Plate Tectonics, the Fossil Record, and Climate
Some questions and perspectives that can be explored in this context:
- What does the fossil record tell us about
- How might have plate tectonics influenced the
evolution of life?
- How might plate related processes influenced global climate?
The first question was more important during
early arguments on continental drift, and Alfred Wegener definitely considered the distribution of fossils as favorable to the idea of continental drift. The second question has become
more important as plate tectonics has been accepted, and the third has developed as humanity has sought to understand global climate change better.
Glossopteris leaf fossil - one of the fossils common to Pangea continental partners - an example of the information available in documenting paleobiogeographic distribution. This particular sample is 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
Some background on history of life on earth you can delve into.
a critical discipline here - looks at the geographic distribution of organisms and seeks explanations. Evolutionary biology a crucial science that overlaps with biogeography. Using the general approach of uniformitarianism, understanding the present distribution of life can inform our understanding of the distribution of past life (as evident the fossil record).
Example of a biogeographic map, in this case of biodiversity. Note the strong latitudinal control. However, also note the local departures from a strict latitudinal control. At least some of these departures reflect tectonic topography. Can you pick out some examples?? Image source: USGS - http://gapanalysis.usgs.gov/species/news/ .
What environmental factors influence biogeographic distribution? Then consider, how does tectonics influence such factors?
Two important concepts within biogeography:
- Speciation of peripheral communities that
get isolated. Darwin's finches a classic example.
- Niches - think of job availability, what
are the opportunities for making a living as an organism.
- combination of physical and biologic factors.
- again, can you think of physical factors that help define a niche that are influenced by tectonic processes?
A few lessons from the present
There is generally more biodiversity in warmer climates than colder for terrestrial organisms, but not necessarily for marine organisms. Increased biodiversity can also be associated with mountains.
A variety of ant eaters:
Wallace's line and other contributions:
- ants are everywhere, and thus represent a widely available food source.
- 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 can occur 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.
- Wallace 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
This is usually covered in some degree in a Historical Geology course.
Hallam's faunal assemblage behavior:
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 another's pathway).
- Disjunct Endism:
fossil species limited to distinct environments of limited distribution,
that are found on now widely separated continents. What are are examples of a good index organism for disjunct endism?
What events explain the stratigraphic distribution of a fossil species in a region?
- local speciation (punctuated equilibrium informs expectations).
- local extinction.
- global extinction.
- change in preservation conditions.
Dispersal mechanisms (that aid migration):
- Charles Darwin: 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 Species, was on Geographical Distribution, 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 some organisms (e.g. mountains, or climate zones).
- Sweepstakes routes:
life on floating logs. Galapagos and other Pacific islands.
- Land bridges at time of polar ice caps.
Barriers to migration:
- physical vs. climatic barriers.
- physical: mountains, land for marine, sea
- For shallow shelf organisms deep waters.
- 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
- are there tectonic processes that drive sea level changes?
- one aspect to consider is the time frames over which these various barriers or pathways come and go.
In class exercise: Supercontinents
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 (more on this later upcoming). Break up into groups of 2-3 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. Use as many of the relevant terms introduced above in your diagram. Consider different types of organisms: marine vs. terrestrial
is a major distinction, but there are others. After fifteen minutes of brainstorming, a spokesperson
will present the groups results to the class.
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.
Examples in the fossil record
Gondwana associated examples (classic historical geology content):
- Mesosaurus: stratigraphically 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, herbivorous 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 of the importance of plate tectonics is the connection between North and South America
(see Hallam's figures in handouts). The long skinny central America connection between North and South America is a geologically recent development. 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 the change would appear sudden.
- 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.
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 in a much narrower North Atlantic, 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
- Trilobites great index fossils, but not globally widespread, distinct paleogeographic provinces.
- Two different faunal provinces of Cambrian trilobites
on either side of the Caledonides, but by Silurian they converge
Caledonide ocean narrow enough.
- Baltic affinity trilobites in the Carolina terrane of the southern Appalachians are distinct from time-equivalent North America trilobite assemblage (Sampson et al. 1990). Supports idea that this is an exotic terrane.
