Interpretation of gravity profiles across the northern Oaxaca terrane, its boundaries and the Tehuacán Valley, southern Mexico

•Shallow crustal structure across northernmost Oaxaca Terrane.•Caltepec fault juxtaposes vertically the Oaxaca and Mixteca terranes.•Oaxaca Complex continues stepwise northwards beneath younger rocks.•E.dipping faults downwards displace the Oaxaca complex beneath the Tehuacan through.•Tehuacan through limited by the Oaxaca (east) and Tehuacan (west) faults.•Oaxaca west dipping fault system downwards displace the Oaxaca Complex.•Caltepec, Santa Lucia and Tehuacan faults continue NW beneath younger rocks.

A gravity study was conducted across the northern Oaxaca terrane and its bounding faults: the Caltepec and Oaxaca Faults to the west and east, respectively. These faults juxtapose the Oaxaca terrane against the Mixteca and Juarez terranes, respectively. The Oaxaca Fault also forms the eastern boundary of the Cenozoic Tehuacán depression. On the west, at depth, the Tehuacán valley is limited by the normal buried Tehuacán Fault. This gravity study reveals that the Oaxaca Fault system gives rise to a series of east tilted basamental blocks (Oaxaca Complex). The tectonic depression is filled with Phanerozoic rocks and has a deeper depocenter to the west. The gravity data also indicate that on the west, the Oaxaca Complex, the Caltepec and Santa Lucia faults continue northwestwards beneath Phanerozoic rocks. A major E-W to NE-SW discontinuity is inferred to exist between profiles 1 and 2.