Nailed to the craton: Stratigraphic continuity across the southeastern Canadian Cordillera with tectonic implications for ribbon continent models

M.E Mcmechan,P.S Simony,K.G Root,D.R.M Pattison

doi:10.1130/g48060.1

Abstract

Abstract Cambrian and Upper Devonian to Mississippian strata can be confidently traced westward, without strike-slip offset, from the autochthonous section above North American basement into the southeastern Canadian Cordillera, and are thus “nailed” to the craton. These strata are in turn stratigraphically pinned to older (Mesoproterozoic Belt-Purcell Supergroup, Neoproterozoic Windermere Supergroup, and Ediacaran), intermediate-aged (Ordovician–Silurian), and younger (Permian to Middle Jurassic) strata found only in the mountains, thus linking them to the adjacent autochthonous craton. The overlapping distribution of linking successions, regionally traceable unique stratigraphic horizons in the Belt-Purcell and Windermere Supergroups, and across-strike stratigraphic features show that the entire Cariboo, northern Selkirk, Purcell, and Rocky Mountains are directly tied to the adjacent North American craton without discernible strike-slip or oblique displacement, or substantial purely convergent plate-scale (&gt;400 km) horizontal displacement. They link the entire width of the Belt-Purcell and Windermere basins in the southeastern Canadian Cordillera to the adjacent craton and show that any proposed Cretaceous ribbon continent suture, with its thousands of kilometers of proposed displacement, cannot run through the southeastern Canadian Cordillera.

Highlights

Several hypotheses have been proposed in recent decades postulating that there is a major suture or subduction zone of Cretaceous age within the foreland of the Canadian and American Cordillera that separates far-traveled or non–North American terrane or “ribbon continent” rocks from North American rocks
STRATIGRAPHIC LINKAGES Five main tectono-stratigraphic sequences comprise the stratigraphic succession exposed in the southeastern Canadian Cordillera: (1) the Mesoproterozoic Belt-Purcell Supergroup (BPSG); (2) Neoproterozoic Windermere Supergroup (WSG); (3) Ediacaran–Silurian and (4) Middle Devonian–Middle Jurassic sedimentary strata deposited along the rifted margin of the North American craton; and (5) Upper Jurassic–Paleocene foreland basin strata (e.g., Price, 1981)
The Cordilleria, SAYBIA, and Rubia ribbon continent models were inspired in large part by paleomagnetic data, which indicated that western and central portions of the northern Cordillera had been displaced northward by as much as 3000 km between 90 and 50 Ma (e.g., Beck and Noson, 1972; Irving et al, 1996)

Summary

Introduction

Several hypotheses have been proposed in recent decades postulating that there is a major suture or subduction zone of Cretaceous age within the foreland of the Canadian and American Cordillera that separates far-traveled or non–North American terrane or “ribbon continent” rocks from North American rocks. In the southeastern Canadian Cordillera, the surface location of the suture is interpreted to be along the Southern Rocky Mountain Trench in the Cordilleria model, or adjacent to or at the Kicking Horse Rim Lower Paleozoic facies change in the SAYBIA and Rubia models (Fig. 1).

Results

Conclusion