Structural and stratigraphic evidence for the offshore extension of the Central Range fault zone of Trinidad into the eastern offshore region
M. David Soto
GPS studies in Trinidad have shown that 80% of the right-lateral strike-slip motion between the Caribbean and South American plates is accommodated by the ENE-striking, 50-km-long Central Range fault zone. We integrate 2D and 3D seismic data from block 2ab to show the subsurface effects of this fault on the Middle Miocene and younger stratigraphy over a 60-km-long and 30-km-wide swath of the eastern shelf of Trinidad. Three surfaces were mapped in detail to generate isochron maps to illustrate the complexity of basins formed within and adjacent to anastomosing strands of the Central Range fault zone: 1) the middle Miocene angular unconformity, a prominent surface separating underlying thrust-deformed rocks from a much less deformed overlying section; 2) an Late Neogene angular unconformity that is not developed across the entire block; and 3) the sea floor. Fill patterns indicate a combined influence of strike-slip faulting and reverse throw on major fault strands which are highly oblique to the interplate slip vector. The Quaternary section includes a large, 14-km-long fluvial channel that has been right-laterally offset by a distance of 322 to 506 m by the main trace of the Central Range fault zone. Assuming the channel formed during the last glacial maximum about 20,000 years ago, a rate of 16 mm/yr of offset can be calculated that is rough agreement with rates calculated from onland GPS-based surveys.