Depression Zone Research Articles

Study of urban puddle sediments for understanding heavy metal pollution in an urban environment

Natural processes cause sedimentation in local surface depressed zones of the urban landscape with the formation of micro water bodies (puddles). The urban puddle sediments can be defined as a separate peculiar subtype of geochemical traps of the recent technogenic and anthropogenic sediments. Accumulation of pollutants over space and time is a remarkable advantage of urban sediments in comparison with urban soils. The relevance of urban puddle sediments as an object for the assessment of heavy metals pollution (Pb, Zn, Cu, Ni, Co, Mn, Fe) of an urban ecosystem was studied on the example of Ekaterinburg city, Russia. Samples of urban puddle sediments were collected from 213 locations in residential areas. The study of heavy metals pollution in Ekaterinburg city showed that the puddle sediments provide further opportunities for the analysis of the urban environment.

Hydroecological approach for determining the width of riparian buffer zones for providing soil conservation and water quality

Riparian buffer zones have important ecological functions such as sustainability of water quality, reducing sediment accumulation, and preventing erosion. However, it is often very difficult to develop a general rule for these areas since each riparian zone may have different rainfall characteristics and soil properties. In this study, the width of riparian buffer zone was determined around a sample dam lake to achieve sustainable water quality and soil conservation. The research was conducted in Palandoken Dam Lake located in the eastern city of Erzurum in Turkey. For the implementation of the riparian buffer zone, firstly, flood conditions were taken into account based on series of satellite images and then depression zone was calculated using Archydro software based on Digital Elevation Model. Two satellite images of the study area taken in August 2008 and April 2011 were compared to determine the potential flooded areas. Then, potential depression zone, which are around and beyond the flooded areas, were determined based on terrain structure (sink areas). Finally, the width of the riparian buffer zone was determined by including reserve zone and management zone onto the depression zone. The results indicated that depression area was 5,774 ha. The area and perimeter of riparian buffer zone were 6,364 ha and 59 km, respectively. It was found that hydroecological approach using geographical information system technology can be successfully implemented to provide maximum sustainable protection of water and soil resources in riparian zones, especially in the lake basins.

