Theoretical process-based models of braided alluvial architecture suggest that aggradation rate is a primary controlon the geometry, stacking and heterogeneity of sedimentary deposits. This hypothesis is tested at the scale of thechannel and bar using a combined field and flume modelling study, which quantifies the impact of a change inaggradation rate on the frequency of occurrence and geometry of the key depositional units that dominate coarsegrained,braided alluvial architecture. Aggradation of a 1 : 50 scale model of the braided Ashburton River, NewZealand, produces realistic alluvial architecture that closely corresponds to 7 km of logged field prototype outcrop.A twofold change in aggradation rate in the flume model and an order-of-magnitude change in the field outcrop,have no influence on the geometry and vertical distribution of fine- and coarse-grained depositional niches.Braided alluvial architecture at the channel scale therefore is determined by the local ‘instantaneous’ aggradationrate, related to individual flood events, rather than the long-term, regional aggradation rate.
|Title of host publication||Fluvial Sedimentology VI|
|Editors||N.D. Smith, J. Roger|
|Place of Publication||UK|
|Number of pages||14|
|Publication status||Published - 1 Jan 1999|
|Name||Special Publication of International Association of Sedimentologists|