20 Portarlington Pier - Geological Section and Platform

This information has been developed from one or more of these publications:

Sites of Geological and Geomorphological Significance in the Westernport Bay Catchment (1984) by Neville Rosengren.
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 Environmental Significance in the Flood Plain of the Upper Yarra Valley Region (1983) by Neville Rosengren, Douglas Frood and Kim Lowe (as part of a study of Sites of Environmental Significance by the University of Melbourne for the then Upper Yarra Valley and Dandenong Ranges Authority).

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 section of the Geological Society of Australia website for details of geological heritage reports, and a bibliography.

Location	944789. Coastal cliff from opposite Fisher St, approximately 400 m east of the Portarlington Jetty.	Site 20, Portarlington Pier
Access	The Esplanade.
Ownership/Managing Authority	Crown land (Portarlington Foreshore Committee of Management and Department of Conservation, Forests and Lands).
Site Description	A degraded coastal cliff, partly covered by slump deposits, exposes Older Volcanics basalt and tuff and overlying sediments. The volcanics are best exposed nearer to the Portarlington Jetty where they form a wide, smooth gently sloping shore platform with variable gravel cover. In the platform, the basalts have a regular joint system which in places is infilled with secondary calcite plates. The cliff sections are higher than at Steeles Rock (Site 19) but slumping has obscured most of the significant exposures and makes access and study of the sections difficult.
Significance	Regional. Although the geological sections are of the same materials to those at Steeles Rock, the degraded state of the high cliffs reduces the significance of the exposures and contacts. The display of joint infilling in the basalts is of particular interest and the shore platform is a clear example of a broad, horizontal platform segment developed in weathered Older Volcanics.
Management Considerations	Class 2. The best exposure of the infilled joints is at the base of the cliff and the inner parts of the shore platform. It would be preferable not to build protective structures or beaches over this sector but to leave the outcrops exposed.
References	Jutson, J.T. & Coulson, A. (1937, 1940) Hills, E.S. (1938)

Site 20, Portarlington Pier

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