A landscape history of the Wantabadgery area, N.S.W.
Creators: name: McConnell, Anne Denise
Publisher: name: The Australian National University
Year: 1979
Subjects: subject: Wantabadgery (N.S.W. : District)

description: The landscape and soils of the Wantabadgery area lie on the western slopes of the Great Divide, immediately to the north of the Murrumbidgee River, and provide both a landscape history of the area and an insight into the mechanisms and effects of landscaping and pedogenic processes in small, granodiorite catchments in southeastern Australia. The surficial materials at Wantabadgery are granodiorite-derived, except for minor isolated areas of p a m a accession. On the basis of radio­ carbon dates, the surficial materials which form colluvial hillslope mantles have been deposited since ca. 40,000 years BP, and the predominantly alluvial valley terraces have been deposited in the last 10,000 years. On the basis of textural, mineralogical, micromorphological and landscape analyses, these deposits and the soils formed thereon, are considered to have been deposited under similar environmental conditions as exist at present. Variations in the surficial material and soil are attributed to intrinsic variations in geomorphic micro-environment, different degrees of transportation and pedogenesis, and to the deposition of materials from a range of sources within the area. The effects of weathering, transport, deposition and pedogenesis are explained by a model of evolution of detritus. It has been found that at all stages of the evolution of detritus, transport- ational and depositional processes result in much greater textural and mineral­ogical modification than pedogenesis, and all processes are strongly controlled by the nature of the granodiorite. A model has also been constructed to explain the large scale land­ scape variations, e.g. the formation of the different landscape units, terracing, variations in channel deposits, discontinuous gullying, hillslope mantle variations and the lack of correlation between catchments. The model proposes that landscaping occurs primarily through complex-responses and internal re­adjustments to the attainment of threshold states within the landscape system or subsystems. External stimuli are not necessarily required to initiate change. In cases where they are trigger mechanisms however, high magnitude, low frequency events are of equal or greater importance than large scale regional changes. Comparison with other southeastern Australian soil and landscape studies reveals that 1) landscapes and landscape instability are not reliable palaeo- climate indicators, 2) pedogenesis is similar to that on colluvial, granodiorite- derived deposits and alluvial deposits elsewhere in Australia, 3) granodiorite texture, mineralogy and fabric exerts a strong control over the mode of pedogenesis and the resultant soil type and features, and 4) the regional correlation of soil-stratigraphic units is of questionable validity. Many of the problems encountered are considered to arise from problems inherent in the scientific philosophies, theories and methodologies used in landscape analysis; and from the way in which they are used.