U–Pb isotopic ages and provenance of some far-travelled exotic pebbles from glaciogenic sediments of the Polonez Cove Formation (Oligocene, King George Island)

Abstract

Zircon grains from nine erratic pebbles of granite, granodiorite–tonalite and quartzite from the Polonez Cove Formation (southern King George Island) were studied for their U–Pb isotope ages and provenance. The calculated concordia ages of the studied pebbles are 108.79 ± 0.89, 119.7 ± 2.2, 178.6 ± 2.8, 180.7 ± 1.9, 207.4 ± 3.1, 231.1 ± 1.9, 1087.5 ± 4 and 1833 ± 4 Ma. The source area of individual pebbles was analysed and defined. Pebbles of crystalline rocks were derived from the Antarctic Peninsula, as well as from the Antarctic mainland. The erratic made of quartzite was eroded from the southernmost part of the Ellsworth Mountains (Linder Peak Member of Howard Nunatak Formation). Our isotope data analytically support the earlier thesis that the Oligocene ice-sheet covered a substantial part of Antarctica and its nucleus was located in its central part. Supplementary material: The U–Pb isotope data (Table S1) are available at https://doi.org/10.6084/m9.figshare.c.5233335