Sedimentologic and paleoclimatic reconstructions of carbonate factory evolution in the Alborz Basin (northern Iran) indicate a global response to Early Carboniferous (Tournaisian) glaciations

© 2016 Elsevier B.V.The Lower Carboniferous Mobarak Formation records the development of a storm-sensitive pervasive carbonate factory on the southern Paleo-Tethyan passive margin following the opening of the Paleo-Tethys Ocean into the Alborz Basin along the northern margin of Gondwana. Its depositional facies encompass inner ramp peritidal environments, peloidal to crinoidal shoals, storm to fair-weather influenced mid-ramps, proximal to distal shell beds and low energy outer ramps. Sedimentological analyses and foraminiferal biostratigraphy reveal four events affecting carbonate platform evolution in the Alborz Basin during the Lower Carboniferous: (1) A transgression following global temperature rise in the Early Tournaisian (middle Hastarian) caused the formation of thick-bedded argillaceous limestones. This interval correlates with Early Tournaisian nodular to argillaceous limestones in the Moravia Basin (Lisen Formation, Czech Republic), the Dinant Basin (Pont d'Arcole Formation, Belgium), and at the Rhenish Slate Mountains (Lower Alum shale, Germany). (2) Late Hastarian–early Ivorian glaciations previously identified in Southern Gondwana but had not yet recognized in Northern Gondwana were recorded through a sequence boundary. (3) During the Late Tournaisian–Early Visean?, a differential block faulting regime along the basin's margin caused uplift of the westernmost parts of the Alborz Basin and resulted in subsidence in the eastern part of the central basin. This tectonically controlled shift in depositional regime caused vast sub-aerial exposure and brecciation preserved in the top of the Mobarak Formation in the western portion of the Central Alborz Basin. (4) Tectonic activity coinciding with a progressive, multiphase sea level drop caused indirectly by the Viséan and Serpukhovian glaciations phases ultimately led to the stagnation of the carbonate factory. Paleothermometry proxies, the presence of foraminiferal taxa with a northern Paleo-Tethyan affinity and evidence for arid conditions in the terrestrial hinterland place the Alborz Basin at lower latitudes than the approximately 45ο–50ο southern paleolatitude reported thus far

Mixed Middle Jurassic sedimentation from North East of Iran: sedimentological model and carbonate production versus detrital inputs influence

peer reviewe

Delta and deep basin Jurassic deposits from Iran: relationship between magnetic susceptibility and facies

This study concerns, the Kashafrud Formation from Kopet Dagh Basin in its type section, which corresponds to the first Jurassic sedimentary cycle in Iran,. Sedimentary studies were carried out to propose a paleoenvironmental model of the sedimentary succession. Furthermore, magnetic susceptibility (MS) measurements were performed and compared with sedimentological evolution. The MS curve evolution is related to the abundance of magnetic minerals, which itself is related to lithogenic supplies which could be related mostly to sea level and climatic changes. Theoretically, a regression will lead to a more important proportion of landmass exposed and so to an increase of detritic minerals in the sedimentary system and so to an increasing MS. A transgression will decrease MS (Ellwood et al., 2000). Palaeoenvironments of this Jurassic succession from base to top are: flood dominated delta, deep basin deposits, silisiclastic and mixed silisiclastic and carbonate shoreface deposits. Comparison between facies evolution and MS curve shows that the facies which are deposited in delta and shoreface zones have low MS values; on the contrary basinal deposits are presenting high MS values. The facies deposited in mixed silisiclastic and carbonate shoreface have lowest MS values. So it appears that the deeper basinal deposits have the highest MS values and the shallower deltaic and shorelines facies have the lowest MS values, in opposition with theoretical background. This could be related to water agitation and sedimentation rate during deposition. In the deltaic and shoreface environments, a high water agitation could prevent the detritic particles to settle and a high sedimentary rate could dilute the magnetic minerals (see Da Silva et al., 2009). It actually seams that the carbonate production in the upper parts of the studied interval has led to a dramatic decrease in MS values. This study clearly shows the significant role of MS in environmental analysis, and the importance of a strong sedimentological background. Ellwood, B.B., Crick, R.E., El Hassani, A., Benoist, S.L. & Young, R.H., 2000. Magnetosusceptibility event and cyclostratigraphy method applied to marine rocks: detrital input versus carbonate productivity. Geology, 28: 1135-1138. Da Silva, A.-C., Mabille, C. & Boulvain, F., 2009. Influence of sedimentary setting on the use of magnetic susceptibility: examples from the Devonian of Belgium. Sedimentology, 56: 1292-1306

Sedimentologic and paleoclimatic reconstructions of carbonate factory evolution in the Alborz Basin (northern Iran) indicate a global response to Early Carboniferous (Tournaisian) glaciations

