坡折发育及油气地质意义

对应晚二叠世—早三叠世地球系统转换期(简称P—T转换期),准噶尔盆地玛湖凹陷P_(3)-T_(1)经历了从前陆冲断向整体拗陷的转变,发育T_(1)/P、P_(3)w/P_(2)w_(2)期大型不整合及上乌尔禾组(P_(3)w)、百口泉组(T_(1)b)_(2)套退覆型低位沉积,形成了一批大型—特大型砾岩油田。针对T_(1)/P和P_(3)w/P_(2)w_(2)个三级层序界面,识别出与构造挠曲和侵蚀作用相关的2类坡折带:构造挠曲坡折带受控于持续性古隆起,控制层序界面之上地层向斜坡高部位逐层“单向超覆”,侵蚀坡折带受控于古残丘,控制层序界面之上地层向古残丘“双向超覆”或沿下切沟谷低位充填。2类坡折带均控制地层沉积变化,有利于形成上倾超覆型、低位充填型和地层削截型岩性地层圈闭。研究成果对于指导古地貌背景坡折控制下的大型岩性地层油气藏勘探具有重要意义。

NUMERICAL SIMULATION OF TOPOGRAPHY CHANGE IN RECLAIMED LAND ALONG COAST OF SOUTH CHINA SEA

A formula for total sediment transport rate was worked out based on field surveys and experiments, which could be used to predict the topography change under wave climate. The sediment transport and wave induced hydrodynamics were solved separately, which is more convenient to predict long-term beach evolution than solving a coupled equation. In applying the sediment transport equation to wave model, the topography change was considered to give a new bathymetry as input for the wave equations, which in return will give a time-dependent hydrodynamic environment. The wave transformation including wave breaking was simulated by solving Boussinesq-type wave equations, together with some verification and comparisons. The longshore currents due to eddy viscosity was simulated by the model under unidirectional waves, which have been applied in erosion control of reclaimed land by headland breakwaters. The topography is found in equilibrium by headland breakwaters and the equilibrium process is simulated with comparison to the engineering practice in the South China Sea.

Fingerprinting sediment sources in a typical karst catchment of southwest China

Due to the complex hydrogeological conditions in karst regions,it is difficult to measure sediment source contributions at a catchment scale directly.The objective of this study was to quantify the relative contributions of sediment sources and their temporal variability in a karst catchment in southwest China.Karst depressions can trap eroded sediment similar to a dam or reservoir and,thus,are representative and typical test beds for identifying sediment sources in karst regions.Three sediment cores were taken from a karst depression,58 soil samples from three potential sediment sources were collected,and 18 soil properties were analyzed.The relative contributions of cropland,forestland,and fissure or crack soils were calculated using a multivariate mixing model.The fingerprinting results demonstrated that the cropland was the main sediment source in karst catchment.Specifically,according to the mean sediment contributions of the three deposited sediment cores,the sediment contribution from cropland topsoil was 69.3%,varying from 46.9%to 92.3%,and forestland soil and crack soil accounted for 8.6%and 22.1%of the sediment yield,and varying from 2.8%to 16.5%and 4.8%-36.6%,respectively.This result indicated that great attention should be paid when using only a single core to quantify sediment provenance.Due to the deposited sediment was generally disturbed as cropland in the karst depression,the area that has not been disturbed in recent decades in depression was more appropriate to trace sediment sources in karst catchment.To the best of our knowledge,this study was the first to quantify the contributions of sediment sources in the karst catchment of southwest China.This study provides valuable information and a preliminary reference for applying a composite fingerprinting technique to quantify sediment sources in karst catchments.