Life of the Bellingshausen plate

The onset of independent Bellingshausen plate movement in the South Pacific is estimated at just after chron C33o. This event closely follows a change in the offset sense on the transform arm of the Late Cretaceous Pacific-Phoenix-Antarctic triple junction and accompanies the creation and/or lengthening, by different mechanisms, of long-offsets on the Pacific-Antarctic ridge at the Udintsev, Tharp, Heezen and V transforms, as the triple junction stepped away from the ridge. At around chron C27, the Bellingshausen plate ceased to move independently and the Pacific-Antarctic ridge inherited the set of long offset transforms. Shortly afterwards, the gravity fabric on the flanks of much of the ridge displays evidence for a spreading rate decrease possibly related to transpression on the long-offset transforms. We speculate on a link between these events and regional tectonic changes around chron C27.