| dc.description.abstract | On Mars, several deltaic morphologies are observed. The deposits of these morphologies
indicate sediment transport by river systems creating deltas in standing
bodies of water. Comparison between Earth and Mars is possible, but the gravitational
differences influence the sediments and their transport. This study aims
to provide insight in the effects of lower particle density on delta morphology,
as an approximate representation of decreased gravitation. The focus is on the
impact of ’gravity’ on delta formation, analysing the advection length, depositional
slope, channel behaviour and shoreline morphology. Eight experimental deltas are
used to compare two different density sediments, sand (2650 kg/m3) and nutshell
(1200-1400 kg/m3). Two different grain size distributions are used to analyse
the effect between poorly sorted and uniform sediment in different gravitational
conditions. In the final experiments, a fixed ”river mouth” is modelled to simulate
natural inlet systems. The results of the experiments indicate changes in the delta
formation by differences in sediment transport.
First, the advection length increases, decreasing the depositional slope, by
enhanced sediment transport and decreased settling velocities. The sediments are
transported further into the basin by a higher efficient transport rate.
Second, the channel system becomes more stable and less obstruction of the
channel path occurs. High-density sediments show high avulsion rates, evenly
spreading the sediments over the delta front creating smooth shorelines. The high
settling velocity increases delta height by sediment deposition on the delta plain.
Low-density sediments decrease the avulsion rate, as lower settling velocities result
in less channel obstruction. The higher sediment mobility is expected to increase
erosion, particularly for uniform sediment distributions, and therefore increase
lateral migration. More stable channels increase the progradation over longer
periods in one direction, creating more rugose shorelines and increasing shoreline
length and surface area.
The experiments demonstrate that lower gravity increases the mobilization of
sediments, forming longer advection lengths and therefore lower depositional slopes.
The delta forms lower delta plains and, with an increase in channel stability, a more
rugose shoreline. The research provides insight into the formation of the observed
deposits on Mars. | |