典型峰丛洼地耕地、聚落及其与喀斯特石漠化的相互关系案例研究

PDF HTML阅读 XML下载 导出引用 引用提醒 典型峰丛洼地耕地、聚落及其与喀斯特石漠化的相互关系——案例研究 DOI: 10.5846/stxb201302010217 作者: 作者单位: 贵州师范大学地理与环境科学学院,贵州师范学院地理与旅游学院,中国科学院地球化学研究所环境地球化学国家重点实验室,贵州师范大学地理与环境科学学院,贵州师范大学地理与环境科学学院,贵州师范大学地理与环境科学学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（41261045）；国家科技支撑计划重大课题（2014BAB03B02）；教育部人文社会科学研究一般项目（10XJAZH002）；贵州省科技专项重大课题（黔科合重大专项字﹝2012﹞6015号） The correlations among arable land, settlement and karst rocky desertification-cases study based on typical peak-cluster depression Author: Affiliation: School of Geography and Environmental Sciences,Guizhou Normal University,School of Geography and Tourism,Chongqing Normal University,National key laboratory of environmental geochemistry,geochemistry institute of Chinese Academy of Science,Guiyang,School of Geography and Environmental Sciences,Guizhou Normal University,School of Geography and Environmental Sciences,Guizhou Normal University,School of Geography and Environmental Sciences,Guizhou Normal University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:喀斯特石漠化，近年来已成为研究热点和引起国家层面重视，但当前研究并没揭示岩溶山地土地为什么会发生石漠化这一现象的本质，没有阐明岩溶山地农户为什么要进行不合理活动。通过典型案例研究从理论上解释岩溶山地农户为什么要进行不合理活动这个问题，以从本质上揭示石漠化发生的机理。为此，在贵州选择了６个典型峰丛洼地，采用2010年的10 m分辨率ALOS影像作为数据源，比较了6种不同的峰丛洼地组合地形中的耕地资源分布、聚落特征和石漠化发育情况。结果表明，6个研究点耕地和聚落数量、分布和石漠化的面积和分布存在一定的相互关系，这些相互关系可阐明土地承载力较低情形、土地承载力中等情形和土地承载力较高情形石漠化发生的过程；发现严重的石漠化只能出现在土地承载力低、人口压力大的区域，并据此进一步总结了峰丛洼地区石漠化形成的理论模型。从理论上揭示了峰丛洼地区土地承载力和人口压力是否协调决定了峰丛洼地区的生态质量状况，有助于从本质上认识石漠化的发生机理和指导石漠化的治理。 Abstract:The Karst Rocky Desertification (KRD) occurred in Southwest China has become a research hotspot and drawn great attention of the Chinese government in recent years. However, the current researches about KRD has not revealed the essential reason why the KRD phenomenon occurred in karst mountains, and has not clarified why the local farmers had undertaken unreasonable agricultural activity in karst mountain areas. This paper attempted to discover theoretically the reason why the local farmers in karst mountain areas carried out irrational activities such as the steep slope land cultivations, and to reveal essentially the occurrence mechanism of KRD through the typical case studies. Firstly, this paper assumes that the low land capacity is the genesis cause of KRD in peak-cluster depression areas. Furthermore, ecological quality of the peak cluster depression zone is determined by the relationship between the area of depressions (negative terrain) and the population of residential area. So, six typical of peak-cluster depression areas of Guizhou province were selected to compare the distribution circumstances of cropland, the characteristics of settlements and the formation of KRD with the help of Alos images in 2010 (with a resolution of 10 m×10 m). The results show that the areas such as closed peak-cluster depression of continuous distribution, shallow peak-cluster depressions and assemblages of peak-cluster depression and canyon are lack of cropland resources, but some terrain such as peak-cluster depression group embraced by flat land and not closed peak-cluster depression are rich in cropland, and the cropland distributed in spatial array of peak-cluster depression, peak-cluster valley and gully area is relatively fewer. There is a negative correlation between the percentage of the cultivated land and the percentage of KRD (including light KRD, moderate KRD and severe KRD) at peak- cluster depressions, serious KRD distributes in the peak-cluster depressions with higher percent of the settlement accounted for the cropland area. It is related to some extent, in the six study areas, between the quantity and spatial distribution of arable land and settlements, and the size and spatial distribution of KRD. The relationship could be concluded as three situations of the process of KRD, where are low, middle and upper carrying capacity of land. The serious KRD is found distribute only in peak-cluster depression areas with fewer flatland, low land capacity and high population pressure, therefore, the theory hypothesis suggested by this paper is correct, to improve the bearing capacity of land should be the primary means to desertification control in peal-cluster depressions. The theoretical models of KRD occurrence mechanism in these areas were summarized further through the comparisons of the arable land resources distribution, the characteristics of settlement and the KRD occurrence situations in these six different peak cluster depression combined topography. The ecological qualities are dominated by the harmonization between land capacity and population pressure in the peak cluster depression areas. And this finding will make contribution to understand essentially the occurrence mechanism of KRD and be guidance to the ecological restoration of KRD land. 参考文献 相似文献 引证文献

Becoming Monument, Activating Windsor

What does it mean to live in a dying place? This auto-critical article asks this question in the context of the Windsor/Detroit region, one of the most economically depressed zones in North America. Using the work of Barthes, Benjamin, and Taussig, I ruminate on the psycho-somatic experiences of trying to navigate a world that most writers have already dismissed as haunted and abandoned.

First Discovery of Plasmobatidae (Acari, Oribatida) in Gabon, redefinition and new species of the genusSolenozetesGrandjean, 1932

ABSTRACT The family Plasmobatidae is herewith reported for the first time from Gabon and Solenozetes makokouensis n. sp. is described. The holotype was collected from litter in dense evergreen humid forest, Makokou, Province Ogoove-Ivindo, north-eastern Gabon. The species is described and illustrated based on adult females. The new species is easily distinguishable by the following combination of character states: cerotegumental layer amorphous, with small tuberculations mixed with granulations; ro seta falcate, inserted on forward-extending visorlike protuberance; in seta wrapped in cerotegumental granulate layer; prodorsal anterior zone complex with irregular protuberances; bothridium horseshoe-shaped, internal rings appearing gear-like; sensillus filiform; notogaster anteriorly with semicircular furrow and depressed zone; macropores opening on foveae; notogastral microsculpture irregular foveate pattern; opisthosomal gland apophysis conical with rounded tip; five pairs of notogastral setae. The genus S...