© 2016 Elsevier B.V.The Lower Carboniferous Mobarak Formation records the development of a storm-sensitive pervasive carbonate factory on the southern Paleo-Tethyan passive margin following the opening of the Paleo-Tethys Ocean into the Alborz Basin along the northern margin of Gondwana. Its depositional facies encompass inner ramp peritidal environments, peloidal to crinoidal shoals, storm to fair-weather influenced mid-ramps, proximal to distal shell beds and low energy outer ramps. Sedimentological analyses and foraminiferal biostratigraphy reveal four events affecting carbonate platform evolution in the Alborz Basin during the Lower Carboniferous: (1) A transgression following global temperature rise in the Early Tournaisian (middle Hastarian) caused the formation of thick-bedded argillaceous limestones. This interval correlates with Early Tournaisian nodular to argillaceous limestones in the Moravia Basin (Lisen Formation, Czech Republic), the Dinant Basin (Pont d'Arcole Formation, Belgium), and at the Rhenish Slate Mountains (Lower Alum shale, Germany). (2) Late Hastarian–early Ivorian glaciations previously identified in Southern Gondwana but had not yet recognized in Northern Gondwana were recorded through a sequence boundary. (3) During the Late Tournaisian–Early Visean?, a differential block faulting regime along the basin's margin caused uplift of the westernmost parts of the Alborz Basin and resulted in subsidence in the eastern part of the central basin. This tectonically controlled shift in depositional regime caused vast sub-aerial exposure and brecciation preserved in the top of the Mobarak Formation in the western portion of the Central Alborz Basin. (4) Tectonic activity coinciding with a progressive, multiphase sea level drop caused indirectly by the Viséan and Serpukhovian glaciations phases ultimately led to the stagnation of the carbonate factory. Paleothermometry proxies, the presence of foraminiferal taxa with a northern Paleo-Tethyan affinity and evidence for arid conditions in the terrestrial hinterland place the Alborz Basin at lower latitudes than the approximately 45ο–50ο southern paleolatitude reported thus far

Sedimentologic and paleoclimatic reconstructions of carbonate factory evolution in the Alborz Basin (northern Iran) indicate a global response to Early Carboniferous (Tournaisian) glaciations

© 2016 Elsevier B.V.The Lower Carboniferous Mobarak Formation records the development of a storm-sensitive pervasive carbonate factory on the southern Paleo-Tethyan passive margin following the opening of the Paleo-Tethys Ocean into the Alborz Basin along the northern margin of Gondwana. Its depositional facies encompass inner ramp peritidal environments, peloidal to crinoidal shoals, storm to fair-weather influenced mid-ramps, proximal to distal shell beds and low energy outer ramps. Sedimentological analyses and foraminiferal biostratigraphy reveal four events affecting carbonate platform evolution in the Alborz Basin during the Lower Carboniferous: (1) A transgression following global temperature rise in the Early Tournaisian (middle Hastarian) caused the formation of thick-bedded argillaceous limestones. This interval correlates with Early Tournaisian nodular to argillaceous limestones in the Moravia Basin (Lisen Formation, Czech Republic), the Dinant Basin (Pont d'Arcole Formation, Belgium), and at the Rhenish Slate Mountains (Lower Alum shale, Germany). (2) Late Hastarian–early Ivorian glaciations previously identified in Southern Gondwana but had not yet recognized in Northern Gondwana were recorded through a sequence boundary. (3) During the Late Tournaisian–Early Visean?, a differential block faulting regime along the basin's margin caused uplift of the westernmost parts of the Alborz Basin and resulted in subsidence in the eastern part of the central basin. This tectonically controlled shift in depositional regime caused vast sub-aerial exposure and brecciation preserved in the top of the Mobarak Formation in the western portion of the Central Alborz Basin. (4) Tectonic activity coinciding with a progressive, multiphase sea level drop caused indirectly by the Viséan and Serpukhovian glaciations phases ultimately led to the stagnation of the carbonate factory. Paleothermometry proxies, the presence of foraminiferal taxa with a northern Paleo-Tethyan affinity and evidence for arid conditions in the terrestrial hinterland place the Alborz Basin at lower latitudes than the approximately 45ο–50ο southern paleolatitude reported thus far

Buckling and first-ply failure optimization of stiffened variable angle tow panels

A computationally efficient two-level design methodology is developed for the optimization of stiffened compression loaded panels having variable stiffness panels as their skin. In the first step extensive bay panel optimization is performed using a Rayleigh-Ritz energy method coupled with a specialized Genetic Algorithm. Results in agreement with lamination parameter optima are achieved by employing distinct steered-fiber configurations in different layers. Additionally, a local equivalent laminate robustness constraint is applied, and it is shown to have detrimental effect on the buckling performance of variable stiffness layups. The optimal results obtained are used to characterize the plate buckling response in laminate stiffness space. An approximate analytical model is developed to analyze the buckling-related failure modes of the stiffened panel. Panels are optimized for a variety of configurations and loads. Variable stiffness designs achieve up to 20% weight reduction compared to their straight fiber counterparts, while 5-7% improvements are possible when a local 10% rule is enforced. Varying the fiber orientation is also shown to increase the weight-optimal stiffener spacing. The results indicate that the application of the concept is most promising for lightly loaded configuration, which are driven primarily by buckling, and not material failure. Alternatively, high weight savings are achieved in cases where large stiffener spacing is enforced by non-performance related requirements.Aerospace Structures & Computational MechanicsAerospace Engineerin

