| 1. |
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| 2. |
- Klionsky, Daniel J., et al.
(författare)
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Guidelines for the use and interpretation of assays for monitoring autophagy
- 2012
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Ingår i: Autophagy. - : Informa UK Limited. - 1554-8635 .- 1554-8627. ; 8:4, s. 445-544
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Forskningsöversikt (refereegranskat)abstract
- In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process vs. those that measure flux through the autophagy pathway (i.e., the complete process); thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from stimuli that result in increased autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field.
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| 3. |
- Abolfathi, Bela, et al.
(författare)
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The Fourteenth Data Release of the Sloan Digital Sky Survey : First Spectroscopic Data from the Extended Baryon Oscillation Spectroscopic Survey and from the Second Phase of the Apache Point Observatory Galactic Evolution Experiment
- 2018
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Ingår i: Astrophysical Journal Supplement Series. - : IOP Publishing Ltd. - 0067-0049 .- 1538-4365. ; 235:2
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Tidskriftsartikel (refereegranskat)abstract
- The fourth generation of the Sloan Digital Sky Survey (SDSS-IV) has been in operation since 2014 July. This paper describes the second data release from this phase, and the 14th from SDSS overall (making this Data Release Fourteen or DR14). This release makes the data taken by SDSS-IV in its first two years of operation (2014-2016 July) public. Like all previous SDSS releases, DR14 is cumulative, including the most recent reductions and calibrations of all data taken by SDSS since the first phase began operations in 2000. New in DR14 is the first public release of data from the extended Baryon Oscillation Spectroscopic Survey; the first data from the second phase of the Apache Point Observatory (APO) Galactic Evolution Experiment (APOGEE-2), including stellar parameter estimates from an innovative data-driven machine-learning algorithm known as "The Cannon"; and almost twice as many data cubes from the Mapping Nearby Galaxies at APO (MaNGA) survey as were in the previous release (N = 2812 in total). This paper describes the location and format of the publicly available data from the SDSS-IV surveys. We provide references to the important technical papers describing how these data have been taken (both targeting and observation details) and processed for scientific use. The SDSS web site (www.sdss.org) has been updated for this release and provides links to data downloads, as well as tutorials and examples of data use. SDSS-IV is planning to continue to collect astronomical data until 2020 and will be followed by SDSS-V.
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| 4. |
- Nicolas, Aude, et al.
(författare)
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Genome-wide Analyses Identify KIF5A as a Novel ALS Gene
- 2018
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Ingår i: Neuron. - : Cell Press. - 0896-6273 .- 1097-4199. ; 97:6, s. 1268-1283.e6
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Tidskriftsartikel (refereegranskat)abstract
- To identify novel genes associated with ALS, we undertook two lines of investigation. We carried out a genome-wide association study comparing 20,806 ALS cases and 59,804 controls. Independently, we performed a rare variant burden analysis comparing 1,138 index familial ALS cases and 19,494 controls. Through both approaches, we identified kinesin family member 5A (KIF5A) as a novel gene associated with ALS. Interestingly, mutations predominantly in the N-terminal motor domain of KIF5A are causative for two neurodegenerative diseases: hereditary spastic paraplegia (SPG10) and Charcot-Marie-Tooth type 2 (CMT2). In contrast, ALS-associated mutations are primarily located at the C-terminal cargo-binding tail domain and patients harboring loss-of-function mutations displayed an extended survival relative to typical ALS cases. Taken together, these results broaden the phenotype spectrum resulting from mutations in KIF5A and strengthen the role of cytoskeletal defects in the pathogenesis of ALS.
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| 5. |
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The Seventeenth Data Release of the Sloan Digital Sky Surveys : Complete Release of MaNGA, MaStar, and APOGEE-2 Data
- 2022
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Ingår i: Astrophysical Journal Supplement Series. - : Institute of Physics (IOP). - 0067-0049 .- 1538-4365. ; 259:2
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Tidskriftsartikel (refereegranskat)abstract
- This paper documents the seventeenth data release (DR17) from the Sloan Digital Sky Surveys; the fifth and final release from the fourth phase (SDSS-IV). DR17 contains the complete release of the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey, which reached its goal of surveying over 10,000 nearby galaxies. The complete release of the MaNGA Stellar Library accompanies this data, providing observations of almost 30,000 stars through the MaNGA instrument during bright time. DR17 also contains the complete release of the Apache Point Observatory Galactic Evolution Experiment 2 survey that publicly releases infrared spectra of over 650,000 stars. The main sample from the Extended Baryon Oscillation Spectroscopic Survey (eBOSS), as well as the subsurvey Time Domain Spectroscopic Survey data were fully released in DR16. New single-fiber optical spectroscopy released in DR17 is from the SPectroscipic IDentification of ERosita Survey subsurvey and the eBOSS-RM program. Along with the primary data sets, DR17 includes 25 new or updated value-added catalogs. This paper concludes the release of SDSS-IV survey data. SDSS continues into its fifth phase with observations already underway for the Milky Way Mapper, Local Volume Mapper, and Black Hole Mapper surveys.
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| 6. |
- Kenna, Kevin P., et al.
(författare)
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NEK1 variants confer susceptibility to amyotrophic lateral sclerosis
- 2016
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Ingår i: Nature Genetics. - : Springer Science and Business Media LLC. - 1061-4036 .- 1546-1718. ; 48:9, s. 1037-1042
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Tidskriftsartikel (refereegranskat)abstract
- To identify genetic factors contributing to amyotrophic lateral sclerosis (ALS), we conducted whole-exome analyses of 1,022 index familial ALS (FALS) cases and 7,315 controls. In a new screening strategy, we performed gene-burden analyses trained with established ALS genes and identified a significant association between loss-of-function (LOF) NEK1 variants and FALS risk. Independently, autozygosity mapping for an isolated community in the Netherlands identified a NEK1 p.Arg261 His variant as a candidate risk factor. Replication analyses of sporadic ALS (SALS) cases and independent control cohorts confirmed significant disease association for both p.Arg261 His (10,589 samples analyzed) and NEK1 LOF variants (3,362 samples analyzed). In total, we observed NEK1 risk variants in nearly 3% of ALS cases. NEK1 has been linked to several cellular functions, including cilia formation, DNA-damage response, microtubule stability, neuronal morphology and axonal polarity. Our results provide new and important insights into ALS etiopathogenesis and genetic etiology.
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| 7. |
- Koyi, Hemin, et al.
