Geologic setting and origin of Terra Meridiani hematite deposit on Mars

We have completed a regional analysis of the hematite deposit in Terra Meridiani and conclude that the unit is in the midst of a 600-m-thick stack of friable layered materials superposed on Middle and Late Noachian cratered terrain. The deposits resemble terrestrial pyroclastics in the fact that they are: (1) thin, parallel bedded deposits that conform to preexisting topography, (2) often extremely friable, and (3) composed of fine particles. Some of the lowermost layered units exhibit possible lava flow textures and features. Abundant outliers indicate that the deposits were once far more extensive and that erosion (primarily aeolian) has removed vast portions of the stratigraphic sequence. The hematite may have formed from thermal oxidation of the volcanic ash during eruption or have been precipitated from the circulation of fluids within the layered materials at a later time. Temporal and spatial association with outflow channels and evidence for cementation along joints and bedding planes within the layered deposits suggest the latter scenario.