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Episodic tectonics in the Phanerozoic succession of the Canadian High Arctic and the “10-million-year flood”

By
Ashton Embry
Ashton Embry
Geological Survey of Canada–Calgary, 3303 33 Street NW, Calgary, Alberta T2L 2A7, Canada
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Benoit Beauchamp
Benoit Beauchamp
Department of Geoscience, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada
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Keith Dewing
Keith Dewing
Geological Survey of Canada–Calgary, 3303 33 Street NW, Calgary, Alberta T2L 2A7, Canada
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James Dixon
James Dixon
Geological Survey of Canada–Calgary, 3303 33 Street NW, Calgary, Alberta T2L 2A7, Canada
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Publication history
24 April 201815 October 2018

ABSTRACT

We have identified 57 large-magnitude, sequence boundaries in the Phanerozoic succession of the Canadian High Arctic. The characteristics of the boundaries, which include angular unconformities and significant changes in depositional and tectonic regimes across the boundaries, indicate that they were primarily generated by tectonics rather than by eustasy. Boundary frequency averages 10 million years throughout the Phanerozoic and there is no notable variation in this frequency.

It is interpreted that each boundary was generated during a tectonic episode that lasted two million years or less. Each episode began with uplift of the basin margins and pronounced regression. This was followed by a rapid subsidence and the flooding of the basin margins. Each tectonic episode was terminated by a return to slow, long-term subsidence related to basin forming mechanisms such as thermal decay. The tectonic episodes were separated by longer intervals of tectonic quiescence characterized by slow subsidence and basin filling.

The tectonic episodes are interpreted to be the product of changes in lithospheric stress fields with uplift being related to increased, compressional horizontal stress and the following time of rapid subsidence reflecting a decrease in such stresses or an increase in tensional stresses. Conversely, the longer intervals of tectonic quiescence would reflect relatively stable, horizontal stress fields. The episodic changes in stress fields affecting the Canadian High Arctic throughout the Phanerozoic may be a product of intermittent, plate tectonic reorganizations that involved changes in the speed and directions of plate movements. The longer intervals of tectonic quiescence would occur during times of quasi-equilibrium in the plate tectonic mosaic.

The tectonic episodes that generated the sequence boundaries were governed by nonlinear dynamics and chaotic behavior, and there is a one-in-10-million chance that a tectonic episode will be initiated in the Canadian High Arctic in any given year. Thus, the major transgression associated with each episode can be referred to as a “10-million-year flood.”

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Contents

GSA Special Papers

Circum-Arctic Structural Events: Tectonic Evolution of the Arctic Margins and Trans-Arctic Links with Adjacent Orogens

Geological Society of America
Volume
541
ISBN electronic:
9780813795416

GeoRef

References

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