Excellent Clues to the coastal/estuarine environments
Post by Joe Michalski, Planetary Science Institute, Tucson, Arizona, USA
On Earth, the most ancient sedimentary rock record has been largely obliterated by plate tectonics and erosion. Those that remain are from the early history of the Earth and are severely deformed and mineralogically altered. Evidence for the earliest life on Earth found within these strata is often controversial because the rocks are so severely changed from their original state.
Image 1: Rugged, eroded terrain in the northwest portion of the image (north is up), and an eroded butte in the southeast contain rocks layered at the scale of decimeters to meters. Reddish-brown colors correspond to surfaces that are rich in nontronite – an Fe-rich smectite clay mineral. The bluish areas surrounding the butte in the central part of the image correspond to surfaces that are rich in hydrated silica and aluminous clay minerals (such as montmorillonite and kaolinite)…
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