2e visible here due to more disruption during extension (data courtesy of PGS Investigação Petrolifera Limitada) (c) 3-D depth-migrated seismic profile (vertical exaggeration 2 : 1) from the Friesland Platform of the onshore Netherlands showing the Zechstein salt (between cyan horizons) with boudins of the Z3 stringer (top of stringer in yellow) generated during thick-skinned extension (adapted from Strozyk et al., 2014). Dooley) (b) 3-D depth-migrated image of a large salt roller from the Santos Basin (vertical exaggeration 1 : 1), with very little of the internal layering seen in Fig. (e) 3-D depth-migrated seismic profile (vertical exaggeration 2 : 1) from the Santos Basin, Brazil, with complex internal deformation shown by layered halite, anhydrite, and bittern salts (data courtesy of PGS Investigação Petrolifera Limitada).Įxamples of extension of salt with internal competent beds: (a) simplified results of analog model in which the polymer layer was thinned and attenuated during thin-skinned extension -the black dashed line shows the original top polymer, and the yellow and blue layers are stronger intra-polymer layers that separated into boudins, with more extension at the deeper, blue level (adapted from Cartwright et al., 2012 model by Tim P. (d) Photograph of tunnel wall in the Wieliczka salt mine, southern Poland, showing anhydritemudstone boudins (medium grey) thrusted and folded within halite matrix (see Krzywiec et al., 2018). (c) Cross section of a diapir in northern Germany constrained by subsurface mine data, showing boudins of anhydrite (purple) entrained in complexly folded halite (adapted from Jackson and Hudec, 2017, itself after Hofrichter, 1980). Sedom diapir in Israel showing vertical beds of halite with bedding-parallel trains of boudins of eroded-out marls showing clockwise rotation and the indicated sense of shear (see Alsop et al., 2015). (a) HyMap image with oblique cross-sectional view of exposed Witchelina diapir in the Willouran Ranges, South Australia black dotted line marks the edge of the diapir, which has randomly oriented stringers of carbonates, siliciclastics, and volcanics in its upper half and a large stringer with recumbent isoclinal folds in the lower half (adapted from Hearon et al., 2015). Seismic and well data may be interpreted to suggest that diapirs and otherĪreas of more intense intrasalt deformation are more halite rich than isĮxamples of intrasalt deformation. Tall passive diapirs because the stringers are near vertical. Strong layers in contractional structures and salt pillows, less likely inĮxtended salt because they might drill between stringers, and unlikely in Similarly, wells are most likely to penetrate Slightly to moderately shortened salt typically have well-imaged, mostlyĬontinuous intrasalt reflectors, although seismic coherency decreases asĭeformation intensifies. Poorly imaged in passive diapirs due to steep dips. Ruptured stringers are often visible where they have lowĭips, as in slightly extended salt layers or beneath depocenters, but are Styles of intrasalt deformation impact seismic imaging of LES and associated Progressively removed from areas of salt thinning and increasingly disruptedĪnd folded in areas of salt growth as deformation intensifies. Finally, in passive diapirs, stringers generatedīy intrasalt extension are rotated to near vertical and encased in complexįolds during upward flow of salt. Stringers dominate beneath suprasalt depocenters, while folded competent bedsĬharacterize salt pillows. In differential loading, extension and the resultant The rheological stratification leading to buckling and fold growth byīedding-parallel shear. In bedding-parallel shortening, competent layers tend to maintainĬoherency while forming harmonic, disharmonic, and polyharmonic folds, with Stringers, within a halite matrix, that become more isolated with increasing Inīedding-parallel extension, boudinage of the strong layers forms ruptured Salt tectonics, even though combinations are common in nature, using aĬombination of conceptual, numerical, and analog models, and seismic data. The deformation of competent intrasalt beds in different endmember modes of Range of effective viscosity up to a factor of 105. This results in a strong rheological stratification, with a (anhydrite and usually non-evaporite rocks such as carbonates and Weak layers (halite and, commonly, bittern salts) and strong layers Layered evaporite sequences (LESs) comprise interbedded
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