Gypsum Beds Research Articles

Stratigraphic relationships between shallow-water carbonates and primary gypsum: insights from the Messinian succession of the Sorbas Basin (Betic Cordillera, Southern Spain)

The lack of modern analogues for the thick primary selenite gypsum deposits formed in the Mediterranean area limits the understanding of the Messinian (Miocene) evaporitic systems and particularly of their lateral relationships, their evolution through time and their related ecosystems. Some complex stratigraphic relationships of these extreme environments are revealed in the Messinian Caños Formation along the northern flank of the Sierra Alhamilla at the southern boundary of the Sorbas Basin (southern Spain). Here, the bottom-grown selenite gypsum beds pinch-out against graded clastic carbonate beds (ooid grainstones, rudstones and mudstones) emplaced by gravity flows. We infer that these tabular bodies formed along a low gradient ramp, derived from the periodic erosion of coeval shallow-water to coastal carbonate factories located on top of the Sierra Alhamilla ridge. The carbonate deposits bear many similarities with the Terminal Carbonate Complex described in the northern, steeper margin of the basin; both deposits show a cyclical pattern given by the repetition of couplets consisting of coarser- and finer-grained deposits. This rhythmic facies organization recalls the precessional-controlled cyclic pattern of the gypsum unit. Clastic carbonates and gypsum were deposited during the same precessional hemicycle but appear to be mutually exclusive. In fact, the clastic carbonates represent the lateral equivalent of the gypsum beds, or are occasionally found at their base or at both their base and top, but never interstratified with them. Such an arrangement suggests that during the peak of the evaporitic phases a strong pycnocline acted as the top boundary for gypsum and the lower boundary for carbonate-bearing gravity flows, with the exception of debrites, high-density gravity flows and slumps. These facies architectures appear to be mainly controlled by the interplay between the variable depth of the pycnocline and the density of the brine within the evaporitic cycle.

Application of DInSAR-PSI Technology for Deformation Monitoring of the Mosul Dam, Iraq

On-going monitoring of deformation of dams is critical to assure their safe and efficient operation. Traditional monitoring methods, based on in-situ sensors measurements on the dam, have some limitations in spatial coverage, observation frequency, and cost. This paper describes the potential use of Synthetic Aperture Radar (SAR) scenes from Sentinel-1A for characterizing deformations at the Mosul Dam (MD) in NW Iraq. Seventy-eight Single Look Complex (SLC) scenes in ascending geometry from the Sentinel-1A scenes, acquired from 03 October 2014 to 27 June 2019, and 96 points within the MD structure, were selected to determine the deformation rate using persistent scatterer interferometry (PSI). Maximum deformation velocity was found to be about 7.4 mm·yr−1 at a longitudinal subsidence area extending over a length of 222 m along the dam axis. The mean subsidence velocity in this area is about 6.27 mm·yr−1 and lies in the center of MD. Subsidence rate shows an inverse relationship with the reservoir water level. It also shows a strong correlation with grouting episodes. Variations in the deformation rate within the same year are most probably due to increased hydrostatic stress which was caused by water storage in the dam that resulted in an increase in solubility of gypsum beds, creating voids and localized collapses underneath the dam. PSI information derived from Sentinel-1A proved to be a good tool for monitoring dam deformation with good accuracy, yielding results that can be used in engineering applications and also risk management.

Late Miocene evaporite geochemistry of Lorca and Fortuna basins (Eastern Betics, SE Spain): Evidence of restriction and continentalization

AbstractThe Lorca and Fortuna basins are two intramontane Neogene basins located in the eastern Betic Cordillera (SE Spain). During the Late Tortonian—Early Messinian, marine and continental evaporites precipitated in these basins as a consequence of increased marine restriction and isolation. Here we show a stratigraphic correlation between the evaporite records of these basins based on geochemical indicators. We use SO4 isotope compositions and Sr isotopic ratios in gypsum, and halite Br contents to characterize these units and to identify the marine or continental source of the waters feeding the evaporite basins. In addition, we review the available chronological information used to date these evaporites in Lorca (La Serrata Fm), including a thick saline deposit, that we correlate with the First Evaporitic Group in Fortuna (Los Baños Fm). This correlation is also supported by micropalaeontological data, giving a Late Tortonian age for this sequence. The Second Evaporitic Group, (Chicamo Fm), and the Third Evaporitic Group (Rambla Salada Fm) developed only in Fortuna during the Messinian. According to the palaeogeographical scheme presented here, the evaporites of the Lorca and Fortuna basins were formed during the Late Tortonian—Early Messinian, close to the Betic Seaway closure. Sulphate isotope compositions and Sr isotopic ratios of the Ribera Gypsum Mb, at the base of the Rambla Salada Fm (Fortuna basin), match those of the Late Messinian selenite gypsum beds in San Miguel de Salinas, in the near Bajo Segura basin (40 km to the East), and other Messinian Salinity Crisis gypsum deposits in the Mediterranean. According to these geochemical indicators and the uncertainty of the chronology of this unit, the assignment of the Rambla Salada Fm to the MSC cannot be ruled out.

