The influence of ancient soil biota on the precipitation and distribution of pedogenic carbonate in paleosols of the Marília Formation (Upper Cretaceous, Brazil)

In arid and semi-arid climates, soil development is strongly influenced by seasonal patterns biogenic activity, often results in pervasive pedogenic horizons consisting of highly concentrated carbonate. Brazil, such enriched calcium carbonate are common relatively well-studied paleosols the Upper Cretaceous Marília Formation. However, detailed analyses on sequence mineral precipitation phases role organisms these processes still lacking. The present work describes eight argillic calcic characterized different degrees accumulation. Argillic show translocation clay structures weak to moderate cementation Calcic contain high accumulations ranging from powdery coatings nodular masses micrite. Carbonate distribution preserved largely as carbonate-cemented macropores produced ichnofossils Planolites, Taenidium, Naktodemasis, Skolithos, Palaeophycus calcareous rhizocretions. Moreover, stable isotope data, respired CO2 function, cathodeluminescence (CL) paleosol samples were used evaluate paleovegetation, paleoproductivity, distinctive stages calcite precipitation. Stable isotopic analysis suggests that paleovegetation cover was predominantly C3-photosynthsizing plants. relationship between bioturbation indices respiration a positive pattern paleoproductivity controlled higher moisture conditions increased activity fauna. Finally, CL imaging shows there multiple with both α-type β-type fabrics interpreted abiotic biotic during pedogenesis.