Viscous flow during salt welding

Wagner, B. H. Van; Jackson, Martin P. A.

doi:10.1016/j.tecto.2011.07.012

Cited by 57 publications

(61 citation statements)

References 82 publications

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“…Like those outside complex walls, internal anticlines at the complex wall ends formed by inward flow and thickening of lower-A1 mobile halite, in this case expelled from beneath flanking minibasins. A2eA4 units are broadly isopachous across the fold hinges, although local thickness changes in A2 and A3 on the anticline limbs may reflect preferential expulsion of halite in these layers as the walls grew (Kupfer, 1968;Wagner and Jackson, 2011;Jackson et al, 2014b). These diapirs could have grown reactively or passively, as discussed below in Section 8.1.…”

Section: Internal Anticlinesmentioning

confidence: 99%

“…Clearly the wide variations in thickness of the evaporite units point to extensive redistribution of the most mobile interbeds. More-mobile halite-rich A1 evaporites would be preferentially expelled into the growing salt structures (Kupfer, 1968;Wagner and Jackson, 2011;Albertz and Ings, 2012;Cartwright et al, 2012;Jackson et al, 2014b). Expulsion would reduce the density contrast within the sequence, so the Santos density contrast could have been higher in the past, thus making Rayleigh-Taylor overturn more likely in the past than the present, which supports the hypothesis presented here.…”

Section: Kinematic Model For the Origin Of Complex Diapirsmentioning

confidence: 99%

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Enigmatic structures within salt walls of the Santos Basin—Part 1: Geometry and kinematics from 3D seismic reflection and well data

Jackson¹,

Jackson²,

Hudec³

et al. 2015

Journal of Structural Geology

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151

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a b s t r a c tUnderstanding intrasalt structure may elucidate the fundamental kinematics and, ultimately, the mechanics of diapir growth. However, there have been relatively few studies of the internal structure of salt diapirs outside the mining industry because their cores are only partly exposed in the field and poorly imaged on seismic reflection data. This study uses 3D seismic reflection and borehole data from the São Paulo Plateau, Santos Basin, offshore Brazil to document the variability in intrasalt structural style in natural salt diapirs. We document a range of intrasalt structures that record: (i) initial diapir rise; (ii) rise of lower mobile halite through an arched and thinned roof of denser, layered evaporites, and emplacement of an intrasalt sheet or canopy; (iii) formation of synclinal flaps kinematically linked to emplacement of the intrasalt allochthonous bodies; and (iv) diapir squeezing. Most salt walls contain simple internal anticlines. Only a few salt walls contain allochthonous bodies and breakout-related flaps. The latter occur in an area having a density inversion within the autochthonous salt layer, such that upper, anhydrite-rich, layered evaporites are denser than lower, more halite-rich evaporites. We thus interpret that most diapirs rose through simple fold amplification of internal salt stratigraphy but that locally, where a density inversion existed in the autochthonous salt, RayleigheTaylor overturn within the growing diapir resulted in the ascent of less dense evaporites into the diapir crest by breaching of the internal anticline. This resulted in the formation of steep salt-ascension zones or feeders and the emplacement of high-level intrasalt allocthonous sheets underlain by breakout-related flaps. Although regional shortening undoubtedly occurred on the São Paulo Plateau during the Late Cretaceous, we suggest this was only partly responsible for the complex intrasalt deformation. We suggest that, although based on the Santos Basin, our kinematic model may be more generally applicable to other salt-bearing sedimentary basins.

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Section: Internal Anticlinesmentioning

confidence: 99%

Section: Kinematic Model For the Origin Of Complex Diapirsmentioning

confidence: 99%

Enigmatic structures within salt walls of the Santos Basin—Part 1: Geometry and kinematics from 3D seismic reflection and well data

Jackson¹,

Jackson²,

Hudec³

et al. 2015

Journal of Structural Geology

Self Cite

151

View full text Add to dashboard Cite

show abstract

“…Three types of weld are recognized based on the structural level at which salt evacuation occurs and the attitude of the weld: (1) a primary weld, which joins strata originally above and below autochthonous salt, and which is typically subhorizontal and occurs at the base of minibasins or in association with salt-detached normal faults and rafts; (2) a secondary weld, which is subvertical and joins minibasins originally situated either side of squeezed and nowevacuated salt diapirs; and (3) a tertiary weld, which is typically inclined and joins strata originally above and below allochthonous salt (Figure 1a) (Jackson and Cramez, 1989). For all three types of weld, specific terms have also been introduced to describe the degree of completeness or continuity of salt welds: (1) a complete weldcontains no remnant salt (compare the original definition of Jackson and Cramez, 1989), (2) an incomplete weldcontains up to 50 m of remnant salt, (3) a discontinuous weldcontains complete and incomplete parts; and (4) an apparent weldappears completely free of salt at a particular scale of observation ( Figure 1b) (Wagner, 2010;Hudec and Jackson, 2011;Wagner and Jackson, 2011;.…”

