• Bollons Seamount;
  • Bellingshausen Plate;
  • Gondwana;
  • rifting;
  • Bounty Trough;
  • Antipodes Fracture Zone

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.