Abstract

Marine deposits at +20 ± 3 m on the tectonically stable coastlines of Bermuda and the Bahamas support the hypothesis of a partial collapse of the Antarctic ice sheet during the middle Pleistocene. Beach sediments fill a sea cave at +22 m in Bermuda, and horizontal, fenestrae-filled beds crop out on platforms at two sites as high as +21 m in Eleuthera, Bahamas. Carbonate beach sands are bound by an early generation of isopachous fibrous cement that is characteristic of a phreatic marine environment. Amino acid racemization and TIMS (thermal-ionization mass spectrometry) dates constrain the age of the deposits to between 390 and 550 ka, while proxy evidence supports a correlation with oxygen isotope stage 11. This direct geologic evidence of a 20% decrease in polar ice during the middle Pleistocene has important implications for the stability of ice sheets during warm interglaciations.

First Page Preview

First page PDF preview
You do not currently have access to this article.