This is thick sequence of densely packed fossil oysters that were living about 2.5 million years ago. There are also other fossils to be found, but the oysters predominate and must have been part of an enormous oyster bed.
The molluscs here would have grown about 30 metres below the sea surface on top of earlier, dead shells, gradually building up the thick sequence into a large oyster reef. This same geological layer can be found over an area about 50kms across. That adds up to a lot of shellfish! In fact, a minimum estimate of the number of oysters preserved in this bed is over 330 billion!
Explore the cliff section and nearby boulders for densely packed beds of oysters, as well as a variety of scallops, snails and brachiopods.
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Directions/Advisory
Follow SH 4 for 14km north of Wanganui and take the turning signed to Pipiriki and the Whanganui National Park. Follow the Whanganui River Road, for 13km until you see the cliffs on your right. Find a safe spot to park by the roadside.
The cliff has been modified by roadworks since this GeoTrip was published, so some of the really well cleaned fossils are harder to see, but they are still there!