Collaborative Research: Displacement history of the Pearya terrane, Ellesmere Island - evaluating a strike-slip origin for the Canadian Arctic margin

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This project is a structural, petrologic and geochronologic study of basement rocks that comprise the Pearya terrane of Ellesmere Island, which forms the northernmost landmass of North America. This tectonic terrane has geologic affinities with continental crust in Svalbard and Greenland. It is postulated that the Pearya terrane is the best example along the Canadian Arctic margin of a crustal fragment that has been displaced by plate tectonic processes. A proposed tectonic model for the origin of the Pearya terrane (the Paleozoic Northwest Passage model) postulates that many exotic or far-travelled geologic terranes that make up the northwestern Cordillera (e.g. Alaska) originated in the Caledonian orogenic belt shared by Greenland and Scandinavia, and subsequently traveled westward on a strike-slip fault to their current location about 400 million years ago. The lack of documentation on the timing and movement sense of the Pearya terrane severely limits understanding of the tectonic evolution of the Arctic margin of North America, leaving room for recent models that claim Pearya was stationary and was not the result of tectonic displacement. This project includes field observations and sample collection from remote southern boundary of the Pearya terrane that will be used to test these models. The project is part of the 2017 Circum-Arctic Structural Events Expedition organized by the German Federal Institute for Geosciences and Natural Resources, who will provide logistical support for the fieldwork. The project will involve international collaboration with scientists from five countries. In addition to the scientific contributions of the project, the study will contribute to training of graduate and undergraduate students in an important science, technology, engineering and mathematics (STEM) discipline, which is important in contributing to the enhanced compatibility of the U.S. workforce. The project will also contribute to broadening of underrepresented groups in STEM. Research results will be shared with the public through lectures and will be published in the peer reviewed scientific literatures and presentations at professional society meetings. Understanding the geological evolution of the North American Arctic margin is critical to informing important scientific, political and economic issues associated with the Arctic region. This award is cofunded by the NSF Office of International Science and Engineering.The ultimate goal of this project is to establish a stratigraphic, structural and metamorphic framework for the evolution of the complex southern boundary of the Pearya terrane. The study entails integrated kinematic, petrochronologic and argon-argon thermochronologic analysis of the crystalline basement and major faults at the southern Pearya terrane margin; and detailed stratigraphic comparison across the terrane boundary through sandstone petrography, detrital zircon uranium-lead and hafnium analysis, and major, trace element and neodymium isotope geochemistry on mudstone. Although the Canadian Arctic margin is often cited as an example of large magnitude terrane translation, little is known about the structures that may have accommodated such profound displacement. The project will evaluate possible strike-slip tectonics in light of structures associated with transpression, which may reconcile the earlier observations of straight contraction. The results of this study will provide critical timing on the age of metamorphism and the early ductile history of the shear zones in order to see through the pervasive overprinting. The principal investigators will also evaluate the stratigraphy of the overlap assemblage in different fault blocks to determine whether it is a single assemblage or, in fact, time correlatives of spatially separate depositional systems. By producing a robust data set tied to the geology, this project will help discriminate among the disparate models that currently exist for the Pearya terrane and the larger tectonic development of the Arctic.