Geoscience for Land and Water Management: Cainozoic geology and hydrogeology of Uluru-Kata Tjuta National Park, Northern Territory

Integrated datasets (airborne magnetic and gamma-ray spectrometric imagery, Landsat Thematic Mapper imagery, a digital elevation model, and water-bore logs) have contributed to an investigation of Cainozoic geology and hydrogeology, and their ecological impact on the habitat of a vulnerable species of marsupial, in a -2600-km2 area of semiarid central Australia in and around the Uluru-Kata Tjuta National Park. They show that a heterogeneous basement topography of domes and basins with 100 m of vertical relief (a buried 'mini-Kata Tjuta') underlies the Dune Plains, an extensive tongue-shaped sand plain between Kata Tjuta, Uluru, and Yulara. 
A significant feature of this buried landscape is a palaeodrainage valley, now the setting for a compound bedrock-Cainozoic-sediment aquifer system which is a major source of water supply for the inhabitants and tourists of this World Heritage Area. Major faults traverse the basement beneath the Dune Plains area, and a local elevation of bedrock causes a subsurface constriction near Yulara; both these features are important aquifer influences. The palaeovalley was originally a closed valley with discrete depocentres in which lacustrine and alluvial-fan sediments accumulated. Later, a river evolved, and flowed north to Lake Amadeus, not eastward as previously mapped. North of Yulara the palaeoriver spread out in a broad deltaic braid plain to the lake. The braid plain has received recent episodic floodwaters that have disrupted the Quaternary dunefields. 
Groundwater calcrete, and a sheetwash landscape unit composed of red earth, are important Quaternary geological units. The sheetwash landscape unit forms broad, gently sloping aprons around outcrops and supports banded mulga shrub land. During rainfall, surface run-off from this unit constitutes a distinctive 'sheetflow recharge' mechanism that maximises water conservation and infiltration for the underlying aquifer. 
The sheetwash landscape unit appears to have an important bearing on the ecosystem of the mulgara, a vulnerable marsupial that inhabits the Dune Plains. Whereas mulgara populations elsewhere in the Park contract during droughts, the Dune Plains population historically has survived. The transitional zone between the sheetwash red earth-mulga shrubland and the adjacent sandplain-spinifex association coincides with this core mulgara habitat. The hydrodynamic processes of the sheetwash unit carry concentrated nutrients to this zone, at the base of the slope, where infiltration occurs; these processes may be favourable to the mulgara's survival in the Dune Plains. 
Research into the soil, water, and nutrient cycles and processes in the sheetwash red earth-mulga shrubland and its adjacent transitional zone is recommended because of the interpreted importance of the surface and near-surface hydrodynamics to the distinctive ecosystem and to the recharge of the aquifer system. Further investigation of the locally complex hydrogeology is required, and a review of the groundwater resources in the Dune Plains aquifer system is recommended.

Tags: AU-NT, EARTH SCIENCES, GA Publication, Published_External, geology, monograph
Organization: Geoscience Australia Data