A faithful record of channel mouth bifurcation angles in river delta stratigraphy on Earth and Mars

Robert Clyde Mahon , John B Shaw

Which geomorphologic features of sedimentary systems persist into the stratigraphic record? In modern river deltas, channel mouth bifurcation angles have been shown to be consistent with network growth in a Laplacian flow field proximal to the channel margins. This results in a characteristic bifurcation angle of 72 . However, the persistence of this formative angle through channel evolution and preservation into the stratigraphic record remains untested. Stratigraphic river delta channel mouth bifurcations were measured using stratal slices from 3D seismic as well as Mars HiRISE orbital imagery. We find that channel mouth bifurcations interpreted from terrestrial strata exhibit a mean angle of 72.8 ± 4.1 (95% confidence interval) and those from martian strata exhibit a mean angle of 73.9 ± 6.0 . This is both consistent with theory and with observations from modern river deltas, implying the persistence of this geometry throughout network evolution and preservation, and may therefore be used as a predictive tool. The consistency between terrestrial and martian bifurcation geometry shows the generality of process between planetary systems, independent of differences in gravitational acceleration.