Stream is a window to ancient past

EVERY PICTURE TELLS A STORY: Palaeontology student Ben Hines uses a rock saw to take samples from layers of mudstone strata in Mangaotane Stream. These strata were laid down 94 million years ago, during an environmental crisis when large parts of the world’s oceans were ‘anoxic’ — meaning the water contained little or no oxygen and marine life suffered widespread extinction. By contrast, the red colour of these rocks suggests that in the New Zealand region there was oxygen in the water. Picture supplied

SCIENTISTS believe a small stream north of Gisborne could hold the key to understanding a 94-million-year-old “global catastrophe” as well as revealing what global warming could have in store for the planet.

About two years ago, researchers from GNS Science and Victoria and Otago universities collected rock samples from the Mangaotane Stream.

Palaeontologist James Crampton said samples taken from the rock strata dated back about 94 million years to the Cretaceous period, when the dinosaurs were living, and New Zealand had “just” broken away from the southern super continent of Gondwana.

“Mangaotane Stream preserves an amazing history of what was happening at that time.

“One of the things it preserves is that 94 million years ago there was a global ecological crisis. Nobody yet knows what triggered that but large parts of the world’s oceans lost oxygen, so it became basically fatal for marine life.”

Professor Crampton said fieldwork done in 2015 had now indicated that oceans in the Southern Hemisphere had been quite different to elsewhere.

“We’re still trying to tease that all out but what we’re finding is that in our part of the world, it looked like the waters were actually rich in oxygen.”

A lot of the marine animals still died out.

“One reason for that might be that the oceans might have been acidic, which is something that is happening today, but we don’t know why yet.

“There is a lot more chemistry to be done.”

Further work on the rock samples was undertaken by chemists at the University of Otago, with more results expected in a few months, he said.

The research also had implications for today’s rapidly-changing environment.

“One way to try to understand that is to look at times in the past, when the world changed rapidly, to see why it changed and what effects the change had. So we are looking back into time to figure out what might happen in the future.

“If you want to understand how the world is going to react to rapid global warming or ocean acidification, one way to figure that out is to look at these natural experiments of the past.”

The stream, located on the Waiau River, runs along the boundary of the Maungataniwha Native Forest and was also the site of the discovery in 2014 of the largest giant clam fossil ever found in New Zealand.

Mangaotane Trust chairman Hayden Swann said the research added further to the importance of the land.

“To hear some of the research that has been going on is quite important as a reference point in geology. For us as trustees of that land and area, we are really privileged that we are the kaitiaki or custodians.”

It was also necessary to ensure that the site was protected, so it could continue to be used by researchers.

“We need to think now when we are harvesting the forest, for instance, to make sure that the methods look after and preserve those areas and continue access for people like James.”