MEGA GEOLOGY ’s giant landforms

Millions of years before Aboriginal peoples roamed the land of Western Australia, earth movements buckled and faulted rocks, causing them to rise and lower, creating giant landforms. Some of our favourite natural areas such as the and Karijini have an incredible geological history and significance. by Professor Ross Dowling AM and Mike Freeman ome 200 million years ago the supercontinent Pangaea broke into two land masses—Laurasia in the north and Gondwana in the south. Australia was part of the latter supercontinent, known Sgeologically for being ‘old, flat and red’. In the west, former mountain ranges have been eroded with the sediments creating large flat areas, or being washed into basins on the edge of the continent. Delve deeper and we find the landscapes, landforms and rocks of Western Australia show remarkable diversity and significance. WA’s national parks contain many different geological provinces as well as many of the State’s giant landforms. Some examples are captured in the national parks of Mount Augustus, Karijini, Stirling Range and Cape Range.

MOUNT AUGUSTUS at the time of the collision and finally of much of these layers, but left a prominent ceasing around 900 million years ago. mountain consisting mostly of the river- 1109 kilometres from Perth, After the collision, at about 1600 deposited sand named the Mount Augustus 474 kilometres from Carnarvon million years, rivers deposited sands and Sandstone. This is Mount Augustus, a Mount Augustus (Burringurrah) is in conglomerate eroded off the cratons prominent elongate inselberg (German an area between two large and old blocks and later the ocean flooded the area and for ‘island mountain’), a peak rising to an of the Earth’s crust, termed cratons, deposited more sand with layers of mud altitude of 1105 metres about 700 metres which form the nucleus of the continent. and volcanic lavas. Uplift resulted in erosion above the surrounding landscape. The southern Yilgarn Craton contains rare mineral grains up to 4400 million years old, the oldest parts of Earth, and were formed a mere 100 million years—just Mount Augustus and the boy called Burringurrah after the solar system formed from the Mount Augustus and surrounds are the traditional lands of the Wajarri people. original solar nebula. The northern Pilbara Burringurrah is the Wajarri name for Mount Augustus. In times of plenty, the Wajarri Craton contains fossil stromatelites, the people would roam over a wide area of the Gascoyne. In times of drought, they would oldest proven forms of life on Earth dated return to areas where water was available, such as the natural springs along the base of at 3450 million years old. The Yilgarn Mount Augustus. Aboriginal occupation is evident by engravings on rock walls at Mundee, Craton and the Pilbara Craton collided, Ooramboo and Beedoboondu visitor sites, and numerous stone tools discovered in these starting about 2200 million years ago areas. Burringurrah continues to be a significant site for the Wajarri people. continuing to about 1800 million years According to the Wajarri Dreamtime story, Burringurrah was undergoing his initiation ago, producing a 250-kilometre-wide area into manhood. The rigours of this process so distressed him that he ran away, thereby called the Capricorn Orogen. breaking Aboriginal law. Tribesmen pursued the boy, finally catching up with him and The Orogen was then affected by spearing him in the upper right leg as his punishment. Burringurrah fell to the ground; many periods of earth movements that the spearhead broke from its shaft and protruded from his leg. The boy tried to crawl folded, buckled and faulted the rocks, away but was hit with a mulgurrah (fighting stick). Burringurrah collapsed and died, lowering and raising them up — it was lying on his belly with his left leg bent up beside his body. You can see his final resting a zone of ongoing earth activity starting pose when you approach Mount Augustus from the south. The geological fracture lines at the western end of the inselberg indicate the wounds inflicted by the mulgurrah. Look for the spear stump in his leg that today is called Edney’s Lookout.

Previous page Main Hamersley Range, Karijini National Park.

