The Bartlett Trough is a submarine depression extending east-west at least 1,600 km from Guatemala to the Windward Passage. New bathymetric, seismic-reflection, and magnetic data have been obtained from the western part of the trough.

The Cayman Ridge bounds the trough on the north, and appears to end about 100 km from the shelf off British Honduras. A basement high, here named the "Bonacca Ridge," bounds the trough on the south from the Bay Islands as far east as Swan Island. North of the Bay Islands, a previously uncharted deep (here named "Bonacca Deep") lies at the base of the southern escarpment of the trough. Many basins, ridges, and banks were found south of the trough between the Bonacca Ridge and the Nicaragua Rise.

New bathymetric and magnetic maps and seismic-reflection profiles illustrate the main structural features of the area. Attempts to derive reasonable structural models that fit the observed magnetic, bathymetric, and seismic data were unsuccessful.

No evidence for large lateral offset parallel with the axis of the structure has been found, nor has evidence been found for subsidence of the central block of a large graben. Instead, the trough appears to be an area of normal oceanic depth between two parallel ridges composed of continental crust.