Parnell Baths

This site is a handy place to examine some of the features of the Waitemata Sandstones. Waitemata Sandstones underlie much of the Auckland region and underlie Auckland’s volcanic rocks. The Waitemata Sandstones were deposited on the floor of a 1000-2000 m-deep marine basin (known as the Waitemata Basin) during the early Miocene period, 21-18 million years ago. This deep marine depression was formed by rapid subsidence of the whole Auckland region (22-20 million years ago) as northern New Zealand started to feel the effects of the newly active boundary between the Pacific and Australian plates, with both compression and subduction forces.
Here within the Waitemata Sandstone sequence there is a thick layer of darker and coarser sandstone that may even contain cobbles or pebbles at its base, but is most commonly composed of granules and is therefore called Parnell Grit. These beds are composed almost entirely of volcanic grains and pebbles with characteristic red oxidised volcanic grains that show that some of the sediment had been erupted on land (and oxidised in contact with the air- hence red iron-oxides). These dark volcanic-derived beds come from a completely different source than the usual Waitemata Sandstone beds. The source was an active basalt-andesite volcano on the side if the Waitemata Basin, possibly in the vicinity of the Kaipara Harbour mouth and/or in the vicinity of Whangarei Heads.

Can you see the thick bed of darker sediment in the cliff face above the baths building?
Why do you think it is darker and thicker than the Waitemata Sandstones around it?
Does the Parnell Grit overlie or underlie Waitemata Sandstone here? Look in several places.
Where was the beach when humans first arrived at this place and what do you think the cliff looked like when Hochstetter visited it in 1859?