(författare)
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Numerical models of ductile rebound of crustal roots beneath mountain belts
- 1999
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Ingår i: Geophysical Journal International. - : Blackwell Publishing. - 0956-540X .- 1365-246X. ; 139:2, s. 556-562
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Crustal roots formed beneath mountain belts are gravitationally unstable structures, which rebound when the lateral forces that created them cease or decrease significantly relative to gravity. Crustal roots do not rebound as a rigid body, but undergo intensive internal deformation during their rebound and cause intensive deformation within the ductile lower crust. 2-D numerical models are used to investigate the style and intensity of this deformation and the role that the viscosities of the upper crust and mantle lithosphere play in the process of root rebound. Numerical models of root rebound show three main features which may be of general application: first, with a low-viscosity lower crust, the rheology of the mantle lithosphere governs the rate of root rebound; second, the amount of dynamic uplift caused by root rebound depends strongly on the rheologies of both the upper crust and mantle lithosphere; and third, redistribution of the rebounding root mass causes pure and simple shear within the lower crust and produces subhorizontal planar fabrics which may give the lower crust its reflective character on many seismic images.
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| 8. |
- Treat, Claire C., et al.
(författare)
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Widespread global peatland establishment and persistence over the last 130,000 y
- 2019
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 116:11, s. 4822-4827
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Tidskriftsartikel (refereegranskat)abstract
- Glacial-interglacial variations in CO2 and methane in polar ice cores have been attributed, in part, to changes in global wetland extent, but the wetland distribution before the Last Glacial Maximum (LGM, 21 ka to 18 ka) remains virtually unknown. We present a study of global peatland extent and carbon (C) stocks through the last glacial cycle (130 ka to present) using a newly compiled database of 1,063 detailed stratigraphic records of peat deposits buried by mineral sediments, as well as a global peatland model. Quantitative agreement between modeling and observations shows extensive peat accumulation before the LGM in northern latitudes (> 40 degrees N), particularly during warmer periods including the last interglacial (130 ka to 116 ka, MIS 5e) and the interstadial (57 ka to 29 ka, MIS 3). During cooling periods of glacial advance and permafrost formation, the burial of northern peatlands by glaciers and mineral sediments decreased active peatland extent, thickness, and modeled C stocks by 70 to 90% from warmer times. Tropical peatland extent and C stocks show little temporal variation throughout the study period. While the increased burial of northern peats was correlated with cooling periods, the burial of tropical peat was predominately driven by changes in sea level and regional hydrology. Peat burial by mineral sediments represents a mechanism for long-term terrestrial C storage in the Earth system. These results show that northern peatlands accumulate significant C stocks during warmer times, indicating their potential for C sequestration during the warming Anthropocene.
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| 9. |
- Abirifard, Mahmoud, et al.
(författare)
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Jahani Salt Diapir, Iran : hydrogeology, karst features and effect on surroundings environment
- 2017
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Ingår i: International Journal of Speleology. - 0392-6672 .- 1827-806X. ; 46:3, s. 445-457
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Tidskriftsartikel (refereegranskat)abstract
- The Jahani Salt Diapir (JSD), with an area of 54 km(2), is an active diapir in the Simply Folded Belt of the Zagros Orogeny, in the south of Iran. Most of the available studies on this diapir are focused on tectonics. The hydrogeology, schematic model of flow direction and hydrochemical effects of the JSD on the adjacent water resources are lacking, and thus, are the focus of this study. The morphology of the JSD was reevaluated by fieldwork and using available maps. The physicochemical characteristics of the springs and hydrometric stations were also measured. The vent of the diapir is located 250 m higher than the surrounding glaciers, and covered by small polygonal sinkholes (dolines). The glacier is covered by cap soils, sparse trees and pastures, and contains large sinkholes, numerous shafts, several caves, and 30 brine springs. Two main groups of caves were distinguished. Sub-horizontal or inclined stream passages following the surface valleys and vertical shafts (with short inlet caves) at the bottoms of nearly circular blind valleys. Salt exposure is limited to steep slopes. The controlling variables of flow route within salt diapirs are the negligible porosity of the salt rocks at depth more than about ten meters below the ground surface and the rapid halite saturation along the flow route. These mechanisms prevent deep cave development and enforce the emergence points of brine springs with low flow rates and small catchment area throughout the JSD and above the local base of erosion. Tectonics do not affect karst development, because the distributions of sinkholes and brine springs show no preferential directions. The type of spring water is sodium chloride, with a TDS of 320 g/l, and saturated with halite, gypsum, calcite and dolomite. The water balance budget of the JSD indicates that the total recharge water is 1.46 MCM (million cubic meter)/a, emerges from 30 brine springs, two springs from the adjacent karstic limestone, and flows into the Firoozabad River (FR) and the adjacent alluvium aquifer. The FR cuts through the northern margin of the salt diapir, dissolving the glacier salts at the contact with JSD, increasing the halite concentration of the 17.7 MCM/a of the FR from 100 mg/l to 12,000 mg/l. This is a permanent process because the active glacier flows rapidly down the steep slopes into the river gorge from the nearby vent. The possible relocation of the FR channel would enhance the FR water quality, but disrupt the natural beauty of the diapir.
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| 10. |
- Aftabi, Pedram, et al.
(författare)
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InSAR mapping and modelling of an active Iranian salt extrusion
- 2010
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Ingår i: Journal of the Geological Society. - : Geological Society of London. - 0016-7649 .- 2041-479X. ; 167:1, s. 155-170
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Tidskriftsartikel (refereegranskat)abstract
- Interferometric synthetic aperture radar (InSAR) imaging is a powerful technique that is increasingly used to extract detailed 3D information on Earth surface structures, including exposed diapiric surfaces. We have used InSAR to map, for the first time, the cumulative surface deformation in a 6 km × 3 6 km region surrounding an active salt diapir (Syahoo) and its associated surface salt flow (or namakier) exposed in the Zagros Mountains of southern Iran. Images provided by the European Space Agency were acquired in 12 increments (ranging in length between 35 and 1248 days) over a 14 year interval between July 1992 and May 2006. The deformation of the salt surface is non-steady, with (extrapolated) rates of displacement varying between surficial uplifts of +1.4 mm day-1 (+511 mm a-1) and subsidence of -2.2 mm day-1 (-803 mm a-1). Growth of a central topographic dome occurs following short wet intervals to create a salt fountain morphology, which then slowly decays during the intervening long dry periods. Salt associated with dynamic 'bulging' of the central dome during wet intervals may flow laterally via gravity spreading into the surrounding salt sheet, resulting in deflation and subsidence of the dome, which is counteracted by growth and inflation of the adjacent namakiers. Salt 'bulges' that migrate down the namakier, resulting in local inflationary and deflationary cycles of the surface, may be regarded as episodic pulses of gravity spreading. Areas of inflation and deflation are also observed to commonly reverse during dry to wet periods, as the overall salt system effectively self regulates as it continually strives for dynamic equilibrium. As long as the source of salt remains undepleted, gravity spreading of the dome ultimately results in more buoyancy-driven salt flowing up the diapiric neck to replenish and feed the extrusion and maintain the gross fountain morphology.
