Mesoproterozoic Tasmania: Witness to the East Antarctica–Laurentia connection within Nuna

Most recent paleogeographic reconstructions of the supercontinent Nuna juxtapose theNorth Australian craton, Mawson continent (South AustraliaEast Antarctica), and Laurentiabetween 1.6 Ga and 1.3 Ga but differ in their relative positioning. The > 10-km-thick siliciclasticRocky Cape Group of Tasmania was deposited in an opening marine basin on the marginof East Antarctica during Nuna breakup. Based on a similar detrital zircon signature anddepositional age, the Rocky Cape Group has been correlated with the upper Belt-Purcell Supergroupin Laurentia, thus representing a key tie point within Nuna. Here the detrital zirconage signature of Mesoproterozoic Rocky Cape Group quartzites is investigated by comparingnew detrital zircon U-Pb-Hf isotopic data to an extensive compilation of zircon isotopic datafrom Australia, East Antarctica, and Laurentia. Our analysis demonstrates that the RockyCape Group is unlikely to have been sourced from any geological terrane exposed in presentdayAustralia. Instead, zircon U-Pb-Hf isotopic data from basement terranes in Laurentia andEast Antarctica show striking similarities to the Rocky Cape Group detrital signature. Paleocurrentdata indicate that the majority of sediment in the Rocky Cape Group was sourcedfrom Laurentia, which was to the southeast (present-day coordinates) of Tasmania, supportinga SWEAT-like (southwest United StatesEast Antarctica) configuration for Nuna. We suggestthat rifting left a thinned continental connection between East Antarctica and Laurentia ontowhich the lower-middle Rocky Cape Group was deposited between 1.45 and 1.30 Ga.