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- 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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- 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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- 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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- Persson, K., Sjöström, H., Koyi, H. A., Mulugeta, G., Weinberg, R. and C.J. Talbot
(författare)
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Ytor på djupet.
- 1999
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Ingår i: Naturvetenskapliga forskningsrådets årsbok 1998/1999. ; , s. 39-51
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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