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| 11. |
- Bahroudi, A, et al.
(författare)
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Effect of ductile and frictional decollements on style of extension
- 2003
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Ingår i: Journal of Structural Geology. - 0191-8141 .- 1873-1201. ; 25:9, s. 1401-1423
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Tidskriftsartikel (refereegranskat)abstract
- Scaled analogue models were used to study the effect of frictional and ductile detachments on thin-skinned extension. Models consisted of two halves; one half is the ductile and the other has a frictional detachment. Extension occurred above two different basal configurations: a stretchable rubber sheet and a folded, banded sheet intended to produce homogeneous and heterogeneous extension, respectively. Model parameters varied systematically and included the brittle/ductile thickness ratio, rheologies, and bulk strain. Structures in the two halves are compared in profiles and plan views. A series of graben developed above both halves of models extended above a banded sheet, although there were differences in style, propagation rate and width of the deformation zone between the two halves. Different rates of propagation of structures in the two halves led to the formation of an accommodation or transfer zone parallel to the extension direction. Most relay ramps and inflection of normal faults in this zone indicate differential extension between the two halves.In contrast, in models extended above a stretchable rubber sheet, extensional structures such as horst and graben developed only above the ductile detachment. Model results indicate that heterogeneous mechanical stratigraphy and displacement rate have no effect on extensional structure above a rubber sheet. However, above 20% bulk extension, deformation becomes heterogeneous along multiple sets of conjugate faults oblique to the extension direction.
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| 12. |
- Cosgrove, John W., et al.
(författare)
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A train of kink folds in the surficial salt of Qom Kuh, Central Iran
- 2009
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Ingår i: Journal of Structural Geology. - : Elsevier BV. - 0191-8141 .- 1873-1201. ; 31:10, s. 1212-1222
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Tidskriftsartikel (refereegranskat)abstract
- The many subaerial extrusions of salt current in Iran are smaller and faster versions of steady state extrusions of metamorphic rocks from crustal channels in mountain chains. The extruded salt develops a variety of internal folds as the salt accumulates ductile displacements that can reach metres a year. Weather-induced elastic strains de-stress the outer layers of salt extrusions to a brittle carapace of broken dilated salt. Qom Kuh, situated in Central Iran, is a comparatively small and slow example of a viscous salt fountain and, as a result, its brittle elastic carapace may be thicker than most This may account for Qom Kuh being the only salt fountain known to have a train of 10 m scale kink folds in its surficial salt. We attribute these folds to lateral shortening and back-shear of a surface-parallel planar mechanical anisotropy in the surficial salt induced by gravitationally driven ductile flow of the underlying salt. When it is dry, the elastic carapace is relatively strong and acts as a stiff corset impeding gravity spreading of the underlying confined salt. However, the carapace weakens and kinks on wetting, allowing the underlying salt to gravity spread. These folds illustrate how the weather can affect gravity spreading of surficial salt masses and how complex the interplay of tectonic and climatic signals can be in "steady state" mountains.
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| 13. |
- Ghasemi, A, et al.
(författare)
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A new tectonic scenario fro the Sanandaj-Sirjan Zone (Iran)
- 2006
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Ingår i: Journal of Asian Earth Sciences. - : Elsevier BV. - 1367-9120 .- 1878-5786. ; 26:6, s. 683-693
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Tidskriftsartikel (refereegranskat)abstract
- Recent geochemical studies of volcanic rocks forming part of the ophiolites within the Zagros and Naien-Baft orogen indicate that most of them were developed as supra-subduction ophiolites in intra-oceanic island arc environments. Intra-oceanic island arcs and ophiolites now forming the Naien-Baft zone were emplaced southwestward onto the northeastern margin of the South Sanandaj-Sirjan Zone, while those now in the High Zagros were emplaced southwestward onto the northern margin of Arabia. Thereafter, subduction continued on opposite sides of the remnant oceans. The floor of Neo-Tethys Ocean was subducted at a low angle beneath the entire Sanandaj-Sirjan Zone, and the floor of the Naien-Baft Ocean was subducted beneath the Central Iranian Micro-continent. The Naien-Baft Ocean extended into North-West Iran only temporarily. This failed ocean arm (between the Urumieh-Dokhtar Magmatic Assemblage and the main Zagros Thrust) was filled by thick Upper Triassic-Upper Jurassic sediments. The Naien-Baft Ocean finally closed in the Paleocene and Neo-Tethys closed in the Early to Middle Eocene. After Arabia was sutured to Iran. the Urumieh-Dokhtar Magmatic Assemblage recorded slab break-off in the Middle Eocene.
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| 14. |
- Hessami, Khaled, et al.
(författare)
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Active deformation within the Zagros Mountains deduced from GPS measurements
- 2006
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Ingår i: Journal of the Geological Society. - : Geological Society of London. - 0016-7649 .- 2041-479X. ; 163:1, s. 143-148
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Tidskriftsartikel (refereegranskat)abstract
- We present and interpret the results of Global Positioning System (GPS) measurements at 35 stations in and beside the Zagros Mountain belt, SW Iran, for three campaigns ending March 1998, December 1999 and June 2001. Preliminary motion estimates show clearly the change in character along the strike of the belt. Stations to the SE move at 13–22 ± 3 mm a–1 towards N 7 ± 5°E with respect to Eurasia. Most of the shortening indicated by the GPS velocities seems to occur in the SE Zagros along two major seismic zones and along the Zagros front. To the NW, stations move oblique to the trend of the belt towards N 12 ± 8°W, at 14–19 ± 3 mm a–1. Most of the shortening in the NW Zagros seems to occur along the Mountain Front Fault with its major earthquakes as well as along the Zagros front. The change in direction and magnitude of the velocity vectors across the north–south-trending Kazerun and Karebas faults involves extension of up to 4 mm a–1 along the strike of the Zagros belt.
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| 15. |
- Hessami, Khaled, et al.
(författare)
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Progressive unconformities within an evolving foreland fold-thrust belt, Zagros Mountains.
