Pj. Hearty et al., A +20 m middle Pleistocene sea-level highstand (Bermuda and the Bahamas) due to partial collapse of Antarctic ice, GEOLOGY, 27(4), 1999, pp. 375-378
Marine deposits at +20 +/- 3 m on the tectonically stable coastlines of Ber
muda and the Bahamas support the hypothesis of a partial collapse of the An
tarctic ice sheet during the middle Pleistocene. Beach sediments fill a sea
cave at +22 m in Bermuda, and horizontal, fenestrae-filled beds crop out o
n 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 t
hat is characteristic of a phreatic marine environment. Amino acid racemiza
tion and TIMS (thermal-ionization mass spectrometry) dates constrain the ag
e of the deposits to between 390 and 550 ha, while proxy evidence supports
a correlation with oxygen isotope stage 11. This direct geologic evidence o
f a 20% decrease in polar ice during the middle Pleistocene has important i
mplications for the stability of ice sheets during warm interglaciations.