Department of Earth Sciences
St. Francis Xavier University, Antigonish, Nova Scotia, Canada
External Research Grants (Current) | Field Experience | Geological Community Involvement
Co-leader, International Geological Correlation
Canadian Leader, International Geological
Correlation Program 497
NSERC Discovery Grant: 2009-2014
The origin of Pangea
Over the last 20 years, evidence has been amassing that Pangea, a super-continent which formed 300 million years ago, is just the latest in a series of supercontinents that have formed repeatedly since the Archean, only to break up and reform again. Although the mechanisms responsible are controversial, many geoscientists agree that repeated cycles of supercontinent amalgamation and dispersal have had a profound effect on the evolution of the Earth's crust, atmosphere, climate and life. The existence of Pangea, which broke up about 200 million years ago, is a cornerstone of plate tectonics, and its assembly and fragmentation have governed the evolution of the Earth's crust for the past 500 million years. To a first order, we know where and when Pangea formed, but not why. Over the next grant cycle, I intend to investigate why Pangea formed. My approach is to combine field work with laboratory analyses of samples selected from sites which expose critical relationships between rock units. I will continue to work on the evolution of the Rheic Ocean, an ocean that formed about 500 million years ago between dispersing continents (an interior ocean), and whose closure about 300 million years resulted in the amalgamation of Pangea. However, to obtain a global view, I also need to study rocks that document the evolution of the Paleopacific ocean, an "exterior" ocean that surrounded the dispersing continents. If the evolution of these oceans is dynamically linked, then contraction of the interior ocean, which began about 440 million years should be coeval with expansion of the exterior ocean. The dual approach of field work augmented by laboratory analysis will allow me to test the potential geodynamic connection between interior and exterior oceans and to test various hypotheses (including some of my own) that have been proposed for the amalgamation of Pangea.
NSERC Discovery Grant (2003-2008)
The origin and evolution of the Paleozoic Rheic Ocean: implications for the amalgamation of Pangea.
Although the existence of the supercontinent Pangea is a cornerstone of plate tectonics, the mechanisms responsible for its amalgamation are poorly understood. The goal of the proposed research is to investigate the origin and evolution of the Paleozoic Rheic Ocean, the closure of which produced terminal collision in the Ouchitan-Appalachian-Caledonide-Variscan Orogen and was one of the principal events in the Late Paleozoic assembly of Pangea. Despite its importance to Paleozoic paleogeography and understanding the processes that gave rise to Pangea, there are major uncertainties in the identification of its margins, the mechanisms and timing of its initial rifting and opening, and the geodynamics of its closure.
The Rheic Ocean is generally thought to have opened during the Late Cambrian to Early Ordovician when a number of terranes (e.g., Avalonia, Carolina) rifted from the Amazonian-West African margin of Gondwana. It has not received the same attention as the Iapetus Ocean, whose opening produced the rifted margin of eastern Laurentia and whose closure resulted in the collision of this margin with Baltica, Avalonia, and other peri-Gondwanan terranes. Rheic geology was widely dispersed by the breakup of Pangea, and occurs in North and Central America, Western, Central, and Eastern Europe. I plan to focus on two key regions of Rheic geology; Iberia (in collaboration with Cecilio Quesada, IGME), where evidence of its initial rifting and final suturing are well preserved in the Central Iberian and Ossa Morena zones, and southern Mexico (in collaboration with Duncan Keppie, UNAM) where an extensive oceanic fragment of the Rheic Ocean between Amazonia and Laurentia is preserved in the Acatlan Complex as eclogite-amphibolite complexes. The tectonic history of these key regions, their structure, geochemical, isotopic and petrologic evolution will be studied. I, and my graduate students will investigate the field relationships, especially the contacts between key tectono-stratigraphic units. Representative samples will be probed for mineral composition to aid in the deduction of their metamorphic histories, and will be analyzed for major, trace and REE elements as well as for Sm-Nd isotopes to constrain their tectonic setting and petrologic evolution. Samples will be selected for U-Pb dating to determine the timing of tectonic events. The products of the research will provide a greater understanding of the origin and evolution of the Rheic Ocean, its role in Paleozoic tectonostratigraphy, magmatism, and orogenesis, and will provide insights into the processes that resulted in the amalgamation of Pangea.
