[S22-1] Lithosphere structure and dynamics

[S22-1-01] GPS Space Geodesy in Colombia, South America: Velocities and the construction of the Eastern Cordillera of the Colombian Andes

^○Hector Mora-Paez¹, Dave Mencin², Peter Molnar², Hans Diederix¹, Leonardo Cardona-Piedrahita¹, Yuli Corchuelo¹, Juan-Ramon Pelaez-Gaviria¹ (1.Colombian Geological Survey, Space Geodesy Research Group, Bogota, Colombia, 2.Department of Geological Sciences, Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado, USA)

Tectonic and volcanic activity in northwestern South America is directly related to the interaction of the South America, Nazca, Cocos and Caribbean plates, and the smaller North Andean, Maracaibo, Choco and Panama blocks. In Colombia, the GeoRed network is a dedicated GNSS network for geodynamic studies installed by the Colombian Geological Survey. For this work, using GPS data from nine CGPS sites and twenty campaign sites, a GPS velocity profile across the northeast-trending Eastern Cordillera of Colombia are estimated and compared with results from previous studies based on paleobotanical derived elevations. The geodetic velocities show oblique convergence at 8.8 ± 1.7 mm/yr, consisting of 8.0 ± 1.7 mm/yr of right-lateral strike-slip shear along the mountain range, and 3.7 ± 0.3 mm/yr of shortening. From this, we conclude the following: first, relative movement of the regions east and west of the Eastern Cordillera includes a large fraction of right-lateral shear; second, the convergence rate, the component of velocities west of the Eastern Cordillera relative to those east of it and perpendicular to the trend of the belt is only ~4 mm/yr; and third, at the northeast end of the Eastern Cordillera, shortening is essentially perpendicular to the local trend of the belt, and the highest mountain elevations lie in this region. The strike-slip shear corroborates geologic work suggesting such movement both southwest and northeast of the range. Given the ~200-km width of the Eastern Cordillera, to accommodate ~ 100-150 km of crustal shortening, which has been inferred from balanced cross sections and is implied by recent estimates of crustal thickness, would require ~25-40 Myr of shortening at 4 mm/yr or a complex velocity history. From our results, we can conclude that the present-day GPS velocities are inconsistent with the inference, based on paleobotanical observations, that the Eastern Cordillera rose 1500-2500 m since 3-6 Ma.