Past Geology Speaker Tours

 

Deanne Lab

2014-15 Speaker Tour

Dr. Deanne Van Rooyen
Department of Geology, Cape Breton University

Uncluttering and reactivating and the western Laurentian basement: lessons from the margins of the Thor-Odin dome in southeastern British Columbia

Over the last half century, the southeastern Canadian Cordillera has been a test case for a number of hypotheses regarding the involvement of basement rocks in compressional phases of orogens, and their subsequent exhumation. When high-grade metamorphic rocks were recognized in the core of the Cordilleran orogen, they were seen as mostly passive participants in the orogenic cycle, exposed through erosion or faulting after the orogen had collapsed. Basement rocks were generally thought to preserve pre-orogenic structures and events, and not considered to be major drivers in the orogenic cycle. This changed with the proposal of the core-complex model to explain the crustal architecture of the Cordillera. At this time, crustal scale extension was recognized as an important mechanism for exhuming basement, and this insight lead to a number of new interpretations of the nature and origin of exposed high-grade rocks.

Mechanisms to account for extension-related exhumation of mid-crustal rocks in the Canadian Cordillera can be divided into two broad categories. The first involves exhumation during post-convergent gravitational collapse and includes: (i) core complex models where exhumation post-dates convergence and buoyant crustal material rises in the footwall of low-angle outward dipping shear zones; (ii) large-scale extension models where large tracts of mid-crustal rocks are exhumed in the footwalls of extensional faults; (iii) and vertical flow models in which diapiric ascent of partial melts play a large role. The second broad category of extrusion mechanisms involves ductile extrusion and channel flow in which mid-crustal rocks flow (and sometimes extrude) in a channel during compression in the orogen.

Recent work in the Monashee Complex and other tectonothermal culminations in southeastern BC has highlighted a number of different ways that basement rocks are involved in the Cordilleran orogen, and how inherited crustal architecture contributes to orogenic evolution. This talk will examine some of the important historical interpretations of Cordilleran tectonics, and discuss how the views and interpretations of the so-called “basement” of the Cordilleran orogen have evolved, using examples from the Thor-Odin dome in southeastern BC.

February 9, University of New Brunswick (Fredericton)
February 10, St. Mary’s University
February 11, Acadia University

CompSci-no photo

Dr. Chris McFarlane
Department of Earth Sciences, University of New Brunswick

Talk 1: Hydrothermal alteration: the role and record of coupled dissolution-reprecipitation
Talk 2: From grain scale to mountain scale: timing and timescales of evolving orogenic processes

March 9, StFX
March 23, MUN
TBA, Dalhousie

 

2013-14 Speaker Tour

Dr. Danika Van Proosdij
Saint Mary’s University

Complexities of space and time: challenges to effective modelling of intertidal ecomorphodynamics

Interpretation of past landscapes and sedimentary sequences within the coastal zone requires an appreciation of the spatial and temporal variability in transport and depositional processes as well as an understanding of feedbacks and interactions with biological agents in the surrounding environment. This understanding is further complicated in the contemporary environment by anthropogenic activities (e.g. tidal power development, dyking, coastal engineering) that influence or constrain natural coastal ecosystem function.  Modelling future behaviour of coastal systems to a changing climate or human activities then needs to distinguish between natural (including episodic events) versus anthropogenic drivers of change. Ecomorphodynamics is the study of the interaction between sediment dynamics, geomorphology and biota across a range of spatial and temporal scales. This presentation will examine the influence of scale in modelling ecomorphodynamics within intertidal ecosystems in the Bay of Fundy as well as the influence of episodic events (e.g. hurricanes, ice) and human activities (e.g. coastal engineering, dyking and salt marsh restoration). The use of geomatics technologies, hydrodynamic modelling, empirical data collection and disaggregated grain size analysis will be explored.

  • Mar. 7, 12:15 p.m. – 1:05 p.m, St. Francis Xavier
  • Mar. 14, 1:00 p.m. – 2:00 p.m, Memorial University
  • Date & time TBA, Dalhousie University

Dr. Hugo Beltrami
Saint Francis Xavier University

Continental heat gain in a warming climate: Inferences from geothermal data

  • Mar. 5, 12:30 p.m. – 1:30 p.m, Acadia University
  • Mar. 10, Saint Mary’s University
  • Date & time TBA, University of New Brunswick

2012-13 Speaker Tour

Trevor McHattie, Nova Scotia DNR Geological Resources Branch

Mantle plume dynamics and the chemical and thermal structure of the Archean mantle: Evidence from mafic-ultramafic volcanic successions within the ca. 2.7 Ga Prince Albert Group, Nunavut, Canada

