Newly available seismic reflection data are applied to an interpretation of the Cibao basin of Hispaniola. The data include multichannel seismic reflection profiles from Samana Bay and the central part of the Cibao Valley, and single-channel seismic profiles from the western offshore extension of the Cibao Valley and the Windward Passage. A single track of GLORIA imagery through the Windward Passage is also used. The data in Samana Bay reveal a major, active, easterly oriented normal fault (transcurrent?) and a significant increase in sedimentation from the north, which probably began during Miocene to Pliocene time. A seismic reflection line in the central part of Cibao Valley demonstrates that the sedimentary material in the valley is at least 5 km thick, with the thickest section in the north adjacent to the Septentrional fault. The southern margin of the Cibao Valley appears to be the locus of a hingeline, although minor faults may be present. The oldest sedimentary basin fill overlying Cretaceous basement is probably of middle Miocene age based on outcrops of rock. At the western end of the Cibao Valley, the Septentrional fault curves northwesterly before going offshore. In addition, the Tortue fault, which extends offshore along the north coast of Haiti, is an extension of either the Guayubin-Hispaniola fault zones or is a southwestern branch of the Septentrional fault. It can be identified on the sidescan sonar images in Windward Passage.

Abstract 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 long 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.

Abstract Three-dimensional seismic data from the Torosa Field (Torosa 3D Survey) in the Browse basin of the North West Shelf, Australia display a series of well imaged isolated carbonate platforms that evolve from platform initiation to terminal drowning. The application of seismic geomorphology allows recognition of various carbonate geomorphic elements (depositional and diagenetic) including prograding margins, slope fan and gullied slope deposits, platform interior patch reefs, and karst fabrics. Mapping these features in successive horizon-slices and comparing the spatial changes with changes in seismic geometries (cross-sectional view) allow a more detailed understanding of platform response to relative changes in sea level and the relative complexity of the systems through time. Platform growth initiates as a series of kilometerscale buildups characterized by a circular to elliptical morphology (in plan view). These small-scale buildups quickly coalesce into a series of build-up complexes (2-6 km) with progradational margins. These complexes display either elliptical or rhombohedral shapes. Individual patch reefs can be observed in the platform interiors of the build-up complexes. A second phase of coalescence occurs and the build-up complexes combine into a larger platform (25 × 10 km). This large platform then backsteps and is characterized by a strongly elongate and elliptical shape. The backstepped platform progrades up to 3 km prior to final drowning and burial. The growth of elliptical and rhombohedral buildup shapes appear to be influenced by focused currents between the platforms. A distinct windward-leeward asymmetry has not been recognized in the platforms. The rhombic platform complexes are characterized by a unique “pointed promontory” morphology that develops (perpendicular to the long dimension) as the elliptical complexes evolve into more rhombic shapes through time. Sand waves are also observed in the bottom of the interplatform seaways. The backstepped platforms display prograding seismic reflectors that terminate laterally and are confined to areas of the platform margin protected from influence of currents. Coalescence of the platforms followed the growth of small buildups in the mouths of the interplatform seaways, effectively blocking the seaways and allowing sediment to accumulate in the previously current swept passage. This dataset provides an alternative growth model for platforms strongly influenced by currents, rather than the more common model of progradation with sediment flux dominated by windward-leeward sediment transport.