Physics
Scientific paper
Dec 2005
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005jgre..11012s15i&link_type=abstract
Journal of Geophysical Research, Volume 110, Issue E12, CiteID E12S15
Physics
57
Planetary Sciences: Solar System Objects: Mars, Planetary Sciences: Solid Surface Planets: Erosion And Weathering, Planetary Sciences: Solid Surface Planets: Surface Materials And Properties
Scientific paper
To explain the much higher denudation rates and valley network development on early Mars (>~3.6 Gyr ago), most investigators have invoked either steady state warm/wet (Earthlike) or cold/dry (modern Mars) end-member paleoclimates. Here we discuss evidence that highland gradation was prolonged, but generally slow and possibly ephemeral during the Noachian Period, and that the immature valley networks entrenched during a brief terminal epoch of more erosive fluvial activity in the late Noachian to early Hesperian. Observational support for this interpretation includes (1) late-stage breaching of some enclosed basins that had previously been extensively modified, but only by internal erosion and deposition; (2) deposition of pristine deltas and fans during a late stage of contributing valley entrenchment; (3) a brief, erosive response to base level decline (which was imparted as fretted terrain developed by a suite of processes unrelated to surface runoff) in fluvial valleys that crosscut the highland-lowland boundary scarp; and (4) width/contributing area relationships of interior channels within valley networks, which record significant late-stage runoff production with no evidence of recovery to lower-flow conditions. This erosion appears to have ended abruptly, as depositional landforms generally were not entrenched with declining base level in crater lakes. A possible planetwide synchronicity and common cause to the late-stage fluvial activity are possible but remain uncertain. This increased activity of valley networks is offered as a possible explanation for diverse features of highland drainage basins, which were previously cited to support competing warm, wet and cold, dry paleoclimate scenarios.
Craddock Robert A.
Howard Alan D.
Irwin Rossman P.
Moore Jeffrey M.
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