Te Kaukau Point

BY KLAYTON AMAI (VICTORIA UNIVERSITY)
Accessibility: EASY
Seal on top of some of the limestone beds at Te Kaukau Point. K.Amai / VUW
Here at Te Kaukau point you can find well bedded limestone interbedded with some sandstone beds containing the greenish mineral glauconite. The layers of rock are dramatically folded and dip mostly to the south-west.
First section of the limestone beds when crossing the gravel bar. K.Amai / VUW
These rocks are limestones. They are made up almost entirely of the calcium carbonate shells of microscopic plants and animals that lived in the ocean about 60 million years ago. The masses of dead plankton (floating organisms) sank to the sea floor and slowly formed many thin layers of limestone each of which is thought to have taken thousands of years to form.
The same types of life live in today’s ocean and their dead shells are all that is found is vast tracts of ocean floor. In these ancient rocks, the fossil shells can still be extracted and identified and paleontologists use the different species present to determine how old the rock is and what the ocean environment was like when the fossils were alive.

Geologists have named these layers the Mungaroa Limestone Formation. Here at Te Kaukau Point the upper section of the formation outcrops extensively. These limestone beds are interbedded by large influxes of sand which was carried into the deeper water from shallower areas by turbidity currents (underwater liquid landslides or mudflows). The sand-laden turbidity currents also carried glauconite (a greenish mineral) with them into the deeper ocean to form the thick brownish sandstone beds. What remains of the limestone and sandy mudstone sequence is only a very small portion of what was once in the area.
Looking down over the south-west dipping Mungaroa Limestone, Te Kaukau Point. K.Amai / VUW
If you look around you will see that the rocks have been dramatically folded into a variety of zig-zag patterns. This occurred as slumping of the sediments when the rock was still soft and could bend without fracturing. Some of the slumping may have occurred as a result of earthquakes. They are referred to as 'slumping folds'.
Can you see any faults, where some of the layers have been dislocated and offset?
If you scratch the grey sandstone layers you may find that there appears to be a green lustre to it, which is the glauconite mineral.
Directions/Advisory

Follow White Rock Road, just after the final right hand turn before reaching the coast you will find an area where you can park. Head towards the rocks through a gate reading 'White Rock Station'.

There are often seals in the area. Take care NOT to disturb them!

Google Directions

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Accessibility: EASY

During low tide you can walk safely across the gravel bar to Te Kaukau Point in about 20 - 30 mins

Features
Sedimentary Fossils Rock Deformation Active Erosion
Geological Age
Mungaroa Limestone beds ~ Late Cretaceous to Paleocene period (about 60 million years)
Zealandia Evolution Sequence
Haerenga Supergroup (Submergence): 85-35 million years ago