Geomorphological analysis of paleo drainage systems and their environmental implications in the desert of Kuwait

 A well-developed drainage network is carved in the hard calcretized and gypcretized gravelly sand of the Pleistocene Dibdibba Formation in northern Kuwait. The present-day aridity suggests that these drainages were developed during pluvial episodes that took place in the post-Pleistocene time and, therefore, are considered as paleo-drainage. Detailed morphometrical analysis of the endoeric drainage systems was performed and the degree of correlation among their different morphometric parameters was investigated. Based on these parameters, the studied drainage basins are statistically grouped into three groups. Such grouping was confirmed by discriminant analysis. The categorical data analysis demonstrated the dependence of these groupings on the surface geology, regional topography, and local geomorphological settings. Infiltration measurements revealed that the drainage bedrocks have a low infiltration rate (<20 cm h^–1), whereas the drainage fill deposits have a relatively high infiltration rate (67–30 cm h^–1). The impact of the drainage system pattern and morphometry on the hydrological conditions is discussed and potential near-surface low salinity to freshwater aquifers is delineated. The role of the studied drainage systems in the occurrence of mobile sand and sand dunes, rainwater harvesting, and land capability are discussed. Received: 8 September 1995 · Accepted: 24 October 1995     

Sedimentological characteristics of the surficial sediments of the Kuwaiti marine environment, northern Arabian Gulf

The textural characteristics, carbonate content and the coarse fraction components of the Recent bottom sediments of the marine environment off Kuwait are described and the faunal-sediment associations discussed. The sediments were subdivided into seven textural classes, namely sand, silty sand, muddy sand, sandy silt, sandy mud, silt and mud. Most of the study area is covered with muddy sediments whereas sandy deposits are restricted to the rocky bottoms near the southern flat of Kuwait Bay, the southern coast of Kuwait and around the islands and bathymetric highs. The textural classes, carbonate contents and faunal types of the coarse fraction were used to construct a biolithofacies map of the marine bottom sediments off Kuwait, in which nine facies are identified. The sedimentological characteristics of the Recent marine bottom sediments off Kuwait reflect the interaction between autochthonous calcareous fragments mostly of biogenic origin, lime rock fragments derived from beachrocks and submerged reef flats, and allochthonous terrigenous detritus transported to the area mainly by dust storms. The Kuwaiti offshore area is generally a low energy depositional environment with little sediment transport.     

鄂东南地区赋存于沉积岩中金矿床的勘查进展和研究现状

赋存于沉积岩中的金矿床包括了绝大部分卡林型、少数造山型和部分斑岩成矿系统外围浸染型金矿床.鄂东南地区是长江中下游七个重要矿集区之一,发育一系列与岩浆岩有关的矽卡岩型、斑岩型矿床,以往的勘探和研究也主要围绕着岩体及接触带附近的斑岩、矽卡岩型矿床展开.对于岩浆岩外围赋存于沉积岩中的金矿床虽然也有发现,但并未引起足够重视.近...     

Diatom biostratigraphy of tsunami deposits: Examples from the 1998 Papua New Guinea tsunami

Distinctive diatom assemblages may be associated with tsunami sediments and may often contrast with the assemblages found within sediments underlying the tsunami deposit as well as those associated with the modern coastal environment. Sediments associated with the 1998 tsunami that destroyed much of the Sissano lagoon area in northern Papua New Guinea have been investigated. Surface sediments from three transects across the sediment spit near Warapu have been examined for diatom content and preservation. The preservation is variable, and the data show an, often chaotic, assemblage that can be attributed to the tsunami waves incorporating and depositing diatoms from distinctive habitat zones during their runup and subsequent backwash. The diatoms identified within the Warapu sediments indicate an origin from within the inter-tidal and offshore area rather than from the beach–sand spit complex. The sand deposits disclose a high percentage, in excess of 75%, of broken diatom valves, and a predominance of centric (circular) species due to preferential preservation. The study demonstrates that the application of diatom biostratigraphy to modern tsunami deposits can be used in conjunction with other stratigraphical lines of evidence to interpret the source and provenance of historical and palaeo-tsunami deposits.     