Controls on deposition of shallow marine carbonates and evaporites – lower Permian Gipshuken Formation, central Spitsbergen, Arctic Norway

AbstractThe interbedded shallow marine carbonates and evaporites of the 95 to 105 m thick lower Permian Vengeberget member in central Spitsbergen form a lowstand to possibly early transgressive wedge sandwiched between open marine highstand carbonates along the northern margin of Pangea. Deposition took place on a wide (much greater than 40 000 km2) evaporitic platform separated from the open marine environments to the east by an inferred shelf margin barrier. Based on detailed description of facies in unique mountain‐scale outcrops, five CaSO4 and nine carbonate facies have been identified, all reflecting deposition in shallow evaporitic environments. The gypsum beds represent subaqueous deposition in broad hypersaline lagoons whereas the carbonates were deposited in protected shallow marine to peritidal environments and ooid‐dominated grainstone shoals. Cyclicity is expressed both as lithological shifts from carbonate to CaSO4 deposition and in the stacking of facies during CaSO4 and carbonate deposition. The number of carbonate–evaporite cycles varies from 12 to 28, but the overall thickness of the succession varies only slightly as a result of variations in cycle thickness, from 0·5 to 13·0 m. Two basic types of carbonate units can be recognized and reflect a combination of allocyclic and autocyclic controls. In addition, differential subsidence along older north–south orientated lineaments added to the complexity of cyclicity. The study provides insight into the complexity of the controls on deposition, architecture and dynamics of large‐scale mixed carbonate–evaporite successions formed in the shallow inner part of an epeiric sea or platform.

New insights on Messinian evaporites based on field and seismic interpretations in the Neogene Antalya Basin, SW Turkey

In situ/primary Messinian upper evaporite is absent in the onland (onshore) sections of the Aksu and Manavgat subbasins (Antalya Basin), where gypsum blocks, gypsum conglomerate, and laminated gypsum beds mixed with siliciclastic materials are collectively present in the uppermost Messinian-?lowermost Pliocene succession. The metric-size resedimented evaporite blocks, mainly derived from selenite-dominated marginal/upper evaporite, were deposited time-equivalent to the lower-middle parts of the reefal Gebiz limestone in the Aksu subbasin. Resedimented bedded evaporites were accumulated after siliciclastic-dominated (fluvio-deltaic) sedimentation of the Taslik Formation in the Manavgat subbasin (nearby Antalya city). Some bedded/?resedimented gypsums were defined within the Gebiz limestone and the Eskikoy Formation, as observed in the logs of the Aksu-1, Manavgat-1, and Manavgat-2 wells. Effects of the Messinian salinity crisis are seen on the seismic boundary of the Messinian erosional surface in the Aksu subbasin resting directly on the Karpuzcay Formation and in the lower and middle parts of the fluvio-deltaic Eskikoy Formation and reefal Gebiz limestone. As for the Manavgat subbasin, Manavgat-1 and -2 well logs indicate the existence of bedded/?resedimented evaporites in the Taslik and Eskikoy Formations, which is supported by the seismic sections. Additionally, onshore and offshore seismic sections indicate that the upper evaporite layer could be traceable both in onshore and offshore areas. The relationship between evaporite and nonevaporite units is explained by the Aksu phase, which caused compressional deformation leading to significant uplift in the region around the Gebiz High. This uplift is also involved in relative sea-level drop, which resulted in alternating deposition between siliciclastic (Eskikoy and Taslik Formations), resedimented-bedded gypsum, and transgressive shallow marine reefal Gebiz limestone.

