Abstract

MICHAUD, François et al. The Tosco-Abreojos fault zone: an active dextral system between the Pacific plate and the Baja California peninsula. Bol. Soc. Geol. Mex [online]. 2005, vol.57, n.1, pp.53-63. ISSN 1405-3322.  https://doi.org/10.18268/bsgm2005v57n1a3.

At 12.5 Ma, after the subduction of the Guadalupe below North America plate has stopped, a right lateral transform motion occurred along the margin, between Pacific and North America plates. The Tosco-Abreojos fault zone, located along the margin of present southern Baja California has been interpreted as the main transform fault between both plates until early Pliocene, when the transform plate boundary has been transferred to the east along the Gulf of California, with the capture of Baja California Peninsula by the Pacific plate. Nevertheless, the morphology and the seismic activity of the Tosco-Abreojos fault zone suggest a present-day right lateral strike-slip motion. The Tosco-Abreojos fault zone is characterized by bathymetric scarps and asymmetric basins filled by recent sediments which are deformed. These observations are compatible with cinematic data (GPS and global cinematic models) which suggest that the relative motion of the Pacific plate with respect to the North America plate is partitioned along faults among which the Tosco-Abreojos fault zone, that is not a relict structure, even if the main right-lateral motion is absorbed by the Gulf of California faulted and spreading system. In that way the Baja California Peninsula is considered as an individualized block limited to the west by the Tosco-Abreojos and San Benito fault zones and by the Gulf of California transform boundary to the east.

Keywords : Tosco-Abreojos fault; Seafloor morphology; plate boundary; Baja California peninsula; Pacific plate.

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