Impacts of heavy groundwater pumping on hydrogeological conditions in Libya: Past and present development and future prognosis on a regional scale

Abstract Elgzeli, Y.M., Ondovčin, T., Hrkal, Z., Krasny, J. and Mls, J. 2011. Impacts of heavy groundwater pumping on hydrogeological conditions in Libya: Past and present development and future prognosis on a regional scale. Acta Geologica Polonica, 63 (2), 283-296. Warszawa. Libya, like many other regions with arid climates, suffers from inadequate water resources to cover all the needs of this rapidly developing country. Increasing amounts of water are needed to supply the population, as well as for agricultural irrigation and industrial use. As groundwater is the main water source in the country, it represents a natural resource of the highest economic and social importance. Conceptual and numerical models were implemented on a regional scale to show how the natural situation has changed following heavy groundwater abstraction during the last decades in the northwestern part of the country. The results of the numerical model indicated that the current zones of depression of the piezometric surface could have been caused by smaller withdrawn amounts than previously estimated. The differences in the assessed withdrawn groundwater volumes seem to be quite high and might have a considerable influence on the future possibilities of groundwater use in the study region.

The main controlling factors and developmental models of Oligocene source rocks in the Qiongdongnan Basin, northern South China Sea

Coals developed in the Oligocene Yacheng and Lingshui formations in the Qiongdongnan Basin have high organic matter abundance, and the dark mudstones in the two formations have reached a good source rock standard but with strong heterogeneity. Through the analysis of trace elements, organic macerals and biomarkers, it is indicated that plankton has made little contribution to Oligocene source rocks compared with the terrestrial higher plants. The organic matter preservation depends on hydrodynamics and the redox environment, and the former is the major factor in the study area. During the sedimentary period of the Yacheng Formation, tidal fiats were developed in the central uplift zone, where the hydrodynamic conditions were weak and the input of terrestrial organic matter was abundant. So the Yacheng Salient of the central uplift zone is the most favorable area for the development of source rocks, followed by the central depression zone. During the sedimentary period of the Lingshui Formation, the organic matter input was sufficient in the central depression zone due to multiple sources of sediments. The semi-enclosed environment was favorable for organic matter accumulation, so high quality source rocks could be easily formed in this area, followed by the Yacheng salient of central uplift zone. Source rocks were less developed in the northern depression zone owing to poor preservation conditions.

High-resolution reflection seismic investigations of quick-clay and associated formations at a landslide scar in southwest Sweden

We present high-resolution reflection seismic data from four lines (total 1.9 km) that cross a quick-clay landslide scar located close to the shore of the Göta River in southwest Sweden, and compare the results with geotechnical data from boreholes. The seismic data allow the imaging of bedrock topography and normally to weakly consolidated sediments to a subsurface depth of about 100 m. Different types of seismic sources, including sledgehammer, accelerated weight-drop and dynamite were utilized and compared with each other. Analysis of their power spectra suggests that weight-drop and dynamite have higher frequency content and energy than the sledgehammer, which makes these two sources suitable also for waveform tomography and surface-wave data analysis. The shallowest non-bedrock reflector is observed at about 10–20 m below the surface, it overlays the bedrock, and is interpreted to originate from the contact between clay formations above and a coarse-grained layer below. The coarse-grained layer appears to be spatially linked to the presence of quick-clays. It is a regional scale formation, laterally heterogeneous, which deepens to the west of the study area and correlates well with the available geotechnical data. Continuity of the coarse-grained layer becomes obscured by the landslide scar. There may be a link between the coarse-grained layer and landslides in the study area, although this possibility requires further hydrogeological and geotechnical investigations. Reflectors from the top of the bedrock suggest a depression zone with its deepest point below the landslide scar and a bowl-shaped structure in the northern portion of one of the seismic lines.