Advance Mosul Dam Break Analysis by Integrated Hydrologic Modeling and Gene-Expression Programming

Mosul dam is one of the biggest water driven structures in Iraqi nation. It is situated on Tigris River, north of Iraq. It is the fourth biggest dam in the Middle East, 3.4 Km long, 113 m in stature and has a capacity limit of 11.1 billion cubic meters. It is an earth fill dam, built on bedrocks of Fatha Formation, which comprises of gypsum beds. In this manner, it is chosen as a contextual analysis to foresee flood fiascos brought about by a conceivable dam disappointment because of its establishment issues. In this examination, Simplified Dam Break (SMPDBK) model is added to watershed displaying framework (WMS) rendition 10 as a pressure driven model to mimic a theoretical Mosul dam break by utilizing Digital rise model (DEM), land use maps and satellite pictures as a mean information sources. WMS was utilized to investigate the DEM information to separate the River way centerline downstream the dam. Five situations; 330 m as most extreme activity level, 320, 310 and 300 m.a.s.l as least activity level in extra to 290 m.a.s.l were used to mimic the dam disappointment. The disastrous outcomes in the event of the dam break as per this examination at the most extreme activity level (330 m.a.s.l.), Mosul city will be immersed with the greatest water level of 228.72 m.a.s.l., the most extreme release of flood will be 229519 m3/sec, while the greatest water profundity will reach to 21 meter over the bed of normal Tigris River inside (5.43) hours from the beginning of the dam disappointment. The overwhelmed territory between the dam site and Mosul city was anticipated to be 237 km2. The immersion maps for the most perilous mimicked situation were organized by utilizing WMS to demonstrate the flood profundity and flood height maps along downstream of the considered dam. The SMPDBK model yields incorporate flood releases, time to top profundities, flood profundities and flood rises steered along stream centerline and the fundamental immersed territories in Mosul city were perceived. At long last, Gene Expression Programming (GEP) were utilized to break down the model yields to build up an emblematic relapse articulation to foresee flood releases, flood time and flood level conditions. The exhibition of the GEP prescient conditions were tried by the level of assurance coefficient R2. The aftereffects of R2 values for the three prescient conditions are demonstrated the effectiveness of GEP for this examination, since all R2 esteems is more noteworthy than 0.9 .

The depositional history of near-surface Qatar aquifer rocks and its impact on matrix flow and storage properties

Carbonates and evaporites of Paleogene age form the shallow-aquifer rocks mantling most of Qatar, including the Paleocene and Lower Eocene Umm er Radhuma Formation and the Lower to Middle Eocene Rus and Dammam Formations. A core-based study was carried out to improve general understanding of the stratigraphic controls on aquifer matrix properties in Qatar. A cumulative total of 377 m of 10-cm-diameter core was recovered from three boreholes in central and northern Qatar, drilled to depths of greater than 120 m. Sedimentological attributes of these rocks were investigated through core and thin-section description, X-ray diffraction-based mineralogical assessment, as well as whole-rock stable isotopic analysis and integrated with interpretation of gamma-ray logs. Stratigraphic correlation of the penetrated intervals was then undertaken using sequence stratigraphic concepts and isotope stratigraphy (δ13C trends) in the context of recently published regional paleomaps and structural studies. In the area of Qatar, the Umm er Radhuma Formation and the overlying Traina Member of the Rus Formation were deposited in marine settings of two different basins. These basins, which extended to the south and north of Qatar, respectively, are interpreted to have been separated by a topographic high, the location of which was controlled by the presence of high-angle normal faults. The southern basin was more restricted and was the site of extensive evaporite and clay-rich siliciclastic deposition during early stages of Rus Formation. Similar evaporites and fine siliciclastic deposits are not observed in time-equivalent strata of the northern basin. During subsequent deposition of the Al Khor Member of the Rus Formation, as well as the Dammam Formation, the basins appear to have been interconnected, and fine-grained siliciclastic deposits are interbedded with, but subordinate to, carbonate strata across Qatar. Most rocks recovered for this study are dolomitic, and dolomitic rocks free of other mineral phases tend to have significant porosity (20–50%) and permeability (10–1000 mD). Decreased connectivity, flow, and storage capacity are caused by (1) the presence of gypsum beds and nodules (only southern Qatar, upper Umm er Radhuma Formation, and Rus Formation), (2) the presence of pore-occluding clays (typically palygorskite) to varying degrees in all formations, and (3) the occurrence of diagenetic calcites, most commonly in the Dammam Formation. Aquifer quality of the near-surface rocks of Qatar is in large part a function of their depositional history and is to a degree predictable using reconstruction of basin architecture, as well as sequence stratigraphic concepts.

