KEY POINTS:
A study of New Zealand's climate 42 million years ago shows greenhouse conditions with warmer seas and little or no ice.
The study - based on analysis of fossilised micro-organisms at Hampden Beach, near the Moeraki Boulders in North Otago - suggests Antarctica at that time was yet to develop extensive ice sheets.
Back then, New Zealand was about 1100km further south, closer to Antarctica, at the same latitude as the southern tip of South America.
But the researchers found the water temperature was 23C to 25C at the sea surface and 11C to 13C at the bottom.
"This is too warm to be the Antarctic water we know today," said Dr Catherine Burgess from Cardiff University's School of Earth and Ocean Sciences. She worked with Hugh Morgans of GNS Science to dig the fossils out of a cliff at Hampden Beach.
The seawater chemistry revealed by the calcium carbonate shells of the exceptionally well-preserved fossils of marine micro-organisms called foraminifers showed there was little or no ice on the planet, she said.
The rock sequence from the cliff face covered a time span of 70,000 years.
A temperature oscillation seen in the fossils - with warming and cooling by approximately 1.5C about every 18,000 years - was likely to be related to the Earth's orbital patterns around the sun, known as Milankovitch cycles.
- NZPA
