Topical Collection: Coastal aquifers in the Middle East and North Africa region

The Middle East and North Africa (MENA) region suffers from low precipitation and high evaporation. Coastal areas of the MENA region are usually densely populated; hence, the coastal aquifers are easily over-exploited beyond their safe yield, and seawater intrusion and aquifer salinization have been caused by the groundwater-level declines. Four studies in MENA coastal aquifers, on seawater intrusion modeling and aquifer recharge and salinization using isotopes, have been brought together in a topical collection and are discussed in this essay. A brief overview is given of managed aquifer recharge as an effective method to combat groundwater-level decline, seawater intrusion and aquifer salinization in MENA counties.     

Substitutes for water are being found in the Middle East and North Africa

Evident mismatches exist between the demand and supply of water in many countries particularly in the semi-arid and arid worlds. The resulting food gaps which concern both the national governments of these countries as well as the international agencies which extend assistance to them, appear at first sight to pose challenges beyond the economic and political capacity of peoples and institutions to make the necessary adjustments. The institutions with responsibility for the allocation and planning of water use at international, national and local levels do not seem to be robust enough, or informed enough, to provide the necessary leadership to ensure that scarce water is used sustainably.It will be argued that despite the great difficulties which governments and users face in coping with the need to manage water so that it brings a sound return, as well as according to principles of equity, safety, and ecological sustainability, everywhere there are examples of conflict over water being avoided. And while the avoidance of conflict can in many cases be calculated to have been at a cost to the environment, nevertheless, to date conflict of a hot nature has been avoided. Case studies from a region seen to have the worst water resource future outside the industrialised world, the Middle East and North Africa, will be discussed which exemplify the numerous strategies adopted by countries in their various ecological, economic and political circumstances. A fortunate few governments have substituted oil capital for water while others have filled the food gap, which is generally an expression of the water gap, by ceding economic and political autonomy.     

A quantitative assessment of groundwater resources in the Middle East and North Africa region

The Middle East and North Africa (MENA) region is the world’s most water-stressed region, with its countries constituting 12 of the 15 most water-stressed countries globally. Because of data paucity, comprehensive regional-scale assessments of groundwater resources in the MENA region have been lacking. The presented study addresses this issue by using a distributed ArcGIS model, parametrized with gridded data sets, to estimate groundwater storage reserves in the region based on generated aquifer saturated thickness and effective porosity estimates. Furthermore, monthly gravimetric datasets (GRACE) and land surface parameters (GLDAS) were used to quantify changes in groundwater storage between 2003 and 2014. Total groundwater reserves in the region were estimated at 1.28 × 10⁶ cubic kilometers (km³) with an uncertainty range between 816,000 and 1.93 × 10⁶ km³. Most of the reserves are located within large sedimentary basins in North Africa and the Arabian Peninsula, with Algeria, Libya, Egypt, and Saudi Arabia accounting for approximately 75% of the region’s total freshwater reserves. Alternatively, small groundwater reserves were found in fractured Precambrian basement exposures. As for groundwater changes between 2003 and 2014, all MENA countries except for Morocco exhibited declines in groundwater storage. However, given the region’s large groundwater reserves, groundwater changes between 2003 and 2014 are minimal and represent no immediate short-term threat to the MENA region, with some exceptions. Notwithstanding this, the study recommends the development of sustainable and efficient groundwater management policies to optimally utilize the region’s groundwater resources, especially in the face of climate change, demographic expansion, and socio-economic development.     

Nomadism and desertification in Africa and the Middle East

Desertification in areas where traditional pastoral nomadism was common is a phenomenon of this century. Nomads possessed institutions and management practices that avoided excess concentrations of people and animals, rotated grazing pressure seasonally between major pasture zones, protected dry season resources that were critical to their survival, and limited access to pastoral resources. These systems of management and control have broken down and degradation of pastoral lands has been the result. The pressures promoting desertification include agricultural expansion into pastoral zones, the loss of critical dry season pasture, sedentarization of former nomads, the impacts of war and civil conflict, nationalization of pastoral resources, the collapse of traditional common property resource management systems, and social change and economic intensification. These processes have concentrated pastoral pressures into more limited spaces and increased the stress placed on natural resources to the point where land degradation takes place. These adverse changes can be avoided and desertification arrested if principles of proper management are applied. By planning holistically, using the ethnoscientific wisdom of nomadic pastoralists as a basis for development, protecting zones critical to the survival of pastoralists, retaining mobility and flexibility in contemporary pastoral systems, and strengthening common property systems developed by nomadic pastoralists, land degradation in dryland rangelands can be halted.     

