Holocene marine terraces on two salt diapirs in the Persian Gulf,Iran: age,depositional history and uplift rates

Slightly inclined Holocene marine terraces cover parts of two circular salt diapirs (Hormoz and Namakdan) in the Persian Gulf. Their relative altitude above present sea level results from a combination of general marine transgression/regression affecting the whole area, and of local uplift related to salt diapirism. Differential uplift rate of the studied diapirs in centre‐to‐rim profiles was calculated from results based on: (i) radiocarbon ages of skeletal remains of benthic faunas (19 samples), which originally grew close to sea level; (ii) original altitude of samples, estimated from general sea‐level oscillation curves for the last 10 kyr, and (iii) present sample altitude measured in the field. Calculated uplift rates increase from rim to centre on both diapirs in the range from: 2 mm yr^?1 at the rim to 5–6 mm yr^?1 at the interior of Hormoz, and 1–3 mm yr^?1 at the rim to 3–5 mm yr^?1 at the interior of Namakdan. Such uplift rate distributions fit into the parabolic profile of Newtonian fluid rather than to profiles typical for pseudoplastic fluids. The increase in uplift rate with distance from rim to centre of diapirs is gradual as demonstrated also by generally smooth surface of marine terraces. No tectonic dissections were found. The depositional history on both salt diapirs is similar although they are situated more than 100 km apart. Marine sedimentation started at about 9.6k cal. yr BP on Hormoz and at 8.6k cal. yr BP on Namakdan. Owing to rapid transgression, the sea partially truncated both salt diapirs and rapidly deepened, and carbonate mud was deposited on the peripheries of both salt diapirs. Between 7 and 5k cal. yr BP beach deposition replaced carbonate mud. Soon after 5k cal. yr BP, the sea retreated from most of the marine terraces on both salt diapirs. Copyright © 2006 John Wiley & Sons, Ltd.     

Evaporate deposits and salt diapirs of the Urvantsev trough on the North Kara Sea

The Evaporate Urvantsev Trough was recognized on the basis of new geophysical seismic data. The trough is filled with Lower Paleozoic deposits, with a regional unconformity located at the Devonian-Carboniferous boundary. Salt diapirs of various shapes are a typical peculiarity of the trough. By analogous wtih the sections of Severnaya Zemlya and the Timan-Pechora basin, the age of the salts is defined as Early Ordovician.     

Mixing of carbonate waters

When mineral solutions of different compositions are mixed, the molalities and activities of individual ions in the mixture are often non-linear functions of their end-member values. This non-linearity is particularly significant in determining mineral saturation levels. Mixtures of saturated solutions may be either undersaturated or supersaturated depending on the end-member compositions and the physical conditions in which end-members and their mixtures exist. In carbonate solutions important non-linear effects occur due to redistribution of carbonate species. In extreme cases this causes mixture pH to be below both the end-member pH values. A simple but precise computer program (WATMIX) has been developed for calculating mixture composition for closed and open system mixing of arbitrary end-members. A number of mixing examples are considered which allow one to isolate three important processes leading to non-linear behaviour: the algebraic effect, the δP_CO2 effect, and the ionic strength effect.     

Geological and geophysical study of salt diapirs for hazardous waste disposal

Solving the problem of waste is one of the central tasks of environmental protection. It is becoming increasingly difficult to find suitable sites that are acceptable to the public. Salt and salt formations have relevant properties to be utilizing as a repository for each kind of waste. The favourable properties of salt make rock salt highly suitable as a host rock, in particular for non-radioactive and radioactive wastes. Tehran and suburb as an industrial state require a waste reservoir. The Great Kavir (the largest salt desert in Iran) with more than 50 diapirs has surrounded the eastern and southern part of Tehran Province. The Qom and Garmsar basins are the nearest salt diapirs to Tehran province, and there are suitable repository for waste disposal. Great Kavir diapirs have been investigated as a case study based on surface and subsurface studies for its suitability to host a repository for various types of waste. The procedure should be based on field work for surface investigation and also include geophysical studies for subsurface investigations. This research work is presented in regard to site selection in the Central Iran Salt Basins for deposition of only certain types of waste. Results of this study will indicate if the Central Iran Salt Basins are appropriate place to deposit industrial wastes in the deep bedded salt.     

