Geology of the Catlins
The Catlins has some of New Zealand’s oldest sedimentary rocks. The geological processes that laid the foundations of the Catlins began about 200 million years ago. At that time, New Zealand was part of the Gondwanaland super-continent. Today these Triassic and Jurassic rocky foundations, which contain many dinosaur-age fossils of marine and plant life, provide much interest. The rocks were initially laid down horizontally in, or near, the seas of the time and then were subjected to geological uplift, folding and faulting.
For the last 80 million years or so, the area has been geologically stable, compared with most other parts of New Zealand. However, in the cliffs, the rock faces, and in the shape of the hills, the evidence of these past upheavals is very obvious. Fault lines are visible in the cliffs at Nugget Point and at the Cathedral Caves where sea erosion has carved out caves and chasms along the faults. Fossils in the Catlins famously include ferns and tree species that grew on Gondwanaland before ancestral New Zealand broke away about 80 million years ago. These ancient plants still have their descendants in the tree ferns, podocarps and beech trees of the present forests.
Plant fossils are found throughout the Catlins but are more frequent in the south and west. This reflects the location of land in Gondwanaland times. Curio Bay is the location most well known for seeing the trunks of ancient trees as well as thin seams of coal and associated leaf impressions. Plant fossils are also common in the places where younger rocks are exposed. This is because the land with trees on it was slowly extending out into the sea over time. The youngest rocks (mid Jurassic) of the Catlins are to be found at Otara and in the Waikawa, Chaslands, Tahakopa and Catlins River valleys.
Fossils of animals that lived in the sea are very common. They are usually in the form of impressions of bivalve and brachiopod shellfish; and the remains of ancient cephalopods such as belemnites and ammonites are also reasonably common as are the traces of animals such as worms. The best places to look for marine fossils are where rocks are freshly exposed along the coast from Nugget Point to Papatowai.
The Catlins area has a diverse landscape made up of many ranges and valleys, streams and rivers. It is a predominantly green landscape as a result of plentiful rain throughout the year. Winds from the ocean bring in copious amounts of nutrients such as sulphates, magnesium, calcium, potassium; and along with the salty air this makes for excellent pasture growth and healthy growing conditions for grazing animals which are the mainstay of the local economy. The modest clover plant which fixes nitrogen in the soil as well as providing nutritious feed for sheep, cattle and deer, is the key to the Catlins’ agricultural production.
Farm homes are generally surrounded by thick shelter belts designed to deflect wind up and over the homestead area. Flaxes, olearia and cupressus macrocarpa are commonly used for shelter belts. Macrocarpa is one of the few large trees which can resist the salt in the winds from the sea, and 100 year old windshorn shelter belts planted around the first homesteads, for instance at Slope Point, ( the southernmost point of the South Island), provide dramatic photographic opportunities.
In pre-human times the land was covered with native forest to the seashore. The Catlins Forest Park provides reminders of this original cover. Plant species are diverse in this forest. There are broad-leaved flowering trees like kamahi and fuchsia; ancient podocarps like totara, rimu, matai and miro; and orchids, grasses, perching plants and many species of fern. Native birds such as tui, bellbirds, tomtits, pigeons and fantails may also be seen and heard in the forest.
The Catlins coastline is unlike any other on the east coast of the South Island. It is rugged, forested in places and very scenic. It has sea cliffs which rise to 200 metres, reefs, rock stacks, blowholes, arches, caves, reefs, sandy beaches, estuaries and coves. Most dramatically, it also has the Curio Bay Petrified Forest which allows a glimpse of a young forest of Jurassic-age conifer trees that was vibrant with life 150 million years ago.
The sea coast has many native plants which have adapted to the salty winds. They range from flaxes to blue-grey tussocks and flowering gems such as gentians and sand convolvulus. The increasingly rare pingao, a beautiful green-orange sedge, has been almost completely ousted by the introduced marram grass.
Seaweeds, shells, and colourful gravels and sands add interest to the natural history of the coastline. The gloriously iridescent paua shell is often washed up on the beach, as are Captain Cook’s turbans, brachiopods, fan shells, cats’ eyes, mussels, and wheel shells to name a few. Giant bull kelp impresses visitors as it moves in the surge of the ocean, like the tresses of a mysterious underwater being. There are bright green, white, pink and brown seaweeds on the reefs and myriads of small crabs and chitons under loose rocks.