The opening and closure of the Jurassic-Cretaceous Xolapa basin, southern Mexico

Structural data and cross-cutting relationships in the Xolapa Complex around Puerto Escondido, southern Mexico, indicate the development of two pre-Cenozoic folding systems recorded, in part, by migmatites. The older system is defined by gently SW-plunging, vertical open folds (FS1), related to a southwestward extension. A subsequent FS2 folding system is defined in turn by slightly SE-plunging, northwest-facing asymmetric folds, related to a northeastward transpression. The comparison between our structural data and those available in the literature indicate that both FS1 and FS2 are pervasive in the whole Xolapa Complex. In addition to the reciprocal link between orientation, lineation distribution, and kinematics between folding systems, higher strain components of FS2 and FS1 yield a strikingly similar direction but opposite sense, suggesting a paired tectonic cycle of opening (FS1) and closure (FS2) of a Xolapa Complex basin. From the comparison between crosscutting relationships in the study area and a compilation of U-Pb zircon data from the literature, we deduce that the opening of the Xolapa basin occurred sometime between 158 and 129 Ma; this is between the termination of the continental Nazas arc and the early stages of the extensional Guerrero arc. On the other hand, the closure of the Xolapa basin (FS2) took place between 94 and 72 Ma.