Human impact on the karst of the Venetian Fore-Alps, Italy

People have been exploiting the limestone massifs of the Venetian Fore-Alps since prehistory. The fluviokarstic style of the relief and the location of springs were important controls of settlement and land use. Six principal types of exploitation are recognized and overlapped in time: (1) hunting and early farming, Paleolithic to Iron Age, with the first soil erosion; (2) general deforestation for timber, charcoal, and fuel, Roman to early modern; (3) farm enclosure and improvement, with stone clearing, medieval to modern; (4) trench warfare in World War I; (5) quarrying and specialized farming (dairy, poultry, pigs) since 1950; and (6) developmnent of modern summer and winter tourist facilities. Soil erosion effects from many centuries can still be recognized, war damage remains visible and continues to pollute aquifers, and modern pressure on the karst land and water resources is often severe.     

Multiple fluid components of salt diapirs and salt dome cap rocks, Gulf Coast, U.S.A.

Salt diapirs contain a few percent of anhydrite that accumulated as residue to form anhydrite cap rocks during salt dissolutions. Reported ⁸⁷Sr/⁸⁶Sr ratios of these salt-hosted and cap rock anhydrites in the Gulf Coast, U.S.A., indicate their derivation from Middle Jurassic seawater. However, a much wider range of ⁸⁷Sr/⁸⁶Sr ratios, incorporating a highly radiogenic component in addition to the Middle Jurassic component, has been found in several Gulf Coast salt domes. This wide range of ⁸⁷Sr/⁸⁶Sr ratios of anhydrite within the salt stocks records Sr contributions from both marine water and formation water that has equilibrated with siliciclastics. During cap rock formation this anhydrite either recrystallized in the presence of, or was cemented by, a low-Sr fluid with a Late Cretaceous seawter-type Sr isotope ratio or simply lost Sr during recrystallization. Later, the cap rock was invaded by warm saline brines with high Sr isotope ratios from which barite and metal sulfides were precipitated. Subsequently, low-salinity water hydrated part of the anhydrite bringing to six the total number of fluids that interacted througout the history of salt dome and cap rock growth. The progenitor of these salt diapirs, the Louann Formation, is generally thought to have formed from marine water evaporated to halite and, rarely, higher evaporite facies. Salt domes in the East Texas, North Louisiana, and Mississippi Salt Basins have ⁸⁷Sr/⁸⁶Sr and δ³⁴S values that corroborate a Mid-Jurassic age for the mother salt. However, salt domes in the Houston and Rio Grande Embayments of the Gulf Coast Basin have ⁸⁷Sr/⁸⁶Sr ration ranging to values higher than both Middle Jurassic seawater and all Rb-free marine Phanerozoic rocks. These anomalous ⁸⁷Sr/⁸⁶Sr ratios are probably derived from radiogenic Sr-bearing fluids that equilibrated with siliciclastic rocks and invaded the salt either prior to, or during, diapirism. Potential sources of the radiogenic ⁸⁷Sr component include clay and/or feldspar (located either in older units beneath the Louann Formation or younger units flanking the salt diapirs) and K-salts within the Louann evaporites. Because partial Sr exchange in anhydrite had to take place in a fluid medium, admittance of radiogenic ⁸⁷Sr-bearing fluids into the salt may have led to diapirism by lowering the shear strength of the crystalline salt. The slight number of anomalous ⁸⁷Sr/⁸⁶Sr values in the interior basins indicates that anomalous values are related to areally discrete structural or stratigraphic controls that affected only the Gulf Coast Basin.     

Analysis of karst spring recession curves,west of Iran

The recession hydrographs of karst springs provide important information about aquifer characteristics such as storage properties and drainage potential, karstification degree, and other hydrological features. The Faresban, Famaasb, Gonbad-e-Kabood, and Gian springs are the important karst springs which drain main karst aquifers in west of Iran. In this study, we evaluate hydrological characteristics of these four karst springs using different analytic equations. Almost, all the recession curves were well fitted by a function that consists of three main exponential terms. The initial portion of the recession curve represents the fast drainage of large fractures and conduits, ending with the slowly decreasing curve, where the drainage of rock matrix and small fissures or baseflow is dominant. The Gian spring has the largest storage volume but the lowest drained water (7%). Using Mangin’s equation, it is apparent that the baseflow supplies over 85% of the total drained water to the Gian spring, while a small quantity of total outflow is made up of quickflow periods. Of the water available to the Famaasb, Faresban, and Gonbad-e-Kabood springs, 85, 80, and 70% are drained during period of baseflow, respectively, whereas the quickflow periods have minor importance in some springs. Based on the Coutagne’s equation results, it can be concluded that the catchment of the Famaasb and Gonbad-e-Kabood springs have a karstified saturation zone with drainage channels that provide a rapid discharge with little storage capacity. At Gian catchment area, the initial discharge is not as rapid as karstification but is fairly homogeneous throughout the aquifer.     

