Palaeolatitude drift history of displaced terranes in southern and Baja California

Abstract

The delineation of microplate-tectonic terranes1 which make up western North America, the timing of their accretions to western North America and the identification of their original geological settings are all topics of debate2,3. The most recent addition to this family of terranes is the Santa Lucia/Orocopia allochthon4,5 (SLOA) (Fig. 1), which is made up of Salinia6,7 and several other smaller terranes8 and is located in central and southern California. This composite terrane amalgamated in the Cretaceous and accreted to southern California by the early Palaeogene4,5. We describe here new palaeomagnetic results from localities outboard from the SLOA in southern California (USA) and Baja California (Mexico). These results are used to define a newly identified allochthonous terrane in southern and Baja California (Peninsular Ranges terrane9, PRT) which is outboard from the SLOA, estimate the PRT's palaeolatitude drift history for the past 160 Myr, and infer its original geological setting. PRT and SLOA palaeolatitude drift histories are then combined to produce a new perspective on the tectonic development of southern and Baja California over the past 160 Myr.