In a revised interpretation of the sea-floor spreading pattern in the southwest Pacific Ocean, Stock and Molnar predicted that the modern Australia-Pacific plate boundary through New Zealand formed about 35 Ma and has accommodated about 800 km of relative motion. Geologic constraints onshore in New Zealand, however, suggest that the modern plate boundary formed about 23 Ma and has accommodated only 500 km of relative motion. The 300 km of additional displacement must have been accommodated elsewhere in the Antarctica-Australia-Pacific plate circuit. Lithospheric extension between East and West Antarctica, which formed the Transantarctic Rift system, accounts for at least 138 km of the additional displacement before the modern plate boundary formed in New Zealand.

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