NSERC General Grant (2000-2003)
My research focuses on orogenic (mountain building) processes, with particular reference to Avalonia, the largest suspect terrane in the Appalachian orogenic belt. Avalonia is a well-preserved example of global-scale Neoproterozoic orogenic activity. My research methods include field and laboratory investigations into the Neoproterozoic and Paleozoic evolution of these rocks. Recently, I (and my colleagues) proposed models that relate the evolution of Avalonia and coeval global-scale Neoproterozoic orogenies to the amalgamation and dispersal of a supercontinent. Avalonia was originally situated along the periphery of a supercontinent (Vendia) in the Neoproterozoic and Early Paleozoic and became attached to Laurentia some time in the middle Paleozoic. Therefore, an understanding of its tectonic history has a profound influence on paleocontinental reconstructions for the Neoproterozoic and Paleozoic, and offers an excellent opportunity to study the growth of the North American continent during orogenesis.
In order to test these models, I plan to focus on detailed investigations on selected areas in Avalonia and correlative rocks. In collaboration with my colleagues in Europe, I intend to investigate correlative rocks in Britain, Cadomia (France), and Bohemia in order to accurately position these regions along the Gondwanan margin in the Late Proterozoic and Early Paleozoic. In addition, understanding the timing and nature of the separation of these rocks from Gondwana, and their accretion to Laurentia-Baltica will provide first-order constraints for paleocontinental reconstructions. I also intend to continue research into Avalonian rocks of mainland Nova Scotia. This area is a natural laboratory in which to study and characterize Late Proterozoic orogenic processes. In particular, I plan to investigate the feedback between structural setting and chemical composition in an environment that typifies Late Proterozoic Avalonia, and this study may also serve as a general model for magma plumbing systems in rifted arc settings. My graduate students will complement these efforts by studying relationships between orogenic events and geochemical signatures of important igneous complexes and sedimentary sequences. In summary, this proposal will enable me and my graduate students to contribute to the understanding of orogenic processes, their relationship to supercontinent amalgamation and dispersal, and the growth of the North American continent during Appalachian orogenesis.
NSERC-Industry Collaborative Grant (with Caledonia Mining Inc):
|This was a one year collaborative R&D study (1995-96) to document
the relationship between tectonic setting, sedimentary facies, and paleoplacer
gold deposit potential in the Late Devonian-Early Carboniferous St. Mary's
Basin, Nova Scotia. The research was in collaboration with Caledonia Mining Corp.,
Toronto, and involved post-doctoral fellows and graduate students.
The St. Mary's Basin straddles the boundary between two geological terranes in the Canadian Appalachians which have contrasting geological histories. These terranes are the Avalon (to the north) and Meguma (to the south), separated by an ancient fault zone. The origin and evolution of the St. Mary's Basin is attributed to dextral motion along the fault zone associated with one of the major pulses in the development of the Appalachian mountain chain in the Late Paleozoic (about 370 to 330 milli on years ago). Recent geological mapping of the St. Mary's Basin has been facilitated by excellent exposure and has shown that the basin-fill predominantly consists of continental clastic rocks derived from the Meguma Terrane which is well known for it s abundance of gold deposits and occurrences. Our investigations in the St. Mary's Basin (Murphy et al., 1994, 1995) identified and delineated facies that indicated paleoplacer potential. These investigations attracted the interest of Caledonia Min ing Corp.
The investigation focused on the relationships between basin origin and evolution, facies development and distribution, provenance and geochemical signature, the potential lithochemical indicators of mineralization and identification of the most favourable regions for mineralization.
The collaborative study is intended to provide a conceptual
framework and a database to examine the relationship between basin development,
provenance, and paleoplacer potential within the basin and also facilitate
formulation and testing of predictive models for controls on gold exploration.
