24.4 Cape Otway

This information has been developed from the publications:

Sites of Geological and Geomorphological Significance in the Western Region of Melbourne (1986) by Neville Rosengren
Sites of Geological and Geomorphological Significance on the Coast of Port Phillip Bay (1988) by Neville Rosengren.
Sites of Geological and Geomorphological Significance in the Shire of Otway (1984) by Neville Rosengren.

Geological heritage sites, including sites of geomorphological interest and volcanic heritage sites, are under regular revision by the Geological Society of Australia, especially in the assessment of significance and values. Reference should be made to the most recent reports. See the Earth Science Heritage (external site) section of the Geological Society of Australia website for details of geological heritage reports, and a bibliography.

Location:	24-717958. Coastal cliffs and platforms adjacent to Cape Otway lighthouse.
Access:	Cape Otway Road.
Ownership:	Australian Government (Lighthouse Reserve). Permission for entry (other than for regular open day visits) must be obtained from the Department of Transport, Navigational Aids Section in Melbourne.
Geology/Geomorphology:	Bridgewater Formation dune limestone overlies Mesozoic sandstone east and west of Cape Otway. At the Cape, the sandstones are faulted. East of the fault a shallow syncline/anticline sequence is evident in the shore platform. Below the lighthouse is a deep cleft across the shore platform leading to a cave in the sandstones. The cliffs immediately west of the Cape Otway fault are formed in thin bedded siltstone which is unusual in that these rocks generally erode quickly to form embayments. Gill (1977) presents an analysis of the rock indicating it is predominantly quartzose and lacks cleavage. The shore platform east of the Cape extends for approximately one kilometre. It is made up of both Mesozoic rocks and dune limestones. At the present time, the dune limestone platform which has been formed during the Holocene, is being cut back to reveal a platform in the Mesozoic rocks. Apparently, this formed during an earlier (Pleistocene) sea level episode. This sea level must have been approximately equivalent to the present sea level (Eric Bird, pers. comm.).
Significance:	State. Cape Otway is a major geographical feature of the south coast of Australia. The cliffs clearly display fault and fold structures of the Mesozoic sandstone, and the nature of shore platform development described above appears to be unique on the Victorian coast.
References:	Gill, E. D. (1977). "Evolution of the Otway Coast, Victoria, Australia." Proc. Roy. Soc. Vict. 89 (1&2):143-171.

Cape Otway. The Mesozoic rocks are capped by
Bridgewater Formation dune limestone. The cave
is indicated by A, and the arrow shows the
calcarenite platform overlying an earlier
platform cut in Mesozoic rock.

Site 24.2 to 24.6

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