- 2001
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Ingår i: Journal of the Geological Society. - : Geological Society of London. - 0016-7649 .- 2041-479X. ; 158:6, s. 969-981
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Tidskriftsartikel (refereegranskat)abstract
- A major angular unconformity between the Bakhtyari conglomerates and the underlying Agha Jari Formation has long been interpreted as indicating that orogeny in the Zagros Simply Folded Zone took place in Plio-Pleistocene times. This study uses field evidence of unconformities between older units in conjunction with geological maps and cross sections to argue that the front of the Zagros Simply Folded Zone has propagated in time and space. These unconformities indicate that deformation started as early as end Eocene in the northeast of the Simply Folded Zone and propagated progressively to the southwest, where unconformable contacts are only seen between younger units. As shortening continued, the southwest migration of the deformation front drove the foreland basin in front of it to its present position along the Persian Gulf and Mesopotamia. The climax of orogeny took place at end Pliocene time when the most extensive unconformity in the Zagros Simply Folded Zone developed between the (upper) Bakhtyari Formation and older units. Active seismicity and documented present uplift imply that the Simply Folded Zone is still propagating southwestward.
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| 16. |
- Koyi, Hemin, et al.
(författare)
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Analogue models of salt diapirs and seismic interpretation in the Nordkapp Basin, Norway
- 1995
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Ingår i: Petroleum Geoscience. - : Geological Society of London. - 1354-0793 .- 2041-496X. ; 1:2, s. 185-192
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Tidskriftsartikel (refereegranskat)abstract
- Dynamically scaled analogue models with an overburden of cohesive sand and a viscous "salt" layer were deformed in a centrifuge to mimic real salt structures in the Nordkapp Basin. Like their natural prototypes, model diapirs were aligned in rows parallel to the basin margins. In profile, model diapirs were asymmetric, suggesting that the real diapirs will possess asymmetric geometries. Like many of the real salt structures, model diapirs pierced without developing a pillow stage because they rose along basin margin faults which propagated up through the overburden from the basement during thick-skinned extension. Once their overburden was weakened by faulting, differential loading forced model diapirs to rise as long as buoyant material was supplied. Some real salt diapirs initially rose as conformable pillows during the early Triassic, became diapiric during middle Triassic and spread broad overhangs during slow sedimentation in late Triassic and Jurassic times. Later, the overhangs reactivated asymmetrically when buried by Cretaceous and Tertiary sediments.
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| 17. |
- Koyi, Hemin, et al.
(författare)
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Salt diapirs of the southwest Nordkapp Basin : analogue modelling
- 1993
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Ingår i: Tectonophysics. - 0040-1951 .- 1879-3266. ; 228:3-4, s. 167-187
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Tidskriftsartikel (refereegranskat)abstract
- The geometry and evolution of the salt diapirs in the southwestern segment of the Nordkapp Basin (SW NKB) were interpreted on reflection seismic data. Reflection seismic profiles were used to build a dynamically scaled model analogue to study salt tectonics of the basin. The model was prepared using lengths, densities, and sedimentary histories obtained from seismic and well data. Model results suggest that the salt structures in the SW NKB were influenced by basement faults that horizontally stretched and faulted their overburden and induced salt flow by differential loading. Model diapirs rose only where the overburden was faulted. The salt structures are aligned in two NE-SW rows that parallel the major basement faults that outline the basin. Carboniferous salt in the SW NKB formed conformable pillows in the Early Triassic (Scythian), which became diapiric during the late Early and Middle Triassic. The salt diapirs spread to form asymmetric broad overhangs at superficial levels during slow sedimentation in Late Triassic and/or Jurassic. Diapir overhangs were later reactivated because of burial by Cretaceous and Tertiary sediments. Basement faults were mapped by comparing thickness of the sediments and/or level of the reflectors on either side of the diapirs that had relatively narrow overhangs. Depth conversion and restoration of velocity pull-up of reflectors beneath salt diapirs suggest that the salt diapirs of the SW NKB have broad overhangs above narrow stems.
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| 18. |
- Koyi, Hemin, et al.
(författare)
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Salt tectonics in the north-eastern Nordkapp Basin, south-western Barents Sea.
- 1995
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Ingår i: American Association of Petroleum Geologists Bulletin Memoir. ; 65, s. 437-447
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Tidskriftsartikel (refereegranskat)abstract
- Salt structures in the northeastern Nordkapp subbasin are interpreted on reflection seismic profiles. Thickness variations indicate localized accumulation of the mother salt in Late Carboniferous-Early Permian time. Rapid sedimentation in the Early Triassic accompanied rise of salt into asymmetric salt pillows during regional extension. These pillows domed the prekinematic Permian sediments and became diapiric during the late Early-Middle Triassic, perhaps as a result of thin-skinned normal faulting decoupled by the salt from old basement faults reactivated by thick-skinned regional (northwest-southeast) extension.Variations in size, maturity, and evolution history of individual salt structures can be attributed to local differences in thickness of the initial salt layer and its burial history. Salt structures form three rows concentric to the basin margins and cover ~ 20% of the basin area. Some salt stocks appear to overlie basement faults. Asymmetric primary, secondary, and in places tertiary, peripheral sinks indicate that salt was withdrawn mainly from the basin side of most diapirs throughout Triassic downbuilding.The ratio of net salt rise rate to net aggradation rate (/) increased slowly from <1 to >1 during Middle Triassic time and increased markedly during slow sedimentation in the Late Triassic and Jurassic. By Jurassic time, more than 18 enormous salt fountains extruded downslope and spread a partial salt canopy in the central and northern parts of the northeastern subbasin. Larger and more widely spaced salt extrusions in the northeastern subbasin spread significantly farther than their equivalents in the southwestern subbasin, where Triassic subsidence or downbuilding was slower. Salt extrusion (and perhaps dissolution) ceased during Cretaceous burial but probably resumed locally in the late Tertiary. Salt loss during Cretaceous-Tertiary reactivation of salt rise reduced the area of the salt canopy. Surviving remnants of the salt canopy may still trap any pre-Jurassic hydrocarbons despite hydrocarbon venting throughout the Arctic during Tertiary uplift.
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| 19. |
- Koyi, Hemin, et al.
