PALEOSTRESS ANALYSIS IN THE QUETAME GROUP SECTION FROM COLOMBIA

The Llanos Foothills in Colombia can be structurally described as a brittle shear zone, regional and continuous, parallel and convergent, with a dextral movement. It forms reverse faultings, thrustbelt structures and is associated with en echelon structures related to the Borde Llanero Fault. The mean deformation mechanism determined by mean of aereal photographs, are governed by processes of the precambrian chrystaline Andean Basement and isostatic adjustment of Guayana Cratonic Block. Using the sharp angle-bisectrice methodology to determine paleostresses we determined two vectors of principal stress for two well distinguished tectonic provinces: the first one on Cretaceous Allochtonous Block in 223 grades Azymuth for Sigma1 and 133 grades Azymuth for Sigma2. The second one for Precambrian Andean Basement in 262 grades Azymuth for Sigma1 and 172 grades Azymuth for Sigma2 on the Principal Stresses Plane due by the Anderson Law. The actual position of the vertical axis normal to the principal stresses plane for Cretaceous Allochtonous Block show a trend of 303 grades and a plunge of 0.3. The actual position of the vertical axis normal to the principal stresses plane for Precambrian Andean Basement trend 22.9 grades and plunge 75.8.