Geo-Historical and Geomorphological Evolution of the Sabkhas and Ridges at the Al-Khiran Area, State of Kuwait

The State of Kuwait is located in the northwestern Arabian Gulf. It is characterized by arid to semi-arid weather. This study’s concerned with the southern coastal area of the Al-Khiran. The purpose of this study is to evaluate and study the geo-history and evolution of geomorphologic features, especially coastal Ridges and Sabkhas in the Al-Khiran study area. This study based on the field observations as well as the application of Geographic Information Systems (GIS) and Remote Sensing techniques to establish a geodatabase for the study area in different disciplines. The results showed that the Al-Khiran coastal area was affected by the sea level fluctuation and coastal sedimentation during the Holocene and late Pleistocene. The coastal Ridges were originally coastal dunes, which were composed during the sea regression periods and consolidated with time. These Ridges were developed with time and separated the Al-Khiran area as a closed lagoon. This lagoon dried with time and formed a Sabkha field, especially on the depression zone that intersected or surrounded with the coastal Ridges. The Remote Sensing change detection technique shows that the changes were mainly concentrated on covering Sabkhas in some locations and might be due to the impact of active sand sheets and Aeolian sands. Land development in the Al-Khiran area led to the demolition of most of the coastal Ridges and Sabkha deposits.

Quantitative Study of Elements Migration during the Wall Rock Alteration Process for Gejiu Copper-Polymetallic Deposit inside Rock

With continuous consumption of proven resources, people have to turn to new resources or find new ways for prospecting. As to Yunnan Gejiu Tin and copper polymetallic deposit, deep ore prospecting may be the solution. The newly discovered copper-polymetallic deposit inside the rock of Tangzi’ao depression zone, which located in western part of Yunnan Gejiu east tin mine area, is a new type of deposit in deep ore prospecting. This kind of deposit produced in the alkali-rich, oxidizing environment, potash feldspathization is an important sign of prospecting, and a variety of metallic elements can be comprehensive utilization. It is special that potash feldspathization zone and epidotization zone alternating with each other; the phenomenon may caused by multi-period of hydrothermal fluids. By quantitative calculating the results of altered rocks and original rock samples, the author find out the migration laws of the constant elements and the main ore-forming elements and their associated elements, which provide a basis for prospecting in the future.

Drainage subsidence associated with Arctic permafrost degradation

Arctic sources of greenhouse gas associated with permafrost degradation constitute a large uncertainty in existing climate models. Greenhouse gas release from the Arctic subsurface is mediated by numerous interconnected physical processes; one facet of these is the interplay between surface deformation and melting of subsurface ice. First, we construct analytic solutions describing fluid drainage and soil subsidence subsequent to thawing of a 1‐D permafrost column. These solutions lead to formulas giving the total amount of subsidence as well as the time over which subsidence occurs. We give an example application of the analytic model to peat plateau degradation in the Canadian Hudson Bay Lowland and show that the degree of subsidence predicted from our model is consistent with recorded subsidence of peat in western Norway that was drained for cultivation purposes. Second, we numerically model an initially frozen, fluid‐saturated, 2‐D soil matrix with a thaw zone advancing from the surface downward. With the surface temperature fixed at 5°C, a thaw front propagates to ∼10 m depth within 20 years, and due primarily to drainage of fluid from the pore space, a region of soil depressed by ∼3 m forms above an initially ice‐rich subsurface zone. Soil underlying this depressed zone may have its permeability reduced by between 1 and 2 orders of magnitude; this reduction in permeability can act as a negative feedback to thawing.

The formation environment and development modes of Cenozoic source rocks in the Qiongdongnan Basin

According to the drilling results, there are three sets of source rocks of the Cenozoic Group in the Qiongdongnan Basin, including the Yacheng Formation transitional facies mudstone, the Oligocene Lingshui Formation semi-enclosed marine facies mudstone, and the Miocene neritic-bathyal facies mudstone. The hydrocarbon generating conditions of the source rocks in the study area are mainly controlled by sedimentary environment and organic matter input. The abundance of organic matter in the Oligocene source rocks which were formed in a low-energy back shore environment is confined by organic matter input and hydrodynamic condition. The Miocene source rocks formed in the open marine environment lack terrestrial organic matter input, whose organic matter abundance is constrained by the primary production of the ocean and the preservation condition of organic matter. In addition, the redox conditions are also significant to the formation of source rocks in the study area. According to the differences in key factors controlling the development of source rocks in different time periods and structural belts revealed by drilling practice, three development patterns of source rocks have been put forward. The first one is the transitional facies model featuring a great deal of terrestrial organic matter and weakly hydrodynamic conditions which are apt to develop high effective source rocks in the Yacheng Formation. The second one is the semi-enclosed marine facies featuring abundant terrestrial organic matter, weakly hydrodynamic condition and fine preservation condition in the central depression zone, which are apt to form fine-quality source rocks in the Lingshui Formation. The third one is the marine facies model featuring strong hydrodynamics in the shore-shallow area of northern continental shelf and the lack of benthic algae which are against the development of source rocks. It can be predicted that the continental slope is the perfect place to form source rocks where adequate amounts of light favor the photosynthesis of plants, besides the fine preservation and weakly hydrodynamic conditions. In the deep sea area, although accompanied with weakly hydrodynamic conditions and a reduction environment, it is not suitable for the development of source rocks on account of less aquatic organisms causing low primary production.