Stokes surfaces and the effects of near-surface groundwater-table on Aeolian deposition

ABSTRACT Stokes surfaces in aeolian deposits are caused by wind scour of unconsolidated material to a roughly planar horizon controlled by near-surface water-tables (Stokes, 1968). A water-table forms a downward limit of scour through the cohesion of damp or wet sand near water-table, and through early cementation by evaporites precipitated in the sediments as water evaporates near the sand-air interface. Study of modern analogues reveals that Stokes surfaces exist in a variety of depositional settings, including a coastal offshore prograding sand sea (Jafurah, Saudi Arabia); a coastal onshore prograding sand sea (Guerrero Negro, Mexico) and a continental sand sea (White Sands, New Mexico, USA). These modern analogues indicate that our concept of Stokes surfaces must be broadened to include the following: (i) modern analogues for Stokes surfaces described here cover areas on the order of 25 km². These may be as representative of similar surfaces in ancient rocks as hypothesized plains of deflation requiring removal of entire sand seas; (ii) Stokes surfaces occupy a continuum in scale from local to extensive, and erosional surfaces of different magnitude may be stacked closely in the sediments; (iii) Stokes surfaces, although erosional in nature, are commonly associated with deposits both above and below the Stokes bounding surface which plainly reveal the influence of a near-surface groundwater control on wind sedimentation. Moreover, the erosional relief of the bounding surface itself (as well as other features) reveals the influence of a groundwater-table; (iv) Stokes surfaces may be diachronous, representing the lateral shift of a zone of scour within a sand sea rather than simultaneous removal of all dunes from the area encompassed by the erosional surface; (v) Stokes surfaces and associated deposits are often laterally transitional to surfaces and deposits of adjacent depositional environments, including interdunes, tidal flats, lagoons, beaches, lakes and non-aeolian sabkhas. Finally, modern examples from different depositional settings suggest that while most Stokes surfaces have many features in common (such as erosional ridges due to early cementation), there are some features which may, with further study, be revealed to be distinctive of an individual depositional setting.     

Sodium - a geochemical indicator of emerald mineralization in the Cordillera Oriental, Colombia

Emerald-bearing deposits in the Cordillera Oriental are structurally controlled, localized at the intersection of two fault systems. At these intersections zones of intense fracturing affected by sodium and carbonate metasomatism host the emerald mineralization. Albitization, carbonatization and hydrothermal leaching of potassium and trace metals are characteristics of the metasomatically altered Cretaceous black shales which compose the emerald-bearing tectonic zones.Stream sediments collected in areas which have metasomatically altered shales in the drainage basin have a low K/Na ratio. It is possible to use this ratio, or the sodium content of the sediments, to locate areas worthy of further exploration.     

Occurrence of jarosite within Quaternary coastal sabkha sediments in Kuwait,Arabian Gulf

X-ray diffractometer analysis and SEM investigation confirmed the occurrence of jarosite and alunogen minerals in the Quaternary siliciclastic sabkha sediments of northern Kuwait within the Bahrah oilfield area, Arabian Gulf. Jarosite is relatively abundant in a near-surface whitish sticky tidal muddy sand layer about 60 cm thick that overlies the ferruginous sandstone of the Oligo-Miocene Ghar Formation. Jarosite occurs as clusters of euhedral pseudo-cubes of about 1 μm in size and as agglomerated nanoglobules of 250 nm in size. A hypogenetic origin related to the reaction of sulfuric acid produced by the oxidation of H₂S associated with hydrocarbon gas seepages with K and Fe leachates is suggested. The restricted occurrence of jarosite within near-surface sabkha sediments may be attributed to limited tidal inundation and prevalence of arid climatic conditions.     