Diazotrophy Drives Primary Production in the Organic-Rich Shales Deposited Under a Stratified Environment During the Messinian Salinity Crisis (Vena del Gesso, Italy)

Density stratification between freshwater and brine is periodically formed during massive evaporation events, which often associates deposition of organic-rich sediments. Here, we investigated phototrophic communities and nitrogen cycle during the deposition of two organic-rich shale beds of gypsum–shale alternation, representing the initial stage of the Messinian salinity crisis (Vena del Gesso, Northern Apennines, Italy). The structural distributions and the carbon and nitrogen isotopic compositions of geoporphyrins show a common pattern in the two shales, indicating the predominance of a particular phototrophic community under freshwater–brine stratified conditions. The ~6‰ difference in δ13C of total organic carbon between PLG 4 and 5 shales was associated with similar shift in δ13C of the porphyrins derived from chlorophyll c, suggesting that the eukaryotic algae producing chlorophyll c were the major constituent of the phototrophic community. Importantly, these porphyrins show δ15N values (−7.6‰ to −4.7‰) indicative of N2-fixation. We suggest that nitrate-depletion in the photic zone induced the predominance of diazotrophic cyanobacteria, which supplied new nitrogen for the chlorophyll c-producing eukaryotic algae. The large difference in the δ13C values of porphyrins and total organic carbon between PLG 4 and 5 shales are interpreted to reflect the depth of the chemocline, which fluctuates in response to changes in the regional evaporation–precipitation balance. Such variation in the chemocline depth may have dynamically changed the mode of the nitrogen cycle (i.e., nitrification–denitrification–N2-fixation coupling vs. phototrophic assimilation of ammonium) in the density-stratified marginal basins during the Messinian salinity crisis.

Enterolithic folds in evaporites as microbially induced sedimentary structures: New model of formation and interpretation in the geological record

AbstractEnterolithic structures are stratigraphically localized folds in gypsum beds found in certain saline evaporitic sedimentary units in a wide variety of basins. Different models of formation have been proposed, all related to inorganic processes. These models include: diagenetic transformation of gypsum beds producing either displacive growth of crystals or volume changes; mechanical folding caused by compressional stress; and folding produced by slumping. The analysis of three Cenozoic evaporite sequences in Spain reveals that none of the previous models explains their origin and existence. In these outcrops, gypsum enterolithic structures occur in horizontal beds with parallel troughs and crests of the folds. They appear in shoreline facies of lacustrine environments and did not undergo major diagenetic transformations after the primary lithification of the original sediment. Based on these observations, together with the study of a modern analogue in Minorca, Spain, a new model is proposed for the genesis of enterolithic structures. This new model is based on the existence of a microbial mat exposed to brine concentration–dilution cycles and strong wind events. The high wind flow events enhanced folding of the microbial mat that became subaerially exposed and lithified due to subsequent evaporation. Therefore, the presence of enterolithic structures could be used as an indicator of shallow water environmental conditions subject to variations in brine concentration in areas with strong wind flow events. Previous studies of some evaporitic successions should be revisited, taking into account the proposed model, which would imply new depositional environment interpretations. At the same time, the proposed model could explain the existence of Kinneyia‐type structures, also known as wrinkle structures, formed beneath microbial mats in peritidal zones. Moreover, considering enterolithic structures as microbially induced sedimentary structures could be useful as evidence of microbial life in the ancient geological record and on other planets such as Mars.

Orbitally Forced Hydrological Balance During the Messinian Salinity Crisis: Insights From Strontium Isotopes (87Sr/86Sr) in the Vena del Gesso Basin (Northern Apennines, Italy)

AbstractThe 87Sr/86Sr ratio is a proxy of the hydrologic structure of marginal basins characterized by the mixing between marine and continental waters. This reliable paleoceanographic and paleoclimatic tool is considered a key to the reconstruction of high‐amplitude hydrologic changes that governed the evolution of the Mediterranean region during the Messinian salinity crisis (MSC), when reduced connections with the global ocean resulted in the deposition of the most studied Earth's salt giant. Paleohydrological dynamics leading to the deposition of the Primary Lower Gypsum during the first stage of the MSC were revealed by the study of the 87Sr/86Sr composition of 114 samples from the Vena del Gesso basin (Northern Apennines, Italy). The analysis of seven high‐resolution 87Sr/86Sr profiles from individual gypsum beds suggests a climatic influence of precessional‐scale orbital parameters during evaporite deposition. The variations of Sr isotope ratios over time indicate that gypsum precipitation started from a seawater body dominated by continental contributions, followed by a relative increase of marine input. The overall results show a gradual upward detachment from the global ocean 87Sr/86Sr curve, with crucial steps corresponding to the most extreme eccentricity minima, suggesting an orbital influence on the hydrological balance of the basin. Given the sedimentological and geochemical analogies shared by the Mediterranean marginal basins that hosted the Primary Lower Gypsum deposition, the 87Sr/86Sr evolution of the Vena del Gesso basin may be considered as indicative of Mediterranean‐scale hydrologic dynamics, driven by gradual reduction of exchanges with the Atlantic and variable freshwater input.

