HYPOTHESIS FOR CRETACEOUS RIFTING OF EAST GONDWANA CAUSED BY SUBDUCTED SLAB CAPTURE

In the process of subducted stab capture, a spreading ridge approaches subparallel to a subduction zone following the trailing edge of a dow ngoing plate. Eventually the downgoing plate is too young and small to subduct, and spreading stops. The spreading ridge stalls many tens of kilometres outboard of the subduction zone. The subducted plate welds to the outboard plate across the dormant spreading center and is capt ured by it. The captured plate then acquires the motion of the plate i t welded to. In the southwest Pacific the Pacific-Phoenix ridge approa ched the east Gondwana margin as the Phoenix plate subducted beneath N ew Zealand, the Chatham Rise and Campbell Plateau, the Lord Howe Rise (collectively, Zealandia), and Marie Byrd Land in Cretaceous time. Spr eading and subduction shut delta here between 110 and 105 Ma, and some sections of the Phoenix plate became welded to (captured by) the Paci fic plate. Pacific plate northward motion began in Aptian time, pullin g the captured subducted microplates with it. This movement exerted a basal traction on the overlying east Gondwana margin and resulted in e xtension of Zealandia and Marie Byrd Land, Continued Pacific northward motion rifted Zealandia from Marie Byrd Land at about 85 Ma.