New partially rifted microcontinent identified between Greenland and Canada

Plate tectonics is the driving force behind the Earth’s continental configurations, with the lithosphere (oceanic and continental crusts and upper mantle) moving due to convection processes occurring in the softer underlying asthenospheric mantle. Many earthquakes, volcanic eruptions, and mountain formations are direct consequences of the movements of these plates, which extend across the Earth’s surface, particularly at their margins.

One such plate boundary lies between Canada and Greenland, and formed the Davis Strait, which connects two ocean basins, the Labrador Sea and Baffin Bay. The tectonic evolution of Davis Strait dates back approximately 33 to 61 million years ago (Ma), during the Paleogene, during which a particularly unusual feature formed: a thicker-than-normal (19 to 24 km) fragment of continental crust in the ocean.

It is now a newly recognized, incompletely rifted and submerged microcontinent off the coast of western Greenland: the Davis Strait proto-microcontinent.

Understanding the mechanism and reason for this crustal anomaly is the focus of new research, published in Research on Gondwana. PhD students Luke Longley and Dr Jordan Phethean (University of Derby, UK) and Dr Christian Schiffer (Uppsala University, Sweden) have generated a reconstruction of the plate tectonic movements spanning approximately 30 million years that led to the formation of the proto-microcontinent. They define proto-microcontinents as “regions of relatively thick continental lithosphere separated from the main continents by a zone of thinner continental lithosphere”.

Dr. Phethean explains why this particular location is so important for this research and why it is essential to study the past formation of microcontinents today. “The well-defined changes in plate motion occurring in the Labrador Sea and Baffin Bay, which are relatively unaffected by external complications, make this region an ideal natural laboratory for studying the formation of microcontinents.

“Rifting and microcontinent formation are absolutely ongoing phenomena. With every earthquake, we risk heading towards the next microcontinent separation. The goal of our work is to understand their formation well enough to predict this future evolution.”

To further investigate this question, the research team used maps derived from gravity and seismic reflection data to identify the orientation and age of faults associated with rifting, the mid-ocean ridge (where Greenland separated from the North American plate), and associated transform faults (where two tectonic plates slide past each other).

Scientists have identified that initial rifting between Canada and Greenland began about 118 Ma ago during the Early Cretaceous, with seafloor spreading beginning in the Labrador Sea and Baffin Bay at about 61 Ma.

Subsequently, the period from about 49 to 58 Ma is considered key to the formation of this proto-microcontinent, with the orientation of seafloor spreading between Canada and Greenland changing from northeast-southwest along the pre-Ungava transform margin, to north-south, away from the Davis Strait proto-microcontinent. By about 33 Ma, oceanic spreading ceased when Greenland collided with Ellesmere Island, after which Greenland joined the North American Plate.

In this model, the Davis Strait proto-microcontinent is identified based on crustal thicknesses, where the microcontinent occurs in the range of thinned continental crust 19–24 km thick, surrounded by two narrow bands of thin continental crust (15–17 km) that separate it from continental Greenland and Baffin Island.

This research can be applied to other microcontinents globally to understand their calving from continental crust, including the Jan Mayen microcontinent northeast of Iceland, the East Tasman Ridge southeast of Tasmania, and the Gulden Draak Knoll, off western Australia.

Dr Phethean notes: “A better understanding of how these microcontinents form allows researchers to understand how plate tectonics works on Earth, with useful implications for mitigating plate tectonic hazards and discovering new resources.”

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