Structural Evolution of the Honduras Continental Margin and the Sea Floor South of the Western Cayman Trough

Abstract

The interpretation of 2,500 km of seismic-reflection profiles and its synthesis with the results of previous work reveal a four-stage development for the Honduras continental margin since late Mesozoic time. Late Cretaceous–early Eocene orogenesis deformed basement rocks and pre-orogenic units offshore Honduras. Following subsidence during middle Tertiary time, postorogenic units I and II blanketed the eroded preorogenic rocks, creating a distinct angular unconformity. The widespread distribution and uniform thickness of the postorogenic sediments suggest deposition during a tectonically quiescent period. Pliocene time marked the onset of block-faulting activity which fragmented the crust into irregular ridges and basins in northern Central America and along the Honduras continental margin and the western Cayman Trough. The continental shelf and slope of Honduras have been prograding since the Miocene Epoch; turbidites are now filling the proximal fault basins offshore Honduras. Assuming that regional tectonism and continental margin development are relatable to lithospheric plate interactions, the deformed preorogenic units are interpreted as having been buckled by convergent plate motions during Late Cretaceous–early Eocene time. Plate slippage may have lapsed during middle Tertiary time, as inferred from the nature of the postorogenic units. This phase of plate passivism was terminated during Pliocene time by block-faulting activity, which presumably represents the resumption of plate motions along the Cayman Trough that have persisted to the present in the northwestern Caribbean.