The Geode Nunataks (69°50′S 70°5′W / 69.833°S 70.083°W / -69.833; -70.083) are a group of small nunataks on the west side of Sibelius Glacier, immediately north of the northern extremity of the Finlandia Foothills, in northeast Alexander Island, Antarctica.
They were so named by the UK Antarctic Place-Names Committee in 1977; the nunataks are composed of lava flows with abundant geodes (cavities within the rock containing quartz and calcite crystals).
[1][2] The subdued, scree-covered slopes of the Geode Nunataks expose volcanic rocks of the Finlandia Formation.
Whole rock K–Ar ages from Geode Nunataks basaltic andesite lavas range between 59.9±1.41 and 41.3±1.01 myr.
Whole-rock K–Ar ages from Finlandia Foothills basaltic andesites range between 50.2 ± 1.3 and 45.5 ± 1.3 myr.