 Deep below the Hawkesbury sandstone belt lies Narrabeen Shales which is mixture of shale and sandstone under which and within which are untapped coal seams which run right through Sydney and are mined extensively where they come closer to the surface south of the National Park near Wollongong.Sections of recent alluvium fringes of estuarine watercourse where the endangered ecological communities; swamp oak woodlands and swamp mahogany woodlands grow still.Running the full coastal length of the park is a coastal heathland characterised by hardy, low-growing, salt-tolerant shrubs that spread across rocky, hard terrain with very little topsoil.