Regolith and landscape framework of the Northern Territory project

Regolith is a general term describing the mantle of fragmental and unconsolidated rock material, soil, blown sand, alluvium etc that overlies or covers solid rock. An understanding of the regolith provides a framework for understanding landscape evolution, extractive and placer mineral occurrences, groundwater potential, rangeland management, and environmental geoscience. It is also necessary for effective mineral and diamond exploration, given the fact that a large portion of the most prospective Proterozoic sequences in the Northern Territory is concealed by only a relatively thin blanket of mostly barren Cenozoic sediments or regolith.

This project commenced in September 2003 and is due for completion by September 2005. It is a collaborative program between NTGS and CRC LEME (contributors - CSIRO and Geoscience Australia). The main objectives are to provide a regional regolith-landform framework of the Northern Territory, as a basis for guiding mineral exploration, and to provide a useful tool for addressing other land-use issues. Excellent regional and detailed datasets are now available (see Databases, Geophysical datasets) and should now provide an extended basis for a regional study.

Expected outcomes for the project include the following:

• A regolith-landform model for a large part of northern Australia.
• A major contribution to the understanding of the physical background of processes and regolith materials of central Australian arid environments.
• A first-order framework for guiding geochemical prospecting for minerals and diamonds.
• A firmer basis for identifying and assessing regional groundwater provinces.
• The reconstruction of palaeodrainages of the Northern Territory.

Work program

• Compilation of existing information from various datasets such as elevation, radiometrics, Landsat and geological maps. This process should yield information regarding general landforms, regolith materials and palaeodrainages.
• Three areas have been selected for more detailed study to provide some rigour to the largely interpretative foundation of the framework. The study areas are the Barrow Creek-Tennant Creek-Helen Springs region, the southern Georgina Basin and the Darwin Coastal plains region. The type areas will be the focus of the following activities: regolith-landform mapping; establishing 3D distribution of regolith from drilling and natural exposures; characterisation of regolith materials; and geochronology of regolith materials.
• Establishing the origin and age of ferruginous duricrusts and silcretes.
• Identify and classify relicts of major palaeo-weathering surfaces.
• Use drillhole and geophysical data to make first-order estimates of the depths of weathering or transported overburden in depositional environments.
• Establishing the weathering history and developing landscape evolution models.

Abstract

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