Shales terrestrial weathering

The terrestrial weathering of organic matter derived from shales and soils results in the oxidation of carbon, which generates CO2. Dissolution of this CO2 in water produces carbonic acid. This weak acid serves to enhance chemical weathering reactions... 

The second common lanthanide abundance pattern which is uniform and which has widespread geochemical significance, is that observed in most post-Archean sedimentary rocks such as shales. This pattern, as discussed later, is generally taken to represent that of the upper continental crust exposed to weathering and erosion, so that it forms a suitable base for comparison of terrestrial surface processes affecting the lanthanides. Two different sets of shale abundances have been used for normalisation. The first is the North American Shale Composite (NASC, Haskin et... 

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