Submicromorphology of pedogenic carbonate accumulations as a proxy of modern and paleoenvironmental conditions

Abstract

It is likely that the morphology of pedogenic carbonate accumulations (CAs) relates to soil formation conditions and processes. The technique of electron microscopy is especially efficient and applicable to the description of CAs morphology. This method allows estimating the structure and organization of CAs visually and their composition with the X-ray energy dispersive spectrometer for both buried paleosols and surface soils. The relations between submicromorphological features of CAs and conditions of their formation in soil were established: (i) in contrasting climates (alternation of dry and wet seasons), colloform (cryptocrystalline) films are formed; (ii) in dry periods CAs with perfect crystals and sharp borders are formed; (iii) in more humid periods the CAs crystals become irregular with broken faces and holes on surfaces; (iv) needle-shaped calcite crystals are formed in fast-changing water regimes from saturated solutions; (v) perfect crystals grow in quiet conditions from solutions of normal concentration. Submicromorphological studies of the CAs in pedochronosequences can account for trends in changes undergone by soils/paleosols and permit estimation of the general trend of soil evolution.