Paleozoic vegetation and the Siluro-Devonian rise of fluvial lateral accretion sets

A long-standing hypothesis links the increased prominence of meandering rivers in the Paleozoic to the colonization of terrestrial environments by vegetation. This hypoth- is tested using a data set of Cambrian to Devonian fl uvial literature and fi eld examina- of key stratigraphic units. According to some researchers, Cambrian to mid-Silurian systems were braided in planform, with a sharp increase in the abundance of mean- rivers during the Silurian–Devonian. Although meandering systems were largely fi ed on the basis of thick mudstones and organized channel deposits, the data set of lateral accretion sets appears to be a robust proxy for the abundance of meander- river point bars. Lateral accretion is fi rst recorded from Pridolian–Lochkovian strata, is noted in nearly 40% of fl uvial case studies by the Famennian. This trend matches the record of rooted vegetation, suggesting that vegetation progressively stabilized river and promoted single-thread channels. However, the presence of Precambrian and meandering systems indicates that vegetation is not essential for meander- , and the lack of evidence for Cambrian to Silurian (Ludlow) point bars is surprising. If present, they may largely have been destroyed by extreme fl oods, chute cut-offs in -grained meandering systems, and eolian activity.