(författare)
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Shear zones between rock units with no relative movement
- 2013
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Ingår i: Journal of Structural Geology. - : Elsevier BV. - 0191-8141 .- 1873-1201. ; 50:SI, s. 82-90
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Tidskriftsartikel (refereegranskat)abstract
- Shear zones are normally viewed as relatively narrow deformation zones that accommodate relative displacement between two “blocks” that have moved past each other in opposite directions. This study reports localized zones of shear between adjacent blocks that have not moved past each other. Such deformation zones, which we call wakes, form due to the movement of exotic blocks within a viscous medium (denser blocks sinking within a salt structure, (the paths) between separated boudins), melt in partially molten surroundings (melt movement during migmatisation), or solid blocks sinking through a partially molten magma body (stoping). From the fluid dynamics perspective these shear zones can be regarded as low Reynolds number deformation zones within the wake of a body moving through a viscous medium. While compact moving bodies (aspect ratio 1:1:1) generate axial symmetric (cone like) shear zones or wakes, elongated bodies (vertical plates or horizontal rod-like bodies) produce tabular shear zones or wakes. Unlike conventional shear zones across which shear indicators usually display consistent symmetries, shear indicators on either side of the shear zone or wake reported here show reverse kinematics. Thus profiles exhibit shear zones with opposed senses of movement across their center-lines or -planes.We have used field observations and results from analytical and numerical models to suggest that examples of wakes are the transit paths that develop where denser blocks sink within salt structures, bodies of melt rise through migmatites, between boudins separated by progressive extension and (perhaps) where slabs of subducted oceanic lithosphere delaminate from the continental crust and sink into the asthenosphere. We also argue that such shear zones may be more common than they have been given credit for and may be responsible for some reverse kinematics reported in shear zones.
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| 20. |
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| 21. |
- Mukherjee, Soumyajit, et al.
(författare)
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Estimation of salt Viscosity in the Hormuz- & the Namakdan Salt Diapirs, Persian Gulf
- 2007
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Ingår i: Annual Transactions - The Nordic Rheology Society. - 1601-4057. ; 15, s. 189-196
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Tidskriftsartikel (refereegranskat)abstract
- The Hormuz- and the Namakdan salt diapirs extrude as parabolic profiles in the last 10 4 years. Velocity profiles of salts extruding through these diapirs are derived assuming Newtonian viscous flow of salts. Viscosity of salt in these diapirs are calculated to be 10 18-10 21 Pa s and10 17-10 21 Pa s, respectively.
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| 22. |
- Mukherjee, Soumyajit, et al.
(författare)
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Implications of channel flow analogue models for extrusion of the Higher Himalayan Shear Zone with special reference to the out-of-sequence thrusting
- 2012
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Ingår i: International journal of earth sciences. - : Springer Science and Business Media LLC. - 1437-3254 .- 1437-3262. ; 101:1, s. 253-272
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Tidskriftsartikel (refereegranskat)abstract
- The Higher Himalayan Shear Zone (HHSZ) contains a ductile top-to-N/NE shear zone-the South Tibetan detachment system-lower (STDS(L)) and an out-of-sequence thrust (OOST) as well as a top-to-N/NE normal shear at its northern boundary and ubiquitously distributed compressional top-to-S/SW shear throughout the shear zone. The OOST that was active between 22 Ma and the Holocene, varies in thickness from 50 m to 6 km and in throw from 1.4 to 20 km. Channel flow analogue models of this structural geology were performed in this work. A Newtonian viscous polymer (PDMS) was pushed through a horizontal channel leading to an inclined channel with parallel and upward-diverging boundaries analogous to the HHSZ and allowed to extrude to the free surface. A top-to-N/NE shear zone equivalent to the STDS(U) developed spontaneously. This also indirectly connotes an independent flow confined to the southern part of the HHSZ gave rise to the STDS(L). The PDMS originally inside the horizontal channel extruded at a faster rate through the upper part of the inclined channel. The lower boundary of this faster PDMS defined the OOST. The model OOST originated at the corner and reached the vent at positions similar to the natural prototype some time after the channel flow began. The genesis of the OOST seems to be unrelated to any rheologic contrast or climatic effects. Profound variations in the flow parameters along the HHSZ and the extrusive force probably resulted in variations in the timing, location, thickness and slip parameters of the OOST. Variation in pressure gradient within the model horizontal channel, however, could not be matched with the natural prototype. Channel flow alone presumably did not result in southward propagation of deformation in the Himalaya.
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| 23. |
- Mukherjee, S., et al.
(författare)
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Viscosity estimates of salt in the Hormuz and Namakdan salt diapirs, Persian Gulf
- 2010
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Ingår i: Geological Magazine. - : Cambridge University Press. - 0016-7568 .- 1469-5081. ; 147:4, s. 497-507
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Tidskriftsartikel (refereegranskat)abstract
- The parabolic surface profiles of the Hormuz and Namakdan salt diapirs in the Persian Gulf suggest that they have been extruding with Newtonian viscous rheologies for the last 104 years. We derive velocity profiles for these diapirs, neglecting gravitational spreading and erosion/dissolution while assuming incompressible Newtonian rheology of the salt. Fitting known rates of extrusion at specific points in its elliptical cross-section, the dynamic viscosity of the salt of the Hormuz diapir is found to range between 1018 and 1021 Pa s. Approximating its sub-circular cross-section to a perfect circle, the range of viscosity of the salt of the Namakdan diapir is obtained as 1017–1021 Pa s. These calculated viscosities fall within the range for naturally flowing salts elsewhere and for other salt diapirs but are broader than those for salts with Newtonian rheology deforming at room temperatures. The salts of the Hormuz and Namakdan diapirs are expected to exhibit a broader range of grain size, which matches the limited existing data.
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| 24. |
- Mulchrone, Kieran F., et al.
(författare)
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Constraining the strain ellipsoid and deformation parameters using deformed single layers : A computational approach assuming pure shear and isotropic volume change
- 2014
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Ingår i: Journal of Structural Geology. - : Elsevier BV. - 0191-8141 .- 1873-1201. ; 62, s. 194-206
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Tidskriftsartikel (refereegranskat)abstract
- If the deformation history of individual layers in a deformed rock mass can be appropriately analysed and categorised then the surface of no elongation (snoe) and the surface of no infinitesimal elongation (snoie) may be identified. A computational approach to automatically identify the polar snoe and snoie is presented and tested on synthetic and natural examples. Additionally the equations that allow extraction of parameter values, which quantify the deformation, are derived here. Two fundamental assumptions are made: 1) the progressive deformation is pure shear and 2) the associated volume change is isotropic. The proposed method is tested using data generated from known deformation sequences and is found to work reasonably well. However, as is the case with most methods of analysis, suitable data with a wide range of orientations is required for reliable results.
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| 25. |
- Mulchrone, Kieran F., et al.
(författare)
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Strain estimation in 3D by fitting linear and planar data to the March model
- 2016
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Ingår i: Tectonophysics. - : Elsevier BV. - 0040-1951 .- 1879-3266. ; 686, s. 63-67
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Tidskriftsartikel (refereegranskat)abstract
- The probability density function associated with the March model is derived and used in a maximum likelihood method to estimate the best fit distribution and 3D strain parameters for a given set of linear or planar data. Typically it is assumed that in the initial state (pre-strain) linear or planar data are uniformly distributed on the sphere which means the number of strain parameters estimated needs to be reduced so that the numerical technique succeeds. Essentially this requires that the data are rotated into a suitable reference frame prior to analysis. The method has been applied to a suitable example from the Dalradian of SW Scotland and results obtained are consistent with those from an independent method of strain analysis. Despite March theory having been incorporated deep into the fabric of geological strain analysis, its full potential as a simple direct 3D strain analytical tool has not been achieved. The method developed here may help remedy this situation.
