Cover Image Credits

The article by Bradley and others titled “The Assabet barcode: Mesoproterozoic detrital zircons in Neoproterozoic strata from Mauritania, West Africa” (p. 939–992) presents new evidence bearing on the configuration of the Rodinia supercontinent. The Assabet barcode of the title is a distinctive detrital zircon age distribution from widely separated areas of the West African Craton and its surrounding Pan-African orogens. The most likely source of the zircons is Amazonia. Similar detrital zircon age distributions are found in Neoproterozoic strata in locations now as far apart as Russia, the Northern Appalachians, and Brazil. A recent Rodinia reconstruction by coauthor David Evans shows that the known Assabet-like locations were gathered into a relatively compact area before Neoproterozic breakup of this supercontinent.

Explanation of the cover figure: Sandstones of the Aioun Group part of the intracratonic fill of the vast Taoudeni Basin of West Africa. Most detrital zircons recovered from these and correlative Neoproterozoic sandstones are between 2000 and 900 Ma in age and must be exotic to West Africa. The zircons are believed to have been transported thousands of kilometers from orogenic highlands in Amazonia, which had formed during the collisional assembly of Rodinia.