A lithostratigraphical and chronological study of Oligocene-Miocene sequences on eastern King George Island, South Shetland Islands (Antarctica), and correlation of glacial episodes with global isotope events

John L Smellie,Richard J Hunt,Alexa Troedson,Rowan Whittle,William C Mcintosh

doi:10.1017/s095410202100033x

Abstract

AbstractKing George Island (South Shetland Islands, Antarctic Peninsula) is renowned for its terrestrial palaeoenvironmental record, which includes evidence for potentially up to four Cenozoic glacial periods. An advantage of the glacigenic outcrops on the island is that they are associated with volcanic formations that can be isotopically dated. As a result of a new mapping and chronological study, it can now be shown that the published stratigraphy and ages of many geological units on eastern King George Island require major revision. The Polonez Glaciation is dated as c. 26.64 ± 1.43 Ma (Late Oligocene (Chattian Stage)) and includes the outcrops previously considered as evidence for an Eocene glacial ('Krakow Glaciation'). It was succeeded by two important volcanic episodes (Boy Point and Cinder Spur formations) formed during a relatively brief interval (< 2 Ma), which also erupted within the Oligocene Chattian Stage. The Melville Glaciation is dated as c. 21–22 Ma (probably 21.8 Ma; Early Miocene (Aquitanian Stage)), and the Legru Glaciation is probably ≤ c. 10 Ma (Late Miocene or younger). As a result of this study, the Polonez and Melville glaciations can now be correlated with increased confidence with the Oi2b and Mi1a isotope zones, respectively, and thus represent major glacial episodes.

Highlights

King George Island is the largest of the South Shetland Islands, situated in northern Antarctic Peninsula (Fig. 1)
Because of the relative ease of access and generally low alteration grade compared with other areas in the Antarctic Peninsula region, the geology of the island has been subject to numerous investigations over the past several decades
As a result of our investigation, significant changes that we propose to the lithostratigraphy of eastern King George Island are summarized as follows

Summary

Introduction

King George Island is the largest of the South Shetland Islands, situated in northern Antarctic Peninsula (Fig. 1). Because of the relative ease of access and generally low alteration grade compared with other areas in the Antarctic Peninsula region, the geology of the island has been subject to numerous investigations over the past several decades. This has resulted in a complicated stratigraphy that has been supported by a large number of isotopic ages, mainly determined by the K-Ar method (see summary of published ages by Leat & Riley 2021a).

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Discussion

Conclusion