HYPSOMETRIC AND DRAINAGE NETWORK ANALYSIS OF THE EASTERN CORDILLERA OF THE COLOMBIAN ANDES: EVIDENCE FOR VARIABLE SPATIAL - TEMPORAL UPLIFT INFERRED THROUGH GEOMORPHOLOGICAL PARAMETERS

The Eastern Andes Cordillera of the Colombian Andes, which extends from nearly 2° to 11° of latitude, is currently thought to have risen up to 1500 to 2500 meters, 3 to 6 My ago, which makes it a unique example of rapid uplift in the world. However, this uplift rate has been suggested for the entire Cordillera based mainly from paleobotanical data from the savanna of Bogota, which might not reflect the entire span of the mountainous range. Moreover, climatic changes that this uplift produced (which changed the ecological niches from the plants studied) were also not considered. Here we present a hypsometric and drainage network analysis for the entire range of the Eastern Cordillera. This was done by delineating watersheds for the whole mountain range and calculating its respective hypsometric curve with the ArcMap extension CalHypso, parameters such as hypsometric integral, skewness and kurtosis were calculated for each curve. Also a drainage network analysis was made using 30m resolution DEM data, drainage patterns and flow directions were calculated in order to stablish if there has been a major tectonic re-arrangement of drainages. Based on the hypsometric integral we propose three main zones in which to divide the Cordillera: a young Cundinamarca-Boyacá high-plain zone (in which the savanna of Bogotá is located), an old Cocuy zone (which corresponds to the highest peaks of the Cordillera) and a middle-age south section of the Cordillera. Drainage analysis suggest there has not been a major tectonic re-arrangement for drainages for a long time. Given these results we suggest that the zones shown by the hypsometric integral might reflect spatial-temporal variability for the Cordillera uplift, and therefore the previously calculated uplift age for the cordillera should not be applied for the whole range.