Near-surface lithogeochemical halo as an aid to discovery of deeply buried unconformity-type uranium deposits, Athabasca Basin, Canada

Unconformity-type U deposits are being found to depths of more than 400 m where graphitic rocks underlie the Proterozoic sandstone unconformity. Exploration to date involves drilling weak electromagnetic conductors that reflect the graphitic basement. The deposits are believed to have formed through circulation of heated formation waters which discharged essentially vertically above the deposits. Geochemically detectable zones of alteration are reported for cross-sections through the Deilmann, Midwest, and McClean deposits. Information on the areal dimensions of near-surface haloes was required to justify the drilling of grids of shallow holes along conductors or favourable structures as a cost-effective exploration alternative to deep holes, and to define grid spacings.Orientation surveys were undertaken by sampling the uppermost 10 m of sandstone in a selection of holes from the Cigar Lake, Dawn Lake, and Wolf Lake areas where the deposits are, respectively, 400–430 m, 100–160 m, and 180–210 m below surface. The first two deposits have published reserves of 385 and 30–40 million pounds U₃O₈, respectively, while Wolf Lake is much smaller.Well-developed anomalies lie vertically above the richest portion of the Cigar Lake deposit in an area 150 × 600 m and a weak anomaly in many elements continues over the 1800-m length that was sampled. Total and leachable U are 13 to 8 times background with maximum values of 53 and 26 ppm, respectively. Anomalies of 14 to 8 times background are also present for V, Na₂O and Zn, and 5 to 3 times background for Sr, Y, Pb, Th, As, and P.Of the four Dawn Lake mineralized zones, only the 11B Zone was studied, with partial coverage of the 11A Zone. Anomalies 50–100 m by 250–600 m in size are often displaced up to 100 m northeast of the 11B Zone. B, MgO, Pb and both total and leachable U anomalies are 16 to 8 times background with Y, V and As 7 to 5 times background.By contrast, at the Wolf Lake deposit, only irregular variations occur for most of these elements. The unusual patterns may reflect post-alteration tectonism of the sandstone overlying the deposit as regional thrust faulting occurs nearby.Detection of near-surface lithogeochemical haloes using grids of shallow holes would facilitate discovery of deep deposits and reduce expensive, deep drilling.     

Textural characteristics and genesis of the aeolian sediments in the Kuwaiti desert

Several types of aeolian deposits have been recognized in Kuwait: (a) smooth sand sheets that resemble desert floor sand, (b) immobile sands that include rugged vegetated sand sheets and wadi fill deposits, and (c) mobile sands that form active sand sheets and sand dunes. Simple size frequency curves illustrate the genetic relationship between the various aeolian sediment types. The four size parameters, namely, mean size, sorting, skewness and kurtosis, were calculated. Scatter plot diagrams of sorting versus mean size and sorting versus kurtosis are effective in differentiating smooth sand sheet deposits from dune sands. Active sand sheet deposits can also be recognized because they are usually located between the two end members–smooth sand sheets and dune sands. Size parameters change with location regardless of their types. Coarsening and positive skewness usually increase downwind. Mineralogical and textural characteristics of the aeolian deposits in Kuwait revealed that they are mostly derived from the lower Mesopotamian muddy flood plain deposits, the sand fraction of the Al-Dibdibba gravelly deposits and the disintegrated material from calcretic and gypcretic duricrusts. Distribution of depositional and deflational areas indicates that the northern desert of Kuwait is characterized by a positive sand budget, whereas the southern desert has a negative sand budget.     

Exfiltrative Mineralization in the Bukantau Ore District (Central Kyzyl Kum Region,Uzbekistan)

Manganese and gemstone (turquoise and cacholong) deposits of the central Kyzyl Kum region formed during the development of the sedimentary cover. Aggressive metal-bearing fluids were formed within the cover due to equilibration of sediments. Tectonic reactivation of the region resulted in the formation of erosion windows in the sedimentary cover and ascending gleyey (H₂S-free) solutions were discharged within the erosion windows. Various geochemical barriers in near-surface zones favored the concentration of Mn, gem-stone-forming elements, and associated components. Their virtually simultaneous deposition from the same ore-forming fluids at different geochemical barriers was responsible for the differentiation of mineralization in the cross section. Processes of recent activation migrated from the southeast to northwest with the successive formation and erosion of ephemeral manganese and gemstone deposits in the same direction. At present, only the youngest deposits located in the northern central Kyzyl Kum region are sufficiently well retained.     

