ScienceDaily (Apr. 29, 2009) — The interplay between tectonic deformation, uplift and erosive processes creates the topography of mountain ranges, which, in turn, influences atmospheric circulation patterns and the distribution of precipitation. As a result, the erosional products will be carried into the lowlands straddling the flanks of mountain ranges.

However, often it is not known when, and at what rates these processes have taken place. In the adjacent lowlands of the Andes thick sediment accumulations occur that are of economic value, because they often contain important hydrocarbon-bearing rocks. In the study by Parra et al., the formation of topography of the Eastern Cordillera of the Colombian Andes has been revealed through a multidisciplinary study combining an estimate regarding the time when the present-day range began to be eroded in response to tectonic deformation and uplift. Sediments produced by the combination of uplift and erosion were subsequently deposited in the adjacent foreland basin system to the east.

Thermochronological techniques that measure the temperature and time-dependent generation of fission tracks in zircon minerals reveal that the onset of erosion associated with initial uplift of the range began approximately 25 million years ago. The detailed study of sedimentary characteristics in the adjacent Medina Basin, about 30 km to the east, show deposition in a developing foreland basin with a source area in the present-day Eastern Cordillera.

The locus of subsidence and sediment accumulation in the basin and coeval erosion of the ranges constrains the position of the early Miocene deformation front of the Colombian Andes, helping to better assess the spatiotemporal tectonic and sedimentary evolution of this poorly known sector of the Andean mountain belt.

This research was published by Mauricio Parra et al. (Institut fur Geowissenschaften, Universitat Potsdam, D-14476 Potsdam, Germany) in the May-June issue of GSA Bulletin (pages 780-800).

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