 |
| Titel |
Tectonic uplift related to inclined transpression with oblique extrusion: Preliminary data from the Torcal shear zone (External Betics, southern Spain) |
| VerfasserIn |
Manuel Díaz-Azpiroz, Carlos Fernández, Leticia Barcos, Alejandro Jiménez, Juan Carlos Balanya, Inmaculada Expósito, Luz M. Portillo, Dyanna M. Czeck |
| Konferenz |
EGU General Assembly 2014
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250091521
|
| Publikation (Nr.) |
 EGU/EGU2014-5821.pdf |
|
|
|
|
|
| Zusammenfassung |
| Transpression results where plate convergence vectors are oblique to plate boundaries, and
hence it should be considered as the general situation in both dominantly convergent and
strike-slip tectonic settings. In consequence, understanding tectonic uplift produced in
transpression is crucial to a better knowledge of mountain building. Tectonic uplift produced
at monoclinic transpression has been modeled previously. In this contribution, the model of
triclinic transpression with oblique extrusion is implemented to estimate tectonic uplift in
more general transpressional settings.
Transpression is kinematically defined as the combination of simple shearing parallel to
the shear zone boundary and a coaxial strain producing shortening orthogonal to the shear
zone boundary and extrusion parallel to it. Monoclinic transpression occurs in vertical shear
zones where simple shearing is parallel to the shear zone direction. In these cases, the simple
shear component produces only lateral displacement and tectonic uplift is generated uniquely
by vertical coaxial extrusion.
In contrast, triclinic transpression occurs where the simple shearing direction is oblique to
the shear zone direction (a direct consequence of an inclined shear zone) and/or
the extrusion produced by the coaxial component is oblique to the shear zone dip
direction. Tectonic uplift produced in these situations is more complex. Oblique simple
shear component produces both lateral and dip parallel displacement, the latter
contributing to tectonic uplift. The tectonic uplift produced by the simple shear
component S(v) can be defined in terms of the total displacement produced by simple
shearing S(γ), the transpression obliquity angle Ï and the dip of the shear zone
δ:
PIC
Furthermore, the extrusion due to the coaxial component of strain is never vertical in
inclined shear zones. Considering the possibility of oblique extrusion, the tectonic uplift of
any rock level produced by this coaxial deformation E(v)is a function of the initial distance
of the considered rock level to the basal decoupling level Z(t0), the coaxial strain
rate
PIC
, the extrusion obliquity angle Ï
and time t:
PIC
The total tectonic uplift in inclined triclinic transpressional zones is the sum of S(v) and
E(v).
This theoretical modeling is being applied to the Torcal shear zone (TSZ), a dextral
triclinic transpressional shear zone at the external Betics (southern Spain) that has been active
since the Miocene. According to kinematic measurements, the original distance between the
topographic surface and the basal decoupling was Z(t0) = 4500-6500 m, the extrusion was
nearly dip-parallel (Ï
= 0o) and
PIC
t = 0.2 – 0.27. With these data, the surface tectonic uplift due to the coaxial deformation
acting at the TSZ was 1000-2000 m, which should be considered a minimum as the
contribution of the simple shear deformation to the total tectonic uplift has not been
considered. These results are compared with preliminary data of altitude differences of
Tortonian-Messinian rock levels inside and outside the TSZ (700 m in the central part of
the TSZ). Differences with respect to theoretical results could be likely related
to the age of deformation and/or overestimation of input kinematic parameters. |
|
|
|
|
|
|