Mineralogical-petrographical study of evaporites from Mali Kukor, Vranjkovići and Slane Stine quarry (Upper Permian evaporites from Dalmatia, Croatia)

The evaporite deposits examined in this study are located in the central part of middle Dalmatia, Croatia. In this region, Upper Permian evaporite sediments were deposited under favourable conditions onto the Variscan basement around the northern margins of Gondwana. These sediments can be subdivided into three members, a lower evaporite unit (an anhydrite member), a middle evaporite unit (a gypsum member), and an upper unit (a clastic member), and are mainly comprised of secondary gypsum that formed via the hydration of precursor anhydrite rocks. The middle evaporite unit comprises beds of gypsum as well as early diagenetic dolomites that contain gypsum sequences, extending up to 60 m maximum thickness, and overlying clastic sequences that themselves are up to 20 m thick. These Upper Permian evaporite sediments contain horizontal, irregular, gypsum lithofacies that exhibit pronounced enterolithic and boudinage structures. The characteristics of these sediments are indicative of deposition in supratidal and sabkha settings (i.e., early diagenetic dolomites and evaporites) within a shallow epicontinental marine environment with highly varied coastlines, bays, and lagoons. The secondary gypsum seen within this Upper Permian middle evaporite unit displays alabastrine and porphyroblastic secondary textures and includes corroded anhydrite relics; associated minerals include muscovite, chlorite, potassium (K)-feldspar, quartz, and amphibole. The Upper Permian evaporite sediments discussed in this study are composed of irregular, locally brecciated secondary gypsum that probably formed as a result of multiple synsedimentary collapse of pre-existing soluble mineralsand/or synsedimentary and post-sedimentary tectonics.

A model of basin evolution in the Qa’ Al-Azraq, Jordan using sulfur isotope analysis to distinguish sources of sulfur and gypsum

The closed basin of the Qa’ Al-Azraq, Jordan records gypsum and sulfur depositions. Analysis of the cored sediments used smear slides, isotope geochemistry of gypsum and sulfur, XRD, and SEM. This study distinguishes the sources of gypsum and sulfur in the basin from four different processes. Algae production was responsible for the presence of laminated sulfur at a depth of 48 m where paleolake levels were at a high stand. Primary gypsum, represented by laminated, thick massive beds, records sulfur isotope values of +15.7‰. This period of the paleolake indicates evaporation processes exceeded precipitation, leading to the deposition of thick, massive bed of gypsum. Other sources of gypsum originate from pyrite oxidation, indicated by the overlapping of sulfur isotope values of gypsum and pyrite at −0.7‰. Bassanite and anhydrite identified in this section resulted from dissolution and recrystallization processes. The application of sulfur isotopic analyses identifies environmental distinct formation processes of sulfate minerals in the Al-Azraq basin. This provides the basis for a model of basin evolution and associated changing climates. Finally, this research considers the effect of sulfate minerals on Al-Azraq basin groundwater.

Assessment of the geostress field of deep-thick gypsum cap rocks: A case study of Paleogene Formation in the southwestern Tarim Basin, NW China

Gypsum rocks have extremely low permeability and good pressure sealing capability, and they are widely distributed in different strata all over the world. A deep-thick gypsum cap rock is developed in the Paleogene formation of the southwestern Tarim Basin in China. The regions below the gypsum rocks have huge potential for oil and gas resources. Casing deformation and blockage during tripping operations often occur during the drilling process in the gypsum bed, which severely affects the efficient drilling of deep oil and gas. Therefore, it is necessary to comprehensively assess the geostress field of gypsum cap rocks under high-stress background conditions. Through triaxial synchronized mechanical and acoustic testing experiments, high-stress formation environments were simulated and the mechanical parameters of gypsum rocks were obtained. We used dispersion correction technology to transform the measured high-frequency (1MHz) wave velocities of the samples to the wave velocities of well-logging frequency (20kHz). The transformed wave velocities can be used for the well-logging assessment of rock mechanical parameters and geostress. We built well-logging interpretation models for the shear-wave slowness, mechanical parameters and geostress of the Paleogene gypsum rocks. Each model showed high assessment accuracy. Combined with the paleomagnetic analysis of the Paleogene gypsum bed and the results of the fast shear-wave direction analysis, radial expansion position analysis and induced fracture analysis on the reservoir below the Paleogene gypsum bed, we suggest that the direction of geostress in the study region is NW10°. Three-dimensional finite element method was used to simulate the geostress field of the gypsum bed. The Paleogene formation in the study region does not have faults. The geostress distribution of the gypsum rock layer is mainly controlled by structural relief, burial depth, and lithology. This study provided a typical example of a comprehensive assessment of the geostress field of deep-thick gypsum cap rocks.