Section: Introductionmentioning

confidence: 99%

“…Welding by viscous flow has received little attention but was explored relatively recently by Wagner and Jackson (2011) using analytical and numerical models. Welding by viscous flow has received little attention but was explored relatively recently by Wagner and Jackson (2011) using analytical and numerical models.…”

Section: Introductionmentioning

confidence: 99%

Geological and geophysical expression of a primary salt weld: An example from the Santos Basin, Brazil

Jackson¹,

Rodríguez²,

Rotevatn

et al. 2014

Interpretation

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Primary salt welds form at the base of minibasins in response to complete evacuation of autochthonous salt. Analytical and numerical models suggest it is difficult to completely remove salt from a weld by viscous flow alone, which is especially true in multilayered evaporites, within which flow is likely heterogeneous due to lithologically controlled viscosity variations. Welds are important in the hydrocarbon industry because they may provide a hydrodynamic seal and trap hydrocarbons, or may allow transmission of fluids from source to reservoir rocks. Few papers document the subsurface expression of welds, principally because they have not been penetrated by wells or because the associated data are proprietary. We use 3D seismic and borehole data from the Santos Basin, offshore Brazil to characterize the geological and geophysical expression of a primary weld associated with flow of Aptian salt. The seismic data that we evaluated suggested that, locally, presalt and postsalt rocks are in contact at the base of an Upper Cretaceous minibasin, implying that several apparent welds, separated by low-relief salt pillows, are present. However, borehole data indicated that 22 m of anhydrite, carbonate, and sandstone are present in one of the welds, indicating that this and other welds may be incomplete. We find that seismic data may be unable to discriminate between a complete and incomplete weld, and we suggested that, during the subsurface analysis of welds, the term apparent weld is used until borehole data unequivocally proves the absence of salt. Furthermore, we speculate that preferential expulsion of halite and potash salt from the autochthonous layer during viscous flow and welding resulted in the formation of an incomplete weld, which, when compared with the initial autochthonous layer, is volumetrically enriched in nonevaporite lithologies and relatively viscous evaporite lithologies (anhydrite). The composition and stratigraphy of the autochthonous layer may thus dictate weld thickness and seal potential.

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“…Stocks are locally developed along salt walls, and they are up to 3.5 km (2.2 mi) wide and display up to 4.5 km (2.8 mi) of relief ( Figure 6B). The Zechstein Group is thin between these salt structures, and apparent salt welds (sensu Wagner and Jackson, 2011) are present below subcircular-to-elongated Triassic depocenters that are up to 3.5 km (2.2 mi) thick and 10 km (6.2 mi) wide (assuming a Triassic interval velocity of 3500 m s −1 [11;483 ft s −1 ]) ( Figure 6B). Although seismic imaging of Triassic strata in the salt-bounded depocenters is typically quite poor, areas of good imaging indicate that intraTriassic stratal packages thicken toward the bounding salt walls ( Figure 5).…”

Section: Saltmentioning

confidence: 99%

Shallow-marine reservoir development in extensional diaper-collapse minibasins: An integrated subsurface case study from the Upper Jurassic of the Cod terrace, Norwegian North Sea

Mannie¹,

Jackson²,

Hampson³

2014

Bulletin

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A B S T R A C TUnderstanding the factors controlling the development of accommodation above collapsing salt diapirs and their influence on reservoir distribution is critical in reducing exploration risk in salt-influenced sedimentary basins. In this study, we use an integrated subsurface data set (three-dimensional and twodimensional seismic reflection, wire-line-log, core, and biostratigraphic data) from the Upper Jurassic of the Cod terrace, Norwegian North Sea, to understand the influence of rifting on accommodation creation and shallow-marine deposition during the initial-stage collapse of salt diapirs. We demonstrate that rifting resulted in the rise and fall of salt diapirs, and the formation of supra-diapir minibasin-style depocenters that became sites for deposition and preservation of up to 500 m (1640 ft) thick nettransgressive shallow-marine sandstone reservoirs. Maximum thickness is recorded in the axis of minibasins with a reduction in thickness of up to 65% noted on their flanks. The stratigraphic architecture of individual minibasins is variable. Proximal-todistal facies variations from shoreface to offshore shelf and commensurate changes in reservoir quality occur over scales larger than individual minibasins. These deposits contain large sand volumes, and are not confined to areas of localized sandstone subcrop. In combination, these features suggest that the minibasins

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Viscous flow during salt welding

Cited by 57 publications

References 82 publications

Enigmatic structures within salt walls of the Santos Basin—Part 1: Geometry and kinematics from 3D seismic reflection and well data

Enigmatic structures within salt walls of the Santos Basin—Part 1: Geometry and kinematics from 3D seismic reflection and well data

Geological and geophysical expression of a primary salt weld: An example from the Santos Basin, Brazil

Shallow-marine reservoir development in extensional diaper-collapse minibasins: An integrated subsurface case study from the Upper Jurassic of the Cod terrace, Norwegian North Sea

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