Plate Tectonics and the Fossil Record
Two questions and perspectives that we will explore:
- What does the fossil record tell us about
- How might have plate tectonics affected the
evolution of life?
The first question was more important during
early arguments on continental drift and the second has become
more important as plate tectonics has been accepted.
a critical discipline here. Two important concepts within:
- Speciation of peripheral communities that
- Niches - think of job availability, what
are the opportunities for making a living.
Glossopteris leaf fossil - one of the fossils common to Pangea continental partners. This sample from the Ellsworth Mountains of Antarctica. Image source: (Photo Credit USGS DDS21) as found at http://www.uwsp.edu/geo/faculty/ritter/geog101/textbook/tectonics_landforms/tectonics_evidence.html
The Mesozoic world was a time of
supercontinent dispersal . How might of this affected the history
of life? Source of image - USGS publication - Dynamic Earth.
and biogeographic patterns. Gondwana and Pangea are large
continental masses (super continents) that formed and split apart.
So in addition to the Wilson cycle, which explores the type of
history we would expect on a continent scale, there is a proposed
supercontinent cycle that is thought to have occurred on a global
scale. Break up into groups of four and work on developing a cycle
diagram that depicts how biogeographic patterns would change with
the continental configuration, a la the Wilson and supercontinent
cycle. Think of different types of organisms: marine vs. terrestrial
is a major distinction, but there are others. After fifteen minutes, a spokesperson
will present the groups results to the class.
Hallam's faunal assemblage behavior in plate
increase in faunal assemblage similarity with time.
decrease in faunal assemblage similarity with time.
- Good example in looking at shallow water
marine invertebrates across the North Atlantic (see handout).
convergence of marine at time of divergence of terrestrial or
vice versa (one organisms barrier is anothers pathway).
- Disjunct Endism:
fossil species limited to distinct environments of limited distribution,
that are found on now widely separated continents. What would
be a good index organism for disjunct endism?
- Darwin, Charles: considered dispersal mechanisms
at length because he had to explain how South American critters
got to the Galapagos to then evolve. Chapter 11 of On the Origin
of Speices, was on Geographical Distribtion, and still makes
good reading today. Darwin did an experiment where he took 87
kinds of seeds immersed in seawater, 64 germinated after immersion
of 28 days, and a few survived after immersion of 137 days. "In
the course of two months, I picked up in my garden 12 kinds of
seeds out of the excrement of small birds ... and some of them,
which I tried, germinated."
- George Gaylord Simpson
free migration in both direction (e.g. Panamanian isthmus, or is this more of a filter?).
- Filter bridges:
a corridor with some feature that filters (e.g. mountains).
- Sweepstakes routes:
life on floating logs. Galapagos and other Pacific islands.
- Ice bridges
at time of polar ice caps.
Barriers to migration:
- physical vs. climate barriers.
- physical: mountains, land for marine, sea
- For shallow shelf organisms the sea is critical.
- Role of sea level changes in producing barriers
- example of ammonite diversity as function
of shallow seas (see handout).
- examples of changes in circulation and pathways
A few lessons from the present
More diversity in warmer climates than colder.
A variety of ant eaters:
- South America, Ant Bear (Edentata).
- North Africa and Asia, Pangolin (Philodata).
- Southern half of Africa, Aardvark (Tubulidentata).
- Australia, Spiny Anteater (Monotremata).
- 4 orders have filled the same niche, and
have long snouts and tongues. Convergent (homoplesy) evolution
in divergent faunas.
- Wallace: codiscoverer of natural selection
mechanism for evolution with Darwin, spent many years in the
Malay archipelago (wrote a very interesting account of it), was
very much a biogeographer.
Wikipedia link to map of Wallace's line.
- sharp faunal gap between the islands of Bali
and Lombok. On one side are SE Asian fauna, on the other Australasia.
Line between the two became known as Wallace's line.
- developed a set of biogeographic principles
(some of which listed below, taken from Brown & Lomoline,
- distance does not alone determine biogeographic
- climate is important.
- the fossil record provides insight into past
- living biota are very much influenced by
recent geologic and climatic events (thinking of Ice Age).
- speciation occurs through geographic isolation.
- the distribution of organisms not adapted
for long-distance dispersal gives evidence to past connections
(another type of index fossil).
- extinctions are caused by development of
Examples in the fossil record:
De Geer Route
of mammal dispersal (based on McKenna, 1975).
- Many are familiar with the Bering strait
Asian-American link. However, a Paleogene seaway linking the
Arctic Ocean and Tethys (with W margin along the Urals) should
have isolated Europe from east Asia (see hand out figure 1).