东昆仑东段新生代高原隆升重大事件的沉积响应

根据新生代沉积盆地的地层序列、环境演变及地貌和水系变迁分析将研究区新生代高原隆升过程划分为5个重大事件.首次在研究区内海拔5400m的主夷平面上发现古土壤、岩溶角砾岩及钟乳石等, 认为沱沱河组上段细碎屑沉积及五道梁组石膏沉积(中新世) 是主夷平面形成期的沉积响应, 提出了主夷平面的高程具有东西向排列的盆岭地貌特点, 这种高程差异反映了后期构造隆升的不均衡, 应该是上新世以来差异断块抬升的结果; 早更新世中期(1525.5ka后) 一套河流砂砾卵石沉积是青藏运动C幕的沉积响应, 体现在布尔汗布达山的强烈上升和成山; 早更新世晚期(1113.9~836.3ka) 先湖滨砾石沉积, 后转为河流砂砾卵石沉积, 是昆黄运动在研究区的沉积响应, 并体现在马尔争-布青山的强烈上升和成山, 中更新世早期冰碛物的发育说明昆黄运动后研究区已隆升达到"水汽冻结高度"; 研究区T5阶地沉积前的强烈下蚀, 柴达木盆地内陆水系溯源侵蚀切过布尔汗布达山主分水岭, 袭夺了昆南断裂带原由西向东流向共和古湖的东西向水系并到达阿拉克湖一带, 晚更新世洪冲积角度不整合于中更新世洪冲积之上等是共和运动的具体表现.      

Identification and characterization of tsunami deposits off southeast coast of India from the 2004 Indian Ocean tsunami: Rock magnetic and geochemical approach

The December 2004 Indian Ocean Tsunami (IOT) had a major impact on the geomorphology and sedimentology of the east coast of India. Estimation of the magnitude of the tsunami from its deposits is a challenging topic to be developed in studies on tsunami hazard assessment. Two core sediments (C1 and C2) from Nagapattinam, southeast coast of India were subjected to textural, mineral, geochemical and rock-magnetic measurements. In both cores, three zones (zone I, II and III) have been distinguished based on mineralogical, geochemical and magnetic data. Zone II is featured by peculiar rock-magnetic, textural, mineralogical and geochemical signatures in both sediment cores that we interpret to correspond to the 2004 IOT deposit. Textural, mineralogical, geochemical and rock-magnetic investigations showed that the tsunami deposit is featured by relative enrichment in sand, quartz, feldspar, carbonate, SiO ₂, TiO ₂, K ₂O and CaO and by a depletion in clay and iron oxides. These results point to a dilution of reworked ferromagnetic particles into a huge volume of paramagnetic materials, similar to what has been described in other nearshore tsunami deposits (Font et al. 2010). Correlation analysis elucidated the relationships among the textural, mineral, geochemical and magnetic parameters, and suggests that most of the quartz-rich coarse sediments have been transported offshore by the tsunami wave. These results agreed well with the previously published numerical model of tsunami induced sediment transport off southeast coast of India and can be used for future comparative studies on tsunami deposits.     

Tectonics and sedimentation in the Curitiba Basin, south of Brazil

The Curitiba Basin, Paraná, lies parallel to the west side of the Serra do Mar range and is part of a continental rift near the Atlantic coast of southeastern Brazil. It bears unconsolidated and poorly consolidated sediments divided in two formations: the lower Guabirotuba Formation and the overlying Tinguis Formation, both developed over Precambrian basement. Field observations, water well drill cores, and interpretations of satellite images lead to the inference that regional tectonic processes were responsible for the origin of the Basin in the continental rift context and for morphotecatonic evolution through block tilting, dissection, and erosion. The structural framework of the sediments and the basement is characterized by NE–SW-trending normal faults (extensional tectonic D₁ event) reactivated by NE–SW-trending strike–slip and reverse oblique faults (younger transtensional tectonic D_2′ to transpressional tectonic D_2″ event). This tectonic event, which started in the Paleogene and controlled the basin geometry, began as a halfgraben and was later reactivated as a pull-apart basin. D₂ is a neotectonic event that controls the current morphostructures. The Basin is connected to the structural rearrangement of the South American platform, which underwent a generalized extensional or trantensional process and, in late Oligocene, changed to a compressional to transpressional regime.     

