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[1] Three primary salt tectonic structural styles of the Scotian Basin are compared with plane strain finite element models in order to investigate their origin. Here, we focus on simplified model salt basins with initial rectangular cross-sectional geometries and follow their evolution in the context of tectonic and parametric thermal subsidence and under various sedimentation regimes. Structural style A, an open-ended roho system with a synkinematic wedge, is reproduced by models including deltaic progradation and seaward spreading/ gliding of sediments above a salt detachment. Structural style B, a linked salt tectonic system with landward regional normal faults and allochthonous salt sheets climbing seaward over Late Cretaceous and Paleogene strata, is shown to be a consequence of early aggradation followed by progradation. Structural style C is characterized by salt diapirs and intervening minibasins and is reproduced by models with Rayleigh-Taylor instabilities requiring compaction driven density inversions, weak sediments, and initial perturbations of the overburden-salt interface. Citation: Albertz, M., C. Beaumont, J. W. Shimeld, S. J. Ings, and S. Gradmann (2010), An investigation of salt tectonic structural styles in the Scotian Basin, offshore Atlantic Canada: 1. Comparison of observations with geometrically simple numerical models, Tectonics, 29, TC4017, doi: 10.1029/2009TC002539.

[1] The Perdido Fold Belt (PFB) is a prominent salt-cored deep water structure in the northwestern Gulf of Mexico. It is characterized by symmetric, kink-banded folds of a ~4.5 km thick prekinematic layer and its vicinity to the extensive Sigsbee Salt Canopy. We use 2-D finite element numerical models to study the evolution of the PFB as a gravity-driven fold belt both in a local context and in the context of the larger-scale passive margin, influenced by adjacent allochthonous salt structures. We show that parameters such as overburden strength, salt geometry, or salt viscosity determine timing, extent, and location of the modeled fold belt. Simplified models of the Gulf of Mexico show that toe-of-slope folding is a viable mechanism to develop diapirs in the deep salt basin and to delay folding of the distal overburden. In this scenario, the PFB likely represents the terminal folding of a much larger, diachronously formed fold belt system. doi:l0.1029/2008TC002326.

Abstract: A channel‐like, low‐velocity zone in the lithospheric mantle beneath W Norway coincides spatially with the extension of a recently discovered 200 × 50 km granite batholith, which formed as a result of oceanic subduction beneath the SW Fennoscandian margin between 1.07 and 1.01 Ga. Based on results from numerical modelling, we argue that the low‐velocity zone, at least in part, reflects the thermal (radioactive) effects of the refertilized mantle wedge of this magmatic arc. The geological record in SW Fennoscandia suggests that active‐margin magmatism terminated as a result of rapid slab rollback and trench retreat starting at ca. 1 Ga. The rapid shift from active‐ to passive‐margin processes was probably critical in preserving the mantle wedge, and its identification can therefore shed light on how active‐margin processes terminated in ancient orogens. [ABSTRACT FROM AUTHOR]

Salt canopies are present in many of the worldwide large salt basins and are key players in the basins' structural evolution as well as in the development of associated hydrocarbon systems. This study employs 2D finite-element models which incorporate the dynamical interaction of viscous salt and frictional-plastic sediments in a gravity-spreading system. We investigate the general emplacement of salt canopies that form in the centre of a large, autochthonous salt basin. This is motivated by the potential application to a mid-basin canopy in the NW Gulf of Mexico (GoM) that developed in the late Eocene. Three different salt expulsion and canopy formation concepts that have been proposed in the salt-tectonic literature for the GoM are tested. Two of these mechanisms require pre-existing diapirs as precursory structures. We include their evolution in the models to assure a continuous, smooth evolution of the salt-sediment system. The most efficient canopy formation takes place under the squeezed diapir mechanism. Here, shortening of a region containing pre-existing diapirs is absorbed by the salt (the weakest part of the system), which is then expelled onto the seafloor. The expulsion rollover mechanism, which evacuates salt from beneath evolving rollover structures and expels it both laterally and to the surface, was not successfully captured by the numerical models. No rollover structures developed and only minor amounts of allochthonous salt emerged to the seafloor. The breached anticline mechanism requires substantial shortening of salt-cored, pre-weakened folds such that the salt breaches the anticlines and is expelled to the seafloor. The amount of shortening may be too large to occur in the central part of a salt basin, but may explain canopy evolution closer to the distal end of the allochthonous salt. When applying the different concepts to the northwestern GoM, none of the models adequately describes the entire system, yet the squeezed diapir mechanism captures most structural features of the Eocene paleocanopy. It is nevertheless possible that different mechanisms have acted in combination or sequentially in the northwestern GoM. [ABSTRACT FROM AUTHOR]

The Scandinavian Mountain Chain (the Scandes) exhibits characteristics that are unusual for an old, Palaeozoic mountain belt. These include renewed Neogene uplift in a passive margin setting and the lack of a pronounced crustal root. We investigate the influence of present-day thermal, compositional and geometric structures in the crust and mantle on the topography of the southern Scandes and the resulting implications for the tectonic history of Fennoscandia.A self-consistent 3-D subsurface model of southern Norway and Sweden is constructed from recent geophysical data sets that constrain the crustal architecture, lithosphere geometry, density distributions and thermal properties. Recent seismological studies show evidence for a relatively abrupt transition from seismically slower lithospheric mantle underneath southern Norway to seismically faster lithospheric mantle underneath southern Sweden.We find that a transition from thin subcontinental lithospheric mantle (SCLM) underneath southern Norway to a significantly thicker SCLM beneath southern Sweden can explain this velocity trend. A difference in composition between the two SCLM domains (owing to different depletion/refertilization) is required to satisfy the gravity field and isostatically compensated topography, but contributes only slightly to the observed velocity contrast. Such a lateral transition zone, constituting a major change in the lithospheric structure in southwestern Fennoscandia, can be related to several major Proterozoic and Phanerozoic tectonic events such as the Sveconorwegian orogeny, the Permian Oslo Rift and perhaps even the opening of the Atlantic. [ABSTRACT FROM AUTHOR]