A NEW MODEL FOR TWO-SIDED RODINIA SUPERCONTINENT ASSEMBLY AS YOUNG AS 900-850 MA

The classic concept of Rodinia supercontinent assembly has emphasized a global network of ca. 1300-1000 Ma “Grenvillian” orogens. Many depictions of Rodinia’s history thus infer the supercontinental tenure to last from 1000 Ma until ca. 800-700 Ma breakup. These concepts are even imbued within the geological timescale: the 1000-Ma Stenian-Tonian boundary owes its etymology to Greek words for a presumed global shift from “narrowing” to “stretching” of ocean basins across the supercontinental cycle. One set of Rodinia models, however, incorporates ca. 900 Ma sutures between Australia and Laurentia, consolidating (paleo)North Rodinia at that relatively young age; such models place South China, or more recently hypothesized Greater Tarim Block, as the “missing links” of final regional assembly. We also draw attention to a new model for the assembly of the (paleo)South side of Rodinia, motivated by recent recognition of abundant ca. 1500-880 Ma detrital zircons in the Neoproterozoic Taoudeni Basin on the West African craton. The new ages suggest proximity of West Africa to Grenvillian (s.l.) orogenic sources, which we incorporate into our model of Rodinia assembly as follows: collision of Amazonia+West Africa+Baltica with Laurentia at ca. 1100-1050 Ma (Ottawan orogeny), followed by the addition of Congo-São Francisco at ca. 900-880 Ma. Therefore, both North and South Rodinia appear to have final collisions at least 100 million years younger than originally supposed. Global detrital zircon records show a dwindling number of ages through ca. 900-800 Ma, which we interpret as timing the apex of Rodinia’s existence, broadly consistent with both the above orogenic history and the global inventory of large igneous provinces that likely relate to breakup. Any proposed links between Rodinia amalgamation/dispersal and other aspects of Earth evolution (e.g., rising oxygen levels or eukaryotic development) should accommodate this integrated paleogeographic and statistical timeline.