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Index Geophysics

Deformation of intrasalt competent layers in different modes of salt tectonics


Title (Dublin Core)

Deformation of intrasalt competent layers in different modes of salt tectonics

Description (Dublin Core)

<p>Layered evaporite sequences (LESs) comprise interbedded
weak layers (halite and, commonly, bittern salts) and strong layers
(anhydrite and usually non-evaporite rocks such as carbonates and
siliciclastics). This results in a strong rheological stratification, with a
range of effective viscosity up to a factor of 10<span class="inline-formula"><sup>5</sup></span>. We focus here on
the deformation of competent intrasalt beds in different endmember modes of
salt tectonics, even though combinations are common in nature, using a
combination of conceptual, numerical, and analog models, and seismic data. In
bedding-parallel extension, boudinage of the strong layers forms ruptured
stringers, within a halite matrix, that become more isolated with increasing
strain. In bedding-parallel shortening, competent layers tend to maintain
coherency while forming harmonic, disharmonic, and polyharmonic folds, with
the rheological stratification leading to buckling and fold growth by
bedding-parallel shear. In differential loading, extension and the resultant
stringers dominate beneath suprasalt depocenters, while folded competent beds
characterize salt pillows. Finally, in passive diapirs, stringers generated
by intrasalt extension are rotated to near vertical and encased in complex
folds during upward flow of salt. In all cases, strong layers are
progressively removed from areas of salt thinning and increasingly disrupted
and folded in areas of salt growth as deformation intensifies. The varying
styles of intrasalt deformation impact seismic imaging of LES and associated
interpretations. Ruptured stringers are often visible where they have low
dips, as in slightly extended salt layers or beneath depocenters, but are
poorly imaged in passive diapirs due to steep dips. In contrast, areas of
slightly to moderately shortened salt typically have well-imaged, mostly
continuous intrasalt reflectors, although seismic coherency decreases as
deformation intensifies. Similarly, wells are most likely to penetrate
strong layers in contractional structures and salt pillows, less likely in
extended salt because they might drill between stringers, and unlikely in
tall passive diapirs because the stringers are near vertical. Thus, both
seismic and well data may be interpreted to suggest that diapirs and other
areas of more intense intrasalt deformation are more halite rich than is
actually the case.</p>

Creator (Dublin Core)

M. G. Rowan
J. L. Urai
J. C. Fiduk
P. A. Kukla

Subject (Dublin Core)


Publisher (Dublin Core)

Copernicus Publications

Date (Dublin Core)


Type (Dublin Core)


Identifier (Dublin Core)


Source (Dublin Core)

Solid Earth, Vol 10, Pp 987-1013 (2019)

Language (Dublin Core)


Relation (Dublin Core)

Provenance (Dublin Core)

Journal Licence: CC BY