Geography Reference
In-Depth Information
were in contact with west Antarctica. About 80 mya, the Tasmantis block
(New Zealand and New Caledonia) broke away from west Antarctica and
moved northwest, opening the Tasman Sea. New Zealand and New Cale-
donia were finally separated in the mid-Tertiary (40-30 mya), when the Nor-
folk Ridge foundered, opening the New Caledonian Basin. Australia and
South America remained in contact across Antarctica until the Eocene. Aus-
tralia began to separate from Antarctica in the Late Cretaceous (90 mya),
but both continents remained in contact along Tasmania, and complete sep-
aration did not occur until the Late Eocene (35 mya) with the opening of
the South Tasman Sea. Southern South America and Antarctica remained
in contact through the Antarctic peninsula until the Oligocene (20-28 mya),
when the Drake Passage opened between these continents, allowing the
establishment of the Antarctic Circumpolar Current. After its separation from
Antarctica, Australia began to drift rapidly toward Asia. New Guinea was
then joined to the northern margin of the Australian plate, although only the
southern margin of New Guinea was emergent at that time. The collision of
the Australian and Pacific plates in the Oligocene (30 mya) initiated the tec-
tonic uplift of New Guinea, but by the Early Miocene much of southern New
Guinea was again submerged. Subsequent episodes of uplift in the Mio-
cene, after the collision of the Australian and Asian plates, led to the accre-
tion of numerous terranes to the northern margin of New Guinea. The link
between North and South America, the Isthmus of Panama, was formed in
the Late Pliocene (2 mya).
