Young Mid-latitude Martian Valleys: Evidence from Newton and Gorgonum Basins

Details Young Mid-latitude Martian Valleys: Evidence from Newton and Gorgonum Basins Young Mid-latitude Martian Valleys: Evidence from Newton and Gorgonum Basins

Dec 2009

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agufmep51c0605h&link_type=abstract

American Geophysical Union, Fall Meeting 2009, abstract #EP51C-0605

Physics

[1825] Hydrology / Geomorphology: Fluvial, [5419] Planetary Sciences: Solid Surface Planets / Hydrology And Fluvial Processes

Scientific paper

The mid-latitudes of Mars feature distinctive landforms, including extensive mantling deposits, glacial and periglacial landforms, very young gullies on steep slopes, and sparse, shallowly-incised, fresh-appearing valleys discussed here. These mid-latitude valleys (MLVs) are distinct from the older, late Noachian to early Hesperian valley systems which are deeply dissected, generally of much larger spatial extent and which feature multiple tributaries. The older valley systems extend from equatorial to near-polar latitudes and are much more degraded than the MLVs. Although some MLVs involve rejuvenation of older valley networks, many MLVs are eroded into smooth or rolling slopes and intercrater terrain. The MLVs range from a few meters to more than 300 m in width, with nearly parallel valley walls and planforms that are locally sinuous. Valley floors appear to be nearly flat, sometimes exhibiting faint lineations. These features suggest that the MLVs in many cases are incised channels that were occupied at least intermittently by flows over the entire valley bottom. Particularly diagnostic MLVs occupy parts of the floors of the ~ 300 km Newton and the ~240 km Gorgonum basins on the southern highlands. In Newton basin the MLVs are sourced from the upper basin walls and flow radially inwards towards the basin center, extending across the smooth basin floor (which may have been the site of an earlier paleolake). Incised and depositional sections sometimes alternate in response to variations in basin slope. The valleys terminate in small fans. In some places the valleys appear to anastomose, but it is likely that the multiple valleys record successive flow diversions. There is no evidence that the valleys terminated in standing water in the basin center. MLVs in Gorgonum basin likewise are sourced from the upper basin walls and flow inward, but in this case the valleys disappear at the edge of what has previously been hypothesized to be a late stage, ice-covered lake [Howard and Moore, 2004]. We propose that the MLVs in this region formed from meltwater derived from snow and ice accumulations that primarily occupied the basin rims. The environmental effects of a volcanic eruption or large impact superimposed on an optimal combination of orbital and seasonal forcing were probably required to generate the requisite meltwater. We will report on crater-age dating and discharge calculations for the MLVs.

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