Physics
Scientific paper
Dec 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agufm.u31a0013w&link_type=abstract
American Geophysical Union, Fall Meeting 2009, abstract #U31A-0013
Physics
[5475] Planetary Sciences: Solid Surface Planets / Tectonics, [6250] Planetary Sciences: Solar System Objects / Moon
Scientific paper
The current view of lunar tectonics is that most crustal deformation is directly associated with mare basins. Lunar lobate scarps, in contrast to nearside mare wrinkle ridges, and graben, are found most often in the highlands and are the dominant tectonic landform on the farside. Lunar scarps are relatively small-scale tectonic landforms, only easily resolved in the highest resolution Apollo Panoramic Camera and Lunar Orbiter images. These scarps are interpreted to be the surface expression of thrust faults, yet they have not been well characterized and their global spatial distribution remains unknown. Images from the Lunar Reconnaissance Orbiter Camera (LROC) reveal previously undetected scarps as well as remarkable new features related to some previously known lobate scarps. LROC Narrow Angle Camera (NAC) 1 to 2 m/pixel images show meter-scale tectonic landforms associated with the Lee-Lincoln scarp. The Lee-Lincoln thrust fault scarp cuts across the mare basalt-filled Taurus-Littrow valley near the Apollo 17 landing site, trending roughly north-south between two highland massifs. The fault scarp extends into the highlands of North Massif where it cuts up slope for a short distance and abruptly changes trend to the northwest cutting along slope for kilometers. NAC stereo-derived topography shows a narrow rise associated with the scarp segment in the valley floor. Spatially correlated with the rise is an array of fractures and shallow extensional troughs or graben. The small-scale graben have maximum widths of ~25 m and are typically 100-200 meters in length. The rise is interpreted to be the result of flexural bending of the valley floor basalts with bending stresses causing extension of the upper regolith. Lobate scarps appear to be among the youngest tectonic landforms on the Moon based on their generally crisp appearance and a lack of superposed, relatively large-diameter (>500 m), impact craters. NAC images of known and newly detected scarps reveal evidence of crosscut impact craters as small as ~5-10 m-in-diameter. Crosscut meter-scale craters indicate a young age for the lobate scarps. Until now, the identification of lobate scarps has been limited by the lack of high resolution images with optimal lighting geometry for most of the Moon. The vast majority of the known lunar scarps are confined to the equatorial zone in areas imaged by the Apollo Panoramic Cameras. LROC NAC imaging now makes global detection of the small-scale scarps possible. A previously undetected lobate scarp has been found in the north polar region at ~88 degrees N. This discovery suggests that thrust fault scarps may be globally distributed. The young age of the lobate scarps indicated by crosscutting relations with impact craters and the discovery of a high-latitude scarp suggests global-scale, late-stage contraction. If thrust fault scarps are proven to be globally distributed, this discovery has important implications for the thermal history of the Moon.
Banks Maria Elaine
Bell Jon F.
Beyer Ross A.
Garry Brent W.
Pritchard Mathew E.
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