The Chongón/Colonche orocline transrotational bending and the coeval opening of the Progreso basin in southwestern Ecuador

Comment on “The Chongón/Colonche orocline transrotational bending and the coeval opening of the Progreso basin in southwestern Ecuador” by Alemán et al

“…Contrary to Alemán et al, [2021], we support the CLIP model based on the comprehensive amount of available studies employing geochemical [Lebrat et al, 1985;Reynaud et al, 1999;Hughes and Pilatasig, 2002;Kerr et al, 2002;Mamberti et al, 2003;Van Melle et al, 2008], radiometric [Kerr et al, 2002;Luzieux, 2007;Vallejo, 2007;Vallejo et al, 2009], and paleomagnetic data [Roperch et al, 1987;Luzieux et al, 2006;Luzieux, 2007]. However, Alemán et al, [2021] cast valid doubts on the CLIP interpretation and the single terrane hypothesis based on older ages (85-98 Ma U/Pb in zircons) reported by Macías [2018] for several granitoid rocks intruding the Piñon Formation in SW Ecuador. But we consider that a more complex plateau architecture does not preclude the existence of a single accretional episode.…”

“…A recurrent discrepancy between researchers working with the geology of the Northern Andes is related to the number of oceanic plateaus and accretionary episodes that have taken place since the Late Cretaceous. In this context, Alemán et al, [2021] support the premise of two distinctive intra-oceanic arcs and two episodes of accretion by concurring with Jaillard et al, [1995]. However, Alemán et al, [2021] overlooked the model updates presented by the same authors in Van Melle et al, [2008] and Jaillard et al, [2009].…”

“…In this context, Alemán et al, [2021] support the premise of two distinctive intra-oceanic arcs and two episodes of accretion by concurring with Jaillard et al, [1995]. However, Alemán et al, [2021] overlooked the model updates presented by the same authors in Van Melle et al, [2008] and Jaillard et al, [2009]. For instance, Van Melle et al, [2008] present a re-evaluation of the stratigraphy and geochemical data to conclude that the Piñon block represents a crustal fragmentation of the CLIP with the San Lorenzo built-in arc before the collision.…”

“…Throughout this comment, we also use this opportunity to clarify some of the statements or assumptions made by Alemán et al, [2021] regarding our work in Aizprua et al, [2020] and Witt et al, [2019b]. Furthermore, we provide further elements that reinforce our model, which considers the Progreso Basin as a sensu stricto forearc basin (a neutral-accretionary type based on the classification by Noda [2016]).…”

“…This led them to infer a ~30 • counterclockwise block rotation, without presenting any structural or paleomagnetic evidence. In our opinion, Alemán et al, [2021] not only present a poorly data constrained model, but they also present an approach oriented to obviate and invalidate previous work as a manner to reinforce their own. Thus, this comment is an opportunity to discuss several critical points, which have neither been satisfactorily explained nor adequately constrained by Alemán et al, [2021].…”