The effect of external controls on channel-belt stacking patterns in the fluvio-deltaic domain of a landscape flume
Summary
External controls such as glacio-eustatic sea-level variation are known to have a strong influence on the areas of deposition and erosion, thereby affecting the location of channels, as well as their stacking patterns. Recent studies have shown that paleo-environmental (allogenic) signals preserved in stratigraphy may be overprinted by internally generated (autogenic) sedimentation. However, it is unclear to what affects external controls, such as sea-level change, subsidence, but also sediment mixture may have on the time scale over which there is a transition between allogenic and autogenic stratigraphy. Two sets of experiments were carried out in the Eurotank Flume Laboratory at Utrecht University during which the morphology and the topography of the fluvial system were regularly monitored to determine compensational stacking. Using statistical methods, basin filling trends were quantified. The compensation index (σss) and the compensation time scale (κn) were used to explore how compensation, the tendency for sediment transport to preferentially fill topographic lows, varies over the basin´s length. The observed compensation time scale, which was defined as the break in the basin-filling trend, varies depending on whether there are any sea-level changes. The time scale at which the fluvial system becomes fully compensated will decrease from source to sink with no sea-level change, but increase during sea-level fall. Understanding channel migration and the resulting channel stacking patterns is important as it provides additional insight in deltas as hydrocarbon reservoirs, and enables further study as to how deltas and continental margins prograde.