Syndesmorion stellatum (Fijałkowska) Foster et Afonin chlorophycean algae and associated microphytoplankton from lacustrine successions of the La Veteada Formation (late Permian), Paganzo Basin, Argentina. Paleoenvironmental interpretations and stratigraphic implications

A diverse microphytoplankton assemblage recovered from terrestrial deposits of the La Veteada Formation, north of the La Rioja Province, Paganzo Basin, Argentina, is described and illustrated. The ~180m thick sedimentary type section of the unit in the Los Colorados anticline is composed of a basal gray silcrete covered by gypsum beds and a thick succession of purple mudstones inter-layered with varicolored fine sandstone sheets and laminated yellowish dolomites. The aquatic assemblage is mainly characterized by a great variety of Syndesmorion stellatum (Fijałkowska) Foster et Afonin coenobia, recorded for the first time in the late Permian Gondwanic realm. All the previous morphotypes described for this chlorophycean alga are recognized in this assemblage, and new polymorph-coenobia are described and illustrated. The diversity of coenobia morphotypes of this alga is likely to reflect response to stress conditions. The genera Maculatasporites and Mehlisphaeridium are commonly present, and their algal origin is discussed. Maculatasporites gondwanensis, Maculatasporites amplus, Mehlisphaeridium parvum, and Mehlisphaeridium regulare and Mehlisphaeridium sp. are also described and illustrated. Representatives of the zygnematacean algae, Brazilea scissa, Brazilea plurigenus, Brazilea sp. A, Tetraporina tetragona, ?Lecaniella sp., as well as large clusters of sphaeromorphs incertae sedis chlorophyta algae, are described. In addition, planar colonial chlorococcalean Pediastrum-like forms suggesting hydrodictyaceaen algae are recorded for the first time in late Paleozoic strata of Argentina, and the zygnematalean affinity of Reduviasporonites chalastus as green algae is discussed. The highly diverse La Veteada microphytoplanktonic assemblage is composed by algae that grew in hypersaline lacustrine environment together with species commonly associated with either fresh or brackish water conditions; presumably these taxa were washed in after heavy rainfall and/or flooding events. In general terms, the land-derived palynological composition of the La Veteada assemblage at Central Famatina Range reflects parent vegetation adapted to arid or semi-arid climate as reported from late Guadalupian to late Lopingian in the Paganzo Basin. The whole palynological composition suggests a Lopingian age for the La Veteada Formation at its stratotype, based on the stratigraphic range of all the land-derived miospore species recognized, resulting younger than assemblages assigned to the Lueckisporites–Weylandites Biozone (LW: Wordian–Capitanian). Therefore, it is the youngest Permian palynofloral assemblage recorded up to now in Argentina and South America.

加熱透過法による廃石膏粉体の乾燥特性の評価

This study experimentally examined the drying characteristics of the waste gypsum powder using a permeation of heated air. The powder used was the waste gypsum which the particle diameter was classified into three kinds. As the experimental conditions, the particle diameter of dehydrate gypsum, the heating temperature, the initial mass of powder, the heating time and the mass flux of heated air were varied. When the initial mass of powder was an identical, it is found that the decrease in the time of change from the dehydrate gypsum to the hemihydrate gypsum depends on the increase in the particle diameter and the heating temperature. As the analysis of X-ray diffraction pattern, it can be confirmed a permeation test of heated air was an effectiveness for the evaluation of the change to hemihydrate gypsum. In addition, an effective thermal conductivity and heat flux of the packing bed of gypsum were estimated. It is found that a particle Reynolds number influenced to an effective thermal conductivity in the packing bed of waste gypsum. Also, an effective thermal conductivity including the flow of heated air was high in the case of large particle diameter. Furthermore, it is inferred that a high heat flux acting on the packing bed of gypsum influenced the time of change from the dehydrate gypsum to the hemihydrate gypsum.