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| 26. |
- Nabavi, Seyed Tohid, et al.
(författare)
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Inclined transpression in the Neka Valley, eastern Alborz, Iran
- 2017
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Ingår i: International journal of earth sciences. - : SPRINGER. - 1437-3254 .- 1437-3262. ; 106:5, s. 1815-1840
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Tidskriftsartikel (refereegranskat)abstract
- Three major nappes in the Neka Valley in the eastern Alborz Mountains of Iran allow the Cimmerian to present convergence following the oblique collision between Iran and the southern margin of Eurasia. This work reports the identification of an inclined transpression zone recognized by field investigations and strain analyses of the geometries of formations and detailed mesoscopic structural analyses of multiple faults, folds and a cleavage. The main structures encountered include refolded recumbent asymmetric fold nappes, highly curved fold hinges, in a transpression zone that dips 37 degrees to the NW between boundaries thrusts striking from N050 degrees to N060 degrees. The beta angle (the angle between the zone boundary and direction of horizontal far-field shortening) is about 80 degrees. The north-west and south-east boundaries of this zone coincide with the Haji-abad thrust and the Shah-Kuh thrust, respectively. Fold axes generally trend NE-SW and step to both right and left as a result of strike-slip components of fault displacements. Strain analyses using Fry's method on macroscopic ooids and fusulina deformed into oblate ellipsoids indicate that the natural strain varies between 2.1 and 3.14. The estimated angle between the maximum instantaneous strain axis (ISA(max)) and the transpression zone boundary (theta') is between 6 degrees and 20 degrees. The estimated oblique convergence angle (alpha), therefore, ranges between 31 degrees and 43 degrees. The average kinematic vorticity number (W-k) is 0.6, in a zone of sinistral pure shear-dominated inclined triclinic transpression. These results support the applicability of kinematic models of triclinic transpression to natural brittle-ductile shear zones.
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| 27. |
- Sokoutis, Dimitrios, et al.
(författare)
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Indentation of a continent with a built-in thickness change : experiment and nature
- 2000
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Ingår i: Tectonophysics. - 0040-1951 .- 1879-3266. ; 320:3-4, s. 243-270
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Tidskriftsartikel (refereegranskat)abstract
- Orogens oblique to the direction of plate convergence are currently attributed to obliquity between the margins of one or both of the sutured continents to their direction convergence. We use a single analogue experiment and natural examples to illustrate a potential additional factor: variations in strength of the indented continent at a high angle to the convergence direction. The wavelengths of structures in laterally shortened lithosphere depend on the strength of the most competent layers. Lateral variations in crustal thickness must therefore lead to structures oblique to any applied lateral compression.An analogue experiment was performed to explore this phenomenon. A two-layer ‘indented continent’ was modelled by a brittle upper crust of sand above a lower crust of high-viscosity polymer floating on a single layer of low-viscosity syrup representing the mantle. The well-known strike-slip structures allowing lateral escape to distant weak boundaries were hindered by lateral boundaries in front of the indenter. This allowed us to focus on the effects of a thickness change built into the ‘indented continent’ along a zone parallel to the direction in which a vertical rigid wall advancing at a steady rate represented the indenter. Vertical escape led to an ‘orogenic belt’ oblique to the advancing wall; this obliquity influences subsequent lateral escape. Model scaling and interpretations are based on Extended Thin Sheet Approximation (ETSA) and standard theories of faulting.Four sectors of the Alpine–Himalayan orogen (Iran, Tunisia, the Eastern Alps and the Himalaya) are oblique to the continental convergence direction, and we point to thickness changes at high angles to the suture that may account for this geometry. As crustal thicknesses north of oblique sectors of the Himalayas are not yet known, we speculate on them.We infer from the main difference between our experiment and all our examples chosen from nature that vertical orogenic escape was oblique to our model suture but can be parallel to natural sutures.
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| 28. |
- Solé Navais, Pol, et al.
(författare)
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Genetic effects on the timing of parturition and links to fetal birth weight.
- 2023
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Ingår i: Nature genetics. - 1546-1718. ; 55:4, s. 559-567
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Tidskriftsartikel (refereegranskat)abstract
- The timing of parturition is crucial for neonatal survival and infant health. Yet, its genetic basis remains largely unresolved. We present a maternal genome-wide meta-analysis of gestational duration (n=195,555), identifying 22 associated loci (24 independent variants) and an enrichment in genes differentially expressed during labor. A meta-analysis of preterm delivery (18,797 cases, 260,246 controls) revealed six associated loci and large genetic similarities with gestational duration. Analysis of the parental transmitted and nontransmitted alleles (n=136,833) shows that 15 of the gestational duration genetic variants act through the maternal genome, whereas 7 act both through the maternal and fetal genomes and 2 act only via the fetal genome. Finally, the maternal effects on gestational duration show signs of antagonistic pleiotropy with the fetal effects on birth weight: maternal alleles that increase gestational duration have negative fetal effects on birth weight. The present study provides insights into the genetic effects on the timing of parturition and the complex maternal-fetal relationship between gestational duration and birth weight.
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| 29. |
- Talbot, Christopher J., et al.
(författare)
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An active nappe of in Neoproterozoic rock salt
- 1998
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Ingår i: Fault-related rocks; A photographic atlas. - : Princeton University Press. - 9780691012209 ; , s. 556-557
-
Bokkapitel (refereegranskat)
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| 30. |
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| 31. |
- Talbot, Christopher J., et al.
