Resolving Mesoproterozoic supercontinent configuration with an integrated multi-tool approach to sedimentary provenance analysis

University Of Massachusetts Lowell, Lowell MA

Investigators

Abstract

The supercontinent cycle involves the periodic assembly of the Earth’s continents into a single supercontinent followed by breakup and dispersal. One of the oldest supercontinents for which significant geologic constraints exist is Columbia (also referred to as Nuna), which is thought to have been assembled by about 1.5 billion years ago. Sediments deposited between ~1.5 and 1.4 billion years ago in western North America include minerals that lack known North American sources and thus suggest that another continent was adjacent to western North America within Columbia. However, the identity of this continent and the extent to which any rearrangement occurred between ~1.5 billion years ago and the formation of the next supercontinent (called Rodinia) at ~1.0 billion years ago remains debated. Models have been proposed that place either northern Australia, southern Australia, and/or eastern Antarctica adjacent to western North America. This research will test these different models through detailed analyses of the ages and compositions of minerals within ancient sedimentary rocks in Montana, Idaho, and Arizona and comparison with potential sources in Australia and Antarctica. Further constraints will be provided from comparable analyses of minerals in ancient sedimentary rocks collected from Antarctica. This project will support graduate and undergraduate student research at the University of Massachusetts Lowell (UML), the development of a new summer field geology and ecology course for UML students held in and around Glacier National Park (which is a key locality for the rocks of interest in this project), incorporation of supported research into other undergraduate courses at UML, and collaborations with scientists in Idaho, Arizona, Washington, Texas, and Minnesota. The goal of this project is to test models for the identity and positions of continental blocks that were connected to western North America in the Mesoproterozoic supercontinent Columbia. The study will focus on the provenance of Mesoproterozoic sedimentary rocks in western North America, particularly the Belt Supergroup in Montana/Idaho and similarly aged rocks in Arizona. These sedimentary sequences have previously been recognized as having non-North American input via conventional detrital zircon dating. This work will use an innovative and integrative approach to determining provenance by way of simultaneous U-Pb dating and trace element fingerprinting of detrital zircon, monazite, and rutile, along with Hf and common Pb isotope characterization of detrital zircon and feldspar, respectively. Results will be compared to potential source rocks in the North Australian craton, South Australia craton, and East Antarctic craton. Previously collected sedimentary samples from East Antarctica will also be included in this study in order to expand knowledge of the Precambrian basement geology of that ice-covered continent. 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.