Climate and Plate Tectonics
Pangea was maximally developed at the start of the Triassic, with Panthalassia
(“all ocean”) occupying the other side of the globe, and the
Tethys Ocean
forming an enormous gulf on the eastern
margin of Pangea. Even as the assembly of Pangea was completed, however,
it began to rift apart. By the end of the Triassic, rifting in the
center of Pangea had begun. North America began to pull away from
Europe and Africa, and blocks of crust sank to create rift valleys.
During the Late Triassic and Early Jurassic, these valleys were associated
with the initial formation of the Atlantic Ocean. The sediments that
filled these rift valleys are preserved along the eastern margin of
North America and the western edges of Africa and Europe, and they
contain important evidence of Late Triassic organisms and their environments.
Early Triassic climate was quite similar to that at the end of the
Permian. Much of Pangea was warm and dry, and the
interior of this supercontinent was particularly arid. These environments
were often dominated by conifers and other gymnosperms. However, the
Triassic also saw an increase in seasonality, as well as prominent
monsoon weather cycles. Provincial biotas developed as well. In the
north (Laurasia), these ecosystems included ginkgoes,
bennettitalians, cycads, and tree ferns. In contrast, southern (Gondwanan)
environments were dominated by seed ferns, most prominently one called
Dicroidium.
|