Participants: Brendan Murphy, Randy Rice, Lorne Jennex, Jacquie Stevens.
Analysis of Neoproterozoic to Carboniferous rocks in Nova Scotia, Britain, NW France. Iberia, Spain, Mexico. Field research in mainland Nova Scotia in the Antigonish and Cobequid Highlands and the St. Mary's Basin, analysis of their structural, magmatic, metamorphic, and tectonic histories.
Geological Community Involvement
Editor: Geological Society of America Bulletin (2007-2010)
Associate Editor: Canadian Journal of Earth Sciences, (2008- )
Occasional Journal Reviewerships:
External Academic Service (examples)
Acadia University, Adjunct Professor, (1995-2002; 2008 - )
Atlantic Geoscience Society, Vice-President (1988-89)
Atlantic Geoscience Society, President (1989-90)
Atlantic Geoscience Society,
Atlantic Provinces Council on the Sciences, Chair, (A.P.I.C.S- Earth Sciences, 2006- )
Atlantic Provinces Council on the Sciences,
Geology Division, 1987-1989)
International Geological Correlation Project 319,
International Geological Correlation Project
453, International co-leader, (2000-2005)
NSERC Research Tools and Instruments Selection Committee (2005-2006)
NSERC MRS sub-committee, Chair, (2006-2007)
NSERC Solid Earth Sciences Grant Selection Committee (2005-2008)
NSERC Solid Earth Sciences Grant Selection Committee, Chair, (2007-2008)
Ohio University, Adjunct Professor (1997- )
UNAM, Adjunct Professor (2008 - )
University Partnerships in Cooperation and Development Program (Tier 1), Association of Universities and Colleges of Canada (2006-2007)
Internal Academic Service at St. F. X. University (examples)
Academic Rank and Tenure (2002-2005)
Board of Governors (1997-99; 2005-2008)
Committee of Academic Review (1991- 1994)
Department of Earth Sciences, Chair (2001-2004)
Geology, Chair (1989-1995)
Science Forum, Coordinator (1994-96)
Senate (1984-86; 1998-2000; 2001-2004)
Total of 51 invited, keynote, or guest lectures (examples).
Atlantic Geoscience Society Annual Colloquium, Convener: 1988, 1995, 2002
GEO2002, Wurzburg, Germany, Keynote Speaker, September, 2002
Geological Association of Canada, Short-course lecturer, 1989
Geol. Soc. America Annual General Meeting, Pardee Keynote Symposia, Keynote Speaker, 2007
Geological Society Australia; Structural Geology/Tectonic Studies Group, Keynote Speaker, 2003
Geological Society of London, Tectonic Studies Group, Belgium, Keynote Speaker 2008
Gondwana 13, Dali, China, Keynote Speaker 2008.
IGC, Florence, Italy, Neoproterozoic Tectonics, Keynote Speaker, August, 2004
IGCP 497, Galicia, Spain, Rheic Ocean, Keynote Speaker, July 2007
International Geological Correlation Program 319 annual
conference, Convener, 1994
Outreach in the Community
Cape Breton Post, circulation 40,000, Earth Science columnist, (1992-1996)
CHAD Edmonton (630), Cees Nichols, May 24th, 2006
CKNW Vancouver, Julio Pastor, May 25th, 2006
CKNW Vancouver, Sean Leslie Show, July 2006
Columbus Dispatch, Mike Lafferty, January 16, 2007
Nature of Things (CBC), interviews in the field July, October, 2006
Nature of Things (CBC), interviews with David Suzuki, August, 2007
Nature of Things (CBC), Geologic Journey Series, first aired CBC, October 7th, 2007
New Scientist (via Mike Reilly), December, 2006
New York Times (Bill Broad), January 9, 2007
Quirks and Quarks, (CBC) aired January 20th, 2007
Earth Science talks/field trips involving: Elementary, Junior and High School students; Beavers, Cubs, 4-H, Elderhostel, St. FX Summer Academy, St. FX Africentric Academy, St. FX Alumni, ROMEO (Retired Old Men Eating Out)