塔中气田奥陶系碳酸盐岩岩溶储层预测研究

提要：塔里木盆地塔中地区奥陶系碳酸盐岩岩溶储层具有埋藏深、地震资料分辨率及信噪比不高、非均质性强等特点。为此,利用古地貌、古水流和古断裂等地质主控因素方法与多地震属性信息融合技术相结合的解决思路,对研究区奥陶系鹰山组碳酸盐岩岩溶缝洞型储层进行了分析和预测,刻画了不同类型岩溶储层的分布规律。该方法既降低地震信息的多解性、提高了储层预测的精度,又符合地质规律,研究成果为研究区的勘探生产奠定了坚实的基础。     

Hydrochemical indications of human impact on karst groundwater in a subtropical karst area,Chongqing, China

The application of combined isotopic and hydrochemical compositions may be useful for evaluating water quality problems in karst aquifers in which it is difficult to distinguish the sources of solutes from the natural background of those due to human activities. Multiple isotopes (δ¹³C–DIC, δ³⁴S–SO₄ ^2?) and chemical parameters were measured in rainwater, groundwater and sewage in order to elucidate the solute sources and impacts from human activities and natural background in the Laolongdong karst catchment in Chongqing Municipality, SW China. Overall, the dissolution of carbonate rock controls Ca²⁺, Mg²⁺ and HCO₃ ^? content in rainwater and karst groundwater. SO₄ ^2? originated mainly from gypsum dissolution in karst groundwater. Carbonate rocks in the studied site could be dissolved jointly by H₂CO₃ from the natural CO₂–H₂O reaction and other acids (organic acids and HNO₃) from sewage and soils. Sewage discharge from urban areas and agriculture activities lead to the increase of NO₃ ^?, PO₄ ^3? and Cl^? in karst groundwater. To protect and sustainably utilize the karst aquifer, sewage originating from urban areas must be controlled and treated and the use of fertilizer should be limited.     

Hypogene Zn carbonate ores in the Angouran deposit,NW Iran

The world-class Angouran nonsulfide Zn–Pb deposit is one of the major Zn producers in Iran, with resources estimated at about 18 Mt at 28% Zn, mainly in the form of the Zn carbonate smithsonite. This study aims to characterize these carbonate ores by means of their mineralogy and geochemistry, which has also been extended to the host rocks of mineralization and other local carbonate rock types, including the prominent travertines in the Angouran district, as well as to the local spring waters. Petrographical, chemical, and stable isotope (O, H, C, Sr) data indicate that the genesis of the Zn carbonate ores at Angouran is fairly distinct from that of other “classical” nonsulfide Zn deposits that formed entirely by supergene processes. Mineralization occurred during two successive stages, with the zinc being derived from a preexisting sulfide ore body. A first, main stage of Zn carbonates (stage I carbonate ore) is associated with both preexisting and subordinate newly formed sulfides, whereas a second stage is characterized by supergene carbonates (Zn and minor Pb) coexisting with oxides and hydroxides (stage II carbonate ore). The coprecipitation of smithsonite with galena, pyrite and arsenopyrite, as well as the absence of Fe- and Mn-oxides/hydroxides and of any discernible oxidation or dissolution of the sphalerite-rich primary sulfide ore, shows that the fluids responsible for the main, stage I carbonate ores were relatively reduced and close to neutral to slightly basic pH with high fCO₂. Smithsonite δ¹⁸O_VSMOW values from stage I carbonate ore range from 18.3 to 23.6‰, while those of stage II carbonate ore show a much smaller range between 24.3 and 24.9‰. The δ¹³C values are fairly constant in smithsonite of stage I carbonate ore (3.2–6.0‰) but show a considerable spread towards lower δ¹³C_VPDB values (4.6 to −11.2‰) in stage II carbonate ore. This suggests a hypogene formation of stage I carbonate ore at Angouran from low-temperature hydrothermal fluids, probably mobilized during the waning stages of Tertiary–Quaternary volcanic activity in an environment characterized by abundant travertine systems throughout the whole region. Conversely, stage II carbonate ore is unambiguously related to supergene weathering, as evidenced by the absence of sulfides, the presence of Fe-Mn-oxides and arsenates, and by high δ¹⁸O values found in smithsonite II. The variable, but still relatively heavy carbon isotope values of supergene smithsonite II, suggests only a very minor contribution by organic soil carbon, as is generally the case in supergene nonsulfide deposits.     

