Oligocene and Pliocene interglacial events in the Antarctic Peninsula dated using strontium isotope stratigraphy

Strontium isotope stratigraphy is used to date two interglacial-marine deposits in the Antarctic Peninsula region. On King George Island, interglacial pectinid-rich sediments in the Low Head Member of the Polonez Cove Formation give a strontium isotope stratigraphy age of 29.0(-0.6)(+0.7) to 29.8(-0.7)(+0.8) Ma (mid-Oligocene), which, in conjunction with previous K-Ar dating of volcanic rocks, indicates a glacial episode in the Antarctic Peninsula between middle Eocene (42.0+/-1.0 Ma) and mid-Oligocene time. In addition, an inter-glacial deposit (Pecten Conglomerate) from tectonically-elevated exposures on Cockburn Island is dated as Pliocene (3.5-5.3 Ma). Published data suggest these latter sediments were deposited under shallow marine conditions, which were warmer than those of present-day Antarctica.