Integrated seismic, flexural and gravimetric modelling of the Coastal Cordillera Thrust Belt and the Guárico Basin, North-Central Region, Venezuela

• Published in: Tectonophysics 2008-11, Vol.459 (1), p.27-37
• Main Authors: Jácome, María I., Rondón, Kenny, Schmitz, Michael, Izarra, Carlos, Viera, Ernesto
• Format: Article
• Language: English
• Subjects: Coastal Cordillera Thrust Belt; Deep wide angle seismic data; Flexural modeling; Gravity modeling; Guárico Basin; Marine
• ISSN: 0040-1951; 1879-3266
• DOI: 10.1016/j.tecto.2008.03.008

We constructed two integrated geodynamic transects for the eastern and western areas of the Coastal Cordillera Thrust Belt and the Guárico Basin (North-Central region of Venezuela), based on information from depth-converted reflection seismic cross-sections, surface geology, Bouguer anomaly and deep refraction seismic profiling. These geodynamic transects were modelled in order to: (1) understand the geodynamic processes responsible for the formation of the Guárico Basin, (2) quantitatively determine the contribution of the Coastal Cordillera thrust sheet loading in the generation of the basin fill (i.e. the effective elastic thickness of the northern part of the South American lithosphere, the total shortening of the thrust belt and the maximum subsidence of the basin) and (3) characterize the crustal structure and Moho depth in North-Central Venezuela. We used flexural modelling to obtain important quantitative information related to the total Middle Eocene to Recent shortening of the Coastal Cordillera, the total subsidence observed in the Guárico Basin and the effective elastic thickness of the South American lithosphere in northern Venezuela. We conclude that the load of the Coastal Cordillera on the South American lithosphere is sufficient to generate the subsidence observed in the Guárico Basin. The total shortening and subsidence obtained in the western transect are 44 km and 5 km, whereas they are 10 km and 7 km, in the eastern transect, respectively. The effective elastic thickness of the South American lithosphere obtained from the modelling is 25 km. The seismically-constrained deep structure of North-Central Venezuela indicates that Moho reaches a maximum depth of 45 km under the Guayana Shield and shallows to the north, to 35 km beneath the Guárico Basin. According to the gravity models, Moho is deeper under the Coastal Cordillera Thrust Belt than expected from flexural modelling, pointing to the existence of a crustal root more than 35 km deep. The Moho gets shallower (30 km) towards the Caribbean Sea.