This is known as the Turgai straits marine barrier. Biota then
suggest a Europe American link across the north part of the Atlantic.
- One possible link was Iceland - Faero hot
spot, but that is too young.
- There is evidence that a Euramerican biota
link was severed about 49 Ma.
- A better possibility is across the continental
transform area between Greenland and Svalbard on the Barents
- Is there a polar position filter? Early Tertiary
flora and fauna of Svalbard suggest a cool-temperature climate
with abundant conifers, with an absence of palms.
- Present understanding would suggest the link
should have been finally severed about 37 Ma, when transtension
happened in this area. One can suspect that the Tertiary fold-thrust
belt on Svalbard was at least a partial physiographic barrier
Gondwana associated examples:
- Mesosaurus: occurs near the Carboniferous-Permian
boundary, this was a 2 foot long aquatic reptile that is found
in fresh and brackish water deposits. Fossils are found both
in Brazil and South Africa.
- Glossopteris flora: Glossopteris itself was
a seed fern. Seeds of the flora are millimeters in diameter (not
going to be windborn). See image above.
a fat, short, squat, mammal-like, herbiverous reptile (definitely
not traveling large distances easily) found in Africa, southeast
Asia and Antarctica, and from the lower Triassic.
- Source of image - USGS publication
- Dynamic Earth.
Panamanian isthmus related examples:
- Classic example is North and South America
(see Hallam's figures in handouts). 29 families of mammals in
the S, different from 27 in the N. After bridge 22 in common.
Bridge developed 2.5 million years ago. Note time scale here.
In longer time frame would appear almost instantaneous.
- Debate as to how much is tectonics vs. change
in sea level.
- Divergence seen in marine assemblage on either
side of Panamanian isthmus (Jones and Hasson, 1985). It would
be interesting to see if have divergence or similarity of deeper
water species. This would help sort out the tectonics vs. sea
- An example of complimentarity.
Two faunal provinces of Cambrian trilobites
on either side of the Caledonides, but by Silurian they converge
Caledonide ocean narrow enough. Trilobites informative in
Ural moutains in Russia:
- should provide clear test case.
- Devonian Heterostraci (jawless freshwater
fish), distinctly different on Asian and European sides.
- Start of Mesozoic amphibians and reptiles
across Urals at the same time.
A paper waiting to be done? - what is the role
of suspect and exotic terrance tectonics in biogeographic behavior.
Role of mantle convection and hotspots?
- could argue that this may be as crucial as
- major punctuations in history of life:
- Cambrian faunal explosion.
- Permian-Triassic extinction boundary - same
time as Siberian LIP, poisoning of wrolds oceans, links?
- Cretaceous - time of accelerated sea floor
spreading, LIP production and much else.
- Cretaceous -Tertiary extinction boundary - not everything is plate tectonics related.
Paleo Integration Project (PIP) - still in development.
- Brown, J. H., Lomolino, M. V., 1998, Biogeography, Sinauer
Associates, Sunderland, Massachusetts, 693 p.
- Du Toit, A. L., 1937, Our Wandering Continents, Oliver &
Boyd Ltd., Edinburgh,
- Hallam, A., 1972, Continental Drift and the Fossil Record:
in Wilson, J. T., 1976, Continents Adrift and Continents Aground;
Scientific American, W. H. Freeman & Company, San Francisco,
- Hughes, N. F. (ed.), 1972, Organisms and continents through
time: a symposium. Spec. Pap. Palaeont., London, 12, 334 p.
- McKenna, M. C., 1973, Sweepstakes, filters, corridors, Noah's
Arks, and beached Viking funeral ships in paleogeography. in
Tarling and Runconr, Implications of Continental Drift to the
Earth Sciences, v. 1, 295-308. New York , Academic Press.
- McKenna, M. C., 1975, Fossil Mammals and Early Eocene North
Atlantic Land Continuity; Annals of the Missouri Botanical Garden,
v. 62, p. 335-353.
- Stanley, S. M., 1986, Earth and Life Through Time; Freeman,
N. Y. 690 p.
- Stehli, F. G. & Webb, S. D., 1985, The Great American
Interchange, Plenum Press, New York, 532 p.
- Valentine, J. W. & Moores, E., Plate Tectonics and the
History of Life in the Oceans. in Wilson, J. T., 1976, Continents
Adrift and Continents Aground; Scientific American, W. H. Freeman
& Company, San Francisco, p. 196-206.
materials for Plate Tectonics, GEOL 3700, University of Nebraska
at Omaha. Instructor: H. D. Maher Jr., copyright. This material
may be used for non-profit educational purposes with appropriate
attribution of authorship. Otherwise please contact author.