Pedothem carbonates record the aridification of the Atacama Desert
An especially promising paleoclimate proxy archive in arid and semi-arid climates are pedothems: dense, laminated soil carbonate deposits that integrate climate information during the soil’s period of sub-aerial exposure. We studied a soil on a late Tertiary to early Quaternary alluvial fan that exhibits evidence of an initial wetter period (secondary clay formation) followed by a period dry enough to form secondary carbonate accumulations, sometimes as dense pedothems (from Greek: πέδον, pedon, "soil"; and θέμα, théma, "deposit") on soil gravels. C stable isotope values show a ~4‰ increase in δ13C values through time, reflecting a change towards aridification with decreasing plant density and soil respiration. O stable isotope values show a more complex pattern along the same time axis with variability of up to 10‰. Together this evidence records a shift towards drier climate conditions.