Geologic evidence for the prolongation of active normal faults of the Mona Rift into northwestern Puerto Rico.

Jean-Claude Hippolyte (1) , P. Mann (2) , N. Grindlay (3)

1 LGCA - Laboratoire de Géodynamique des Chaines Alpines
2 IG - Institute of Geophysics [Austin]
3 Center of Marine Science

Topography, bathymetry, regional structural observations, and fault slip measurements support the idea that the Mona rift is an active, offshore extensional structure separating a colliding area (eastern Hispaniola) from a subducting area (northwestern Puerto Rico). Near the city of Aguadilla in northwestern Puerto Rico, paleostress reconstruction through fault slip analysis demonstrates that the Mona rift is opening in an E-W direction. Fault slip analysis also indicates that this opening is oblique in the southern part of the rift. We propose that oblique rifting results from accommodation of E-W extension by oblique right-lateral reactivation of previously mapped, northwest-trending Eocene basement convergent structures (Aguadilla faults, Cerro-Goden fault). The evolution of the stress field during the Miocene and the present E-W opening of the Mona rift support the assumption that the Miocene 25° counterclockwise rotation of Puerto Rico has stopped and that this island is presently moving to the east relative to the colliding Hispaniola.

Domaines: Tectonique

Jean-Claude Hippolyte, P. Mann, N. Grindlay. Geologic evidence for the prolongation of active normal faults of the Mona Rift into northwestern Puerto Rico.. Geological Society of America Special Papers, 2005, 385, pp.161-171. ⟨hal-00100359⟩