Physical properties of aeolian sediments within major dune corridor in Kuwait

A total of 212 sand samples were collected from aeolian surface sediments in a major dune corridor, northwestern Kuwait. Five main physical properties were taken into consideration in analyzing aeolian samples, namely color, shape, roundness, particle morphometry, and surface area. The analysis of quartz particles by the scanning electron microscope shows the influence of transportation on the microfeatures of individual particles. The surface deposits are dominantly unimodal and occasionally bimodal. It is obvious that coarse and medium sand are the dominant size fractions within aeolian deposits. The results according to the Munsell color system between downwind and upwind values show no variations. Also, the average percentages of roundness subclasses for upwind and downwind samples are similar (6.7%). The average values (area, equivalent diameter, perimeter, and elongation) for aeolian samples in downwind are slightly higher than in upwind and Al-Dibdibba Formation samples, but the values overlap at 1 standard deviation. The interrelationship diagrams show that the shapes of the particles within samples in the three groups are running in the same trend. In general, the northwestern (upwind) particles show more mechanical and chemical features compared with southeastern particles (downwind). The slight variation between aeolian (upwind and downwind) samples is attributed to the transportation effect of these particles. This led to a conclusion, based on the overall results of physical properties, that the coarse and medium particles (about 80% of the whole aeolian sample) are dominantly derived from local sources.     

Environmental study of valley fill sediments

The study of Pleistocene and Holocene fluviatile deposits in river valleys is important for environmental protection. Well records allow the mapping of clay, sand, and gravel beds under recent valley floors. Such surveys can also locate active tectonic zones. This technique helps in assessing potential seismic hazards for large industrial sites.The study of fluviatile sediments under recent valley floors is relevant to environmental studies for another reason as well. The permeability characteristics of these formations have a decisive bearing on the spreading of various pollutants entering the rivers or the groundwater along the rivers. Thus, the knowledge of subsurface formations is essential for the siting of factories with dangerous products and deposits of hazardous waste.Fluviatile sediments along the Hungarian stretch of the Danube Valley have been explored by thousands of shallow boreholes. These allowed the geotectonical and hydrogeological study of sites for completed and planned dams and nuclear power stations and assessing potential environmental hazards.     

Geomorphic changes in Ras Al-Subiyah area,Kuwait

The Ras Al-Subiyah area is considered one of the most promising areas in Kuwait for future development. This development will include a new town called Subiyah and its associated infrastructure. This area is also being considered as the location for connection between Boubyan Island, which is now undergoing major development and the Kuwait mainland. The present study investigates the geomorphology of the Ras Al-Sabiyah area in the northern sector of Kuwait. The study area is generally flat, and it is located west of the Jal Az-Zor escarpment. It is bordered on the east by the Khor Al-Sabiyah tidal channel and on the south by Kuwait Bay. The area receives sediments from several sources; currently the most important are aeolian sediments and the deposition of mud delivered through the Khor Al-Sabiyah from the Iraqi marshes. The study area has been subjected to severe environmental changes due to the Gulf wars and the drainage of Iraqi marshes and the associated artificial changes in fluvial system. Twenty-two surface sediments were collected from the Ras Al-Subiyah area. Samples were collected to include the main geomorphologic characteristic features of the study area. Field observations and remote sensing images from 1990 and 2001 were used to produce an updated geomorphologic map for the Ras Al-Subiyah and a map showing geomorphic changes between 1990 and 2001. Grain size of the surface sediment ranges from gravel to medium sand. In general, grain size statistical analysis indicates that most of the areas are composed of two or more classes of sands transported and deposited from different sources including aeolian, sabkhas, river and the bays. The variability in the grain size statistical parameters may be attributed to the complexity of surface morphology as well as the diversity in the type of depositional environment in the Ras Al-Subiyah area. The total area subjected to change during the 12-year period (1990–2001) is about 32 km² as calculated using GIS techniques.     

