Geology
the park covers approximately 85% of the Bherwerre Peninsula, which is underlain with Permian sandstones, siltstone and conglomerates of marine origin. They are part of the southernmost extent of the Sydney basin sedimentary rocks. Dunes and sandy soils overcap the Peninsula. Bedrock is exposed in cliffs, marine platforms and minor exposures in creeks and dune areas. Lake Windemere and Lake McKenzie evolved when streams were blocked by sand. Bowen Island is composed of the same sandstone type as the Peninsula and slopes sharply from cliffs on the eastern oceanic side down to sea level rock platforms on the western, Jervis Bay side. The sandstone on the Island is covered by windblown sand, which supports a range of vegetation communities.
Other features of geological interest in the park include fossil sites and exposed stone walls of a substantial quarry used to supply stone for the construction of the HMAS Creswell breakwall in 1915. These are also of historical interest. The role of the landform and geology of the park in the evolution of ecological processes and landscape features is also of particular scientific and educational interest.
The sandy soils of Bherwerre Peninsula and Bowen Island are unconsolidated and depend upon the presence of vegetation cover for stability. When vegetation is removed, the soils and sand dunes are readily eroded by wind, water and physical disturbance. In the low lying western area of the park the soil is occasionally saturated. In this condition the soils can be easily damaged or eroded by disturbance.
The shallower sand covered section of Jervis Bay is covered by seagrass meadows. Anchoring, mooring and dredging can impact on the seabed and the seagrass meadows.