Large and giant hydrocarbon accumulations in the transitional continent-ocean zone

The petroleum resource potential is considered for the Atlantic, West Pacific, and East Pacific types of deepwater continental margins. The most considerable energy resources are concentrated at the Atlantic-type passive margins in the zone transitional to the ocean. The less studied continental slope of backarc seas of the generally active margins of the West Pacific type is currently not so rich in discoveries as the Atlantic-type margin, but is not devoid of certain expectations. In some of their parameters, the margins bounded by continental slopes may be regarded as analogs of classical passive margins. At the margins of the East Pacific type, the petroleum potential is solely confined to transform segments. In the shelf-continental-slope basins of the rift and pull-apart nature, petroleum fields occur largely in the upper fan complex, and to a lesser extent in the lower graben (rift) complex. In light of world experience, the shelf-continental-slope basins of the Arctic and Pacific margins of Russia are evaluated as highly promising.     

东非大陆边缘地质特征及油气勘探前景

非洲大陆油气资源潜力已越来越引起人们的广泛关注.与盛产油气的西非大陆边缘相比,东非大陆边缘至今还没有显著的原油发现.通过对东非大陆边缘构造演化特征、边缘构造性质及边缘形态等地质条件的分析,以及从油气成藏(烃源岩、储集层以及成熟度等方面)有利与不利因素的角度对其油气勘探前景进行的分析,认为东非大陆边缘具备油气成藏的基本地质条件.其中烃源岩分布,古近系构造抬升、剥蚀破坏作用,构造圈闭,特别是沿岸边缘海上区,以及三角洲地区的勘探工作应是今后研究工作的重点.     

Seismogenic Ancient Structures of the Center and North of the East European Platform

Doklady Earth Sciences - The location of earthquake epicenters in the central and northern parts of the East European Platform in 2009–2016 has been analyzed. The earthquake epicenters have...     

Early Permian to Middle Jurassic rifting and sedimentation in East Africa and Madagascar

Pre-drift sediments of Madagascar (Early Permian-Middle Jurassic) have been studied palynologically. These studies resulted in a more precise dating of individual stratigraphic units and the recognition of minor and major breaks in the succession. Palynostratigraphic and physical evidence of unconformities have been used to subdivide the pre-drift sediments into depositional cycles and to infer rifting events. A comparison with equivalent strata of Mozambique, Tanzania, Kenya, Ethiopia and Somalia shows a general correspondence and provides additional information for the construction of a generalized framework for the East African/Madagascan region which demonstrates the relationships between rifting and sedimentation and elucidates the prehistory of the break-up of Gondwana into a western and eastern fragment during the Middle Jurassic. The predrift succession of East Africa/Madagascar can be subdivided into two major sequences, a Karoo sequence (cycles 1–5, Asselian-early Smithian) and a transitional sequence (cycles 6–9, Ladinian-early Bajocian). The two sequences are separeted by a late Scythian to Anisian hiatus which indicates extensive uplift and erosion before a major rifting event initiated the resumption of sedimentation in the Ladinian. This Middle Triassic event marks the transition from the intracratonic rift stage to the pericratonic basin stage and correlates with a significant event in the Pangaean history, the transition from final coalescence to initial dispersal. The onset of the southward drift of Madagascar is believed to have occurred about 60 Ma later near the Aalenian-Bajocian boundary, contemporaneous with or immediately after the deposition of syntectonic sediments of cycle 9.     

Multidimensional statistical methods used for prediction of hydrocarbon accumulations in Turkmenistan

Conclusions Geological and geochemical data indicate that the Dauletabad area and the Chemenibid anticline fold are promising. The Morgunov uplift has better tectonic characteristics, but a lack of hydrocarbon gas anomalies is less encouraging. This forecast has been supported by data obtained during deep drilling, and by geochemical anomalies found on the surface that are associated with the Dauletabad-Donmez gas field. In the Chemenibid fold, the forecast was substantiated by discovery of commercial quantities of gas from Lower Jurassic deposits in exploratory well N1.     

