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Plate tectonics is the driving force behind 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 a direct result of the movements of these globe-spanning plates, especially along their boundaries.

One such plate boundary occurs between Canada and Greenland, which formed the Davis Strait seaway connecting two ocean basins, the Labrador Sea and Baffin Bay. The tectonic evolution of Davis Strait is dated to ~33–61 million years ago (Ma) during the Paleogene, during which a particularly unusual feature formed—a thicker-than-normal (19–24 km) fragment of continental crust in the ocean.

This is now considered to be a newly recognized, incompletely rifted and submerged microcontinent off the coast of western Greenland: the Davis Strait protomicrocontinent.

Understanding the mechanism and cause of this cortical abnormality is the focus of new research published in Exploring Gondwana. PhD student Luke Longley and Dr Jordan Fetean (University of Derby, UK) together with Dr Christian Schiffer (Uppsala University, Sweden) have created a reconstruction of the ~30 million year plate tectonic movements 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 to this research and why looking at past microcontinent formation is vital today. “The well-defined changes in plate motion that occur in the Labrador Sea and Baffin Bay, which have relatively limited external complications affecting them, make this area an ideal natural laboratory for studying the formation of microcontinents.”

“Rifting and the formation of microcontinents are absolutely ongoing phenomena – with each earthquake we may be working towards the next breakup of the microcontinents. The goal of our work is to understand their formation well enough to predict this future evolution.”

To investigate this further, 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 split apart from the North American plate) and associated transform faults. faults (where two tectonic plates slide past each other).

The scientists determined that the initial rifting between Canada and Greenland began ~118 Ma during the Lower Cretaceous, with seafloor spreading beginning in the Labrador Sea and Baffin Bay at ~61 Ma.

Subsequently, the period ~49–58 Ma is noted as key to the formation of this proto-microcontinent, with the orientation of the seafloor extending between Canada and Greenland changing from northeast–southwest along the pre-Ungava transform margin, to the north- south, separating from the proto-microcontinent along the Davis line. By ~33 Ma, oceanic spreading stopped 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 thickness, where the microcontinent occurs in the range of 19–24 km thick thinned continental crust, surrounded by two narrow strips of thin (15–17 km) continental crust that separate it from mainland Greenland and Baffin Island.

This research is applicable to other microcontinents globally to understand their calving from continental crust, including the Jan Mayen microcontinent northeast of Iceland, the East Tasman Rise southeast of Tasmania, and the Gulden Draak Hills, off the coast of Western Australia.

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

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