Near surface lithology and spatial variation of arsenic in the shallow groundwater: southeastern Bangladesh

This study investigated the relationship between near-surface lithology and the spatial variability of As concentrations using sediment grain-size analysis and electromagnetic induction survey in the southeast Bangladesh. It has been observed that the aquifers overlain by finer sediments have higher concentrations of As in groundwater, whereas As concentrations are remarkably low in aquifers having permeable sandy materials or thinner silt/clay layer at the surface. The near-surface lithology acts as a controlling factor for spatial distributions of groundwater As within the very shallow depths (<15 m). Shallow alluvial aquifers can provide low-As drinking water in many areas of the country when tube wells are properly installed after investigation of the overlying near-surface sediment attributes and hydraulic properties.     

New Recognized Intellect for Prospecting Large‐superlarge Mineral Deposits

Based on the data base of 1285 mineral deposits of 22 commodities in 121 countries of 6 continents of the world, the authors use the linear trend analysis for their reserves to determine the cut-off limited order of reserves to select 36 exceptional superlarge (as peak mineral), 95 superlarge and 314 large deposits as new recognized intellect for their quantitative change. We have projected above 445 large-superlarge deposits on (1:5 M) global tectonic background map and divided 4 metallogenic domains, 21 metallogenic belts. Global metallogeny of large-superlarge deposits are: unity by endogenic, exogenic metamorphic and epigenetic in origin; speciality in different metallogenic domains and belts; preferentiality to ore-forming elements of Cu, Au, Fe, Ag, Cr, Mn, Zn, Pb, Sb, Hg, to continental margins or plate convergent belts, to Intra-continental tectono-magmatic complex belts and Large ductile shear zones; abnormality by the global oxyatmversion (excess oxygen atmospheric event) in Archean, redoxyatmversion (lack oxygen atmospheric event) in Proterozoic-Paleozoic, and tectonosphere thermal erosion (great amount of tectonic magmatic event) in Mesozoic-Cenozoic.     

东营凹陷沙河街组三段层序低位域砂体沉积特征

本文基于构造层序分析和基准面分析原理，利用测井曲线，岩相等资料，重点研究了东营凹陷沙三段3个层序的低位域砂体沉积特征，发育规律及其石油地质意义。应用构造坡折带的概念在该凹陷划分出了4种构造坡折带样式。研究表明：该凹陷沙三段层序低位域砂体发育下切水道充填，低位楔和低位扇。构造坡折带的发育特征和样式控制了低位域砂体的时空展布特征。构造坡折带控制下的低位域砂体发育在层序底部，构造坡折带附近，成藏条件优良，是隐蔽油气藏勘探的主要方向。     

大型-超大型矿床找矿新认知

笔者等根据全球6大洲、121个国家(地区)、22个矿种、1285个矿床的储量数据,进行了储量量变线性回归方程趋势分析.根据回归方程不同系数切割的量变界线,划分出了36个特(超)大型矿床(顶峰矿)、95个超大型矿床和314个大型矿床.据此,笔者等创新地提出了按不同储量量级划分大型-超大型矿床的新认知,继而将3类不同量级的445个大型-超大型矿床投影在1∶2500万全球构造背景图上,并划分出4大成矿域、21个巨型成矿带(区).其全球成矿规律是:内生、外生、变质和后成矿床的全球成矿统一性;不同成矿区带成矿的专属性;`Cu、Au、Fe、Ag、Cr、Mn、Zn、Pb、Sb、Hg不同成矿金属,大陆边缘和板块汇聚带以及陆内构造-岩浆杂岩带和大型剪切带的成矿偏在性;特(超)大型矿床太古代-古元古代全球氧大气变态(过氧事件)、元古代-古生代全球还原大气变态(缺氧事件)和中-新生代构造圈热侵蚀(巨量构造-岩浆事件)的成矿异常性.