Variability of fluvial architecture in a poorly vegetated Earth: Silurian sheet-braided and meandering ancestor river deposits recorded in northeastern Brazil

Rivers with little to no influence of vegetation and their implications for the architecture of Early Paleozoic and Precambrian fluvial deposits are an important topic of investigation for both clastic sedimentology and Earth System evolution perspectives. Despite the long-held concept of a dominant style of wide, shallow sheet-braided sandy channels, growing evidence for a great variability of architectural elements in pre-vegetation settings point to the predictable occurrence of other fluvial styles, which are possibly related to areas of low-slope alluvial plains. The present work brings sedimentological descriptions and fluvial style interpretations of Silurian fluvial successions of the Serra Grande Group in northeastern Brazil, developed in a glaciated basin margin (therefore with little to no effect of vegetation). The comparison of the resulting channel body architectures integrated to paleocurrent data and a diffusion-based numerical model enabled the evaluation of the controls on fluvial architecture variability in unvegetated alluvial plains.