HR: 1340h
AN: P23A-0175    [Abstracts]
TI: Depth and Morphology of Wrinkle Ridge Detachments at Solis Planum, Mars
AU: * Colton, S L
EM: scolton@swri.org
AF: Center for Nuclear Waste Regulatory Analyses (CNWRA), Southwest Research Institute, 6220 Culebra Road, San Antonio, TX 78238-5166 United States
AU: Ferrill, D A
EM: dferrill@swri.org
AF: Department of Earth, Material, and Planetary Sciences (DEMPS), Southwest Research Institute, 6220 Culebra Road, San Antonio, TX 78238-5166 United States
AU: Smart, K J
EM: ksmart@swri.org
AF: Department of Earth, Material, and Planetary Sciences (DEMPS), Southwest Research Institute, 6220 Culebra Road, San Antonio, TX 78238-5166 United States
AB: Wrinkle ridges -- long, linear to sinuous anticlines separated by relatively broad, flat synclinal valleys -- are a fundamental component of Martian geomorphology. The anticlinal crests show variable morphologies, but are often characterized by weak to strong asymmetry with variable vergence directions between adjacent ridges and along strike for any given ridge. Although wrinkle ridges are typically interpreted as contractional features, there is ongoing debate about their underlying structure and whether thrust faults penetrate to tens of kilometers of depth ("thick-skinned shortening") or sole into a detachment in the upper few kilometers of the Martian crust ("thin-skinned shortening"). Previous workers have estimated depth to the detachment horizon using a variety of methods including gravity inversion, geometry of crater-ridge intersections, mechanical modeling, and geometric modeling. Here we use a well-established terrestrial technique to calculate depth to the detachment horizon for wrinkle ridges in the Solis Planum region of Mars. We interpolate topographic profiles perpendicular to the regional trend of wrinkle ridges from Mars Orbiter Laser Altimeter (MOLA) Mission Experiment Gridded Data Record (MEGDR) altimetry data, set vertical reference lines on both sides of the ridge that define the limits of our measurement range, estimate the topographic surface prior to wrinkle ridge formation, and calculate the area uplifted above the original topographic surface. Dividing this excess area by the amount of shortening (the topographic profile length minus the length prior to deformation), provides depth to detachment. We calibrate the results with profiles from the less spatially-extensive but greater along-track density MOLA Precision Experiment Data Record (PEDR). Additional topographic and structural interpretation and analysis of wrinkle ridge morphology are conducted with Mars Orbiter Camera (MOC), Thermal Emission Imaging System (THEMIS), and High-Resolution Stereo Camera (HRSC) images. Our approach involves an important but reasonable assumption that the topographic profile is representative of the fold geometry for at least the upper portion of the Martian lithosphere. Results in the Solis Planum region based on MEGDR data show depths to detachment of tens of kilometers. Depths are significantly affected by calibration with PEDR data. The angle between the topographic surface and the detachment has implications for the relative strength of detachment intervals.
DE: 5464 Remote sensing
DE: 5475 Tectonics (8149)
DE: 6225 Mars
DE: 8005 Folds and folding
DE: 8149 Planetary tectonics (5475)
SC: Planetary Sciences [P]
MN: Fall Meeting 2005