Continental Drift - Rock Sequences
Rock sequences in South America, Africa, India, Antarctica, and
Australia show remarkable similarities. Wegener showed that the same
three layers occur at each of these localities. The bottom (oldest)
layer is called tillite and is thought to be a glacial deposit. The
middle layer is composed of sandstone, shale, and coal beds.
Glossopteris fossils are in the bottom and middle layers. The top
(youngest) layer is lava flows. The same three layers are in the same
order in areas now separated by great distances. Wegener proposed that
the rock layers were made when all the continents were part of Pangaea.
Thus, they formed in a smaller contiguous area that was later broken and
drifted apart.