Effects of road-deicing salt (NaCl) and saline water on water quality in the Urmia area,northwest of Iran

Increased application of road salt for winter maintenance has resulted in increased concentration of deicer constituents in the environment. The runoffs from the deicing operation have a deteriorating effect on water quality. The existence of salt super saturated Urmia lake and easy access to it, causes Urmia municipality to over use the super saturated water of this lake and salt (NaCl) during winter for snow melting, freezing prevention and traffic load facilitation. The aim of this study was investigation of surface and groundwater contaminations in consequence of salt (NaCl) and saline water usage in Urmia city and its surroundings. Studying the chloride ion concentration as a tracer in runoff result snowmelts during winter shows that its amount is differential with respect to time and place sampling. Results indicate that runoff result of snowmelts effected groundwater, soil and plant growth. The contamination of groundwater in study area by road salt and saline water is a slow process and directly related to the amount of road salt and saline water applied.     

Saline waters and residual brines in the Shiraz-Sarvistan basin,Iran

Origin of saline waters in the Shiraz-Sarvistan area, Iran, is determined by a combined isotopic (¹⁸O and D) and chemical characterization. Four types are recognized: (a) fresh water of the anticlinal carbonatic aquifer; (b) fresh and brackish runoff in the synclinal basins; (c) salt springs originating through dissolution of rock salt by type (a) fresh water; and (d) residual brines formed in synclinal closed drainage basins, through evaporation of former water types and loss of the relatively less-soluble salts.     

T27界面与塔中隆起上奥陶统碳酸盐岩古岩溶储层

T72界面为上奥陶统桑塔木组泥岩与良里塔格组灰岩地震反射界面,是塔里木盆地塔中、塔北隆起上奥陶统内部的一个重要构造-层序转换面,是早古生代碳酸盐台地型沉积向陆源碎屑充填沉积转换的标志.过去普遍认为两个组之间为连续沉积,界面性质系海侵上超并赋予"淹没台地"的涵义.但随着近年塔河油田南部地区的勘探和塔中隆起区北缘Ⅰ号断裂带油气富集规律性的深入研究,表明T72界面是一个区域性的古暴露界面和沉积间断界面.界面之下的上奥陶统良里塔格组顶面有明显的削蚀和截切现象,残存厚度在塔北、塔中之间存在极大的差异,反映塔北隆起T72界面的构造及风化壳岩溶作用明显强过塔中隆起.古暴露和风化壳岩溶作用导致T72界面之下的良里塔格组碳酸盐岩广泛发育岩溶,是塔中低凸起北缘Ⅰ号断裂构造带的主要油气藏聚集层位;在塔河南部,形成了一套厚度最大可达300m并贯穿良里塔格组与下伏恰尔巴克组、一间房组和鹰山组的古岩溶洞穴系统,造就了塔河油田今天以南部斜坡区上奥陶统良里塔格组灰岩古岩溶洞穴系统为主要油气储层的勘探大场面.     

塔里木盆地奥陶系碳酸盐岩岩溶分类、期次及勘探思路

奥陶系海相碳酸盐岩已成为塔里木盆地最重要的勘探开发层系,岩溶作用则是形成优质碳酸盐岩储集层的关键因素之一。针对塔里木盆地碳酸盐岩岩溶分类方案不统一、岩溶术语界定不清楚、生产应用难度大的现状,作者分析了奥陶系不同地区、不同层位、不同时期岩溶储集层特征及岩溶发育程度的差异性,依据岩溶成因及主控因素提出了塔里木盆地奥陶系碳酸盐岩岩溶分类,划分出风化岩溶、礁滩体岩溶和埋藏岩溶3大类,其中风化岩溶又分为潜山岩溶和层间岩溶2个亚类。研究指出礁滩体岩溶、层间岩溶、潜山岩溶是塔里木盆地的重要勘探岩溶类型,并以构造运动为主线将奥陶系岩溶划分为5期,开展了不同类型岩溶特征及分布规律研究,指出了3种重要类型岩溶的勘探思路。此次研究统一了塔里木盆地奥陶系岩溶分类及期次,对勘探开发生产和研究工作具有较强的指导性,具有重要的理论指导及实践应用意义。     

3D gravity modeling of the Triassic salt diapirs of the Cubeta Alavesa (northern Spain)

