Physics
Scientific paper
Dec 2002
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002agufm.p71a0445b&link_type=abstract
American Geophysical Union, Fall Meeting 2002, abstract #P71A-0445
Physics
1815 Erosion And Sedimentation, 1824 Geomorphology (1625), 5470 Surface Materials And Properties
Scientific paper
Athabasca Valles is the youngest known channel system on Mars. Evidence of its fluvial origin is provided by a variety of geomorphic features in the channel, including transverse dune-like forms similar in appearance to subaqueously-formed dunes in terrestrial floodscapes. We used a 1-D photoclinometry technique to measure the stoss and lee slopes of the dunes, and dune topography. The stoss slopes are shallower than the lee slopes, indicating the features are dunes formed at lower Froude number subcritical flow. This is in contrast to anti-dunes, which have steeper stoss slopes than lee slopes, and form at higher Froude number subcritical or supercritical flow. The measurements also show the dunes have flat upper surfaces, which suggests they are depth-limited dunes. A model for estimating paleoflow depths and velocities from dune morphology was previously developed and applied to relict flood dunes in the Altai Mountains of Siberia. The Altai dunes are on the order of a few tens of meters long and a few meters high, and the model gives a velocity of a few meters per second. We are applying the same model to the Athabasca Valles dunes. Photoclinometry techniques are sensitive to albedo, so that light-colored dust in the troughs introduces error into our topographic measurements. However, we have developed a way to constrain the amount of dust in-fill in the dune troughs, allowing us to estimate that error. We will use the dune geomorphology-based model with the photoclinometric measurements of the dunes to estimate the channel's paleoflood velocity. This velocity, in conjunction with the cross-sectional area, will provide a volumetric discharge estimate.
Beyer Ross A.
Burr Devon M.
Carling Paul A.
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