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| Titel |
Evaporite Detachment Characteristics and their controls on Fold-Thrust Belt Style: an Example from the Amadeus Basin, Central Australia |
| VerfasserIn |
Lachlan Richards, Rosalind King, Alan Collins, Guillaume Backé, Chris Morley |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250077787
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| Zusammenfassung |
| Although there is a wealth of information on the structural styles in fold-thrust belts,
specifically with regards to the nature of the stresses (far-field, near-field, or a combination of
both) associated with the tectonic regime, the precise nature by which detachment zones
control deformation is largely unknown.
Field observations of ancient and exhumed analogues at sites located in Australia,
Pakistan, and Canada, as well as sample analysis are used in this work to document salt
detachment characteristics (thickness, lithology, dip and dip direction, strain patterns,
temperature of deformation and thrust front propagation rates). The use of analogues is
justified as the most prominent examples of active fold-thrust belts are located in
inaccessible, typically deepwater, environments and onshore examples generally lack surface
outcrop of the detachment zone itself.
‘Classic’ structural techniques, such as constructing cross-sections and field observations
are used in this project to determine the thickness, lithology, dip and dip direction of salt
detachments. In addition, “modern analytical techniques such as, electron backscatter
diffraction, electron microprobe analysis with calcite-dolomite thermometry and 18O stable
isotope analysis, and piezometric calculations” are used to characterise further
fold-thrust belt properties, such as crystallographic preferred orientation and strain
pattern, temperature of deformation, and palaeopressure. By integrating ‘classic’
and ‘modern’ techniques it is possible to characterize a range of salt detachment
properties and develop our understanding of their control on structural style and
deformation.
Initial work in the Neoproterozoic Amadeus Basin, central Australia has focused on
microstructural analysis and seismic interpretation. The Amadeus Basin is bounded to the
north by 400-300Ma Alice Springs Orogeny and to the south by the 570-530Ma Peterman
Orogeny. The main deformation pattern observed in the Basin at present-day is mostly related
to these two major events of crustal shortening and is compatible with a NW-SE trending
compressional tectonic regime.
Seismic interpretation of 2D data confirms the structural style observed at surface, with
multiple occurrences of salt-cored anticlines and diapirs. The pervasive salt member observed
both in the field and on seismic data corresponds to the main detachment surface
in the basin, the Gillen Member of the Bitter Springs Fm. (775Ma-710Ma). This
member consists of a basal dolomite sequence covered by a thick succession of
halite, capped by dolomite and gypsum. 1 -4 core samples collected from nine wells
penetrating the detachment layer contained significant, highly crystalline, pure halite with
subordinate primary anhydrite and gypsum. Microstructural analysis of these samples
has been fundamental in explaining the mechanisms by which the detachment has
accommodated the deformation and the cause of the subsequent fold-thrust belt
style. As an example, the Amadeus Basin works well in demonstrating the utility of
combining these techniques in characterizing the properties of salt detachments. |
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