Wednesday, November 2, 2016

Highlights—Paleosol Geochemistry and Paleoclimate: A Cautionary Tale

The geochemical attributes of paleosols have been used to estimate paleoenvironmental and paleoclimatic conditions through much of the Phanerozoic. Here, Michel et al. use plane-polarized and cathodoluminescence petrography, electron microprobe, and stable isotope ratio mass spectrometry observations of paleosols from Permo-Carboniferous strata of the Lodève Basin, France to evaluate the role of post-depositional alteration on geochemistry of paleosols. The results illustrate that macrofeatures within paleosols are retainend and can be used for paleoclimate reconstruction; however, geochemical signatures are neither reflective of soil formation nor appropriate to use in paleoclimate reconstruction due to diagenetic alterations. Yet, the paleosol carbonate cements and matrix clays preserve information that reflects a complicated calcite-cement stratigraphy recorded in nodules, and quartz, barite, dolomite, and Fe-rich calcite cementation. These results emphasize that pedogenic nodules, rhizoliths, and paleosol matrix should systematically evaluated for diagenetic alteration prior to applying geochemical based proxies to reconstruct paleoclimate.

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