Interpreted ages from new geochronology have allowed the definition of the ten stratigraphic, volcano-sedimentary associations and their grouping into the Southern Cross Supergroup. These associations yield magmatic crystallization ages between 3.01 and 2.92 Ga and are mapped in several belts along a 750 km corridor within the Youanmi Terrane, Yilgarn Craton. These associations comprise six named formations and four other greenstone successions, which we combine into the Southern Cross Supergroup. The formations are locally well preserved in the stratigraphically lower portions of greenstone belts and are interpreted to unconformably underlie the c. 2.8 Ga Murchison Supergroup. The Southern Cross Supergroup consists of equal parts of meta-basaltic and meta-andesite–dacite–rhyolite rocks, and variable proportions of metasedimentary rocks. In many areas, there are spatially associated synvolcanic tonalite–trondhjemite–granodiorite (TTG) plutons. Whole-rock geochemistry of felsic volcanic rocks indicates multiple source depths and locally highly fractionated compositions. More widely distributed TTG gneisses in the Youanmi Terrane, with magmatic crystallization ages between 3.05 and 2.99 Ga, may have formed basement to the 3.01 – 2.91 Ga volcano-sedimentary rocks, as their chemical compositions are consistent with melting of lower-crustal sources. After deposition of the Southern Cross Supergroup, a magmatic hiatus occurred between 2.91 and 2.82 Ga. Zircon Lu–Hf data for two of the formations of the Southern Cross Supergroup and their proximal, synvolcanic TTGs yield a unimodal peak in εHf values spread over 40 Ma, with εHf indistinguishable from CHUR and with no indication of significant crustal contamination. Distal to the volcanic rocks of the Southern Cross Supergroup, TTG gneisses of the Thundelarra Supersuite are slightly more evolved, with εHf(i) between 0 and -2, indicating minor contributions from a >3.3 Ga crustal component. We consider the geometry of these formations, their homogeneous mantle source, and the punctuated chronology over 100 Ma to be consistent with a rift setting, in which the rift axis was coincident with the juvenile Cue Isotopic Zone (Sm–Nd TDM2 = 2.95 Ga) immediately to the east. Additional data may be needed to rule out other tectonic processes during this time interval. We consider the wide distribution of supracrustal rocks and TTGs from 3.01 – 2.91 Ga to represent a significant building block and a protocratonic stage of the Yilgarn Craton.