Abstract
Eight seismic reflection profiles, two dimensions, were collected in a sector of the Magdalena Shelf, Baja California, Mexico, which contains a forearc basin, providing a spatial view of faults and seismic reflectors in this basin. Two small asymmetric basins were configured; Tosco-Abreojos and San Lázaro controlled by the Tosco-Abreojos and Santa Margarita-San Lázaro Faults. These faults accommodate a great part of the transtensional stress in the shelf and control the bathymetry and show great deformation in the western sector. Seismic horizons illustrate that the depocenter of the San Lazaro basin reaches depths of ~4 km, while the Tosco-Abreojos account reaches depths of around ~5.5 km, being present at these depths a diffuse reflector that is considered the acoustic basement.
Highlights
The Baja California micro-plate is a fragment of separated continental crust from the continental region of Mexico and captured by the Pacific plate 10-15 Ma [1,2,3,4,5]
The acoustic basement reflector is the finale of structures that we can see, because to more deep, the image is diffuse. This is because as from the final reflective, we have a single rock probably associated with magmatic rocks where the seismic energy is absorbed. It has identified the acoustic basement in most seismic profiles; this has the form of the longitudinal block along the Magdalena shelf that develops as a consequence two half-graben controlled by two regional faults (Tosco-Abreojos and Santa Margarita - San Lazaro faults) and some minor extensional faults
The interpretation of the San Lazaro-Santa Margarita fault indicates that these structures are relays between them, taking into account what was reported by [10], and including the characteristics of the complete Bouguer anomaly of the map constructed from the data of [18]
Summary
The Baja California micro-plate is a fragment of separated continental crust (detached) from the continental region of Mexico and captured by the Pacific plate 10-15 Ma [1,2,3,4,5]. This is because as from the final reflective, we have a single rock probably associated with magmatic rocks where the seismic energy is absorbed It has identified the acoustic basement in most seismic profiles; this has the form of the longitudinal block along the Magdalena shelf that develops as a consequence two half-graben controlled by two regional faults (Tosco-Abreojos and Santa Margarita - San Lazaro faults) and some minor extensional faults. The Tosco-Abreojos fault is not present in the seismic profiles of this work, but it is observed in the geomorphology of the seabed, and it is the one that controls the basin of the same name This fault is regional, while the San Lazaro fault is relayed with the Santa Margarita fault (Figure 8) and with a normal-type listric geometry submerged in the depression, San Lázaro. The main contribution of the sediment to the basins comes from the continental arc of Baja California, as suggested [26]
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