Jamestown 3D Interactive Module

The Jamestown region is located in the mid-north of South Australia. Basement rocks in the area consist of Proterozoic sediments, including siltstones, dolomites, sandstones, quartzites, limestones, tillites, feldspathic sandstones, pyritic shales, calcareous siltstones and sandstones. Structural deformation and associated contact and regional metamorphism has folded and altered these rocks. The overall structural trend is north-south with anticlinal and synclinal folds clearly delineated on the digital elevation model. Landforms consist of low-relief colluvial and alluvial fans, floodplains and pediments through to rises, low hills and hills.

The thickest sediments consisting of silt, clay, fine sand and minor gravels occur in the Belalie and Bundaleer valleys. The Caltowie valley has a thinner sediment cover and is less hydraulically-conductive than the other two catchments. Low angle pediments characterise the upper parts of the Caltowie catchment.

An understanding of the gamma-ray imagery provides insights into the compositional and textural fill of the valleys. A relationship between surface soil texture on depositional plains and airborne K concentrations can be used to predict the surface silt content in each of the main valleys. High K values over the depositional plains within the Belalie and Bundaleer valleys are associated with silt size mica (muscovite) and illite grains, whereas, lower K responses indicate coarser sediments with a higher proportion of quartz. These quartz rich sediments are common within the Caltowie valley and appear black in the ternary image or blue in the K image.

Figure captions (right):
Figure A: Shallow soils over saprolite occur over hills and ridges.
Figures B and C: Depositional materials occur in three main valleys: the Belalie (B), Bundaleer and Caltowie (C).
Figure D: Coalescing colluvial and alluvial fans of Quaternary age have filled these valleys to depths of up to 40 metres.