Underlying fracture zone nature of Astrid Ridge off Antarctica's Queen Maud Land

Abstract

New geophysical data are used to refine the extent and setting of Astrid Ridge, a volcanic edifice lying off the Princess Astrid Coast section (5°E to 20°E) of Queen Maud Land in Antarctica. New findings presented here include a well‐defined fracture zone, occurring as a narrow basement ridge which extends northeast from Astrid Ridge, and an adjacent set of Mesozoic magnetic anomalies M0 to M9, which are offset by 120 km from an identical, previously described set. These two sets of anomalies are combined with the conjugate Mozambique Basin anomalies to define an Africa‐Antarctica rotation pole at 10°S, 29°W for anomaly M2 time. The northern edge of Astrid Ridge and the sharp southern margin of the Mozambique Ridge on the African plate are probably related to the same cessation of excess volcanic activity near the end of the Cretaceous normal polarity interval. Both features had their eastern and western limits confined by a contiguous pair of fracture zones. A possible major swing in fracture zone trend prior to anomaly M9 is also suggested.