We present a δ¹³C record from the Anti-Atlas mountains of Morocco and place it in the context of a detailed regional tectonostratigraphy. We place the litho- and chemostratigraphic record in a temporal framework using precision U–Pb zircon geochronology of ashes interbedded with the same carbonate units that provide δ¹³C data. The variations in δ¹³C of carbonate occur on a wide range of time scales, suggesting that different mechanisms are involved, including non-steady state release of isotopically depleted carbon reservoirs on short (<100 000 years) time scales and changes in nutrient recycling and organic carbon burial on longer (≥1 Ma) time scales. Through a correlation with more fossiliferous, albeit condensed, sections in Siberia, we examine the pattern of cyclic δ¹³C variation in the context of the reappearance and diversification of skeletonized metazoa during the Early Cambrian.