Geology Reference
In-Depth Information
group of plants that are thought to have lived in ancient swamps). Glossopteris fossils
are found on all the continents in the southern hemisphere and in India.
Critics had argued that plant seeds can be spread by wind and water and could have
crossed from one continent to another. However, the seeds of this early fern-type plant
were too large to be carried by wind and could not have survived travel in salt water.
Therefore, the presence of these fossils across so many continents provides strong sup-
port for the idea that the southern continents must have been connected.
Another geologist in the early twentieth century, Eduard Suess, proposed that a land
bridge must have at one time connected South America to Africa. This would explain
how land-living creatures (and plants) could have moved from one continent to another.
The continents of South America, Africa, India, Australia, and Antarctica
linked by these plant and animal fossils are thought to have been connected as a
single, large landmass, which Suess call Gondwana or Gondwanaland.
The combined distribution of these different fossils is illustrated in Figure 8-3. Together
they provide a compelling case for the existence of Gondwana.
Stratigraphic stories
As I explain in Chapter 7, sedimentary rocks are laid down in layers and may cover great
distances. Due to this feature of rock layer formation, geologists can match sequences of
rock layers, or strata, from different geographic locations and create a picture of the en-
vironment at the time the sediments were deposited. (See Chapter 16 for details on the
study of rock layers, or stratigraphy. )
The patterns of rock strata on Antarctica, South America, Africa, India, and Australia are
illustrated in Figure 8-4. The similarity in rock sequences lends strong support to the
idea that these continents were once connected to one another.
Figure 8-3: Distri-
bution of fossil
evidence on Gond-
wana continents.
Search WWH ::




Custom Search