Geological control on the morphology of estuarine shore platforms: Middle Harbour, Sydney, Australia

Abstract

Middle Harbour, Sydney, Australia is a microtidal environment formed in resistant Triassic quartzose sandstone (mean N-type Schmidt Hammer rebound value of 37 ± 6). Wave energy is dominated by deep-water ocean swell which is dissipated rapidly as it propagates through the estuary mouth and is absent 1.5 km upstream. The small fetch of the harbour also means locally-generated wind waves are insignificant, generally 2 m in the most exposed locations. All the platforms are semi-horizontal and appear to occur where a joint or bedding plane is coincident with intertidal elevations, although there is little correspondence with a particular tidal limit, with surfaces occurring at all levels betwee..