Barrenjoey is a locality in the suburb of
Palm Beach, at the most northern tip of
Pittwater. The
headland is mostly made up of
Hawkesbury sandstone which overlays Narrabeen shale. Around 10,000 years ago the headland was cut off from the mainland due to the rising sea level; subsequent buildup of a sand spit or
tombolo reconnected the island to the mainland (a '
tied island'). It is the location of the
Barrenjoey Head Lighthouse, a lighthouse that was first lit in 1881.