  • November 26: St. Francis Xavier University
  • November 27: Dalhousie University
  • November 29: Memorial University

Spring 2013:  Penny Morrill

2011-12 Speaker Tour

When Magmas Attack
Dr. Cliff Shaw, University of New Brunswick

Visiting:

    • March 13: Memorial University
    • March 15: St. Francis Xavier University
    • March 16: Dalhousie University

 

Fraser-Keppie-294x300

How do supercontinents breakup? Evaluating the type example of Pangea in Middle America
Dr. Fraser Keppie, NS Department of Natural Resources

Visiting:

  • Acadia University
  • University of New Brunswick
  • Saint Mary’s University

Abstract: The periodic formation and breakup of supercontinents through geologic time is a notable characteristic of the plate tectonic evolution of Earth. Are supercontinents simply a statistical consequence of an arbitrary system of plate boundaries, or do they correspond to fundamental changes in the patterns of mantle convection? Once formed, what are the forces which lead to the breakup of supercontinents? In order to answer these questions,  obtaining plate kinematic constraints for key examples is prerequisite. The most recent and best known example of a supercontinent is Pangea, an assembly of continental blocks inferred to be together during the late Carboniferous and early Mesozoic. Inspection of tectonic models reveals that the kinematic constraints on the breakup of Pangea are uncertain, however. For example, whether South America was off the southern United States (Pangea A), or east of Florida (Pangea B), is an unresolved issue. Also, the Gulf of Mexico is believed to have opened in a counter-clockwise fashion during the Jurassic, but candidate mechanisms that could have caused such extension have been speculatively identified at best. I show here how the Gulf of Mexico may have opened initially during the Jurassic as a pull-apart basin between the Mojave-Sonora and West Florida Megashears. Further, I show how pirate mode or pull-up tectonics provides a mechanism for counter-clockwise extension in the western Gulf of Mexico during the late Cretaceous and Cenozoic. If either or both of these processes operated in Middle America, during and after the breakup of Pangea, established tectonic models require revision. Regardless, this analysis suggests that the breakup of Pangea and earlier supercontinents may have been facilitated by shear zones connecting deformation at their exterior margins to deformation within their interiors.

2010-11 Speaker Tour

Tour Coordinator: Ian Spooner, Acadia University

Dr. Peir Pufahl, Dept. of Earth and Environmental Science, Acadia University
Precambrian carbonates and the evolution of the atmosphere

Bioelemental sediments, a new term that encompasses iron formation, chert, and phosphorite, provide the framework for understanding early Earth evolution. Because bioelemental sediments are composed of the nutrient elements, Fe, Si, and P, their precipitation is intimately linked to biological processes that modify ocean-atmosphere chemistry. This talk highlights how sedimentology and the use of modern stratigraphic principles are used to interpret the microbial ecology and geochemistry of Precambrian bioelemental depositional systems.

  • January 25: St. Francis Xavier University
  • March 8: Dalhousie University
  • March 25: Memorial University

Dr. Yana Fedortchouk, Dept. of Earth Sciences, Dalhousie University
A window into the Mantle

Diamonds store an incredible record of Earth’s history due to their Archean ages and the residence at great depths as deep as the lower mantle. Diamonds come to the surface by entrainment in kimberlites — the deepest mantle-derived magmas. Kimberlites are also famous for their extremely complex composition, poorly understood origin, presumably explosive eruptions indicating very volatile-rich nature, and the absence of the modern examples. In my talk I will show how we can use diamonds to constrain conditions in kimberlite magmas and in various diamond-bearing reservoirs in the mantle. Diamonds undergo partial dissolution during transportation in kimberlites and during residence in the mantle. The morphology of dissolution features strongly depends on the composition and the conditions of the diamond-destructive fluids. Combination of high-pressure-temperature experiments with morphological studies of the natural diamond parcels demonstrated a strong link between diamond dissolution features and the geology of kimberlite pipes. Surface features are different on diamonds recovered from volcaniclastic and hypabyssal kimberlites reflecting presence or absence of the free fluid phase and the mechanism of kimberlite eruption. Further I will show how diamond morphology can help us to constrain the fluid history in various mantle reservoirs and to learn more about the complex evolution of subcratonic mantle.

  • January 12: Acadia University
  • January 26: Saint Mary’s University
  • February 10 or 11: University of New Brunswick, Fredericton