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NINGALOO: Australia’s Untamed Reef
1. The Ningaloo Coast
The Ningaloo Coast consists of an arid, sparsely vegetated strip along the Indian Ocean that, initially, appears to
contrast the underwater splendour of Ningaloo Reef. This idea could not be further from the truth. Besides
displaying an impressive range of habitats and a surprising biodiversity, the coast bears the marks of a spectacular
geological history. The Cape Range peninsula, in particular, is one of the state’s most treasured environments
where marine fossils from millions of years ago riddle the terrain and fascinating organisms inhabit a unique cave
system of international significance under the surface. The terrestrial environment of the Ningaloo Coast has also
played a considerable part in the evolution of the adjacent marine environment and should, therefore, not be
overlooked but regarded as an integral part of the Ningaloo ecosystem.
The Emergence of Cape Range
For anyone familiar with Australia’s western coast,
the region between Carnarvon and North West Cape,
i.e. the Ningaloo Coast, looks different. Where in
other parts the coastal strip consists mainly of sandy
flats that lack dominant structures, here we find a
landscape that includes several ranges close to the
shore1. The most prominent of these formations is
Cape Range, a series of hills that probably emerged
from the ocean less than 5.5 million years ago and
that, at present, forms the backbone of the Cape
Range peninsula along which we find the most
diverse section of Ningaloo Reef2. Because this
structure and the geological processes that are
responsible for it have strongly influenced the
region’s evolution and biodiversity we should start
the story of Ningaloo right here, on the dry limestone
hills of Cape Range.
Cape Range is an anticline, a fold in the
earth’s terrain that is formed by upward shifting
blocks of bedrock several kilometres under the
surface1. Sometime during the first half of the
Miocene (23 - 14 million years ago), and kilometres
from what was then the mainland coast, the Cape
Range anticline started to take shape on the seabed2,1.
Continued tectonic activity over the next few million
years drove the tip of the fold closer and closer to the
surface of the ocean and, eventually, beyond it. From
the shore, the anticline would first have been visible
as a series of islands off the coast before it gained
height and connected to the mainland to form the
Cape Range peninsula. Finally, a further significant
period of uplift within the last 5 million years
increased the elevation of the range to the present
level (i.e. up to 330 m above sea level)2,1.
A tectonic process like uplift typically
occurs in a stop-start manner rather than at a slow
and continuous pace. This is made clear on the west
side of the range where staircase-like structures give
an indication of where the process came to a
temporary halt. These four wave-cut marine
terraces, as they are called, are the marks left by
previous sea levels with the highest on the range
being the oldest and from a time when most of the
current peninsula was still under water3,1.
The surface of Cape Range consists
predominantly of several types of limestone,
hundreds of metres deep and over 20 million years
old, that once formed underwater reefs2. After its
emergence from the ocean, the limestone peninsula
was covered by forests and cut by numerous streams
during wetter periods4,1, at least until a climate shift
towards much more arid conditions at the end of the
Tertiary (~2.5 million years ago5,4). As the streams
dried up and the forest vegetation disappeared, the
surface of the range eroded – once again exposing the
original limestone of the former reefs. This is clearly
demonstrated today by the wealth of marine fossils
throughout the entire range, each fossil silent
evidence of the fascinating aquatic history of the
peninsula.
The addition of Cape Range peninsula to
Western Australia has been an important event for
the region, as it effectively brought the mainland a lot
closer to the edge of the continental shelf. At this
edge, the shelfbreak, the downward slope of the
seabed suddenly increases to meet the ocean’s
abyssal plain thousands of metres below the surface.
Along most of the west coast the shelfbreak is usually
reached about 40-80 km from the coast, whereas, off
Cape Range peninsula, it lies only 6-10 km from the
shore. This has been of enormous consequence for
the marine ecosystem because the shelfbreak marks
the path of the Leeuwin Current, a unique narrow
band of southward-flowing tropical water providing a
constant supply of warm, clear waters and an influx
of organisms from the tropics (See page 30: The
Leeuwin Current). Closing the gap between the
western coast and the Leeuwin Current has, therefore,
greatly facilitated the later development of Ningaloo
Reef and, no doubt, positively influenced its
biodiversity.
The Ningaloo Coast
Top: Yardie Creek and Cape Range from the
air (looking south). The cliffs on either side of
the Creek clearly reveal the limestone base of
the peninsula. (Photo: Craig Kitson)
Right: A euro (Macropus robustus) about to
take off. (Photo: Henk Schilt)
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NINGALOO: Australia’s Untamed Reef
An Australian pelican
(Pelecanus conspicillatus) and a
silver gull (Larus
novaehollandiae) at Tantabiddi
with Cape Range in the
background. Note two clearly
visible ‘wave-cut terraces’ that
appear as horizontal ridges on
the western side of the range.
(Photo: Blue Office / MIRG
Australia)
Four euro’s (Macropus robustus) drinking
from a rare puddle of rainwater on the range.
(Photo: Ian Anderson)
Although almost devoid of vegetation at
present, Charles Knife Canyon in the middle
of Cape Range (looking east) conjures up
images of a long and steady stream of water
slowly cutting through limestone. Exmouth
Gulf lies in the background. (Photo: Blue
Office / MIRG Australia)
The Ningaloo Coast
Cape Range cross-section (after Figure 5 in: Allen (1993), Western Australian Museum).
As Cape Range peninsula is
riddled with marine fossils, it is
not uncommon to find remains
of long-gone species, such as
Carcharocles megalodon – an
enormous species of shark that
is thought to have gone extinct
about 1.6 million years ago.
Adult megalodon teeth may
reach 17 cm in enamel height –
thought to relate to a length of
up to 16 m (and 48,000 kg in
weight)! This megalodon tooth
shows the serrated edge that
some scientists believe to be
one of the features that justify
megalodon to be grouped with
Carcharodon carcharias, the
great white shark. (Photo: Craig
Kitson)
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