(författare)
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Diapiric spokes pattern
- 1991
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Ingår i: Tectonophysics. - 0040-1951 .- 1879-3266. ; 188:1-2, s. 187-201
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Tidskriftsartikel (refereegranskat)abstract
- Not all finger-like diapirs evolve from or into linear walls as previously supposed. That would imply that all contemporaneous finger diapirs lie in rows and many do not. Physical models demonstrate that diapiric linear walls or rows of fingers have to be forced by lateral forces, lateral boundaries, or internal edge effects. By contrast, the kinematics of the simplest isothermal gravity overturns responsible for finger-like diapirs are geometrically, kinematically and dynamically similar to the “spoke patterns” of vigorous thermal convection. This is because Rayleigh-Taylor (RT) diapirism and Rayleigh-Bènard (RB) thermal convection are end members of a continuous dynamic spectrum due to any combination of compositional or thermally induced density inversions. All simple RT overturns are dynamically similar, but the vigour of thermal convection varies with the heat flow.The kinematics of spoke patterns are difficult to study in rapid, multiple overturns of thermal convection in low viscosity fluids. However, spoke patterns in slow, isothermal diapiric analogues can be analysed at any stage during their single overturn. Such studies indicate that two sets of spokes conduct fluids of different densities horizontally along the top and bottom boundaries to finger-like diapiric stems or plumes where they rise or sink to spread in polygonal bulbs at the opposite boundary. Spokes converge to hubs at the bottom boundary beneath stems feeding diapiric bulbs at the top boundary and vice versa. If the movement cells are considered centred on rising plumes, the cell corners are mapped by sinking plumes.The differences between spoke patterns and previously understood diapiric patterns are illustrated by geological examples with emphasis on relevance to the search for oil and gas. Physical arguments suggest that spoke patterns are probably the most common geometries of gravity-driven overturns in layered rocks of both the crust and the mantle.
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| 32. |
- Talbot, Christopher J.
(författare)
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Empirical paths of poles to planes (eppps) constrain the kinematics of geological shear zones
- 2014
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Ingår i: Journal of Structural Geology. - : Elsevier BV. - 0191-8141 .- 1873-1201. ; 66, s. 309-333
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Tidskriftsartikel (refereegranskat)abstract
- Ductile shear zones are tabular bodies of deformed rocks bound by less deformed wall rocks. This work introduces a simple empirical approach to analysing the 3D kinematics of shear zones. The orientations of pre-shear planar markers distorted across natural shear zones by local strains are systematically measured and plotted as poles on lower hemisphere equal area projections that constrain smooth empirical paths of poles to planes (eppps). Such eppps recording local strain gradients are used to fix a reference frame to the plane of greatest shear in any homogeneous bulk strain. Assuming that space can be taken as a proxy for time, the curvatures of pre-shear planar markers across shear zones are interpreted as the records of the 3D bulk strain histories of shear zones. The sig- or zig-moidal symmetries of sheared markers record different amounts of the same general strain within the same overall movement pattern (i.e. in a constant flow field) whatever its geometry or history. In effect eppps represent the strain memories of shear zones with successively inward readings recording successively younger shearing. In planes other than the bulk XY, great circle eppps indicate simple shear while hyperbolic eppps indicate pure shear. Eppps for suites of shear zones in Proterozoic gneisses in Sweden exhibit the parabolic shapes indicative of pure rather than simple shear.
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| 33. |
- Talbot, Christopher J.
(författare)
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Hydrothermal salt - but how much?
- 2008
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Ingår i: Marine and Petroleum Geology. - : Elsevier BV. - 0264-8172 .- 1873-4073. ; 25:2, s. 191-202
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Tidskriftsartikel (refereegranskat)
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| 34. |
- Talbot, Christopher J.
(författare)
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Lessons from the first 100 minimum strain ellipsoids constrained in gneisses deformed at high metamorphic grade
- 2014
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Ingår i: Earth-Science Reviews. - 0012-8252 .- 1872-6828. ; 138, s. 231-267
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Tidskriftsartikel (refereegranskat)abstract
- The Talbot 1970 method for constraining minimum strain ellipsoids has recently been updated by a computational approach and theory that can automatically constrain more complete strain ellipsoids with sufficient data. It is thus worth appreciating the lessons learned from the 100 minimum strain ellipsoids constrained mainly in gneisses deformed at high metamorphic grades published over the last four decades. In essence, the method measures the strikes and dips of either competent or incompetent active single layers with shortened or extended deformation structures (on scales of <1 m) imparted by inhomogeneous strains to constrain ellipsoids on larger scales. The data reviewed here describe the homogeneous strains of similar to 100 localities (1-200 m(2)) in 16 districts (10-similar to 200 km(2)) in 8 gneiss regions (1-200 km(2)). Relating these ellipsoids to the natural reference frames provided by structures on intervening and larger scales allows study of the dynamics of deformation geology rather than merely structural geology. Several limitations expected on (outdated) theoretical grounds were overcome so that treating deformation fields as paths on a variety of deformation plots allowed recognition of multiple deformations, rotations, volume changes and even the distinction of contemporary pure and simple shears. By restricting measurements to single layers with length/thickness ratios >10, the competence contrast between the markers and their country rocks does not affect the ellipsoids - but can be seen to affect the structures that develop on intervening and larger scales.
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| 35. |
- Talbot, Christopher J.
(författare)
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Palaeoproterozoic crustal building in NE Uto, southern Svecofennides, Sweden
- 2008
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Ingår i: GFF. - : Informa UK Limited. - 1103-5897 .- 2000-0863. ; 130, s. 49-70
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Tidskriftsartikel (refereegranskat)abstract
- Evidence is presented that the greywackes of Uto were recycled by mass flows in an accretionary prism subducting the floor of an ocean open to the east. The prism built a shelf of siliclastic sediments capped by carbonate banks that were episodically smothered by falls of silicic pyroclastic rocks as intrusions of mixed andesitic to rhyolitic melts from the follow-up magmatic arc began to convert the accretionary prism into crystalline Svecofennia at about 1904 Ma. The NE trending Uto Shear Zone (USZ) juxtaposes greywackes tectonised in two major phases at different structural levels. Two generations of porphyroblasts (andalusite cordierite garnet) indicate that greywackes south-east of the USZ were never sufficiently deep to melt. Three generations of migmatites (Migs(1-3) +/- fibrolite) indicate that similar greywackes north-west of the USZ were subducted to temperatures that partially melted them. Mig(1) leucosomes fed the older sheet granites that were foliated and deformed by the first nappes that verged westward across N-S axes during open-ocean crustal building. Mig(2) leucosomes are axial planar to upright NE trending second folds and fed the graphic pegmatites and younger granites as the region thickened during continental convergence. Mig(3) neosomes axial planar to the third folds are only local and probably contemporaneous with the late Li-RE pegmatites (1820-1815 Ga). Lateral tectonic escape along the USZ occurred along gneiss and schist zones hundreds of m wide before localising to metre-wide mylonite zones and then millimetre-wide seismic pseudotachylites. Kinking of these structures indicate the onset of tectonic constraint as Uto rose through the ductile-brittle transition zone.
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| 36. |
- Talbot, Christopher J., et al.
