• DOI:10.2110/PEC.12.102.0001
• Corpus ID: 132583034

The Sedimentary Rock Record of Mars: Distribution, Origins, and Global Stratigraphy

@inproceedings{Grotzinger2012TheSR,
  title={The Sedimentary Rock Record of Mars: Distribution, Origins, and Global Stratigraphy},
  author={John P. Grotzinger and Ralph E. Milliken},
  year={2012}
}

• J. Grotzinger, R. Milliken
• Published 2012
• Geology

The last decade of Mars exploration produced a series of discoveries that provide compelling evidence for the existence of sedimentary rocks on Mars. Previously, Mars was regarded principally as a volcanic planet, the dominant surface processes of which were eruption of lavas and pyroclastic deposits, although early studies did recognize valley networks, enormous outflow channels, and the required transport of sedimentary materials to the northern plains of Mars. In contrast, our new view of Mars shows a rich history of interactions between water and the surface, with weathering, transport, and deposition of sediments by water as well as eolian processes. Surprisingly thick accumulations of stratified rocks extend back into the Noachian Era—the oldest of which were likely formed over 4 billion years ago, making these rocks much older than any sedimentary rocks preserved on Earth. Some sedimentary rocks were formed and deposited locally, whereas others accumulated as vast sheets that can be correlated for hundreds of kilometers or farther. Local deposits were formed in alluvial fan, deltaic, sublacustrine fan, and lacustrine environments in addition to deposits that fill canyons and valleys possibly carved during catastrophic floods. These former deposits indicate more gradual erosion and sedimentation, perhaps even involving meteoric precipitation, and they provide support for the notion of clement conditions on early Mars. In contrast, rapid erosion and sedimentation may have occurred within large, regional outflow channels thought to have resulted from outbursts of groundwater. Regionally extensive sedimentary deposits have less obvious origins, but the presence of hydrated sulfate minerals indicates that some of these deposits may have formed as lacustrine evaporites, particularly in the Valles Marineris network of open and closed basins. Others may have involved eolian reworking of previously deposited sulfates, or perhaps aqueous (groundwater) alteration of previously deposited basaltic sediments. Another major type of regionally extensive sedimentary deposit occurs as meter-scale stratification with highly rhythmic organization. These deposits occur in several places in the Arabia Terra region of Mars and are also observed at the top of a 5-km-thick stratigraphic section in Gale Crater. The significant lateral continuity of relatively thin beds, their distribution over broadly defined highs as well as lows, and the lack of strong spectral absorption features indicate that these rocks may be duststones, formed by weak lithification of fine particles that settled from the Martian atmosphere. The most ancient sedimentary deposits on Mars may be dominated by stacked, impact-generated debris sheets, similar to those seen on the Moon, and may include