Last interglacial reef growth beneath Belize barrier and isolated platformreefs

We report the first radiometric dates (thermal-ionization mass spectrometry ) from late Pleistocene reef deposits from offshore Belize, the location of the largest modern reef complex in the Atlantic Ocean, The results present ed here can be used to explain significant differences in bathymetry, sedim entary facies, and reef development of this major reef area, and the result s are significant because they contribute to the knowledge of the regional geology of the eastern Yucatan. The previously held concept of a neotectoni cally stable eastern Yucatan is challenged. The dates indicate that Pleisto cene reefs and shallow-water Limestones, which form the basement of modern reefs in the area, accumulated ca. 125-130 ka. Significant differences in e levation of the samples relative to present sea level (>10 m) have several possible causes. Differential subsidence along a series of continental marg in fault blocks in combination with variation in karstification are probabl y the prime causes, Differential subsidence is presumably related to initia l extension and later left-lateral movements along the adjacent active boun dary between the North American and Caribbean plates. Increasing dissolutio n toward the south during Pleistocene sea-level lowstands is probably a con sequence of higher precipitation rates in mountainous southern Belize.