Damage resistance of dispersed-ply laminates

This paper presents the design procedure of a quasi-isotropic (QI) laminate employing dispersion of ply orientations. The goal is to improve damage resistance of a laminate under low velocity impact (LVI). The LVI is treated as a quasi-static loading and instead of a plate a laminated beam is considered. Therefore, this situation simplifies the problem to an interlaminar shear (ILS) test. Although the specimen might experience several failure mechanism, only delamination which influence the load carrying capability of it drastically under compression after impact (CAI) is considered here. By studying the interlaminar shear stresses through the thickness of the laminate, initiation of crack can be inspected in every layer using a quadratic initiation criterion (QIC). Finally, employing a modified ant colony optimization (ACO) algorithm (two-pheromone ACO algorithm) a fully dispersed QI laminate is designed. The domain of the orientation angles is between -85º to 90º with a 5º interval. The results showed that the interface angles does not present a decisive influence on the crack onset. On the other hand, the dispersion tends to have as large as possible angles near the middle of the laminate to minimize the maximum value of QIC, and some small angles in the outside to provide enough bending stiffness.Aerospace Structures & MaterialsAerospace Engineerin

Dispersed-ply design and optimization to improve the brittle flexural behaviour of composite laminates

This work aims to improve the flexural behaviour of unidirectional fibre-reinforced laminates by means of coupling an optimization procedure for quasi-isotropic configurations with the design space opened by dispersed-ply orientations. The design approach consists of finding suitable alternatives to traditional laminates (with fibre orientations limited to 0°, ±45∘, and 90°), while maintaining their stiffness characteristics. This strategy isolates the interlaminar response as the objective function that is optimized to improve their flexural behaviour. To this end, a modified Ant Colony Optimization was implemented and geared towards optimizing the interlaminar stress profile, allowing plies at every possible 5° orientation, with the ultimate goal of delaying delamination. To validate the approach, a traditional reference laminate and derived fully dispersed designs were experimentally tested. The correlated responses show that it was not possible to improve flexural resistance. However, the typical flexural brittleness of laminates can be modified into a pseudo-ductile behaviour.Aerospace Structures & Computational Mechanic

Tectonically controlled sedimentation: impact on sediment supply and basin evolution of the Kashafrud Formation (Middle Jurassic, Kopeh-Dagh Basin, northeast Iran)

peer reviewedThe Kashafrud Formation was deposited in the extensional Kopeh-Dagh Basin during the Late Bajocian to Bathonian (Middle Jurassic) and is potentially the most important siliciclastic unit from NE Iran for petroleum geology. This extensional setting allowed the accumulation of about 1,700 m of siliciclastic sediments during a limited period of time (Upper Bajocian–Bathonian). Here, we present a detailed facies analysis combined with magnetic susceptibility (MS) results focusing on the exceptional record of the Pol-e-Gazi section in the southeastern part of the basin. MS is classically interpreted as related to the amount of detrital input. The amount of these detrital inputs and then the MS being classically influenced by sea-level changes, climate changes and tectonic activity. Facies analysis reveals that the studied rocks were deposited in shallow marine, slope to pro-delta settings. A major transgressive–regressive cycle is recorded in this formation, including fluvial-dominated delta to turbiditic pro-delta settings (transgressive phase), followed by siliciclastic to mixed siliciclastic and carbonate shoreface rocks (regressive phase). During the transgressive phase, hyperpycnal currents were feeding the basin. These hyperpycnal currents are interpreted as related to important tectonic variations, in relation to significant uplift of the hinterland during opening of the basin. This tectonic activity was responsible for stronger erosion, providing a higher amount of siliciclastic input into the basin, leading to a high MS signal. During the regressive phase, the tectonic activity strongly decreased. Furthermore, the depositional setting changed to a wave- to tide-dominated, mixed carbonate–siliciclastic setting. Because of the absence of strong tectonic variations, bulk MS was controlled by other factors such as sea-level and climatic changes. Fluctuations in carbonate production, possibly related to sea-level variations, influenced the MS of the siliciclastic/carbonate cycles. Carbonate intervals are characterized by a strong decrease of MS values indicates a gradual reduction of detrital influx. Therefore, the intensity of tectonic movement is thought to be the dominant factor in controlling sediment supply, changes in accommodation space and modes of deposition throughout the Middle Jurassic sedimentary succession in the Pol-e-Gazi section and possibly in the Kopeh-Dagh Basin in general