Dynamics and genesis of calcic accumulations in soils and sediments of the Argentinean Pampa

Micromorphology of calcic accumulations (calcite, whewellite and gypsum) and geochemical indices were considered as indicators of genesis and evolution of pedogenic accumulations in soils and paleosediments of the Argentinean Pampa. Two groups of separate and independent calcic accumulations were studied using scanning electron microscopy: (i) in situ Argiudolls, reflecting the current soil formation; (ii) in the layers of calcrete (locally named tosca), reflecting the past environments and conditions of these layers sedimentation. New pedogenic gypsum accumulations in Argiudolls were described and possible ways of their formation were suggested. Combined analyses of morphology of carbonate accumulations and geochemical indices in different horizons of Argiudolls and layers of tosca showed that the tosca is paleopedocomplex with complicated formation history. Influence of current environment on tosca morphology is absent, so it is possible to use these pedofeatures for paleoreconstructions in further studying.