New rift microcontinent not fully identified between Greenland and Canada

Plate tectonics is the driving force behind Earth’s continental configurations, with the lithosphere (oceanic and continental crust and upper mantle) moving due to convection processes occurring in the softer asthenospheric mantle. Many earthquakes, volcanic eruptions and mountain formations are a direct consequence of the movements of these plates that span the globe, especially at their edges.

One such plate boundary occurs between Canada and Greenland, which has formed the Davis Strait seaway that connects 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 at the ocean.

This is now considered to be a newly recognized, rifted and subducted microcontinent offshore of western Greenland: the Davis Strait proto-microcontinent.

Understanding the mechanism and reason for this crustal abnormality is the focus of new research, published in Gondwana Exploration. PhD researcher Luke Longley and Dr. Jordan Phethean (University of Derby, UK) along with Dr. They define proto-microcontinents as “regions of relatively thick continental lithosphere separated from the main continents by an area of ​​thinner continental lithosphere”.

Dr. Phethean explains why this particular site is so important to this research and why looking at past microcontinent formation is vital for today. “The well-defined changes in plate motion occurring 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.

“The rifting and formation of microcontinents are absolutely continuous phenomena – with each earthquake we can work towards the next microcontinent breaking up. The goal of our work is to understand their formation well enough to predict that future evolution.”

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

Scientists identified 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 marked as key to the formation of this proto-microcontinent, with the orientation of the seafloor extension between Canada and Greenland changing from northeast-southwest along the Pre-Ungava Transform Margin, to the north- south , breaking off the Davis Straight proto-microcontinent. By ~33 Ma, oceanic spreading ceased after Greenland collided with Ellesmere Island, after which Greenland merged with the North American plate.

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

This research has applicability to other microcontinents globally to understand their calving from continental crust, including the Jan Mayen microcontinent in northeast Iceland, East Tasman East in southeast Tasmania, and Gulden Draak Knoll, offshore Western Australia.

Dr. Phethean notes, “Better knowledge 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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