塔里木盆地构造不整合成因及对油气成藏的影响

本文利用钻井及区域地震资料,对塔里木盆地6个关键构造不整合的结构特征、分布范围开展了详细的研究,确定了不整合面与下伏地层的夹角、遭受剥蚀的方向、剥蚀程度及不整合面的分布,对不整合的成因及其油气成藏作用进行了探讨。加里东中期形成的志留系与上奥陶统构造不整合(T⁰₇)主要为由南向北剥 蚀,向北剥蚀范围可达阿-满坳陷南部;在盆地南部西昆仑、阿尔金早古生代中期造山构造作用下,形成和田古隆起和卡塔克古隆起,塔北隆起仅在西部有活动。加里东晚期形成的上泥盆统-石炭系与中下泥盆统不整合(T⁰₆)主要表现为双向角度不整合特征,盆地受来自南缘和北缘造山带的挤压作用,形成了北、东、南三面连接的周缘环形隆起,塔北隆起构造活动强度及范围大于卡塔克隆起、和田-巴楚隆起。海西期形成的三叠系与二叠系不整合(T⁰₅)主要为由北东向南西的剥蚀,存在两个剥蚀阶地现象,盆地主要遭受来自北东和北部的挤压,在塔北隆起西部形成了高角度不整合。印支运动形成的侏罗系与前侏罗系不整合(T⁶₄)主要存在于盆地的东北部及西南部,塔北和孔雀河地区形成了中等角度单斜型角度不整合,塔东隆起形成了褶皱角度不整合,巴楚隆起成为塔西南坳陷的前缘隆起。燕山期形成的白垩系与前白垩系不整合(T⁰₄)表现为北北东-南南西、北北西-南南东两组方向的抬升剥蚀,盆地西南、东南断隆剥蚀强度大。喜马拉雅早期主要受南北向挤压,形成古近系与前古近系双向的角度不整合(T¹₃),后期巴楚隆起持续抬升剥蚀,大部分缺失白垩系-古近系,盆地受挤压、走滑构造作用明显增强。构 造不整合的形成与区域构造运动及不同时期盆地周缘的造山带形成响应,不同时期构造运动的主要作用范围、强度,不仅控制了构造不整合的结构特征和分布,而且控制着古隆起的发育演化,构造不整合对不整合圈闭油气成藏有控制作用。     

Metal accumulations in acidic waters from gold mines in South Africa

Heavy metal contents have been investigated in sediment and water samples from gold and platinum mining areas of South Africa. Waste waters from Witwatersrand and Orange Free State gold mines exhibit characteristically low pH-values due to the formation of sulphuric acid by oxidation of sulphide ore minerals. Acid leaching of iron, manganese, nickel, cobalt, copper and zinc effects a 1,000–10,000-fold increase of metal concentrations as compared to the respective values in unpolluted river water. Lack of carbonate buffering prevents rapid immobilization and may lead to widespread distribution of toxic metals in the aquatic systems. These findings illustrate that modern ore refining techniques have little effect on the water quality as long as unchecked hydrometallurgical processes take place outside the production plant.     

Prediction of the phase state of hydrocarbon accumulations in the Mesozoic deposits of northwestern Siberia

The phase state of hydrocarbon accumulations was predicted using recent drilling data for three oil and gas complexes of the northern regions of the West Siberian petroliferous basin: Lower and Middle Jurassic, Upper Jurassic, and Berriasian-lower Valanginian (Achimov member); these results were compiled in simplified maps presented in the paper. In order to develop a plausible model and distinguish the zones of hydrocarbon accumulation of various phase states, we analyzed and systematized the existing concepts on the distribution of oil, oil-gas condensate, and gas condensate pools in the Mesozoic sequences of this region, types of organic matter in rocks, and stages of catagenetic alterations. Based on the data of the Tyumen SG-6 superdeep well, the oil-generating capacity of source deposits was assessed. Three zones differing in the phase state of hydrocarbons, oil, gas condensate-oil (transitional), and gas condensate, were distinguished in the map of the distribution of hydrocarbon accumulations in the Early-Middle Jurassic petroliferous complex of northwestern Siberia. Only two zones of hydrocarbon accumulations, oil and transitional, were detected in the Late Jurassic complex of the Nadym-Taz and Ust’-Yenisei regions. The same zones but within different boundaries were distinguished in the Achimov sequence. In contrast to the Jurassic beds, the zone of occurrence of oil accumulations in the Achimov member occupies a larger area and extends further north. In terms of density, the oils of the Achimov deposits were subdivided into three types: ultralight, light, and medium. The zones of their occurrence are shown in the map. Original Russian Text ? S.A. Punanova, T.L. Vinogradova, 2006, published in Geokhimiya, 2006, No. 9, pp. 983–995.     