Depositional stages of the Eğribucak inner basin (terrestrial to marine evaporite and carbonate) from the Sivas Basin (Central Anatolia, Turkey)

The Sivas Cenozoic Basin and coeval Central Anatolian basins such as Çankırı and Tuz Gölü are characterized by both marine and terrestrial sediments ranging in age from the Eocene to early Miocene. The evaporite regime here generally appeared during the late stage of Eocene transgression and persisted through the Oligocene time. However, marine-induced Oligocene evaporites are less known because of less paleontological evidence and regional tectonics and salt diapirism that mostly caused the destruction of their original stratigraphic positions. The Eğribucak area studied here, located about 25 km southeast of Sivas, provides a well-stratified key section to shed light on the depositional history of the Oligocene marine evaporite (coastal lagoon or sabkha complex) and other associated carbonate and siliciclastic units. The Eğribucak succession has a thickness of approximately 400 m and rests on thick fluviatile sediments commencing with red beds (mudstone, sandstone, and gravelly sandstone), and upwards, terrestrial gypsums are present within the red units as thin beds that are overlain by thick marine gypsum beds with rhythmical alternations of gray and green colored sandstone-marly limestone and limestone. The limestones alternating with the thick gypsum beds are rich in benthic foraminifers yielding a Rupelian-Chattian age. At the top of the section evaporites disappeared and lagoon-type limestone turned into thick platform carbonate dated as Oligocene-early Miocene. The Eğribucak succession shows a wide variety of depositional environments ranging from terrestrial to restricted marine to open marine from bottom to top. The short periods of the lithological alternations from siliciclastic to carbonate and evaporite indicate that the evaporite environment was not consistent through the Oligocene period. This would be formed as a marginal evaporite environment, presumably a coastal lagoon/sabkha affected by seasonal variations with arid and humid periods as well as eustatic sea-level changes. The Oligocene transgression culminated in the area with the deposition of platform-type carbonates and it continued during the early Miocene.

Mosul Dam: A Catastrophe Yet to Unfold

Mosul Dam is multipurpose earth fill dam. It is 3.4km long, 113m in height and its storage capacity reaches 11.11 km3 of which 2.95 km3 is dead storage. The dam is located on the River Tigris in the northern part of Iraq about 60 km in north west Mosul city. The dam was built on highly karstified alternating beds of gypsum, marl and limestone. The dam was operating in 1986 and since then, seepage problems started due to the solubility of the gypsum beds, presence of karstification and the effect of the local groundwater aquifer. Insensitive grouting program was put to stop the seepage and ensure the stability of the dam but it did not stop. The situation became worse in 2014 when ISIS occupied the dam area and grouting operations which were halted. Recent evaluation of the conditions indicates that the dam is in its worst conditions. The failure models of the dam indicate that 6 million people will be affected, and 7202 km2 of land will be inundated. To stop this catastrophe, grouting operations should be continued intensively to elongate the span life of the dam. Water level within its reservoir should be kept at a very low level to minimize the damages in case of dam failure. As a permanent solution, another dam should be built downstream Mosul Dam so that it can take the wave of Mosul Dam in case of its failure.

Is Mosul Dam the Most Dangerous Dam in the World? Review of Previous Work and Possible Solutions

Mosul Dam is an earth fill dam located on the Tigris River in North Western part of Iraq. It is 113 m in height, 3.4 km in length, 10 m wide in its crest and has a storage capacity of 11.11 billion cubic meters. It is, constructed on bedrocks which consist of gypsum beds alternated with marl and limestone, in cyclic nature. The thickness of the gypsum beds attains 18 m; they are intensely karstified even in foundation rocks. This has created number of problems during construction, impounding and operation of the dam. Construction work in Mosul Dam started on January 25th, 1981 and started operating on 24th July, 1986. After impounding in 1986, seepage locations were recognized. The cause of seepage is mainly due to: 1) The karsts prevailing in the dam site and in the reservoir area. 2) The existence of gypsum/anhydrite rock formations in the dam foundation alternating with soft marl layers and weathered and cavernous limestone beddings. 3) The presence of an extensive ground water aquifer called Wadi Malleh aquifer, which affects considerably the ground water regime in the right bank. The dissolution intensity of the gypsum/anhydrite ranged from 42 to 80 t/day which was followed by a noticeable increase in the permeability and leakages through the foundation. Inspection of the dam situation in 2014 and 2015 indicates that the dam is in a state of extreme unprecedentedly high relative risk. In this work, possible solutions to the problem are to be discussed. It is believed that grouting operations will elongate the span life of the dam but do not solve the problem. Building another dam downstream Mosul Dam will be the best protective measures due to the possible failure of Mosul Dam, to secure the safety of the downstream area and its’ population.

