The problem of paleo-planforms

Abstract Reconstructing river planform is crucial to understanding ancient fluvial systems on Earth and other planets. Paleo-planform typically interpreted from qualitative facies interpretations of strata, but these can be inconsistent with quantitative approaches. We tested three well-known hydraulic predictors in Cretaceous strata (in Utah, USA) where there a facies-derived consensus paleo-planform. However, the results each predictor are other. found that one analytically best suited for geologic application favors single-thread planforms. Given this was originally using just 53 data points natural rivers, we compiled new set geometries rivers (n = 1688), which spanned >550 globally widespread, sand- gravel-bed various climate vegetative regimes. existing criteria misclassified 65% multithread our set, modification resulted useful predictor. show depth/width (H/W) ratio alone sufficient discriminate between (H/W > 0.02) < suggesting bank cohesion may critical determinant planform. Further, slope/Froude (S/Fr) process rivers; i.e., whether generation threads an avulsion-dominated (anastomosing) or bifurcation-dominated (braided) process. Multithread likely anastomosing when S/Fr 0.003 (shallower slopes) braided (steeper slopes). Our successfully modern examples, they offer effective approach predict past