2 Encountering the Ningaloo Coast, a Traveller Can Take

DESCRIPTIONDESCRIPIPTTION 2 Encountering the Ningaloo Coast, a traveller can take 2.A DESCRIPTION OF a journey through the Cenozoic era, moving through a PROPERTY layered history that spans more than 25 million years of The Ningaloo Coast is located on the remote western change. Beginning on a cliff top looking seaward, the coast of Australia. Its marine environment is traveller proceeds in geological time from the antique dominated by the spectacular Ningaloo Reef, which heights above Mandu Mandu Gorge (carved into is spread out beneath the red limestone ramparts tropical marine sediments of the Oligo–Miocene epoch), of Cape Range.1 More than a set of physical, biotic down the escarpment, across Plio–Pleistocene fossil reef and climatic attributes superimposed over bedrock, terraces incised into the coastal plain, over the Holocene the outstanding value of the Ningaloo Coast derives sand dunes and beach, into the shallow lagoon and out from its functionally integrated reef and karst system over Ningaloo Reef, into the present (Figure 2.2). lying along an arid coastline. The Ningaloo Coast is also treasured for the rich record it offers of past life and landscapes. Marine biologists, karst specialists, geologists, geomorphologists, palaeontologists, and zoologists can see beneath the surface of the land and sea, to uncover ancestral relationships and explore lost ecosystems. FIGURE 2.1 View of Shothole Canyon, Cape Range. Photograph © BJK Ben Knapinski PREVIOUS PAGE Photograph Tony Howard © Western Australian Department of Environment and Conservation 14 Ningaloo Coast FROM REEF TO RANGE GEOLOGICAL TIME MILLION YEARS BEFORE PRESENT Holocene epoch 0.01–present Quaternary period (2.6–present) Pleistocene 2.6–0.01 Pliocene 5.3–2.6 Neogene period (23–2.6) Miocene 23–5.3 Cenozoic era (65–present) Oligocene 34–23 Palaeogene (65–23) Eocene 56–34 Paleocene 65–56 Phanerozoic eon Cretaceous 144–65 Mesozoic era (250–65) Jurassic 200–144 Triassic 251–200 Permian 299–251 Carboniferous (Mississippian and Pennsylvanian) 359–299 Palaeozoic era Devonian 416–359 (545–250) Silurian 444–416 Ordovician 488–444 Cambrian 542–488 FIGURE 2.2 Geological timescale of the Phanerozoic eon, 542 million years ago to the present (not to scale) The subterranean environment of the Ningaloo Coast retreated underground to evolve in isolation, throwing tells even older stories of bygone worlds, reaching off high-energy adaptations to surface life: growing pale, hundreds of millions of years back to the Mesozoic shedding their wings and losing their eyesight.2 era. These histories are represented in communities of terrestrial and aquatic underground fauna that inhabit The climate, biota, hydrosphere, stratigraphy and the Ningaloo Coast today. The ancestors of some of the landforms, together with the processes that shape them, aquatic invertebrates of the Cape Range aquifer were interact as a unitary whole through time and across separated from their free-floating marine relatives in the spatial scales. The term ‘geoecology’ usefully describes middle-Mesozoic era, more than 150 million years ago, these links. The marine, terrestrial and underground when tectonic forces broke the supercontinent Pangaea systems, and flora and fauna of the Ningaloo Coast, can apart (Figure 2.2). be considered as a perpetually changing, functionally- integrated geoecosystem.3 This movement of continents, driven by forces deep beneath the crust, was accompanied by climate change. Growth of the modern reef has been shaped by past Since the Miocene, Australia has moved further north reef morphologies and sea levels. At the peak of the last away from Antarctica and developed its present arid interglacial stage, approximately 125,000 years ago, the character. Tropical rainforests, along with their leaf- sea level was up to five metres higher than today. This litter dependent fauna, retreated to the north-east of change is reflected in the fossil reef terraces. Today, Australia. Trapped in an increasingly inhospitable Ningaloo Reef grows on a substrate of fossil reefs that surface environment, the invertebrates of Cape Range formed during the last glacial stage, which peaked approximately 20,000 years ago when sea levels were 15 up to 135 metres lower than modern levels. Several Together Ningaloo Reef and Cape Range, along with a kilometres of the now submerged continental shelf mosaic of related interdependent marine and terrestrial were exposed as coastal plain. As sea levels rose again, ecosystems, form a functionally integrated limestone corals recolonised the carbonate substrate of the former structure. The Ningaloo Coast is unusual and important coastal plain. The modern reef grows in the narrow band in a number of ways: of shallow nearshore waters between the western