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Pinnacle Lookout at Northern end of Coolah Tops National Park

Giant Grass trees near Barracks camping area
Basalt cliff-face at base of Pinnacle Lookout. Photo Courtesy Shannon Hawkins
A shallow lava cave located on the track to the deeper lava cave. This track is extremely difficult to access with rock falls and steep rock faces.
Columnar basalt formations at Bald Hill Creek Falls
Columnar basalt formations at Bald Hill Creek Falls
Near horizontal columnar basalt formations at Battery Hill Rest Area 15km east of Merriwa

Coolah Tops National Park

Latitude -31.757635, Longitude ,150.083772

Located in the Central Western Region of NSW, nearest town Coolah

Source:National Parks and Wildlife Service

Source Magnetic pole information:http://digitalcommons.calpoly.edu/physsp/45

Author: Nathan M. Padilla

Link to Detailed Map

The Coolah Tops National Park lies on a basalt plateau and protects extensive tall open forests, including areas of old growth and the tallest recorded individuals of silvertop stringybark, Eucalyptus laevopinea and snow gum Eucalyptus pauciflora. The park is known for its very large grass trees particularly near the Barracks camping area where they are believed to be around 300 years old. The forest supports high populations of arboreal mammals and several threatened plant and animal species. The park was once the home of the Gamilaraay (or Kamilaroi) indigenous people whose territory stretched from Dunedoo and Merriwa northwards into Queensland. Today the area is a part of the Walhollow Local Aboriginal Land. A relatively large number of Aboriginal sites have been recorded in the park, indicating that the area was used quite intensively by the Gamilaraay people. The name Coolah is an Aboriginal word meaning "Valley of the Winds".

Coolah Tops is an elevated basalt plateau at the junction of the Liverpool Range and the Warrumbungle Range (part of the Great Dividing Range). The plateau rises steeply above the surrounding lands and is flanked by cliffs along its northern edge.

Columnar basalt formations are found scattered along the northern escarpment of the plateau with readily accessible examples located at Tamalie Creek Falls and also at Bald Hill Creek Falls.

The columnar fractures in the above- mentioned basalt formations are a result of the cooling process. The basalt cools rapidly from the outside toward the center, causing shrinkage cracks to form, usually in a hexagonal pattern. The shape of the columns is attributed to tensional stress. The basalt is known as the Liverpool Range Beds and is thought to have originated from volcanic vents further to the east on the Liverpool Range during the Tertiary period. Rock types in the area mostly consist of olivine basalt and dolerite with occasional sediment interbeds.

Most of the park is above 1000m ASL, with the eastern end being a little higher than the western end. The Liverpool Range runs through the middle of the park and from here numerous creeks drop into deep narrow valleys to the south and northwest. Waterfalls occur on several of the creeks. The headwaters of the Talbragar River are located in the centre of the park. The creeks flowing northwards ultimately drain into the Namoi River and those to the south drain into the Macquarie or Goulburn Rivers.

Small caves have formed in some of the basalt flows within the park. The largest cave contains 70m of passage, including an entrance chamber 20m wide and 12m high. The caves are not lava tubes but appear to have been formed by groundwater erosion of zeolite rich amygdaloidal basalt (Osborne, 1979).

Zeolite cave. Photo Courtesy Stephen Reilly, National Parks and Wildlife Service

Evidence of an intriguing event is evident in the volcanic rocks of the Liverpool Range that form part of the landscape of the Coolah Tops National Park. From time to time the earth's magnetic field reverses. This reverse-to-normal transition, recently dated at approximately 40 million years ago, was first reported in Nature in 1986. In March 2011 some 200+ cores were drilled from several sections about the volcanic range-Jemmy's Creek, Bald Hill, Rock Creek, Yarraman, and Coolah Tops Road. Results from this program show the earth's magnetic field was in the reverse direction for all 24 distinct lava outcrops sampled.

The Earth's magnetic field displays two polarities: normal, like the field of today when a free compass needle points north, and reverse, at those times when a free compass needle would have pointed south. The actual mechanism by which such transitions occur is poorly understood, although it is generally agreed that the Earth's magnetic field is generated in the highly electrical conducting fluid of the outer core.

Volcanic rocks such as the basaltic lavas that erupted along the Liverpool Range record the direction of Earth's magnetic field while cooling to ambient temperature. As the lava cools, more and more magnetic grain directions start to line up with the dominant external magnetic field. Usually, the dominant field is the Earth's dipole field (approximation of the rather complex true Earth's magnetic field). For rocks to hold a magnetic direction they must contain ferromagnetic (iron) minerals.

A virtual geomagnetic pole can be calculated using the direction of magnetization found in a rock sample showing if the earth's field was reversed, normal, or in transition at the time the lava cooled.

If you travel to Coolah via the Golden Highway make sure you stop at Battery Hill picnic area which is approximately 15 kilometres east of Merriwa. In the rock adjacent to the picnic area, there is an amazing example of polygonal basalt columns also known as columnar jointing. The columns are nearly horizontal (not like those at Bald Hill Falls which are vertical). Around 35 mya, the basalt lava erupted at a temperature estimated to be about 1,200 degrees. The jointing is caused by shrinkage as the lava slowly cools; normally columns like these are vertical as the lava cools from top to bottom when the flow of lava is horizontal. In this case the flow must have been nearly vertical and the flow has cooled from the outside face causing the jointing to form inwards from the outer face in a near horizontal plane. There is a picnic table and toilets at the site. Keep an eye out for venomous snakes at this site which is adjacent to a small reedy creek.

Information

Coolah Tops National Park is located on the Liverpool Range near the town of Coolah in central NSW. The park is about 30km east of Coolah and is reached via The Forest Road which runs through the park, providing access to all the main sites. The road should not be used during wet weather.

Bald Hill Creek Falls is reached via The Forest Road, onto Hildegard Road and then onto Bald Hills Road. A picnic area is available at this location.

To find the basalt caves of Coolah Tops National Park take the Pinnacle Road to Pinnacle Lookout, accessed from the Bundella Lookout car park. A walking track leads to the lookout which provides views of the Warrumbungle Range. A very rough unmarked track leads around the escarpment towards Rocky Creek and the caves, but this is a difficult path crossing rock falls, declines, cliff edges, slippery rock surfaces and loose rocks, and is suitable for fit and experienced walkers only.

Due to elevation and high rainfall weather conditions can change rapidly in this area so make sure you have adequate clothing and pay attention to weather reports. Also, be on the lookout for venomous snakes whilst exploring this region.

http://www.nationalparks.nsw.gov.au/safety


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