Autogenic cycles of channelized fluvial and sheet flow and their potential role in driving long-runout gravel progradation in sedimentary basins

摘要: The paleoslope estimation method uses a threshold-shear-stress criterion, together with field-based measurements of median grain size and channel depth in alluvial gravel deposits, to calculate the threshold paleoslopes sedimentary basins. Threshold are minimum slopes that would have been necessary transport sediment those In some applications this method, inferred sufficiently steeper than modern large-magnitude tectonic tilting must occurred order for sediments transported their present locations. paper, we argue autogenic cycles channelized fluvial sheet flow basins result spatial temporal variations slope can, under certain conditions, cause prograde out distances much longer previously thought possible based on theory (i.e., several hundred kilometers or more from source region). We test hypothesis using numerical models two types basins: (1) an isolated basin prescribed upstream, (2) dynamically coupled postorogenic mountain belt. models, entrainment varied stochastically through time amplitude equal analysis geometry data rivers. Our show when local values vary supply is relatively low compared capacity, gravels can persistently at far below predicted by theory. holds whether stochastic changes autocorrelated along entire profile occur localized sections profile. As such, our model results suggest long-runout do not require steep regional occur. conclude progradational adjacent ranges functions both mean coefficient variation water-flow depths as well density texture bed sediment.