The tectonic setting of the North America-Caribbean plate boundary has been studied intensively,but some aspects are still poorly understood, particularly along the Oriente fault zone. Guantanamo Bay, or southern Cuba,is considered to be on a coastline that is under a transpressive tectonic regime along this zone, and is hypothesized to have a low uplift rate. We tested this by studying emergent reef terrace deposits around the bay. Reef elevations in the protected, and inner fragment of the bay are ∼1112 m and outer-coast,wave-cut benches are as high as ∼14 m. Uranium-series analyses of corals yield ages ranging from ∼133 ka to ∼119 ka, correlating this reef to the peak of the final interglacial period, or marine isotope stage (MIS) 5.5. Assuming a span of possible paleo-sea levels at the time of the final interglacial period yields long-term tectonic uplift rates of 0.02–0.11 m/ka,supporting the speculation that the tectonic uplift rate is low. Nevertheless, on the eastern and southern coasts of Cuba, or east and west of Guantanamo Bay,there are flights of multiple marine terraces, at higher elevations, and that could record a higher rate of uplift,implying that Guantanamo Bay may be anomalous. Southern Cuba is considered to have experienced a measurable but modest effect from glacial isostatic adjustment (GIA) processes. Thus, with a low uplift rate, and Guantanamo Bay should expose no evidence of emergent marine terraces dating to the ∼100 ka (MIS 5.3) or ∼80 ka (MIS 5.1) sea stands and results of the present study support this.
Source: usgs.gov