Hardpans in the Wodonga-Tallangatta Region

In north-eastern Victoria, both duripans and fragipans are found. Many of the soils of the valley piedmont between Wodonga and Tallangatta have a hardpan at the base or within the solum. The soils above the hardpans typically have fine particle-size modes which indicate the presence of significant aeolian accessions (Rowe 1994). The stratigraphic relationships between the soils and the hardpans suggest that the latter mark the change from a period of widespread surface erosion to a period of sediment accession on less-steep slopes. It was therefore proposed that these hardpan layers initiatially occurred during a period when aridity had caused a decline in vegetative ground-cover and increased surface run-off and widespread erosion and sedimentation.

Peaks of aridity in south-eastern Australia have been ascribed to glacial periods (Galloway 1965; Bowler et al. 1976; Williams 1984) and it is proposed that the initiation of the hardpans occurred during these periods when desiccation of surface materials would have been severe. Some of these materials would have undergone consolidation as a result of high suction pressures resulting from removal of water from the finer soil pores (Aitcheson 1956, 1971; Smeck et al. 1989; Chartres et al. 1990). The degree of consolidation possible would depend on the presence of sufficient fines to create high suction pressures. Coarse surface materials would need to be infiltrated by clays to achieve these conditions (Brewer et al. 1972) and aeolian accessions during arid periods would meet this requirement. Well weathered saprolite of granitic or other similar coarse grained rocks, exposed by surface erosion at these times would also have been susceptible.

Location of the hardpan sites within the Wodonga-Tallangatta region.

This map shows sites studied by Ken Rowe as part of his PhD thesis on the development of pedogenic hardpans in North east Victoria. Information relevant to many of these sites is presented on this website.