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Geology and Geomorphology

The geology of the Jervis Bay region, including Bherwerre Peninsula can be described as undulating sandstone mass overlain by varying depths of windblown and water deposited sands.

The base rock is made of geological units belonging mainly to the Permian Shoalhaven group of sedimentary rocks which form the southern edge of the extensive Sydney Basin system. These ancient sandstones (c. 280-225 million years) are overlain by Tertiary aged alluvial sediments in low lying areas (Cho et al 1995).

Water and wind deposited sediments of Quaternary age capped the older landscape with fine alluvial and formed sandy beaches. On Bherwerre Peninsula, the end of the Quaternary era is represented by small inlets comprising mudflats with mangroves and salt marshes, across which tidal channels meander.

The perched sand dune lakes and swamps of Lakes Windermere and McKenzie, Blacks Waterhole and Ryan’s Swamp were formed during the Quaternary era (Cho et al 1995). Formation of the bay in its present appearance occurred around 6000 years ago when the sea level finished rising. Before this time, during the ice age (20 – 15,000 years ago), the sea level was about 120 metres lower than today and the land extended 25 kilometres further eastward.

The headlands would have been low mountain ranges and Bowen Island a hill. ‘Jervis Bay’ was an open vegetated valley, with a creek flowing outwards between what are now Bowen Island and Beecroft Peninsula (Booderee National Park Board of Management and Director of National Parks 2002).

Rising sea levels carried sand landward, forming two major sand barriers, cutting off St Georges Basin and Beecroft Peninsula and depositing sand in the extensive dune sheets along Bherwerre Peninsula. The geology of the region is very relevant to Aboriginal occupation as weathering of the sandstone cliffs has created the rock shelters where people lived and left their artwork on the walls.

The eroded marine rock platforms are the habitat for many shellfish species and under the sea ‘bombies’ and other submarine features support a diverse range of fish and crustacean species.

Knowledge of these species – their ecology and lifecycles – and how to hunt and gather them is a significant component of the traditional and local knowledge of the Wreck Bay Aboriginal Community.