Constraining the Formation Timescale, Sediment Transport Rates and Median Grain Size of Eberswalde Delta, Mars

Abstract

The highly sinuous meandering channels of the Eberswalde Delta on Mars suggest that the delta was long lived somewhere between 3.7 to 3 billion years ago, but it has been hard to constrain timescale and estimate sediment flux without detailed stratigraphy. The rover missions to Jezero and Gale crater have inspired new sediment transport models and formation timescale calculations. Three papers were selected and applied on Eberswalde to constrain its timeline. Bankfull depth is hard to measure without a stratigraphic record so 2 different depths were taken. The first method required estimations of avulsion timescale, meander migration and aggradation rate to find the minimum formation timescale. This was found to be 8 years for deep waters and 50 years for shallow waters. The minimum timescale was used to estimate intermittency which ranged from 10-4 and 10-6. The total formation timescale was found from source-to-sink methods which ranged from 105 to 107 years. The intermittency factors were applied to 3 sediment transport profiles for different grain sizes to verify the total formation timescale. All 3 profiles vary from each other but predict similar timescales of a few million years for a cold, dry climate. To build high sinuous channels as observed on Eberswalde, the channels would have to carry high concentrations of clay or silt to provide enough cohesion for lateral migration. As such, the channels carried a mix of grains that ranged from small boulder to clay, with the median grain size ranging from coarse sand to pebbles. Given the low intermittency factor, the Noachian was likely cold and dry with brief warming periods in between as observed in the evolution of Eberswalde lobes. Life may have formed in these brief periods but cannot be confirmed without ground-based data or improved spectroscopic techniques.