PLIO-PLEISTOCENE HISTORY OF FERRAR GLACIER, ANTARCTICA: IMPLICATIONS FOR CLIMATE AND ICE-SHEET STABILITY

Vernier Valley (78^o S, 161^o E) opens onto a peripheral lobe of upper Ferrar glacier in the Dry Valleys region of southern Victoria Land, Antarctica. Ferrar 2, Ferrar 3, and Ferrar 4 drifts in lower Vernier Valley were deposited from Ferrar Glacier. The areal distribution of these drifts, along with a relative and numerical chronology afforded by surface-weathering characteristics and ³He / ²¹Ne exposure-age data, imply progressive thinning of upper Ferrar Glacier ice for at least the last 3 to 4 Ma. Ice-surface profiles reconstructed from the distribution of Ferrar 2, 3, and 4 moraines, combined with ²¹Ne and ³He exposure-age analyses of clasts atop these moraines, indicate that the ice-surface elevation of upper Ferrar Glacier has lowered roughly 50 m throughout the Quaternary Period and roughly 125 m since at least middle Pliocene time. These data illustrate minimal coeval ice-volume change at nearby Taylor Dome. The preservation of undisturbed and unconsolidated sediment beneath Ferrar drifts, the coarse texture of these drifts, and their morphologic similarity with drifts now forming at the surface of Ferrar Glacier all indicate that Ferrar drifts were deposited from cold-based ice. The persistence of thin lobes (< 125 m thick) of cold-based Ferrar Glacier ice implies enduring cold-desert conditions, much like those of today, for at least the last 3 to 4 Ma in lower Vernier Valley.