Above Mount Augustus (Burringurrah). Photos – David Bettini

Right Moon setting over Burringurrah. Photo – Janine Guenther

20 LANDSCOPE KARIJINI it is the highest mountain in Western rich rocks are thought by most geologists Australia. to have been deposited in response to 1250 kilometres from Perth, In an Aboriginal Dreamtime story, the Great Oxidation Event, the greatest 650 kilometres from Exmouth Barrimirndi was a Warlu, or giant sea environmental change arguably the Earth Karijini National Park is located in serpent, who emerged from the sea at has ever experienced, when organisms the Hamersley Range area of the rugged Coral Bay. He meandered his way across started to enrich the atmosphere with sedimentary Hamersley Basin, which lies the land, forming waterways as he went. oxygen. However, since deposition of the south of and covers part of the granite As the legend goes, Barrimirndi became sediments, the region has been little- and greenstone-based Pilbara Craton. angry with two boys who cooked and affected by earth movements except The range extends 300 kilometres east- ate a parrot. Barrimirndi followed the being uplifted, and so the sedimentary west and comprises mostly horizontal scent of the singed feathers in search layering is still horizontal. layers of red, iron-rich rocks dissected by of the boys. Travelling underground, he deep gorges affording spectacular rugged wove his way up the river now known as scenery in ancient geological formations. the Fortescue, cutting gorges and rivers The area has been relatively stable for into the landscape. Sometimes he broke two billion years and is important for its through the surface to check for the scent, minerals, particularly iron ore. After 1960, creating a waterhole before disappearing large iron mines were developed at Mount ● Karijini National Park underground again. ● Mount Augustus National Park Tom Price, Mount Newman, Paraburdoo, While the rocks are regarded as Pannawonica, and other sites. By the being old, they are only about half the ● PERTH early 1990s the range accounted for more age of the Earth, having been deposited than 90 per cent of Australia’s iron ore between about 2800 million years ago production, which is nearly 40 per cent of and 2200 million years ago. They were the global demand for iron and steel. laid down on the Pilbara Craton, mostly In the national park, mountains and in shallow seas. Geologically they contain escarpments rise out of the valleys. The the world’s best-preserved sequence of high plateau is dissected by breathtaking volcanic and sedimentary deposits of gorges, and stony, tree-lined watercourses Archean to Proterozoic age. The iron- wind their way over the dusty plain. Erosion has slowly carved this landscape. There are many beautiful gorges and sites to visit (see ‘Rocking the patterns’ on page Above Fortescue Falls, Karijini National Park. 36) including Dales Gorge with Fortescue Photo – Guy Skillen Falls, one of a number of permanent waterfall in the park. It cascades more Above right Hamersley Range viewed from than 20 metres down a series of natural Mount Meharry. Photo – Cliff Winfield rock steps before finishing in a large, picturesque pool. Also within the national Right Dales Gorge, Karijini National Park. park is Mount Meharry; at 1249 metres Photo – Marie Lochman

LANDSCOPE 21 STIRLING RANGE to earth-movements and heating that metamorphosed the sedimentary rocks, 400 kilometres from Perth, converting some of the shales to slates 95 kilometres from Albany and sandstones to quartzite. This occured The Stirling Range or Koikyennuruff in when the range was thrust upwards to the south of the State stretches for its present elevation. The quartzite is 65 kilometres from east to west as a series tough and resists erosion and is the rock of rugged ranges and isolated peaks. The that preserves the highest peaks. The range is home to Bluff Knoll or Bular Mial, geological setting is enigmatic and still not the tallest peak, standing at 1095 metres clearly understood. The Stirling Range above sea level and a place where the rocks sit on Yilgarn Craton rocks, which local Menang people believe the spirits of are at least 500 million years older, and are Noongar people go after death. Several on the northern margin of the Albany- other peaks rise to between 700 metres Fraser Orogen, the site of a collision and 950 metres. The area is within the between two continental plates between Stirling Range National Park, originally 1300 and 1100 million years ago. There are gazetted in 1916. suggestions similar rocks occur in India as The bedrock of the Stirling Range the Indian subplate once was connected to consists of quartzite, sandstone, shale the west coast of Australia that split apart and slate. These were sediments during one of the Gondwanan break-ups deposited in a sea possibly as early as about 130 million years ago. 2000 million years ago. Later, at about When first upthrust, the range was 1140 million years they were subjected originally much higher than it is today. The large amount of erosion that removed much of the former range has carved the Top left Talyuberlup Peak, Stirling Range present range into various spectacular National Park. Photo – Jiri Lochman formations, especially on the craggy higher peaks. Being so high and surrounded by Left White mountain myrtle (Hypocalymma lowlands between 150 metres and phillipssii). 250 metres altitude, they create a climate Photo – Ann Cochrane of their own and, along with that, there is a huge diversity of more than 1000 species Below View from the top of Bluff Knoll, Stirling Range National Park. of wildflowers, more than 100 of which Photo – Marie Lochman are unique to the Stirling Range.

