Correlation and Late-Stage Deformation of Liv Group Volcanics in the Ross-Delamerian Orogen, Antarctica, from New U-Pb Ages

We present new zircon U-Pb isotopic data for volcanic rocks from deformed metavolcanic-sedimentary successions of the widespread Ross Supergroup in the Queen Maud Mountains, Antarctica. Zircon U-Pb analyses of Liv Group volcanic rocks thought to be Neoproterozoic in age instead have early Paleozoic ages. Zircon U-Pb analyses of five samples assigned to the Fairweather Formation have yielded 524 +/- 9 to 514 +/- 9 Ma (2 sigma) crystallization ages, whereas six samples assigned to the Taylor Formation have yielded 510 +/- 12 to 490 +/- 6 Ma (2 sigma) crystallization ages. Although these ages imply that the Fairweather Formation is generally older than the Taylor Formation, the age uncertainties show a 17-My overlap that is consistent with previous suggestions for temporal correlation of these formations. On a regional scale, Liv Group volcanism overlapped with the emplacement of approximate to 535-490 Ma plutonic rocks associated with the early Paleozoic Queen Maud batholith as well as igneous rocks found elsewhere along the early Paleozoic Pacific-Gondwana margin. Collectively, these igneous rocks provide plausible zircon sources for similar age detrital zircon populations found in outboard siliciclastic rocks belonging to the Leverett, Taylor, Fairweather, Greenlee, and Starshot Formations of the Queen Maud Mountains. The youngest crystallization age yielded by the deformed Taylor Formation (approximate to 490 Ma) assumes regional significance because it represents the youngest volcanic rock yet identified within the Ross orogen in Antarctica and provides important new evidence for latest Cambrian or younger deformation, possibly associated with orogenic collapse during slab rollback at the terminal stages of the Ross orogeny.