Te Kaukau Point

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.

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.