Weathering rinds on clasts: Examples from Earth and Mars as short and long term recorders of paleoenvironment

• Published in: Planetary and space science 2012-12, Vol.73 (1), p.243-253
• Main Authors: Mahaney, W.C., Fairén, Alberto G., Dohm, James M., Krinsley, D.H.
• Format: Article
• Language: English
• Subjects: Debris; Frames; Mars; Minerals; Nanostructure; Paleoenvironmental reconstruction from clast rind alteration; Pollen; Recorders; Simulated ‘wetting fronts’ correlated with paleosols; Weathering; Weathering rinds on Earth and Mars; Wetting
• ISSN: 0032-0633; 1873-5088
• DOI: 10.1016/j.pss.2012.08.025

Weathering rinds on clasts of different lithologic species are an underappreciated inventory of paleoenvironmental information and, as recorders of long term exposure to the subaerial atmosphere and in some cases to burial and influx of groundwater followed by exhumation, they provide logged information over varying planetary time spans. Whereas weathered coatings of nanometer thickness have been explored by numerous workers, rinds in cold environments have not received much attention except as relative-age indicators. Rinds in terrestrial materials in certain circumstances may reveal weathering trends over time, snapshots often extending back millions of years and containing weathering zones not unlike horizons in paleosols. Wetting ‘fronts’ in rinds on coarse clastic debris (i.e. boulder, cobble, and pebble grade size material) are similar to wetting ‘depths’ in similar chemically-energized paleosols resident in moraines or mass wasted debris. Even considering erosion along terrestrial clast surfaces, new data reveal variations in primary mineral alteration, development of secondary mineral complexes, embedded pollen, fossil microbes, and various internal distributions of Fe oxides. Similar long-range recorders of paleoenvironment deduced from meteorites analyzed by the Opportunity rover on Meridiani Planum provide evidence of weathering over a ∼Gy time frame in the humid Noachian paleoenvironment of Early Mars followed by subsequent burial and later exhumation. Despite lithological variations between different sets of clasts—terrestrial and Martian—the retention of rinds as paleoweathering recorders over long and short time frames illustrates their value in paleoenvironmental reconstruction. ► Terrestrial weathering rinds. ► Clast rind alteration on Mars. ► Paleoenvironmental reconstruction from clast rinds. ► Microbial data archived in rinds.