Paleogene accretion and dextral displacement of an oceanic terrane in northern Peru

Western Ecuador is made up of oceanic allochthonous terranes accreted betwe en the Late Cretaceous and the Late Paleocene. Boulders of calc-alkaline mi crodiorites are found in a Latest Paleocene-Earliest Eocene conglomerate ex posed near Paita. The geochemistry of the microdiorites indicates that they developed in an intra-oceanic are setting. Their occurrence in the conglom erate demonstrates that oceanic terranes were being eroded similar to 55 Ma ago in northwestern Peru. Since the closest oceanic terranes are presently located in Ecuador, i.e. 250 km farther north, these terranes have migrate d NNE-ward along dextral wrench faults, at a minimum rate of 4.5 mm.yr(-1). ((C) 1999 Academie des sciences / Editions scientifiques et medicales Else vier SAS.).