shores • biologically, through the combination of high of the Cape Range peninsula and deeper ocean waters. terrestrial endemism and a rich marine environment Ningaloo Reef forms an unusual nearshore barrier reef that extends for almost 300 kilometres from Red Bluff • structurally, as a large nearshore coral reef off a in the south to the fringing reefs of the Muiron Island limestone karst system group north of the Cape Range peninsula, and around • climatically, for the juxtaposition of a tropical marine the top of the peninsula to Bundegi Reef in Exmouth setting and an arid coast 4 Gulf (Map 1.1). • topographically, as a barrier reef lying alongside a The Cape Range peninsula is characterised by the low, steep limestone range. steep karst limestone of Cape Range, built from Most of the people in the region live in the port town the skeletons of marine creatures deposited in of Exmouth and the smaller community of Coral Bay. vanished tropical seas and eroded over millennia into The region’s permanent human population is around the majestic shapes of the karst terrain. The oranges, 3,000. Pastoralism is the principal land use—sheep pinks and browns of the range contrast with patches graziers have adopted a form of low-intensity land of sage green vegetation and vibrant red dune fields. use suited to the hot, dry environment. Tourism is an A series of wave-cut terraces stretching for a distance increasingly important industry. Visitors from around of 90 kilometres sculpts the western side of the range— the world travel vast distances to see the wonders of the legacy of former high sea levels and recent terrestrial tropical reef life juxtaposed against the ramparts and uplift. Parched ephemeral river beds wind their way gorges of Cape Range. The beauty of the region does not through the rocky gullies, recharged only occasionally disappoint those who make the long journey of around by heavy rains from the north. 13 hours drive from Perth, the nearest state capital Below the sunbaked surface lies a hidden network of city. Visitors and locals experience this beauty walking caves and smaller solutional conduits that are home through the winding gorges of the ancient limestone, to a diverse array of cryptic fauna. Their evolutionary swimming alongside majestic whale sharks (Rhincodon histories recall nearly 200 million years of geological typus) or simply enjoying the changing colours of the and biological change, since the supercontinent ocean and sky. Pangaea came together and shortly afterwards began to break apart, foreshadowing the modern distribution of oceans and continents.5 This cave fauna is found in and around a complex system of groundwater streams, pools and aquifers. 16 Ningaloo Coast FROM REEF TO RANGE FIGURE 2.3 View of Sir Charles Knife Gorge, Cape Range. Photograph © BJK Ben Knapinski FIGURE 2.4 Yardie Creek, deeply incised into the arid coastal plains south of Cape Range, flows into the Ningaloo Reef lagoon and through it to the Indian Ocean. Photograph Tony Howard © Western Australian Department of Environment and Conservation 17 A GEOLOGICAL HISTORY OF THE NINGALOO The mainly carbonate rocks of the Cape Range COAST REGION peninsula consist of three limestone units deposited in different marine environments, dating to the middle Miocene epoch. The oldest of the group, the Mandu Regional overview Limestone, is overlain by the Tulki Limestone, which The Ningaloo Coast lies on the western margin of makes up the bulk of Cape Range. The youngest of the Australian continent, described as ‘one of the the group, the Trealla Limestone, caps the northern classic passive continental margins in the world’.6 and western parts of the range, grading into the The margin has its origin in the successive break-up of calcareous sandstones of the Pilgramunna Formation the supercontinents Pangaea and Gondwana, which and the younger Vlaming Sandstone, deposited late occurred from around 180 to 50 million years ago. As in the Miocene epoch. Offshore, carbonate deposition the Indian and Australian tectonic plates separated and continues on Ningaloo Reef, which maintains close the Indian Ocean opened, the rifting formed a number geomorphic and hydrologic relationships with the of sedimentary basins, including the Carnarvon Basin. terrestrial and subterranean parts of the Cape Range 9 Thousands of metres of sedimentary rock were laid down peninsula. in the basin over hundreds of millions of years from For most of its existence, the Cape Range peninsula the Palaeozoic era to the Holocene period (present day) has been part of the mainland, although it is likely (Figure 2.2). During the Cretaceous, much of the area that it was separated from the mainland a number of that now comprises the western seaboard of Australia times

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