Tectonic plate that existed during the early Paleozoic through late Cenozoic time
Phoenix Plate
The Panthalassa Ocean 250 million years ago, showing the Phoenix Plate in the south, the Farallon Plate in the northeast and the Izanagi Plate in the northwest.
By the Late Jurassic–Early Cretaceous 150–130 million years ago, the
Pacific Plate arose from the Izanagi-Farallon-Phoenix triple junction, resulting in the creation of the Izanagi-Pacific-Phoenix and Farallon-Pacific-Phoenix triple junctions.[2] Subduction ceased east of
Australia about 120 million years ago, during which time a transform/transpressional boundary formed.[3] This transform/transpressional boundary with the Phoenix Plate lasted until about 80 million years ago as the plate continued to descend southwards as a result of
Late Cretaceous subduction under the
Antarctic Peninsula.[3][4]
During the Late Cretaceous or early Cenozoic, the southwestern part of the Phoenix Plate fragmented into the
Charcot Plate, much in the same way in which the
Rivera and
Cocos plates were formed by the fragmentation of the Farallon Plate.[5]
The
Antarctic-Phoenix Ridge, a
mid-oceanic ridge between the Antarctic and Phoenix plates, initiated following Late Cretaceous to early Cenozoic times when the Phoenix Plate had
divergent boundaries with the
Bellingshausen and Pacific plates in the southwestern
Pacific Ocean.[6] A major decrease in spreading rate of the Antarctic-Phoenix Ridge and the
convergence rate of the Phoenix Plate with the Antarctic Plate occurred around 52.3 million years ago, followed by subduction of a segment of the Antarctic-Phoenix Ridge between 50 and 43 million years ago.[7][8]
Although active subduction occurred for over 100 million years, it stopped or slowed dramatically about 3.3 million years ago when
seafloor spreading on the Antarctic-Phoenix Ridge ceased, leaving a small remnant of the former Phoenix Plate incorporated in the Antarctic Plate.[6] This remnant underlies the southwest
Drake Passage and is surrounded by the
Shackleton Fracture Zone in the northeast, the
Hero Fracture Zone in the southwest, the
South Shetland Trough in the southeast and the extinct Antarctic-Phoenix Ridge in the northwest.[6][9]