Evaluation of monitoring items for adverse ground conditions in subsea tunneling

Three monitoring items, i.e. displacement vector orientation, preceding displacement, and water inflow, were compared to determine which one best provided supplementary and valuable information on the ground ahead of a subsea tunnel face when used with probe drilling. The geotechnical factors affecting tunnel stability were selected from the case studies on the construction of subsea tunnels, and six representative types of adverse ground condition were built with combinations of the factors. The capabilities of monitoring items were compared in depression and weakness zone types that were selected as major adverse ground conditions with three criteria, i.e. the capability of categorizing the type of adverse ground condition, the early-warning time, and the response capability. A three-dimensional finite element analysis program was used to simulate the process of subsea tunnel excavation, and the Analytic Hierarchy Process was used to select the optimum monitoring item. A comparison of the results showed that the vector orientation was the optimum item for categorizing ground type, and the preceding displacement and the water inflow possessed the best capability for early warning according to ground type. The response capability of water inflow was assessed as the best for three types of weakness zones, and that of vector orientation was best for depression type. In 13 cases where the priorities of comparison criteria were different, the vector orientation and the water inflow were respectively chosen in six cases, and there was little difference between the two items in the case where the criteria were equally important. While the application of one item alone may be vulnerable to a specific adverse ground condition, the monitoring capability could be overall improved by the adoption of both items.

Hazardous gas emissions from the flanks of the quiescent Colli Albani volcano (Rome, Italy)

Abstract Gas hazard was evaluated in the three most important cold gas emission zones on the flanks of the quiescent Colli Albani volcano. These zones are located above structural highs of the buried carbonate basement which represents the main regional aquifer and the main reservoir for gas rising from depth. All extensional faults affecting the limestone reservoir represent leaking pathways along which gas rises to the surface and locally accumulates in shallow permeable horizons forming pressurized pockets that may produce gas blowout when reached by wells. The gas, mainly composed of CO 2 (>90 vol.%), contains appreciable quantities of H 2 S (0.35–6 vol.%), and both represent a potentially high local hazard. Both gases are denser than air and accumulate near ground where they may reach hazardous concentrations, and lethal accidents frequently occur to animals watering at local ponds. In order to evaluate the rate of degassing and the related hazard, CO 2 and H 2 S diffuse soil flux surveys have been repeatedly carried out using an accumulation chamber. The viscous gas flux of some important discrete emissions has been evaluated and the CO 2 and H 2 S air concentration measured by portable devices and by Tunable Diode Laser profiles. The minimum potential lethal concentration of the two gases (250 ppm for H 2 S and 8 vol.% for CO 2 ) is 320 times higher for CO 2 , whereas the CO 2 /H 2 S concentration ratio in the emitted natural gas is significantly lower (15–159). This explains why H 2 S reaches hazardous, even lethal, concentrations more frequently than CO 2 . A relevant hazard exists for both gases in the depressed zones (channels, excavations) particularly in the non-windy early hours of the day.