22 LANDSCOPE CAPE RANGE unique local biodiversity in different cave systems, showing the evolution of the 1300 kilometres from Perth, ● Cape Range National Park troglofauna and stygofauna (animals that 50 kilometres from Exmouth live in caves, either in the air or under The Cape Range peninsula lies within water) in isolated cave systems and did PERTH ● the Carnarvon Basin geological province, ● Stirling Range National Park not mix with other systems along Cape the host to the huge oil and gas reservoirs Range. of the North West Shelf. The range was Local cavers have recorded more formed as a result of uplift associated with than 580 caves in this karst landform. It is tectonic compression during the break important because it is a relatively young habitat of remipedes; a class of blind, up of Gondwanaland. This tectonic uplift limestone whereas most other karsts in colourless crustaceans (Kumonga exleyi). has resulted in an anticline extending for Australia are formed in older limestone. While the State’s national parks 100 kilometres in a north-south direction The karst system is still active, particularly contain magnificent fauna and flora, with a structural relief of 450 metres on the flanks of the range and beneath they are also home to some wonderful comprising spectacular limestone hills, the coastal plain, and it demonstrates landscapes, landforms and geologic gorges and coastal scenery. simultaneous erosional and depositional features, many of which have been The range hosts an extensive karst karstic processes. interpreted on sign boards and brochures system of national and international Bundera sinkhole lies within the within the parks. So, next time you visit significance, its importance being that Cape Range peninsula anchialine system one of our parks, take time to appreciate formed over a sequence of different and hosts rare and unique aquatic the landscape and landforms as they climatic phases from wet to arid subterranean animals It is the only known underpin all that lies above. conditions. This has been an important driver of biological evolution as demonstrated through the significant speciation and adaptation evident in the subterranean fauna of the area (see ‘Endangered! Subterranean animals of the North West Cape’, LANDSCOPE, Spring 2001). Of major note is the presence of

Professor Ross Dowling AM is an Honorary Professor of Tourism at BUSH BOOKS Edith Cowan University where he specialises in research on geotourism and GEOLOGY &

Above Bundera sinkhole, Cape Range geoparks. He can be contacted at [email protected] or 0419 930 987. LANDFORMS BUSH BOOKS BUSH peninsula anchialine system. Mike Freeman is a widely experienced geologist and amateurBUSH BOOKS naturalist of the South-West GEOLOGY & Photo – Tiffany Taylor BUSH BOOKS LANDFORMS who loves spreading the word to the community of the fundamental joy of the Pilbara that can be obtained by a knowledge of the geology that is all around us. Above right Cape Range National Park. He can be contacted at [email protected] or 0412 689 978. Photo – Tourism WA WA’s beloved Bush Book series features publications about the geology and

ISBN 978-0-7307-5516-6

landforms of Pilbara and South-West. You can purchase them for $6.95Department each of Biodiversity, Conservation and Attractions WA NATURALLY WA NATURALLY GOVERNMENT OF RECREATION GUIDE Right Yardie Creek, Cape Range National Park. from shop.dbca.wa.gov.au. WESTERN AUSTRALIA Photo – Cliff Winfield What landform is that?

20180029 Geology of SW COVER.indd 1 15/6/18 2:14 pm What landform is that? LANDSCOPE 23