donderdag 24 mei 2012

Australia, Purnululu National Park

The 239,723 ha Purnululu National Park is located in the State of Western Australia. It contains the deeply dissected Bungle Bungle Range composed of Devonian-age quartz sandstone eroded over a period of 20 million years into a series of beehive-shaped towers or cones, whose steeply sloping surfaces are distinctly marked by regular horizontal bands of dark-grey cyanobacterial crust (single-celled photosynthetic organisms). These outstanding examples of cone karst owe their existence and uniqueness to several interacting geological, biological, erosional and climatic phenomena.

Purnululu National Park is located in the East Kimberley Region of Western Australia located 300 km by road south of Kununurra in Western Australia's Ord Region; the listed area is almost 240,000 ha. There is an adjacent buffer zone to the north and west (the Purnululu Conservation Zone) of approximately 79,600 ha, which is not part of the nominated area. The park comprises four major ecosystems: the Bungle Bungle Mountain Range, a deeply dissected plateau that dominates the centre of the park; wide sand plains surrounding the Bungle Bungles; the Ord River valley to the east and south of the park; and limestone ridges and ranges to the west and north of the park.
The Bungle Bungle Mountains are an unusual and very dramatic plateau of Devonian quartz sandstone, created through a complex process of sedimentation, compaction, uplift (caused by the collision of Gondwanaland and Laurasia approximately 300 million years ago and the convergence of the Indo-Australian Plate and the Pacific Plate 20 million years ago), as well as long periods of erosion. The Bungle Bungle landscape comprises a mass of beehive-shaped towers with regularly alternating, dark grey bands of cynobacterial crust (single-cell photosynthetic organisms). The plateau is dissected by 100-200 m deep, sheer-sided gorges. The cone-towers are steep-sided, with an abrupt break of slope at the base and have domed summits. Their surface is fragile but stabilized by crusts of iron oxide and bacteria. They provide an outstanding example of land formation by dissolutional weathering of sandstone, with removal of sand grains by wind, rain and sheet wash on slopes.
The Bungle Bungle Range is one of the most extensive and impressive occurrences of sandstone tower karst in the world
The grassy Ord River valley on the east and south of the park is deeply incised as a result of crustal uplifting during relatively recent geological times. The wide sand plains between the uplands and the river are composed of infertile black soil covered with grassland and scattered trees. The limestone ridges to the west and Osmand Range to the north are better wooded, especially in the forested Osmand Creek valley. These rocks are believed to be of Cambrian age (550-500 million years old). There are stromatolites in the Osmand range.
Purnululu also has a rich Aboriginal cultural heritage spanning over some 20,000 years. The park provides exceptional testimony to this hunter-gatherer cultural tradition, which has survived to the present day despite the impact of colonization.

Historical Description

Human activity in the area has occurred over some 40,000 years. Radiocarbon dating places the earliest known occupation of the Ord valley, downstream of the Park, some 20,000 years ago. Long-term use of the area is suggested by a plentiful archaeology, as yet incompletely discovered.
The first survey of the area was in July 1879. The first colonists arrived in the Middle Ord region in the mid- 1880s. Gold was discovered 1885 but stock raising became the main activity. ‘By June 1884 the first mob of 4,000 cattle were brought into the Ord River grasslands…’ 6,000 followed the following year. By 1902 there were some 47,000 cattle.
Overstocking of cattle, which led to over-grazing ‘set in train the destructive process of massive landscape erosion’, a process which saw the Aboriginal population involved in unpaid seasonal labour on pastoral stations, while their natural food resources were diminished. The indigenous population decreased by perhaps as much as 50%.
Form 1967 procedures to reverse this process were started. Control of stock and re-vegetation programmes were put in place and the 1968 Pastoral Award stopped the abuse of Aboriginal labour. However, in moving people out of the cattle stations, the measures helped create new living sites – ‘humpies’ – which came to be characterised by social deprivation.
‘From around 1985 onwards large numbers of cattle and donkeys (25,000 and 4,000 respectively)’ were removed to reduce overgrazing still further. The National Park was created in 1987, when the area became uninhabited. The same year saw the start of a programme of protective burning to reduce wildfire and create mosaics of vegetation. By the mid-nineties, tourism had become a local feature, despite the difficulties of access, with ground-based visitors numbering ca 20,000 p.a. and perhaps the same number overflying the Park each year.
In spite of more than a 100 years of outside intervention, and the resulting severe changes in the landscape and in social structures, it is claimed in the nomination that Aboriginal people who live near Purnululu still retain communal memories of traditional land management practices, and of Ngarrangkarni associations, and still use the landscape for harvesting wild food and for social gatherings.

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