PUTTY BEACH - SOUTHERN HEADLAND

A snapshot of the Sydney Basin about 230 million years ago The photograph and the diagram together show the formations at the southern end, or surf club end of Putty Beach. Alternating layers of sandstone and shale at the base of the headland were probably laid down on a tidal flat. With cycles of rising and falling sea levels, estuarine burrowed sands were deposited, overlain by burrowed shales with fossilised plant roots. A later drop in sea level led to the erosion of a valley through these shales. With sea-level rise this valley filled with alluvial quartz sands from the Lachlan Fold Belt. This infill formed the yellow-block sandstone that protrudes from the cliff above the 'bogey-hole'. The overlying shale shows that a further sea-level rise produced an estuarine environment where fine sediment accumulated. The uppermost part of the headland consists of Hawkesbury Sandstone. This was deposited when the sea level was falling and an enormous river from the south emptied its sediment into the Sydney Basin. Visit the southern end of Putty Beach to see this amazing headland for yourself.