Collaborative Research: An Alaskan perspective on middle Paleozoic terrane translation, contraction, and subduction initiation in northwestern Laurentia

University Of Iowa, Iowa City IA

Investigators

Abstract

A fundamental concept in plate tectonics is that ancient continental margins undergo a conversion process from “passive” zones of sediment accumulation to “active” zones dominated by subduction, volcanism, and mountain building. The process by which this transition occurs is through subduction initiation along continental margins. However, modern examples and numerical models of subduction initiation remain highly contentious. The late Paleozoic (ca. 450–300 million years ago) conversion of northwestern North America from a passive to an active margin is often cited as a classic example of this fundamental plate tectonic process, but very little is known about the nature and timing of key events in northern Alaska and Yukon, Canada, that led to this subduction initiation event. This study promotes collaboration between academic researchers at three U.S. institutions and government researchers at the United States Geological Survey (USGS) to better inform our understanding of late Paleozoic tectonic events in a remote and understudied region of North America. A diverse group of undergraduate and graduate students will participate in research initiatives at each institution. In addition, the research team will collaborate with the United States Fish and Wildlife Service and the USGS to disseminate geologic knowledge of Arctic Alaska to the public, to enhance the economic competitiveness of the U.S. and facilitate the training of the next generation of Arctic Earth scientists. Recent models for the middle Paleozoic tectonic evolution of North America (Laurentia) highlight margin-parallel transport of circum-Arctic terranes followed by widespread continental subduction initiation from the Yukon to Nevada. However, the timing, nature, and duration of middle Paleozoic orogenic events remain ambiguous. This project will focus on key structural relationships and unique Devonian–Carboniferous synorogenic sedimentary and magmatic rocks within the Arctic Alaska terrane of northern Alaska. The research consists of three major components: 1) the examination of synorogenic rocks coupled with the development of a regional provenance dataset; 2) a petrological, geochemical, and geochronological examination of regional Middle to Upper Devonian igneous rocks; and 3) a field-based structural study integrated with regional seismic datasets to reconstruct the style of Devonian–Carboniferous deformation in Arctic Alaska. This work will provide critical new insights into the Paleozoic tectonic evolution of northwestern North America and the greater circum-Arctic region to assess the viability of several subduction initiation mechanisms. In addition, this project will provide new piercing points for Mesozoic tectonic reconstructions of the Arctic, with relevance to several subdisciplines of the geosciences. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.