New, refined map of lost ancient continent Zealandia

Geologists have produced a refined map of the submerged landmass known as Zealandia using seismic data from the region surrounding New Zealand.

Between 79 and 83 million years ago, Zealandia is believed to have broken away from the ancient supercontinent Gondwanaland. Today, 94% of Zealandia is submerged beneath the sea. The majority of the 6% which breaks through is made up by New Zealand.

In 2017, a team of geologists produced a paper claiming that the 4.9 million km² mass should be considered Earth’s 8th continent. But debate continues to rage as to whether the landmass is best described as a submerged continent, continental fragment or microcontinent.

Zealandia has emerged as an important part of the fossil record as a place where bird species flourished tens of millions of years ago.

Unlike Earth’s other continental masses, Zealandia is mostly under water – making it hard to study. This has produced inconsistencies in the way the landmass has been mapped.

New research, published in the journal Tectonics, has given us our best look yet at the ancient continental mass. The small international team of geologists studied collections of rocks and sediments brought up from the ocean bed. These were mostly collected from drilling sites, whereas others were gathered from the shores of islands in the region.

“Basalts, sandstones, and pebbles were analysed and dated,” the authors write. “The sandstones are Late Cretaceous (∼95 million years old) and contain Early Cretaceous (130–110-million-year-old) granite and volcanic pebbles. The basalts are Eocene (∼40 million years old).”

“Onland and offshore reconnaissance geological mapping of the entire 5million square kilometre Zealandia continent is now complete.”