Micromorphology and mineralogy of a layered red-brown earth profile

Abstract

The micromorphology and non-clay mineralogy of a red-brown earth profile from Pyramid Hill, Vic., have been examined in order to test Butler's postulated genesis based on field criteria. The profile includes four separate parent material layers. The lowest layer appears to have been derived mainly from in situ weathering of granite. The upper three layers have been derived mainly from a source other than the local granite and have microscopic characteristics comparable to those of altered parna, viz. a non-clay fraction which shows a marked peak in the 30-60 µm range, which consists of quartz and felspar with magnetite, ilmenite, leucoxene and titanite and which has a zircon/tourmaline ratio of about 0.5. As well as a solum developed in the upper two parna layers, there appears to be a buried truncated soil associated with the third parna layer. In both soils there has been significant translocation and deposition of carbonates, iron oxides and hydroxides, manganese oxides and hydroxides and clay, with somewhat more material segregated in the lower solum. Weathering and water-table effects at some depth below a prior surface appear to have been responsible for segregations within the lower layer derived from granite. The data support the concepts of Butler, and in addition indicate contamination of the surface layer by reasonably fresh minerals.