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Department News

Ph.D. candidate Morgan Schaller presented his thesis Large Igneous Provinces and Earth's Carbon Cycle: Lessons from the Late Triassic and Rapidly Emplaced Central Atlantic Magmatic Province (11/21/2011)Morgan defended his thesis with flying colors and his committee commented on the completion of a superb dissertation.  Morgan will be in short, filing his dissertation with the graduate school. Congratulations Morgan, job well done!

Dissertation Abstract:

Using stable isotopes of soil carbonates, I demonstrate that the eruption of the Central Atlantic Magmatic Province (CAMP) resulted in a transient perturbation of atmospheric pCO2 in the Late Triassic. I show evidence of a discrete pCO2 pulse (roughly a doubling) immediately after the first CAMP flow-unit preserved in the Newark rift basin, followed by a ~200 kyr falloff toward pre-eruptive concentrations, a pattern repeated above the second and third flow-units. Observations from the Hartford basin indicate that pCO2 had fallen to concentrations well below background by 400 kyr after the final eruptions in the earliest Jurassic.  I use a simple geochemical model to demonstrate that this decrease below pre-eruptive background is most easily accomplished by the extrusion of ~1.12 x 107 km2 of basalt into the equatorial humid belt, which effectively amplified the increase in global continental weathering rate by perhaps as much as 50%.  These results indicate that LIPs can be overall net sinks for CO2.  A test of the Late Triassic equilibrium state from a 33-My record of pCO2, broadly shows a ~3-fold decrease in pCO2 from the Carnian through the Rhaetian.  This decrease is most consistent with the hypothesis that a Late-Triassic increase in continental area within the tropical humid belt, as a result of the slow northward migration of the Pangean Supercontinent, lead to increased rates of continental weathering and CO2 consumption.  A significant implication of this finding is that changes in degassing rates from variable ocean crust production are not driving this long-term decrease in pCO2 since crustal production rates show little variability through the Late Triassic.  Together the results of this work lay the foundation for a revision of our understanding regarding the driving mechanisms behind Earth’s long-term carbon cycle toward a greater emphasis on weathering processes.

 

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Here's a new book on evolutionary theory just out by EPS' Prof. George McGhee!

Convergent Evolution: Limited Forms Most Beautiful

McGhee, G. R. 2011. Vienna Series in Theoretical Biology; Massachusetts Institute of Technology Press, Cambridge (MA), 322 pp.

Read more at Cambridge Press

Description


Charles Darwin famously concluded On the Origin of Species with a vision of "endless forms most beautiful" continually evolving. More than 150years later many evolutionary biologists see not endless forms but the same, or very similar, forms evolving repeatedly in many independent species lineages. A porpoise's fishlike fins, for example, are not inherited from fish ancestors but are independently derived convergent traits. In this book, George McGhee describes the ubiquity of the phenomenon of convergent evolution and connects it directly to the concept of evolutionary constraint--the idea that the number of evolutionary pathways available to life are not endless, but quite limited. Convergent evolution occurs on all levels, from tiny organic molecules to entire ecosystems of species.McGhee demonstrates its ubiquity in animals, both herbivore and carnivore; in plants; in ecosystems; in molecules, including DNA, proteins, and enzymes; and even in minds, describing problem-solving behavior and group behavior as the products of convergence. For each species example, he provides an abbreviated list of the major nodes in its phylogenetic classification, allowing the reader to see the evolutionary relationship of a group of species that have independently evolved asimilar trait by convergent evolution. McGhee analyzes the role of functional and developmental constraints in producing convergent evolution, and considers the scientific and philosophical implications of convergent evolution for the predictability of the evolutionary process.

Product Details ISBN-10: 0262016427
ISBN-13: 9780262016421
Published: MIT Press (MA), 11/01/2011
Pages: 312
Language: English
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