基于10Be暴露年代的北美洲晚第四纪冰川演化序列研究

对北美洲晚第四纪冰川¹⁰Be暴露年代进行汇编与聚集程度置信等级划分,构建了北美洲各区域的冰川演化序列,并进一步对比和分析了冰川演化序列对高分辨率气候事件的响应情况,使用较好和中等聚集程度的暴露年代漂砾组对北美洲各区域进行冰期划分。结果表明：北美洲冰川序列横跨6个深海氧同位素阶段（marine isotope stage,MIS）,保守估计至少在MIS 6/5、MIS 4/3、MIS 2时期出现了规模性冰进,其记录可信区间为约150 ka至今。末次冰盛期（Last Glacial Maximum,LGM）之前的冰川演化存在区域性,这可能与劳伦泰德冰盖的大气效应存在一定的相关性。LGM的冰川达到最大范围的时间不同步,揭示了不同地区冰川演化的影响因素不尽相同。LGM以来的冰川作用对于高分辨率气候事件,如海因里希事件1（Heinrich Stadial 1,HS1）、B-A事件（B?lling-Aller?d,B-A）、新仙女木事件（Younger Dryas,YD）的响应存在同步性。对于全新世更高分辨率的邦德事件（Bond）,北美洲的冰川¹⁰Be暴露年代同样具有很好的对应关系。     

Middle and late Pleistocene glaciations in the Campo Felice Basin (central Apennines, Italy)

The present paper refers to research conducted in the tectonic-karst depression of Campo Felice in the central Apennines (Italy), in which glacial, alluvial and lacustrine sediments have been preserved. Stratigraphic interpretations of sediments underlying the Campo Felice Plain are based on evidence obtained from nine continuous-core boreholes. The boreholes reach a depth of 120 m and provide evidence of five sedimentation cycles separated by erosion surfaces. Each cycle is interpreted as an initial response to a mainly warm stage, characterized by low-energy alluvial and colluvial deposition, pedogenesis, and limited episodes of marsh formation. In turn, a mainly cold stage follows during which a lake formed, and glaciers developed and expanded, leading to deposition of glacial and fluvioglacial deposits. The chronological framework is established by eleven accelerator mass spectrometer ¹⁴C ages and three ³⁹Ar-⁴⁰Ar ages on leucites from interbedded tephra layers. These age determinations indicate five glacial advances that respectively occurred during marine oxygen isotope stages 2, 3-4, 6, 10 and 14.     

Contrasted seismogenic and rheological behaviours from shallow and deep earthquake sequences in the North Tanzanian Divergence,East Africa

We report preliminary results of a seismological experiment, SEISMO-TANZ’ 07, which consisted in the deployment of a local network (35 stations) in the East African Rift System (EARS), North Tanzania, during 6 months in 2007. We compare two earthquake sequences (Gelai and Manyara) occurring, respectively, in the southern end of the Kenya rift and in the North Tanzanian Divergence (NTD). Only distant of ∼150 km, their triggering mechanisms are different. None of the sequences depicts typical swarm or mainshock–aftershock patterns. They highlight the change in the magmatic/tectonic nature of the rift where the eastern branch of the EARS enters the Tanzanian craton. The similar shape and long-axis of the elongate sequences emphasize the preferred locus of active strain release along NE–SW discontinuities which probably root at depth into steep Proterozoic shear zones. At Gelai, the deformation is dominated by aseismic process involving slow slip on normal fault and dyke intrusion within the upper crust (Calais et al., 2008). The spatial and temporal earthquake distribution indicates a possible correlation between the Gelai crisis and the eruption of the nearby Oldoinyo Lengai volcano. At Manyara, the sequence is more uncommon, revealing a long-lasting seismic activity deeply rooted (∼20–35 km depth) possibly related to stress loading transmitted laterally. The yield strength envelope modelled from the depth frequency distribution of earthquakes in the NTD is consistent with the presence of a mafic lower crust and further supports the strength increase of the rifted crust from south Kenya to the NTD.     

海拉尔盆地乌尔逊-贝尔凹陷构造演化对油气成藏的控制作用

从成盆、成源、成烃和成藏4个方面对海拉尔盆地乌尔逊-贝尔凹陷各构造演化阶段的石油地质意义进行了分析。海拉尔盆地成盆的动力机制是中蒙边界区中生代推覆构造形成后的晚造山期伸展垮塌作用,为典型的被动裂陷盆地。乌尔逊-贝尔凹陷形成演化经历了5个时期：山间残留阶段、被动裂陷阶段、主动裂陷阶段、断坳转化阶段和坳陷阶段。被动裂陷阶段沉积物震荡式沉积形成南一段中部砂泥互层的优质烃源岩,主动裂陷阶段盆地强烈裂陷,窄而深的断陷结构控制盆地南一段上部有效源岩分布,断坳转化阶段盆地快速沉降促进烃源岩熟化,伊敏组沉积晚期烃源岩大量排烃控制形成早期原生油藏,伊敏组末期盆地反转,部分油藏受活动断裂破坏调整到大磨拐河组形成次生油藏。不同演化阶段形成多种类型的隆起带,构成有利的油气聚集区带,控制了不同含油气系统油气聚集。