Myofilament Dysfunction in the Infarct Border Zone

Introduction: Soon after myocardial infarction, a poorly contracting border zone forms adjacent to the infarct. Myocardium in the infarct border zone remains normally perfused with blood, and the cause of border zone dysfunction is unclear. Goal: Investigate the role of myofilament dysfunction in the impaired contraction of the infarct border zone. Methods: We studied sheep hearts, 2 or 8 weeks after infarction of the apex of the heart and non-operated controls. Myofilament contraction was assessed using in-vitro contractions of skinned cardiac muscle fibers. Muscle fiber bundles were dissected from the infarct border zone and from multiple regions ranging up to 6 cm from the infarct. Skinned fiber force development was referenced to several measures of the content of contractile material within the samples. Results: In the border zone immediately adjacent to the infarct, maximal force development (Fmax) was reduced by 38 ± 2% (n=7, P<0.001) compared with Fmax of myocardium remote from the infarct. Fmax for remote zone myocardium was similar to that for uninjured myocardium (∼90 mN/mm2). The width of the border zone was defined by a decreased Fmax that extended up to 5-6 cm away from the infarct. Fmax rose in a linear gradient between the infarct and the remote zone. There were no differences between border zone and remote zone in: histological staining for collagen; the area fraction of myocardium occupied by myofilbrils (or mitochondria); or in the abundance of myosin. Therefore, depressed border zone Fmax was not explained by decreased content of contractile material. Moreover, treatment of skinned fibers with protein phosphatase 1 did not affect border zone Fmax, suggesting that myofilament protein phosphorylation was not involved in border zone dysfunction. Conclusions: Myofilament dysfunction contributes to impaired contraction in the infarct border zone.

ГЕОДИНАМІКА

In the paper discusses the features of long-term seismicity (1961-2010) the territory of Transcarpathian depression and separate seismoactive zones (A, B and C). The relationship of these zones with the main tectonic elements of depression is set. It is proved that the boundary between zones A and B passes through Oash deep fault.

Inverted intracontinental basin and vertical tectonics: The Saharan Atlas in Tunisia

The present-day architecture of the Saharan Atlas in Tunisia can be defined by two principal models: (1) The first model emphasizes a general SW–NE geological structure in the North forming successive and parallel bands (the Tellian zone, the diapir zone) and the central Atlas, which are cut by the southern Atlas ranges located within a NW–SE corridor. These zones are bordered to the East by the “North–South Axis”. (2) The second model defines the Tunisian Atlas in terms of an E–W strike-slip corridor, which initially controls the sedimentary facies distribution during the Meso-Cenozoïc, and which then generates elongate en echelon folds in the sedimentary cover by dextral shearing. In this study, we aim to show that the Saharan Atlas in Tunisia appears today as a triangular megablock, that we call the Tunisian Block (TB), bounded by three structural trends (N–S, SW–NE and NW–SE) belonging to the African strike-slip fault network: (1) The eastern boundary appears as a complex faulted and folded corridor limiting the folded zone of the central Atlas in the West and the depressed zone of the Sahel in the East: it corresponds to the “North–South Axis” as defined classically in the literature. (2) The southern boundary also corresponds to a faulted belt (Gafsa–Negrine-Tozeur corridor), which cuts off the continuation of the North–South axis southward into the Gabès region; it corresponds to the Southern Saharan Atlas, delimited by the Gafsa fault in the North and the Negrine-Tozeur fault in the South. (3) The northern boundary, trending SW–NE, appears rather in the form of a reverse tectonic bundle, facing SE or S (oblique convergence), whose major feature corresponds to the El Alia-Téboursouk fault. This northern boundary cuts across and delimits the N–S corridor towards the North, in such a way that its extension is limited at both extremities. Finally, the inner part of the TB actually corresponds to a mosaic of second-order blocks, each of which contains an arrangement of widely spaced SW–NE trending anticlines forming the main relief separated by vast plains very often occupied by sebkhas. The paleogeographic and structural evolution of this region during the Mesozoic and Palaeogene shows that the TB, along with its limits as defined here, developed an increasingly distinct identity at a very early stage, being characterized by an extensive and/or transtensive tectonic regime. Finally, the Tunisian Atlas Chain defines a triangular domain that owes its origin and particular character precisely because of the paleogeographic and structural history of this paleoblock. The boundaries of this paleoblock remain mobile, thus tectonically controlling the geometry and morphology of a typical intracontinental basin. The extension directions and the frequent changes of stress regime (or rotations) are related to the existence of two active basins: the strike-slip margin of the western branch of Tethys and the Mesogea oceanic basin, with tectonic activity becoming alternately dominant in one or other of the basins at different times. In this context, the Tunisian basin is characterized by rhythmic sedimentation, composed of a succession of filling sequences linked to the continuing tectonic instability of the sedimentary floor associated with two major crises: one at the end of the Aptian and the other at the end of the Ypresian. The vertical movements related to the extension and/or transtension of the blocks is accentuated by Triassic salt tectonics, giving rise to linear (salt axes) or point (salt domes) structures that lead to the formation of shoal zones during development of the basin, thus enhancing the vertical tectonics. The diapirism developed slowly and gradually from late Triassic through to Langhian times, leading to numerous sedimentary wedges on the flanks of the structures. The uprise of the diapirs exhibits three pauses corresponding to the end-Aptian, end-Ypresian and pre-Burdigalian. The vertical tectonics is characterized by abundant drape folds giving rise to an extensional fault-related folding and strike-slip/dip-slip faults creating frequent unconformities that are nevertheless always localized. Finally, the folded chain results from the structural inversion of this paleoblock from Tortonian times onward. We can only account for the various folds-axis directions in the context of an intracontinental chain where the pre-existing major vertical faults are able to develop on the surface as draped-folds in a transpressive regime by the local reorientation of stresses in crustal-scale faults. In detail, the structures produced by this vertical tectonic activity, which are profoundly controlled by inheritance, display a highly original style at very shallow levels in the crust.

