SOIL MICROMORPHOLOGY EVIDENCE FOR QUATERNARY CLIMATE CONDITIONS OF THE UPPER SAVA RIVER CHRONOSEQUENCE, SLOVENIA

Soil chronosequences are usually studied to investigate temporal trends in soil properties. These studies assume that time is the primary soil forming factor affecting soil properties and consider the influence of climate and other factors considerably less important. Observed on macroscopic level, soil morphology reflects the cumulative alteration of parent material by soil forming processes and allows the examination of temporal trends, whereas at the microscopic level the effects of soil forming factors can, ideally, be separated. Paleoclimate interpretations derived from the observations of soils of the upper Sava River chronosequence (20 Ka – 1.8 Ma, dated by ¹⁰Be and soil paleomagnetic analyses) formed in predominantly carbonate outwash deposits were based on the examination of the nature and distribution of pedofeatures in soil thin sections. The nature of ferriargillans (FAs) observed in soils younger than 1 Ma suggests that climatic conditions during interglacials (soil forming episodes) of the last 1 Ma were similar to average post-glacial conditions. In contrast, bright red hematite stained early generations of ferriargillans in the oldest soil (1-1.8 Ma, paleomagnetic analyses) suggest that climatic conditions in the area were significantly different during its early stages of development as the present climate does not allow hematite formation. Considerably warmer and/or drier climatic conditions conducive to hematite formation must have prevailed in the area during the interglacials that predated 1 Ma. European pollen records suggest considerably warmer conditions from 1.6 to 2.1 Ma. Therefore, the presence of these FAs indicates that the oldest soil is older than 1.6 Ma and further constrain its age interval.