The Falcón Basin in northwestern Venezuela has a complex geological history driven by the interactions between the South American and Caribbean plates. Igneous intrusive bodies that outcrop along the axis of the basin have been associated with crustal thinning, and gravity modeling has shown evidence for a significantly thinned crust beneath the basin. In this study, crustal scale seismic refraction/wide-angle reflection data derived from onshore/offshore active seismic experiments are interpreted and forward-modeled to generate a P-wave velocity model for a ∼450 km long profile. The final model shows thinning of the crust beneath the Falcón Basin where depth to Moho decreases to 27 km from a value of 40 km about 100 km to the south. A deeper reflected phase on the offshore section is interpreted to be derived from the downgoing Caribbean slab. Velocity values were converted to density and the resulting gravimetric response was shown to be consistent with the regional gravity anomaly. The crustal thinning proposed here supports a rift origin for the Falcón Basin.
Bibliographical noteFunding Information:
Contribution to BOLIVAR and GEODINOS (G-2002000478) projects, funded by NSF and FONACIT, respectively. The authors wish to acknowledge the work of all the participants in the data acquisition campaign: both the volunteers on land and the investigators and crew on board the R/V Maurice Ewing as well as the IRIS-PASSCAL personnel. Recording instruments on land were provided by IRIS Instrument Center, New Mexico, and pre-processing done by their personnel M. Fort, B. Greschke, E. Gutierrez, P. Miller and W. Zamora, is gratefully acknowledged. The authors also wish to thank F. Vernon (UCSD) for providing access to the continuous records of the seismological stations, F. Urbani, C. Zelt and J. Morgan for valuable comments, as well as two anonymous reviewers for their observations that helped improve the manuscript and Miguel Palma of FUNVISIS for providing the seismicity data. Landshots were funded by GEODINOS, FUNVISIS and PDVSA-INTEVEP (project 04-141). Further members of the BOLIVAR active seismic working group are: A. Levander, C. Zelt, M.B. Magnani, D. Sawyer, (Rice U); V. Rocabado, J. Sánchez (FUNVISIS); G. Christeson, P. Mann, A. Escalona (UTIG); N. Nevado (PDVSA-INTEVEP).
- Crustal structure
- Falcón basin