GEOLOGIC MAPPING AND STUDIES OF DIVERSE DEPOSITS AT NOCTIS LABYRINTHUS, MARS

Noctis Labyrinthus consists of a network of intersecting linear troughs and pits along the eastern Tharsis rise that connect eastward to the continuous chasmata of Valles Marineris. We are producing a geologic map of the western portion of Noctis Labyrinthus (-6 to -14°N, -99.5 to -95.0°W), which includes some of the most diverse mineralogies identified on Mars using CRISM data that are associated with light-toned deposits. An improved understanding of the depositional settings associated with these light-toned and hydrated deposits at Noctis Labyrinthus gained through stratigraphic, morphologic and mineralogic characterization has the potential to reveal important information about the climate and sedimentary history of Mars, especially during the Late Hesperian to Amazonian.

We are using THEMIS daytime IR as a basemap, with a 1:500,000 publication scale by the USGS. Constraints from geologic mapping and morphologic and stratigraphic analyses will be key contributions toward deciphering the geologic diversity and history of this portion of Noctis Labyrinthus, with specific implications regarding the role and history of water. An understanding of the history of deformation and collapse within this region will also be important for deciphering the timing of sedimentary deposition and aqueous alteration.

Numerous structural features, including grabens and scarps, are observed throughout the mapping region. Mapping of normal faults and grabens indicate multiple episodes of collapse. Several volcanic shields have been identified along the plateau. Floor deposits within the troughs and pits include light-toned deposits, many of which also exhibit spectral hydration features, and mass wasting deposits, including landslides. Lava flows have also been identified and mapped on several trough floors. No fluvial channels have yet been identified, but a possible volcanic channel sourced by a collapsed rounded depression within one of the troughs indicates younger volcanism occurring after formation of the trough. Topographic profiles illustrate that the light-toned deposits within the pits and troughs all occur below 4 km in elevation, consistent with hydrologic resurfacing by water sourced from aquifers beneath the Tharsis rise.