The layered sandstones and siltstones (mudstones) are seen in the cliff faces and also form the shore platform around the north and west sides of the park.

These softer, generally yellow-brown rocks are approximately 19-20 million years old and are made up of the Waitamata formation (East Coast Bays facies) of early Miocene (Late Otaian) age.

[7] Distortion and faulted dipping, of this once soft strata, can be seen both in the cliffs and in the small ridges of the rock platform extending out from the beach at low tide.

What makes an interesting discovery is that protruding through the softer yellow-brown sedimentary sandstone and mudstone layers, there are ancient (200-million-year-old) tips of greywacke sea stacks from the Jurassic age.

[9] The intertidal ecology is mainly composed of three areas: Ōmana Regional Park has been a traditional home for Ngāi Tai ki Tāmaki for generations.

On the perimeter track, visitors will find a grassed area, overlooking the sea, which was the original site of a Ngāi Tai pā.

This grassed area has a deep ditch whose internal bank would have once been much higher and topped with a strong palisade of posts.

[11] The forest covering the park and surrounding area was felled for timber by European settlers who cleared the land for farming during the mid-1840s.

Kauri felled in the Maraetai hills behind Omana was hauled by bullock teams down to the sea and then floated to mills in Auckland.