Open Session - SWISS GEOSCIENCE MEETINGs

1.
Structural geology, stress and strain across the Eastern Greater Caucasus
Bochud Martin*, Mosar Jon*, Kangarli Talat**
*Science de la Terre, Département des Géosciences, Université de Fribourg, Chemin du Musée 6, CH-1700 Fribourg (martin.bochud@unifr.ch)
**Geology Institute of Azerbaijan (GIA), National Academy of Sciences, H.Javid Av., 29A, Baku AZ1143, Azerbaijan
The Eastern Greater Caucasus is located in the northern part of Azerbaijan to the West of the Caspian Sea. The Greater
Caucasus undergoes a rapid uplift since the Miocene and is submitted to a regional compressional tectonic regime related
to the Alpine closure of Neo-Tethys during the Arabia – Eurasia collision. The near South Caspian Basin is one of the deepest
basins in the world with more than 20 km of sediment and with important oil deposits. This research is part of different
international research projects in the Caucasus-Caspian Sea area including MEBE, INTAS, SCOPES, UNIFR. The focus of the
research is on the Mesozoic to Present evolution of the region and the link between the processes leading to the present
geomorphology and the deeper seated tectonic processes.
Fieldwork since 2003 has made it possible to gather data and present regional tectonic profiles across the easternmost
Greater Caucasus of Azerbaijan. In addition we carried out a thorough stress analyses combined with a fracture and lineament
analyses (remote sensing). Our investigation allowed us to distinguish and document different tectonic phases since
the Middle Jurassic and to highlight some local tectonic stresses associated with the different discrete events.
Overall the geometry of the orogen is one of a doubly vergent fold-and-thrust belt. The present orogeny is associated with
south-directed thrusting and folding in its central and southern parts. The northern regions, to the N of the topographic
crest, around the area of the Shadag, also show important N-directed folding and thrusting. Near the Shadag summit, at an
altitude of 3500m, marine deposits of Sarmatian (Pliocene) age are evidence of the rapid uplift of the area. Both S-directed
and N-directed thrusting appear to be linked to rapid uplift. On top and to some extent contemporaneously, we can observe
vertical to subvertical faults that dissect the whole mountain range with a trend more or less perpendicular to the NW-SE
strike of the major fold and thrusts.
Analysis of paleo-stress data show a combination of thrust-related compressive stresses, but most prominently strike-slip
faults linked with recent anticaucasian faults. We will discuss the different stress/fault families and their relationship with
the recent tectonic evolution.
1.
Mechanical and microstructural changes during torsion testing on
Carrara marble with pre-existing deformation history
Bruijn Rolf* & Burlini Luigi*
* Geological Institute, Leonhardstrasse 19, CH-8092 Zürich (rolf.bruijn@erdw.ethz.ch)
We are conducting extended research on Carrara marbles samples in order to broaden earlier investigations on superimposed
deformation events. Initially three types of experiments were designed to ascertain the mechanical and microstructural
behaviour of double-deformed Carrara marble. These types include: 1. samples deformed to a specific strain followed by reversed
deformation with equal strain, 2. deformation of a composite comprising a deformed (γ=5) part and an undeformed
part, 3. sample deformed until γ=9 with a static annealing pause at γ=5. The results are summarized in Delle Piane and
Burlini 2008.
More recently, a fourth type of deformation experiment was conducted, involving stack of samples previously deformed
anticlockwise (top) and clockwise (bottom part), see figure 1. The first deformation phase reached strains of γ = 1, γ = 2.6 and
γ = 5. The second phase of deformation (i.e. the deformation of the sandwich of samples) is currently under execution and is
going to reach γ = 1, 2.5 and 5 in anticlockwise direction.
This fourth type of Carrara marble sample will allow us to examine the interaction between the different sections of the
sample and the effect that this interaction might have on rock strength and microstructure.
Deformation experiments, using a Paterson type internally heated gas-medium deformation apparatus, were conducted at
300 MPa confining pressure, 1000° K and with a shear strain rate of 3·10 -4 s -1 .
Produced microstructures were examined using light and scanning electron microscopy. In addition, EBSD (Electron backscatter
diffraction) was used to analyse fabrics. The rest of the planned experiments will be at the same strain rate, pressure
1
Symposium 1: Structural Geology, Tectonics and Geodynamics