Titahi Bay North, bedrock structures

This coastal area shows ancient basement rocks (older than 200 million years). They were formed in the ocean off the coast of Gondwana, before New Zealand ever existed. The lighter coloured sandstone layers are coarser grained than the darker, more fractured siltstone layers. These alternating layers are referred to as turbidites and are the product of marine avalanches (turbidity currents) bringing sediment into the deep ocean down a continental slope. Each turbidite consists of a lower sandstone layer, fining upwards into siltstone (argillite).
After millions of years of burial, compression, tectonic movement, uplift and erosion, the rocks are again exposed. Originally they were horizontal, now they are tilted vertically, highly deformed and dislocated, with many folds and faults visible. Faulting often weakens the rocks and makes them more susceptible to erosion hence you will often see a fault associated with a gully or cave where the crushed rock has been eroded out.

Notice the sedimentary layers that look like stripes of rock, tilted up vertically.
There are many faults cutting across the shore. They can be spotted by looking for places where the sedimentary layers have been offset (pushed sideways) along the fault plane. Some of the faults branch and some of them cut through the sedimentary layers at different angles. What is the biggest offset that you can find?
Have a look also for folds in the rock. There are some good examples here.
A close-up look at the rock layers may reveal some sedimentary structures (look for variations in textures, shapes and colours) such as very small scale cross-bedding and graded bedding. These tell us about the processes of sedimentation, such as the direction and strength of the turbidity currents.
There are also good examples of box weathering in places.