Ural mountains in Russia:
- should provide clear test case as a continental suture zone.
- Devonian Heterostraci (jawless freshwater
fish), distinctly different on Asian and European sides.
- Start of common Mesozoic amphibians and reptiles
across Urals at the same time.
Idea that plate tectonics influenced hominid evolution?
A paper waiting to be done? - what is the role
of suspect and exotic terrane tectonics in biogeographic behavior.
Role of mantle convection and LIPs?
The fundamental mechanism here is a change in frequency/type of volcanism influencing surface geochemical systems and thereby climate and ocean chemistry,that in turn influences the history of life (e.g. McKenzie et al. 2014).
Graph modified from Rohde & Muller (2005), and image source: https://commons.wikimedia.org/wiki/File:Phanerozoic_Biodiversity.png .
What are major punctuations in history of life and possible explanations:
- Cambrian faunal explosion and the end of Neoproterozoic (Vendian) glaciations (Snowball Earth).
- Permian-Triassic extinction boundary - same
time as Siberian LIP, poisoning of worlds oceans?
- Cretaceous quiet zone - time of accelerated sea floor
spreading, LIP production and much else, Western Interior Seaway an interesting example of one of the proposed consequences.
- Cretaceous -Tertiary extinction boundary - not everything is plate tectonics related, although the possible role of the Deccan traps in India (a LIP) is still being debated!
Image of tectonic setting of the Western Interior Seaway from the USGS, In part the seaway existed as a foreland basin associated with subduction related crustal thickening, and in part because global sea levels were high at this time.
Origin of life and submarine hot springs and black smokers? Genetic communication betwee vents?
Plate tectonics and the long term carbon cycle
What is the long term carbon cycle?
- weathering and carbonate production draw down carbon dioxide from the atmosphere and sequester it into mineral form.
- metamorphism and volcanic activity return carbon dioxide to the atmosphere.
- the former promotes climatic cooling, whereas the later promotes warming.
Eocene cooling (and start of Antarctic ice cap):
- significant debate as to cause, some of which is addressed in this Wikipedia article on the Eocene.
- one idea (Walker et al, 1981) is that the growth of the Himalayas enhanced the weathering rate (especially since it is at lower latitudes) and contributed to the atmospheric CO2 decreases seen at this time.
Role of geologic return of carbon dioxide in ending the Vendian Ice Ages.
What is the potential role of CCD in the carbon cycle?
- influences sequestration of CaCO3 into sediments.
- function of ocean temperature structure, and of seafloor depth distribution.
- during Cretaceous with younger and hotter oceanic crust was less seafloor bellow the CCD?
Weathering of ultramafics in particular draws down CO2 (USGS site on potential use in carbon sequestration). Specifically the weathering converts carbon dioxide into bicarbonate ions, and the thought is that these then end being precipitated as carbonate minerals.
Plenty of interesting research to be done on this topic.
Paleo Integration Project (PIP) - still in development.
- Bohaty, S. M., and J. C. Zachos, 2003: Significant Southern Ocean warming event in the late middle Eocene. Geology, 31, 1017-1020.
- 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.
- McKenzie, N. R., Huges, N. C., Gill, B. C. & Myron, P. M., 2014, Plate Tectonic influences on NeoProterozoic-earlly Paleozoic climate and animal evolution; Geology, Jan. issue.
- Rohde, R.A. & Muller, R.A. (2005). "Cycles in fossil diversity". Nature 434: 209-210.
- Sampson, S., Palmer, A., Robison, R., & Secor, D. T., 1990, Biogeographical significance of Cambrian trilobites from the Carolina slate belt; GSA Bulletin, 102, 1459-1470.
- 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.
- Walker, J.C.G., Hays, P.B., and Kasting, J.F., 1981, A negative feedback mech- anism for the long-term stabilization of Earth’s surface temperature: Journal of Geophysical Research, v. 86, p. 9776–9782, doi: 10.1029/ JC086iC10p09776.
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.