Sequence Stratigraphic Context of Extensive Basin-Margin Evaporites: Middle Jurassic Gypsum Spring Formation, Wyoming, U.S.A.

Abstract Ancient marine evaporites are commonly far more extensive than any known modern evaporite system. This is true not only for basin-central saline giants, but also for evaporites that occur in basin-margin settings, and the origin of these basin-margin systems is unclear. Extensive basin-margin evaporites of the Middle Jurassic Gypsum Spring Formation are well exposed along the eastern flank of the Bighorn Basin in Wyoming, USA, and a facies and sequence stratigraphic analysis was undertaken to understand the origin of these evaporites and associated deposits. The Gypsum Spring Formation was deposited on a northwestward-dipping mixed evaporate–carbonate–siliciclastic ramp, with facies and depositional environments that include distal ooid shoal grainstone, open-marine shallow-subtidal peloidal–skeletal wackestone to packstone, restricted shallow subtidal laminated lime mudstone, peritidal dolostone and microbialite, as well as red mudstone and gypsum deposited on mud flats, sabkhas, and salinas. Three depositional sequences are present, with the J-1, J-1a, and J-1b sequence boundaries characterized locally by chert-pebble lags, silicified horizons, and iron-rich paleosols. Evaporites accumulated in a basin-margin position, with 1–6 m beds of gypsum forming in salinas and sabkhas, and nodular anhydrite and gypsum forming in red mudstones deposited on sabkhas and mud flats. The limited lateral extent of salina-type gypsum beds and the variable number of these beds among the exposures indicates substantial autocyclic control on the formation of salinas. Salinas are well developed in the TST of the J-1 sequence, and sabkhas and mud flats are well developed in the J-1 HST, the J-1a HST, and the J-1b TST. The great lateral extent of the Gypsum Spring evaporites reflects the original expanse of the depositional environment in which they formed, and is not the result of diachroneity of a narrow evaporite-precipitating belt, such as the modern-day coastal sabkhas of the Trucial coast. The great lateral extent of Gypsum Spring evaporites suggests that they were precipitated mainly from continental brines on an expansive desert mudflat.

Messinian evaporites in the Mesaoria Basin, North Cyprus: facies and environmental interpretations

This study focuses on the depositional environments of the Messinian evaporites exposed in the Mesaoria Basin of Northern Cyprus, which has been considered as a marginal gypsum deposit formed in the upper evaporites. The evaporite unit is divided into several kinds of gypsum facies, such as nodular gypsum (F.1), non-bedded selenite (F.2), bedded selenite (F.3), laminated–interbedded grass-like selenite (F.4), gypsarenite with selenite banks (F.5), gypsum megabreccia (F.6), and non-selenitic laminated gypsum (F.7). Among these, nodular gypsum (F.1) and gypsarenite with thick-bedded selenite banks facies (F.5) occurred on the evaporative shoal, modified by seasonal lowstand–highstand cycles with multiple drying and flooding episodes. Selenite facies (F.2-4) was deposited in a wide range of shallow-subaqueous environments, such as marine-fed salinas divided into deep (perennial), moderately deep and shallow (ephemeral) pans resulted from fluctuations of the pycnocline level in the saline pans. In particular, the shallow pans were temporarily influenced by sheet flood or runoff fresh water, leading to the deposition of the grass-like selenite (F.4) with fresh/brackish water limestone (e.g., Iskele section). The Gypsum megabreccia (F.6) is a mass flow deposit or consists of blocks emplaced by gravity in the deeper basin. This depositional period was indicated by large-scale slope failure and basin margin erosion that was triggered by synsedimentary tectonics towards the end of the Messinian episode. Non-selenitic laminated gypsum beds (F.7) are composed of alternations of resedimented/detrital fine gypsum with (current structures), chemical gypsum cumulates, carbonates and diatomaceous muds (with sulfur nodules). Halite-anhydrite couplets were only inferred in a borehole drilled in Yeri village south of Lefkosa (Nicosia). In contrast to the basin margin erosion between Messinian gypsum and Pliocene marine sediments, the halite-anhydrite grades upwards into the Latest Messinian/Early Pliocene-shelly gray mudstone and peats, presumably indicating Lago-Mare-type deposits. The various kinds of gypsum facies studied here have average values of stable isotopes (δ 87/86Sr = 070896, δ18O = 13.5, and δ 34S = 24.6) which fall into the isotopic range of Messinian marine evaporites.