Eastern Canada

Research I was involved in while a post-doc at Imperial College London working with Ian Bastow, investigating 3 billion years of geological history in eastern Canada, from Archean cratons, to Paleoproterozoic mountain building, to Phanerozoic collisions and rifting.

QM-III deployment

Seismic network in Nova Scotia and New Brunswick

In 2013, the seismology group at Imperial College, in collaboration with North American-based QM-III project researchers at Lamont Doherty Earth Observatory and the universities of Rutgers and Québec à Montréal, embarked on a new effort to image the seismic structure of the North American plate at its southeast cratonic edge. As part of this project we installed 10 SEIS-UK seismometers in Nova Scotia and New Brunswick for 2 years, on a project funded by the Leverhulme Trust. Installation sites included sites including gardens, a Geological Survey of Canada rock store, and a blueberry farm. On Grand Manan, an island in the Bay of Fundy, the station was installed in the museum as the centrepiece of a seismology exhibition.


Publications

Three billion years of crustal evolution in eastern Canada: constraints from receiver functions 

In this paper, published in JGR in 2016, Laura Petrescu used H-k stacking of receiver functions and Baysian inversion methods to develop a model for the crust across SE Canada, spanning 3 billion years of geological history. Her results demonstrate a correlation between geophysical properties and geological terranes and suggest that the Proterozoic Grenville terrane is supported by buoyant mantle material.

Lithospheric deformation in the Canadian Appalachians: evidence from shear wave splitting [PDF]

This paper (GJI, 2016) presents the results of a shear wave splitting study using data from Nova Scotia and New Brunswick. We find that most of the anisotropic fast directions are parallel to the trends of deformation due to the Appalachian Orogeny and reflect fossil lithospheric anisotropy. Mesozoic rifting only has limited local impact within the Bay of Fundy and in southern Nova Scotia.

Seismological structure of the 1.8Ga Trans-Hudson Orogen of North America

Here we present a new shear velocity model and crustal thickness estimates for the Trans-Hudson Orogen around Hudson Bay. The Moho character, present-day crustal thickness, and metamorphic grade, we support the view that southern Baffin Island experienced thickening during the THO of a similar magnitude and width to present-day Tibet. This work was published in G-cubed in 2016.

Subduction beneath Laurentia modified the eastern North American cratonic edge: Evidence from P wave and S wave tomography [PDF]

In this paper, published in JGR in 2016, Alistair Boyce used P wave and S wave relative arrival-time tomography to constrain upper mantle structure beneath southeast Canada and the northeast USA. A near-vertical boundary in mantle wave speed directly beneath the Grenville Front is interpreted as evidence for subduction-driven metasomatic enrichment of the Laurentian cratonic margin, prior to keel stabilisation.

Seismic anisotropy of Precambrian lithosphere: Insights from Rayleigh wave tomography of the eastern Superior Craton

In this 2017 JGR paper, Laura Petrescu used 2-plane-wave surface wave tomography to investigate the deep structure beneath the Archean superior craton. Her results show that the ancient continental root is made up of at least two layers, each with a different formation mechanism. The upper layer preserves the signature of continental deformation older than 2.5 billion years, whereas the lower layer properties suggest later downward growth of the root above a slow-moving mantle. The results support the idea that the thick continental roots formed episodically and across multiple geological periods. 

A tale of two orogens: comparing crustal processes in the Proterozoic Trans-Hudson and Grenville Orogens, eastern Canada [PDF]

In this 2017 paper in Tectonics, lead by Fiona Darbyshire, active and passive sources sesimic studies from the last 20-30 years in eastern Canada are reviewed, with a particular focus on the Paleoproterozoic Trans-Hudson Orogen (THO) and Mesoproterozoic Grenville Orogens, both of which extend for thousands of kilometers along strike and hundreds of kilometers across strike and have been compared to the present-day Himalayan-Karakoram-Tibetan Orogen (HKTO).

The Formation of Laurentia: Evidence From Shear Wave Splitting [PDF]

In this 2017 paper, published in EPSL, Mitch Liddell, uses shear wave splitting to investigate anisotropy in the northern Hudson Bay region. He finds strong evidence for multiple layers of anisotropy beneath Archean zones, consistent with the episodic development model of stratified cratonic keels, and that southern Baffin Island is underlain by dipping anisotropic fabric, providing direct evidence of subduction-related deformation at 1.8 Ga.

Precambrian Plate Tectonics in Northern Hudson Bay: Evidence From P and S Wave Seismic Tomography and Analysis of Source Side Effects in Relative Arrival‐Time Data Sets

In this paper, published in JGR in 2018, Mitch Liddell, presents P and S wave tomographic models of the mantle seismic structure around northern Hudson Bay. The tomographic models reveal a complicated internal structure in the Archean Churchill plate. The mantle lithosphere in the central region of Hudson Bay is distinct from the THO, indicating potential boundaries of microcontinents and lithospheric blocks between the principal colliders. Slow wave speeds underlie southern Baffin Island, the leading edge of the generally high wave speed Churchill plate. This is interpreted to be Paleoproterozoic material underthrust beneath Baffin Island in a modern-style subduction zone setting.

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