Bollons Seamount and early New Zealand–Antarctic seafloor spreading

Abstract

[1] Magnetic anomaly, swath bathymetry and gravity data from the southern Chatham Rise to Bollons Seamount region reveal a history of Cretaceous seafloor spreading in the mouth of the Bounty Trough starting at $85 Ma followed by spreading ridge jumps back to the Marie Byrd Land Margin at 83.7 and 78.5 Ma. The latter ridge jump accompanied the rifting of the Bollons Seamount from the Marie Byrd Land margin. Interpreted magnetic anomalies indicate a pattern of highly asymmetric spreading prior to 78 Ma that varied in bias along the margin on a $100 km length scale. Crustal thickening within the $50 km Bollons Gap linking the Bollons Seamount to the Campbell Plateau is interpreted to be due to excess volcanism associated with the initial rifting-seafloor spreading process and possible thinned continental crust. The elevated 200 km long segment of Antipodes Fracture Zone southeast of Bollons Seamount has been exposed to varying styles of ridge end volcanism and possible normal compression associated with the development during chron 32n.2n of a triple junction at its southeastern limit marking the Bellingshausen-Marie Byrd Land plate boundary.

Zealandia 2008

“…1). The age of the oldest oceanic crust on the Australian and Antarctic sides of Zealandia is c. 85 Ma (Gaina et al, 1998;Davy, 2006).…”

Cretaceous felsic volcanism in New Zealand and Lord Howe Rise (Zealandia) as a precursor to final Gondwana break-up

“…The continent of Zealandia split from Gondwanaland in the Late Cretaceous at about 83 Ma (Sutherland 1999;Mortimer 2004a;Laird & Bradshaw 2004;Davy 2006). Zealandia, about two-thirds the size of the conterminous United States, remains largely submerged as a result of crustal thinning and extension associated with pre-break-up Cretaceous tectonics.…”

Polar dinosaurs on parade: a review of dinosaur migration

“…New Zealand during the Campanian lay within the Antarctic Circle (Fig. 4), and seafloor spreading as early as 85 Ma (Davy 2006) had begun to push the former from the Antarctic mainland. Despite the high latitude, the influence of relatively warm marine currents (annual average temperature *148C) significantly warmed the climate.…”