WEST KIMBERLEY PLACE REPORT - Department of Sustainability ...

coastal regions which may exhibit similarly low-density coastal infrastructure are
probably south-western Tasmania (but this is a much shorter length of coast whose
form is not dominated by fluvial processes apart from one ria inlet at Port Davey –
Bathurst Harbour) and possibly parts of Cape York. The coasts of Cape York are not
well documented but they are clearly different to the Kimberley in many respects. For
example, they are not dominated by intricate, fold and joint-controlled rocky ria coast
(DEWHA 2009c; Sharples et al. 2009; Sharples 2009).
Nowhere else in Australia, or possibly the world, provides the opportunity to study
the effects of macrotidal tide-dominated rocky coast processes, and repeatedly
interacting sea level changes and fluvial landform processes through time, on an
extensively rocky coast that lacks the disturbance caused by extensive high-density
coastal infrastructure (Sharples 2009). There are many ria coasts in the world, and
other ria coasts in Australia, but the Kimberley rocky coast is unique in Australia and
rare in the world for preserving a continuous and intricate dominantly-rocky fluvial
and drowned fluvial landscape over a length of more than 2500 kilometres. As such, it
is the best expression in the country of this type of landscape and the processes that
have shaped and continue to shape it during the Phanerozoic eon.
The west Kimberley coast from Helpman Islands in King Sound to the western
shore of Cambridge Gulf, including islands, peninsulas, inlets and inundated
features, has outstanding heritage value to the nation under criterion (d) for
demonstrating the principal characteristics of a major coastal landform type,
namely a very well-expressed and extensive rocky ria coast, in an extensive
region without significant modification by coastal infrastructure.
A Late Devonian tropical carbonate ramp on an ancient continental shelf can be
reconstructed from the calcareous sediments and geomorphology of the Lennard
Shelf. These limestone complexes lie off the palaeomainland represented by the
folded and faulted, granitic and metamorphic Kimberley Block to the north (described
under criterion (a) as the rocks of the King Leopold orogeny). Present Lennard Shelf
topography 'strikingly resembles' Devonian seafloor (Playford 1980). A multitude of
features and their spatial relations provide an integrated picture of a proto-Australian
tropical continental shelf environment from 390–360 million years ago (Playford and
Lowry 1966; Playford 1980; Webb 2001; Johnson and Webb 2007; Playford et al.
2009). These features include palaeoshores, palaeoinlets, platforms, atolls, interreef
basins, debris flows, islands and archipelagos with fringing reefs (including the
superbly preserved Mowanbini Archipelago of the Oscar Range). The remains of a
barrier reef, including the forereef accumulations, lagoon deposits, patch reefs,
bioherms (mud mounds) that grew on pinnacle reefs rising from the shallow sea floor
of the backreef lagoon are also found here. Limestone nodules found in the lagoons
and on the forereef slope as it grades into shelf sediments preserve entire fish and
crustaceans at the Gogo fossil localities. Classic reef sections are exposed as cross
sections in river gorges, most notably at Windjana Gorge in the Napier Range, and in
Geikie Gorge. The Lennard Shelf complexes probably represent an epicontinental
shelf, separating two emergent parts of a continental shelf, covered by a shallow
inland sea.
A suite of diverse environments is represented on the Lennard Shelf, allowing
reconstruction of a complex, large scale shallow marine environment. The minimal
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