Geology

A Lost Plate Turns Up

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Science  23 Mar 2001:
Vol. 291, Issue 5512, pp. 2277
DOI: 10.1126/science.291.5512.2277d

Reconstructing the position of Earth's continents beyond about 120 million years ago is difficult because most of the oceanic crust of this age or older has been subducted back into Earth's mantle. Oceanic crust covers most of the Earth, but many of the pieces of the plate tectonic puzzle, and even entire plates, have not yet been located.

Sutherland and Hollis report the discovery of an old piece of seafloor northwest of New Zealand. They dated fossils deposited on top of the seafloor to 130 to 145 million years ago, making this the oldest seafloor in the South Pacific (the oldest ocean floor is early Jurassic in age and located in the West Pacific). Paleomagnetic data imply that this crust originated at high southerly latitudes and then moved north by more than 2000 kilometers to its present position. This new piece of the puzzle requires the presence of a new plate—named the Moa plate—and spreading ridge in the South Pacific during the Early Cretaceous, and also requires a large strike-slip fault along the margin of Antarctica. — BH

Geology29, 279 (2001).

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