Towards Prediction of Failure in Ti‐6AI‐4V Aerospace Materials by Surface Observations

Abstract: This paper deals with the development of a methodology for the prediction of material failure in metallic aerospace alloys by evaluating changes in surface characteristics directly prior to unstable fatigue crack propagation. The study is based on in situ nondestructive characterisation of the depression zone ahead of the crack tip of fatigue‐pre‐cracked titanium alloy specimens subjected to static loading. A relationship between the surface characteristics of the deformation zone ahead of the crack and the stress intensity factor of the material was obtained. This relationship was common to a variety of microstructural conditions such as mill‐annealed and β‐annealed microstructures. Based on the analysis, prediction of the impending fracture in cracked samples of the material was enabled. The outcome of this study can be used for optimising the service life of structural components.

Characterization of the Cretaceous aquifer structure of the Meskala region of the Essaouira Basin, Morocco

The aquifer of early Cretaceous age in the Meskala region of the Essaouira Basin is defined by interpretation of geological drilling data of oil and hydrogeological wells, field measurement and analysis of in situ fracture orientations, and the application of a morphostructural method to identify lineaments. These analyzes are used to develop a stratigraphic–structural model of the aquifer delimited by fault zones of two principal orientations: NNE and WNW. These fault zones define fault blocks that range in area from 4 to 150 km 2. These blocks correspond either to elevated zones (horsts) or depressed zones (grabens). This structural setting with faults blocks of Meskala region is in accordance with the structure of the whole Essaouira Basin. Fault zones disrupt the continuity of the aquifer throughout the study area, create recharge and discharge zones, and create dip to the units from approximately 10° to near vertical in various orientations. Fracture measurements and morphometric-lineament analyzes help to identify unmapped faults, and represent features important to groundwater hydraulics and water quality within fault blocks. The above geologic features will enable a better understanding of the behaviour and hydro-geo-chemical and hydrodynamics of groundwater in the Meskala aquifer.

Molybdenite Re‐Os and Zircon SHRIMP U‐Pb Dating at the Baishiding Deposit, Guposhan District: New Evidence for Silurian Mo Mineralization in South China

AbstractThe Baishiding molybdenum deposit is located in the Central‐Middle Guangxi depression zone of the South China Caledonian fold zone. Orebodies occur as quartz‐molybdenite veins within the Guiling monzonite pluton and arkosic quartz sandstone of Zhengyuanling Group in the northeastern Guangxi. They are NEE‐trending with a dip angle of 75–80°. Zircon SHRIMP U‐Pb geochronologic analyses of the Guiling monzonite show age of 424.4 ± 5.6 Ma. It indicates that the Guiling monzonite was emplaced in Silurian. The ore minerals in quartz‐molybdenite veins contain molybdenite, pyrite, chalcopyrite and scheelite. Six molybdenite samples yield Re‐Os ages between 433.3 ± 6.3 Ma and 417.2 ± 5.7 Ma, with a weighted mean age of 424.6 ± 5.7 Ma, which agrees with the zircon age of the Guiling monzonite pluton. It suggests that the deposit was formed in the Silurian, not the Jurassic as previously thought. The Baishiding deposit is the only Silurian molybdenum deposit so far recognized in the South China. It was probably formed in a crustal shortening setting along the continental margin in the Silurian.