Baylys Beach

Kaipara North and South Heads are sand barriers that have built across the front of Kaipara Bay in the last 2 million years, creating New Zealand's largest harbour - the Kaipara. At Baylys Beach, out of Dargaville, you can see a belt of mostly sand dunes that have been added on the seaward side of the older North Kaipara barrier in the last few hundred thousand years.
This belt of dunes is currently eroding, creating sea cliffs of fairly soft sand. In the cliffs you can see evidence of how this belt of sand has been added. At various places within the sequence there are lenses of black lignite (0-8 m thick and 10-100 m or more wide). These lignites are dead plant material that accumulated in swamps within the sand dunes at times when the dunes were stabilised and had become forest-covered. The swamps were located in flat sections of small stream valleys or in depressions between sand dunes.
Lignite lenses can be seen near the base of the cliffs just to the north and south of the Chases Gully access to the beach.
The thin lignite lens to the north contains a 5 cm thick white layer of fine glass which is volcanic ash that was erupted from the centre of the North Island in a huge eruption cloud and blown north to here, where it fell out of the sky and was preserved in the swamps.
In some places you can still see the stumps of trees, some are large kauri trees, in growth position within the base or top of a lignite lense, where they died and were buried and preserved as fossils. Lumps of kauri gum are sometimes found in the swamp lignite.
In the sand sequence seen in the cliffs north of Chases Gorge there is evidence of at least five periods when the dunes were stabilised and became partly or fully covered in vegetation.
In some places the sand has layering within it at angle of 20-30 degrees to the horizontal (called cross-bedding). These layers record the moving steep front of a sand dune being blown along by the winds.
Some horizontally layered sand bodies low in the cliffs may have been deposited on a beach.

Look for black lignite lenses in the beach or cliffs.
Can you see any wood or tree stumps in the lignite?
Look for sand with layers at a high angle - can you decide which way the sand dune was being blown?
For 90% of the time in the last 2 million years, sea level has been lower than today. What do you think this dune belt looked like when the sea was much lower and the coast way out to the west?
Each lignite lense is buried by a layer of further sand - what do you think happened at these times?