Up to now subsurface information permitted the delineation of the top of the Triassic salt, all throughout the Cantabro–Navarro domain, although little was known on the location and geometry of its base and thus on the estimation of the total salt thickness. A 3D-gravity inversion scheme combined with a 3D analytic method has been conducted to map out the geometry of the main salt structures of the basin. The gravity modeling results have been constrained by well log information and available geological and reflection seismic data. The combined 3D scheme integrated with available geological and geophysical data has allowed us to obtain the geometry of the main diapirs that characterize the central and marginal regions of the basin.From our interpretation, the Salinas de Añana diapir has almost vertical flanks and can be divided into two different parts, one of them forming a lateral overhang of the main body.The Salinas de Oro diapir has near vertical flanks and a main axis in the N–S direction. Also, the anomaly is rather more extensive than the outcrop of the diapir, which implies an important expansion of non-outcropping salt in this area. Like the Hoz-Sobrón diapir, the Salinas de Ollo diapir is long and narrow. stretching in the NW–SE direction, which includes three important highs, plus an intense zone of salt migration.The Estella and Alloz diapirs crop out individually in spite of being connected at depth. Also two non-outcropping salt domes have been detected to the south of Atauri that, like the Estella diapir, are related to the thrust front. We point out the gravity signature of the Murguia diapir, which shows an intense gravity high probably due to the presence of high-density rocks in the cap rock or more probably due to the existence of Triassic volcanites of ophitic texture pinched-off into the diapir.     

Interconnection of karst systems and flow piracy through karst collapse in layered carbonate rocks

A new mode of interconnecting karst systems separated by impermeable bed due to karst collapse was discovered in the study of dam site in Guizhou, South China. Karst flow may be diverted from conduits in one layer to another, thus forming a connected karst system. Comprehensive methodology and techniques used in the investigation included surface geological surveys, geophysical investigations, special drilling, and tracer tests. In the stage of preliminary study, the karst conduits were considered to be developed separately along individual karstified layers. However, further investigation shows that karst collapse may be associated with conduit and cavern development, damaging the impermeable bed and its watertight function. Accordingly, a new pattern of karst conduit system was reestablished. The results obtained enable the dam designer to plan a reliable alternative for seepage protection.     

Radium geochemistry of ground waters in Paleozoic carbonate aquifers,midcontinent, USA

The purpose of this study was to elucidate the processes controlling the distribution and behavior of the longer-lived Ra isotopes in continuous Paleozoic carbonate aquifers of parts of Missouri, Kansas, and Oklahoma. Activities of (²²⁸Ra) and (²²⁶Ra) were analyzed in fresh and saline ground waters, brines, and rocks. The fluids have a wide salinity range (200–250,000 mg l⁻¹ total dissolved solids). The (²²⁶Ra) activity ranges from 0.66–7660 dpm kg⁻¹ and correlates with salinity and other alkaline earth element (Ca, Sr, and Ba) concentrations. The range of (²²⁸Ra:²²⁶Ra) ratios in the fluids (0.06–1.48) is similar to that in the aquifer rocks (0.21–1.53). The relatively low mean fluid (²²⁸Ra:²²⁶Ra) ratio (0.30) reflects the low Th:U ratio of the predominant carbonate aquifer rock. Radium occurs mostly (≥77%) as Ra²⁺ species in the fluids. Salinity-dependent sorption–desorption processes (with log K values from 10⁰–10⁴ and negatively correlated with salinity), involving Th-enriched surface coatings on aquifer flow channels, can explain the rapid solid–fluid transfer of Ra isotopes in the system and the correlation of Ra with salinity.     

The origin of dolomite associated with salt diapirs in central Tunisia: Preliminary investigations of field relationships and geochemistry

Black and white dolomite crystals (mm to cm width) of different isotopic composition are associated with Triassic diapirism in central Tunisia, as well as with evaporite minerals and clays. The white dolomites occur mostly in the Jabal Hadifa diapir near the contact with Cretaceous limestones, whereas the smaller black dolomites occur in the Jabal Hamra diapir. The former dolomite has a narrow range of δ¹⁸O and δ¹³C values (− 3.83‰ to − 6.60‰ VPDB for δ¹⁸O; − 2.11‰ to − 2.83‰ VPDB for δ¹³C), whereas the latter dolomite has a wider range and more depleted values (− 4.92‰ to − 9.97‰ for δ¹⁸O; − 0.55‰ to − 6.08‰ for δ¹³C). However, the ⁸⁷Sr / ⁸⁶Sr ratios of most of the samples are near Triassic seawater values. Dolomite formation is due to at least two different fluids. The main fluid originated from deeper hydrothermal or basinal sources related to the Triassic saliferous rocks and ascended through faults during the diapiric intrusion. The second, less important fluid source is related to meteoric water originating from Cretaceous rocks.