Interpretación de la Estructura Geológica y la Tendencia Paleoambiental durante el Eoceno-Pleistoceno de la Subcuenca del Río Teusacá, Cundinamarca.

Abstract

The objective of this work was related to make an interpretation of the geological structure and the paleoenvironmental tendency during the Eocene to the Pleistocene sub-basin of the Teusacá River, Cundinamarca. Observations were made directly on the rocks, heading and dive data were taken. To find the stress-strain pattern, the graphic method of Anderson (1951) was used. For the design of the Paleoclimatic and Paleoenvironmental Curve, the Simplex model was used and the work carried out by Adriessen et al. (1993), IGAC (2000) and Harland et al. (1989) was used as a reference. During the Andean Orogeny, the regional main tension σ1 was East-West (80% persistence) and the cut-off voltage σ2 was South-North. The shortening calculated for the elevation of 2800 meters of the Eastern Cordillera in the study area was 28.000 meters. During the final phase of adjustment, structures such as the Bogotá fault, the Teusacá fault, the Pericos fault, the San Lorenzo fault and the Santa Elena fault, with a South-North trend, became dominant for the main regional effort. The uprising of the Cordillera apparently stopped during the Andean Orogeny. The Teusacá River Sub-basin presented two stages in its development: the Andean Orogeny (3My) and the Final Adjustment Phase (1Ma). During the Andean Orogeny, the study area was exposed from sea level, where the dense palynology data of the Mauritia forest was recovered, to its current position of 2800 masl according to Adriessen et al. (1993), IGAC (2000) and Harland et al. (1989). In the Final Adjustment Phase (1Ma), the basin begins with the Glacial Periodicity, the lower level of the Ice layer was 2600 meters above sea level, 36000 years ago during the Winsconsinian period. The structural shape of the Teusacá River Basin could be defined as a Horst Structure Strike on the edge of the Teusacá synclinary, with a South-North trend. In addition, the detachment of the embedded fan failure system becomes the upper part of the hard formation (last upper cretaceous deposits). The only place where it is possible to measure fractures and stratigraphic planes in the area is hard formation (Lower Guadalupe Group), the upper stratigraphic units disintegrated or were subjected to tension. The paleoclimatic curve shows the behavior of the glaciations, their peaks and lower limits of the last 2.2 Ma. The results obtained allowed us to know a model of the geological evolution of the sub-basin of the Teusacá River and understand the paleoenvironmental evolution of the region during the Last cycles in the study area.