(författare)
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Palaeoproterozoic intraplating exposed by resultant gravity overturn near Kiruna, northern Sweden
- 1995
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Ingår i: Precambrian Research. - : Elsevier BV. - 0301-9268. ; 72:3-4, s. 199-225
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Tidskriftsartikel (refereegranskat)abstract
- The tectonic history of the Kiruna area is reexamined on the basis of four newly available digitised geophysical maps, a literature survey and some first-hand field observations.A basement complex of Archaean gneisses was unconformably overlain by a Palaeoproterozoic sequence of metabasalt, andesite and keratophyric porphyries with interstratified tuffs and sediments. The cover was then detached from its basement by an orogeny with a northerly tectonic grain. A pile of ductile nappes separated by mylonites in the east pushed westward an imbricate fold-thrust belt that may have decoupled over an evaporite unit of regional extent. Conglomerates and quartzites accumulated in a foredeep migrating in front of a wedge of emergent thrusts.The allochthonous cover then developed a vertical north-trending foliation in high-T/low-P conditions as it foundered among buoyant diapirs of remobilised granitoid basement. The near-constant lateral spacing of the centres of these diapirs, their mushroom shapes, and the absence of contemporaneous volcanic rocks, suggest that these diapirs rose in the solid state.The region continued to distort episodically even after diapir emplacement. Ductile shear zones evolved through vein systems to faults as the region cooled and was uplifted before the Cambrian. The youngest fault movements clearly displace 9000-years-old glacial deposits.Post- or late-orogenic plutons in the Kiruna area appear to be contemporaneous with syn-Svecofennian plutons further south. We therefore suggest reinstating the label Svecokarelian for the orogeny in the Kiruna area. Heat advected by melts from the mantle is invoked to account for the Archaean basement risking in two convective stages, the first as porphyritic lavas, the second as solid-state diapirs. Melts rose rapidly and erupted before the Svecokarelian orogeny, while the slower diapirs ended it. We attribute the current southwestern dip of the diapir zone to extension of Svecokarelian crust before the Svecofennian magmatic arc was built above it.
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| 37. |
- Talbot, Christopher J., et al.
(författare)
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Potash in a salt mushroom at Hormoz Island, Hormoz Strait, Iran
- 2009
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Ingår i: Ore Geology Reviews. - : Elsevier BV. - 0169-1368 .- 1872-7360. ; 35:3-4, s. 317-332
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Forskningsöversikt (refereegranskat)abstract
- Increasing volumes of potash are currently being discovered in a cluster of diapirs of Hormoz (formerly Hormuz) salt near Bandar Abbas, Iran. Most of the potash beds studied so far occur in complex recumbent folds in a salt mountain that would be difficult to exploit safely. However, Holocene marine erosion removed any salt mountains from a sub-group of near-shore Zagros diapirs and exposed their deeper structural levels. Even though these diapirs are still active, their potash deposits are likely more tractable to safe exploitation than in a salt mountain - as we make clear here for Hormoz Island. Geochemical surveys on Hormoz Island reveal two separate potash anomalies that are valuable pseudostratigraphic markers. Integrating field measurements of the attitudes of bedding with lineaments on air photos suggests that Hormoz Island consists of a mature bell- or plume-shaped mushroom diapir with potash beds wound around a toroidal axis of rotation near current exposure levels. 2D numerical models simulate the salt mushroom on Hormoz Island and its internal circulation. They also suggest that the diapir has a wide overhand above a narrow stem in this gas-rich region. We use the mushroom diapir model to outline a regional exploration strategy that has the potential of influencing the world potash market thereafter.
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| 38. |
- Talbot, Christopher J., et al.
(författare)
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Potash in salt extruded at Sar Pohl diapir, Southern Iran
- 2009
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Ingår i: Ore Geology Reviews. - : Elsevier BV. - 0169-1368 .- 1872-7360. ; 35:3-4, s. 352-366
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Forskningsöversikt (refereegranskat)abstract
- Recent progress in the search for potassium salts in Iran is outlined. After reviewing how most potassium ores form by the evaporation of seawater +/- hydrothermal brines, we focus on how most ores are deformed within salt diapirs. We summarise the history of the 150 or so diapirs of Hormoz salt emergent in the Zagros Mountains of Iran and then consider in detail the nature of potash at Sar Pohl, 60 km west of Bandar Abbas. These deposits are unique in that they occur in salt that extruded sub-aerially and spread over the surrounding ground surface via gravity-driven collapse. Mapping and drilling of the complex structural geology of Sar Pohl found the potash beds to be dispersed in distal salt but concentrated in piles of recumbent folds with axes circumferential to the mountain over lows in the vent rim. Equivalents of the curtain folds surviving in the stems of German diapirs presumably still exist beneath Sar Pohl and would be safer to mine than the recumbent folds in this soluble mountain. However, it should be possible to continuously pump water onto the exposed salt and guide the resulting brines through evaporation ponds and then a crystallization plant on the adjacent plains. This approach would accelerate natural degradation processes but harvest potash currently draining into the gulf.
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| 39. |
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| 40. |
- Zarei, M., et al.
(författare)
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Karst development on a mobile substrate: Konarsiah salt extrusion, Iran
- 2012
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Ingår i: Geological Magazine. - 0016-7568 .- 1469-5081. ; 149:3, s. 412-422
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Tidskriftsartikel (refereegranskat)abstract
- Most karst terranes develop slowly on static limestone substrates as part of the global hydrological cycle. Here we introduce the novel concept of a karst morphology developing very rapidly on a more soluble substrate of salt (NaCl) that is moving through its own global cycle. We open with a reminder of karst features and processes in limestone. We then illustrate the global salt cycle using the 180 or so extrusions of Hormoz salt in the Zagros Mountains of Iran. After describing the geology of an example, we consider how it fits into the evolution of salt extrusions. This example, Konarsiah, was chosen for its simple hydrology. Konarsiah is covered by residual soils of the insoluble components that remain in place as the Hormoz salt is dissolved. Dolines in the surface of these soils enlarge and the soils thicken as the moving salt dissolves. The long-term rate of salt dissolution and soil production on Konarsiah are estimated using traditional methods. The calculated age of the thickest, most distal soil is used to constrain the average rate at which the underlying salt flows downslope after extruding from two vents. The average velocities constrained for salt flow are lower than rates of displacement of markers near the summit of Konarsiah measured at irregular intervals over five years. Salt extruding from recently truncated diapirs near the arid south coast of Iran exhibit all the features seen in classical karst terranes. In the more humid mountains inland, vegetated soils protect salt extrusions like Konarsiah from erosion and limit their salt karst features. Soil covers also probably even out salt flow velocities. Salt extrusions advance when such protective covers grow and thicken in humid conditions. They retreat when such protection is lost to erosion in drier conditions. These external signs complement internal recumbent folds in extruded salt that signal intervals of faster salt flow when wet than dry. They also add to the features that render salt extrusions records of climate change.
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