Isotopic ages of selected magmatic rocks from King George Island (West Antarctica ) controlled by magnetostratigraphy

• Main Authors: Nawrocki, Jerzy, Pańczyk, Magdalena, Williams, Ian
• Format: Article in Journal/Newspaper
• Language: English
• Published: Polish Geological Institute-National Research Institute 2011
• Subjects: Antarctica; King George Island; magnetostratigraphy; isotopic ages; Uchatka Point; West Antarctica; Antarc*
• Online Access: https://gq.pgi.gov.pl/article/view/7721; https://doi.org/10.7306/gq.v55i4.7721

Isotopic and palaeomagnetic studies were carried out in the central part of King George Island. Selected mafic to intermediate igneous rocks were sampled for this purpose. Single-grain U-Pb dating of zircons from basalts to dacites was controlled by a whole rock 40Ar-39Ar data and the magnetostratigraphy. Five magmatic activity phases were distinguished in the SE coast of King George Island. The oldest, late Cretaceous (Campanian) phase represented by basalts of the Uchatka Point Formation are followed by the early to middle Eocene (~5343 Ma) phase documented by the lava flows whose ages decrease from SW to NE. Next younger magmatic activity phases were recorded by the lava flows or vertical intrusions emplaced in the late Eocene (~3735 Ma), late Oligocene (~2825 Ma) and late Pliocene to Holocene. The early to middle Eocene magmatic activity phase was the most extensive, producing the largest volume of magma in the study area. The new age determinations allow a more precise and credible stratigraphic correlation of the interbeds of sedimentary rocks observed in some places within the magmatic succession. The glacial provenance of the Hervľ Cove diamictite is not obvious. It might represent a mountain river environment. Intense volcanic activity could be additional factor modelling the climate conditions of Antarctica in Paleogene