TECTONO-STRATIGRAPHIC REASSESSMENT OF THE EASTERN PART OF THE GUERRERO TERRANE BASED ON NEW 40AR/39AR DATA: SINGLE-ARC VS MULTIPLE-ARC MODEL

The Guerrero terrane is the second largest terrane accreted to the North American Pacific margin. This terrane is composed of a Paleozoic–Triassic metasedimentary basement unconformably overlain by Jurassic–Cretaceous arc and back-arc successions that were developed peripherally to the North American craton. According to the literature, the Guerrero terrane is subdivided into different fault-bounded subterranes that have been interpreted as independent arc-back-arc systems developed at different subduction boundaries and subsequently accreted to the North American craton. The adoption of this scheme resulted in the impossibility of integrating and correlating available data from different parts of the Guerrero terrane in order to obtain a basic regional-scale tectono-stratigraphic framework that permits the formulation of unbiased tectonic interpretations. In this work, we present new ⁴⁰Ar/³⁹Ar ages that show that thrust-faults that were interpreted as subterrane boundaries are post-accretionary structures. In light of our data, we encourage abandonment of the current subterrane subdivision adopted for the Guerrero terrane and propose a new tectono-stratigraphic scheme based on regional stratigraphic correlations. According to this new scheme, the Guerrero terrane is interpreted as a single arc-back-arc system developed marginally to the North American craton rather than multiple and independent arc-back-arc systems developed at different subduction boundaries.