Pedogenic Carbonate
“Calcium carbonate grown in ancient soils”
Pedogenic carbonate consists of calcite nodules, layers, and cements that form within soil profiles in semi-arid to arid climates. These carbonate accumulations are invaluable to geologists because their chemistry records ancient atmospheric CO₂ levels, rainfall patterns, and temperatures.
calcite, minor dolomite, clay minerals, iron oxides, root casts
Great Plains paleosols (USA), Olduvai Gorge (Tanzania), Siwalik Hills (Pakistan/India), Bighorn Basin (Wyoming, USA), Spanish Meseta
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Scientists measure the carbon isotope ratios in ancient pedogenic carbonates to reconstruct atmospheric CO₂ levels going back hundreds of millions of years — they're natural archives of Earth's climate history.
Test Your Knowledge
What crucial information about Earth's past can scientists extract from pedogenic carbonate chemistry?
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