A Pangean rim of fire: Reviewing the Triassic of western Laurentia

Thomas Hadlari,Terry P Poulton,William A Matthews,Derrick Midwinter

doi:10.1130/l643.1

Abstract

A synthesis of U-Pb detrital zircon data from the Triassic of western Laurentia is placed in the context of paleogeographic models for Pangea. We find that an emerging body of evidence supports the hypothesis that a Triassic subduction zone and continental magmatic arc system fringed western Laurentia starting in the southwestern United States, continuing northward along the Cordillera, including arc rocks of the Quesnel and Yukon-Tanana terranes, and extending further into the Arctic region. In the context of this geodynamic setting, the western interior basins of North America would have formed, probably by subduction dynamics, as a collage of backarc and retroarc foreland basins. The convergent tectonic model for western Laurentia is consistent with paleogeographic reconstructions that show a subduction zone encircling Pangea, called the Pangean rim of fire.

Highlights

TRIASSIC PROVENANCE OF SOUTHWESTERN CANADASome paleogeographic models have hypothesized that segments of western Laurentia were convergent margins in the Triassic; here we explore the scenario that these segments were connected in forming a continuous convergent margin
The proposition is that during Permian time Pangea was surrounded by a ring of subduction zones forming an outer Pangean rim (Scotese and Langford, 1995), including western Laurentia, that possibly continued through the Triassic as a Pangean rim of fire (Golonka and Ford, 2000) (Fig. 1)
Evidence for an equivalent arc along the western margin of the southern Canadian Cordillera is based on a combination of crustal-scale seismology, Laurentian affinity of the pericratonic Quesnel and Yukon-Tanana terranes, and Triassic detrital zircon found in the westernmost portions of the Western Interior Basin

Summary

Introduction

TRIASSIC PROVENANCE OF SOUTHWESTERN CANADASome paleogeographic models have hypothesized that segments of western Laurentia were convergent margins in the Triassic; here we explore the scenario that these segments were connected in forming a continuous convergent margin. The pericratonic framework is consistent with upper Triassic sandstones from the far western edge of the Western Interior Basin that have yielded detrital zircon age spectra dominated by 210–200 Ma ages interpreted to be the volcaniclastic record of the Quesnel terrane volcanic arc (Golding et al, 2016b), in addition to ca.

Results

Conclusion