In most of the rivers, the luminescence signals intensities fall with increasing distance from their source and the luminescence of different grain size fractions were variable. Sediment samples composed of poly-mineral and poly-grain sizes were optically stimulated using a Pulsed-Photon Stimulated Luminescence unit. We explore inherited luminescence signals to generate information about different mechanisms involved in mobilization of debris flows in rivers (n = 12) of the Sierra de Juárez (Oaxaca, Mexico), that flow across the Oaxaca and Donaji faults. The models imply that originally the suture was continuous south of the Donaji Fault and provide a constraint for the accretion of the Oaxaca and Juarez terranes. The former suggests that the Donají Fault is a transcurrent fault, whereas the latter implies that it is a transfer fault. The sinistral movement may have taken place either during the Late Mesozoic-Early Cenozoic, Laramide Orogeny as a lateral ramp in the thrust plane or under Miocene–Pliocene, NE–SW extension.

On the other hand, the Oaxaca Fault may either continue unbroken southwards along the western margin of the horst in the Zaachila sub-basin or be offset along with the terrane boundary. 20 km along the E–W Donají Fault, which defines the northern boundary of the Zaachila sub-basin. The new geophysical data suggest that the Oaxaca–Juarez terrane boundary is displaced sinistrally ca. The deeper Zaachila sub-basin, south of Oaxaca city, is a wide V-shaped graben with a horst in the middle. The Etla sub-basin is bounded by the moderately E-dipping, Etla Fault and the more steeply W-dipping Oaxaca Fault, which together constitute a graben that continues southwards into the Atzompa graben.

Cooperative interpretation of six combined gravity and magnetic NE–SW profiles perpendicular to the valleys indicates the presence of a composite depression comprising three N–S sub-basins: the northern Etla and southern Zaachila sub-basins separated by the Atzompa sub-basin. The Oaxaca Fault represents Tertiary extensional reactivation of the Juarez shear zone that constitutes the boundary between the Oaxaca and Juárez terranes. A geophysical survey of the Oaxaca Fault along the north-trending Etla and Zaachila valleys area, southern Mexico, shows a series of NNW–SSE Bouguer and magnetic anomalies with steeper gradients towards the east.

Btr cd juarez