Tectonic interpretation of the morphology of Honduras

Abstract

The morphotectonics of Honduras have been studied using existing geologic and topographic maps and imaging done from satellites, and the following interpretations have been made. During the late Oligocene to early Miocene a wide strike‐slip boundary existed in western Honduras and eastern Guatemala and produced east‐west trending basins containing the coarse clastic rocks of the Subinal Formation. Marine geophysical studies of the continental shelf of Honduras show that during the rest of the Miocene and the early Pliocene the boundary was inactive, but motion resumed in the late Pliocene to Pleistocene and produced horsts on the north coast of Honduras. In northwestern Honduras the east‐northeast trending alignment of the Jocotan, Copan, and Charnelecon river valleys may result from crustal flexuring rather than from faulting, as previously proposed, because the postulated fault (the Jocotan‐Chamelecon fault) cannot be reconciled with available geologic maps. The northwest and northeast flowing rivers of central and eastern Honduras define domains of strike‐slip faulting that have probably rotated 30° from an original set of conjugate fractures. Widespread deposition of conglomerates suggests that strike‐slip movements began in the mid‐Cretaceous and reoccurred at intervals, culminating in the development of pull‐apart basins in western Honduras during the late Pliocene. At the present time, no further strike‐slip movement is possible, as the faults defining each domain lie parallel and perpendicular to the Middle America trench. New conjugate fractures, however, cut Honduras along north‐south and east‐northeast trends and have also separated into domains. In the domain of north‐south fractures, easterly directed, ductile extension of the lithosphere beneath western Honduras and Guatemala is opening up rifts, but the domain of east‐northeast fractures is characterized by strike‐slip motion that has produced left‐lateral pull‐aparts in central Honduras. Early workers identified no rift valley extending from the Gulf of Fonseca to the Caribbean, and there is no fresh evidence upon which to base the existence of one today. The notion of the Honduras Depression, which has persisted over the last half century, stems from misinterpretation of the maps and writings of Karl Sapper.