Fossil Transverse Ribs in Holocene Alluvial Fan Deposits, Depot Creek, South Australia

Regularly-spaced clusters of coarse imbricate gravel in Holocene alluvial fan sediments of Depot Creek, South Australia, are interpreted as fossil transverse ribs. In grain size and morphology they are identical to modern transverse ribs in the creek and fit an extension to higher values of Koster's (1978) grain size-wavelength plot for ribs from a variety of high-gradient gravel-bed streams. Recognition of fossil transverse ribs permits determination of former antidune wavelength, and hence the calculation of paleovelocity, depth and Froude Number.