Lithostratigraphy, age and distribution of Eocene volcanic sequences on eastern King George Island, South Shetland Islands, Antarctica

New mapping and dating of volcanic outcrops on the east coast of Admiralty Bay, King George Island, has demonstrated that Eocene volcanic sequences are dominant and also crop out extensively elsewhere, particularly on the eastern part of the island. The sequences can be divided into at least three formations (Hennequin, Cape Vaureal and Carruthers Cliff) together with Eocene strata at Warkocz and near Lions Rump that are currently unassigned stratigraphically. New and recently published 40Ar/39Ar ages indicate that all of the formations are Early Eocene in age, mainly Ypresian, extending to Lutetian and possibly even Priabonian time in more easterly outcrops. Compositional contrasts exist between the groups (calc-alkaline vs tholeiitic). The formations are mainly composed of lavas, and many show evidence for contemporary inundation by water. They are interbedded with sedimentary rocks deposited mainly during flooding events as debris flows, debris avalanches, hyperconcentrated flows, from traction currents and in lakes. The common presence of juvenile volcanic detritus suggests that the sediments were probably linked to explosive hydrovolcanic eruptions, some of which were possibly rooted in summit ice caps. Other evidence is also permissive, but the presence of Eocene ice on King George Island is not well established at present.

Automated summary

The volcanic outcrops on the east coast of Admiralty Bay, King George Island, are mainly Eocene in age, with compositional contrasts between calc-alkaline and tholeiitic groups. These formations are mainly composed of lavas, interbedded with sedimentary rocks possibly linked to explosive hydrovolcanic eruptions, highlighting evidence of contemporary inundation by water and flooding events. The presence of juvenile volcanic detritus suggests a potential connection to eruptive activities, but the existence of Eocene ice on King George Island remains uncertain.