J. H. Howard III 1979 <p><span class="TextRun SCXW255705338 BCX8" lang="EN-US" xml:lang="EN-US" data-contrast="auto"><span class="NormalTextRun SCXW255705338 BCX8">The </span><span class="SpellingError SCXW255705338 BCX8">Phaethontis</span><span class="NormalTextRun SCXW255705338 BCX8"> quadrangle of Mars is dominated by densely cratered uplands and </span><span class="NormalTextRun SCXW255705338 BCX8">plateaus which form some of the oldest surfaces on the planet. Extensive low-lying areas within the cratered terrains, including the floors of the large craters</span><span class="NormalTextRun SCXW255705338 BCX8">, are covered to different </span><span class="NormalTextRun SCXW255705338 BCX8">degrees by plains-forming material. The youngest plains unit surround </span><span class="NormalTextRun SCXW255705338 BCX8">Tharsis</span><span class="NormalTextRun SCXW255705338 BCX8"> Montes to the north. Various </span><span class="NormalTextRun SCXW255705338 BCX8">erosional processes, including eolian scour and possibly scarp retreat through volatile-release sapping</span><span class="NormalTextRun SCXW255705338 BCX8"> and mass wasting, producing several distinctive physiographic features: knob and mesa terrains, plains and small knobs, and plateaus dissected by furrows, steep walled gorges, and pits.</span></span></p> application/pdf 10.3133/i1145 en U.S. Geological Survey Geologic map of the Phaethontis Quadrangle of Mars reports