Northeastern Section - 43rd Annual Meeting (27-29 March 2008)
Paper No. 34-1
Presentation Time: 1:00 PM-5:00 PM

MORPHOLOGICAL ANALYSES OF MESAS AND KNOBS IN THE NORTHWEST FRETTED TERRAIN OF MARS: CONSTRAINTS ON THE PRESENCE AND DISTRIBUTION OF ICE-FACILITATED MASS-WASTING

BAKER, David M.1, STEWART, Alexander K.1, and HEAD, James W.2, (1) Department of Geology, St. Lawrence University, Canton, NY 13617, dmbake05@stlawu.edu, (2) Department of Geological Sciences, Brown University, Box 1846, Providence, RI 02912

The fretted terrain on Mars (found 30N to 50N and 0E to 80E) is a transitional zone between highly cratered uplands and younger, less cratered lowlands, which exhibits flat-topped, steep-walled mesas and knobs (Sharp, 1973). These mesas and knobs are separated by younger flat-lying lowlands and lineated lobate debris aprons thought to result from ice-facilitated mass-wasting process from either ground or atmospheric sources. Although the origin of lobate debris aprons is still unclear, formational processes may be constrained from the morphologicial analyses of the adjacent mesas and knobs. The distribution and morphology of mesas and knobs within 38N to 51N and 12E to 37E were analyzed using recent data from Mars Orbiter Laser Altimeter (MOLA), High Resolution Stereo Camera (HRSC), Thermal Emission Imaging System (THEMIS), and Mars Orbiter Camera (MOC) with GIS tools. Mesa and knob areas were delineated from their base up and calculated as a function of distance from the dichotomy boundary escarpment. Results indicate no systematic decrease in mesa area northward away from the escarpment to a maximum distance of 500 km. Mesa and knob spatial densities are greatest in two bands at the 15 km and 150 km distances and are the result of local clustering of small knobs <20 km2 in these areas. Maximum mesa relief also decreases from nearly 2 km to 100-200 m with increasing distance from the escarpment. Where mesa walls are high (0.5 km to 1 km), wall erosion typically includes two to tens of small alcoves several kilometers in length with floors exhibiting alcove-wall-parallel lineations. These results differ from a pattern of decreasing mesa size from the highland escarpment, as suggested for the majority of the fretted terrain. Ice-assisted mass-wasting processes may be less active in mesas near or above 50N due to low mesa relief or latitudinal variations in ice placement. Determining the type and the presence of ice-assisted mass-wasting processes in the fretted terrain may provide valuable insight on the past and present distribution of ice on Mars.

Northeastern Section - 43rd Annual Meeting (27-29 March 2008)
General Information for this Meeting
Session No. 34--Booth# 41
Advances in Planetary Geology: Image Analysis, Lab Results, and Analog Studies (Posters)
Hyatt Regency Buffalo: Grand Ballroom C
1:00 PM-5:00 PM, Friday, 28 March 2008

Geological Society of America Abstracts with Programs, Vol. 40, No. 2, p. 72

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