Three-dimensional imaging of the Mérida Andes, Venezuela
- 1German research Center for Geosciences, Near-Surface Geophysics, Germany (jcruces@gfz-potsdam.de)
- 2Free University Berlin, Germany
- 3Potsdam University, Germany
- 4Consulting-GEO, Berlin, Germany
- 5Venezuelan Foundation for seismological Research (FUNVISIS), Caracas, Venezuela
The Mérida Andes are a 100 km wide mountain chain that extends from the Colombian/Venezuelan border to the Caribbean coast. To the north and south, the Mérida Andes are bound by hydrocarbon-rich sedimentary basins. Uplift of the mountains started in the late Miocene due to oblique convergence of the Caribbean and South American tectonic plates and the north-eastwards expulsion of the North Andean Block (NAB). This tectonic interaction fostered major strike-slip fault systems, with associated high seismicity, and the partitioning of the North Andean Block into smaller tectonic units, whose interaction accelerated the uplift of the Mérida Andes since the Plio-Pleistocene.
We present the three-dimensional inversion results of broadband magnetotelluric (MT) data from 72 sites gathered along a 240 km long profile across the central part of the MA, the Maracaibo (MB), and Barinas-Apure (BAB) foreland basins. Directionality and dimensionality analyses suggested 3D structures for the MA section, with the induction vectors indicating off-profile structures, particularly at long periods. Since the distribution of sites predominantly along a single profile can have adverse effects on the outcome of the 3D inversion, we rigorously tested all model features for robustness and excluded artefacts.
One of the main findings is a deep connection (> 10km) between the most prominent faults of the MA, the Valera and Boconó fault systems, with a deep off-profile conductor to the east of our profile. We interpret this conductive structure as a detachment surface of the Trujillo Block, which is part of the NAB and whose expulsion to the NE significantly influences the present-day geodynamic evolution of western Venezuela. A conductive zone under the Maracaibo Basin correlates spatially with the location of a Bouguer low. Both geophysical anomalies may be caused by a SE tilt of the Maracaibo Triangular Block under the Mérida Andes, bound by the north-western thrust system which could reach depths of 30 km.
How to cite: Cruces, J., Ritter, O., Weckmann, U., Tietze, K., Meqbel, N., and Schmitz, M.: Three-dimensional imaging of the Mérida Andes, Venezuela, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15040, https://doi.org/10.5194/egusphere-egu21-15040, 2021.
