I've seen many papers and sites that give the dating of Australia's Dresser Formation as 3.5 Ga (variously 3.48 or 3.49 Ga), but I can't seem to find the source of this.
Where does the dating come from, and what is it based on?
Panorama Formation: Paleoarchean min age: 3427 MA Age method: isotopic, U/Pb-Pb/Pb ion probe
Dresser Formation: Min Age: Ma: 3477 Age method: inferred, overlying unit
McPhee Formation: Min Age: 3477 Age method: isotopic, U/Pb-Pb/Pb ion probe
And a few references in..http://geodocs.dmp.wa.gov.au/viewer/multipageViewerAction.do?documentId=440287&viewMarkId=0&ct=true&at=none&btv=true&atv=false&vmtv=false&ac=ff0000&cabinetId=1101&pg=0&scl=64&bds=0|0|2560|3584