Alligator Rivers, West Arnhem Region, Northern Territory, Australiai

Regional Level Types
Alligator Rivers	- not defined -
West Arnhem Region	Region
Northern Territory	Territory
Australia	Country

The region is approximately 220 kilometres east of Darwin, covering 28 000 square kilometres, and includes the catchments of the West, South and East Alligator Rivers. The region also extends into western Arnhem Land and the former Gimbat and Goodparla Stations. The world heritage listed Kakadu National Park is also within the region.

The region contains internationally recognised wetlands, significant aboriginal rock art, prolific varied flora and fauna, and extensive wilderness areas.

The escarpment of the Arnhem Land Plateau cuts the region from the north-east to the south-west. The plateau is formed by the Kombolgie Sandstone, intricately dissected from water erosion. The 500 kilometre long edge of the plateau forms an escarpment ranging from vertical cliffs to talus slopes, 200-300 metres in height, the plateau itself rising up to 520 metres high. Cliff overhangs and waterfalls are common. The retreating plateau has left significant outliers of rock up to 1 kilometre from the cliff edge. The northern section of the region contains lowlands covered by flood plains.

The region experiences a dry season, and for the other six months a monsoon or wet season with high humidity. Vegetation is varied ranging from tropical woodlands, extensive swamps, and pockets of rainforest. The Kakadu National Park covers most of the region, the remainder being the far western portion of Arnhem Land. There are only two settlements of significance- Jabiru constructed to meet tourism needs for the national park, and Oenpelli which is an indigenous settlement in Arnhem Land.

Gold mining occurred at Mundongie Hill and Temelba in the 1920's. Lead, zinc, silver and copper mining at Zamuck in the mid 1940's. Thirteen uranium mines were operational in the South Alligator River valley from 1959-1965. The only presently operational mine, is the Ranger uranium mine, in an excised portion of the Kakadu National Park.

Uranium prospects named in literature but with little information and not listed on Mindat are Beatrice 36 kilometres south south-west of the former Nabarlek mine; Gurrigarri and Garrunghar 15 kilometres south-west of the former Nabarlek mine; Mordijimuk 8.5 kilometres south-west of the former Nabarlek mine; Arrara 35 kilometres north of Jabiluka; and Tadpole 25 kilometres north-west of the former Nabarlek mine.

Two separate clusters of phonolite dikes occur in the vicinity of Alligator Rivers. They intrude Archean and early Proterozoic granitic rocks of the North Australian Craton. The 2 clusters, known as the Mudginberri and Maningkorrirr phonolites (Stuart-Smith & Needham 1984) are c. 80 km apart.

Geochronology

Mineralization age: Mesoproterozoic : 1316 ± 40 Ma

Important note: This table is based only on rock and mineral ages recorded on mindat.org for this locality and is not necessarily a complete representation of the geochronology, but does give an indication of possible mineralization events relevant to this locality. As more age information is added this table may expand in the future. A break in the table simply indicates a lack of data entered here, not necessarily a break in the geologic sequence. Grey background entries are from different, related, localities.

Geologic Time				Rocks, Minerals and Events
Precambrian
	Proterozoic
		Mesoproterozoic
			Ectasian	ⓘ Phonolite 1316 ± 40 Ma Mudginberri Phonolites, Alligator Rivers, West Arnhem Region, Northern Territory, Australia

Localities in this Region

Other Regions, Features and Areas containing this locality

References