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Geochemical and Nd isotopic evidence for sedimentary-source changes in the Devonian miogeocline of the southern Canadian Cordillera

¹ GEOTOP and Département des Sciences de la Terre, Université du Québec à Montréal, P.O. Box 888 St. C.V., Montréal, Québec H3C 3P8, Canada
² Department of Earth and Planetary Sciences, McGill University, 3450 University Street, Montréal, Québec H3A 2A7, Canada

Sedimentological evidence indicates that clastic sediments of the Western Canada Sedimentary Basin were derived predominantly from the north and east, an exception being the westerly sourced Sassenach Formation in the Upper Devonian. A comparison of geochemical and Sm-Nd isotopic data of the Sassenach Formation and the underlying Perdrix and Mount Hawk Formations, which have easterly sources, support a change in sedimentary provenance. The Frasnian Perdrix and Mount Hawk Formations have initial _Nd values of –7 to –8.5. This range of values is higher than that of the underlying Precambrian basement and reflects a mixture of older and younger crustal detritus (Late Proterozoic to Devonian) eroded and transported from orogens in the Arctic. The overlying Famennian Sassenach Formation yields lower initial _Nd values that decrease from as high as –8.5 at the base to about –11 near the top. The lower _Nd values of the Sassenach Formation imply that the western crustal source of the Sassenach sediments was, on average, older than the eastern crustal sources of the underlying formations. This older western source appears to be related to uplift and reworking of older miogeosynclinal sediments in the west as a result of compression related to the Antler orogeny.

Key Words: Antler orogeny • Canada • Cordillera • Devonian • Nd isotopes • paleogeography

This article has been cited by other articles:

				K. G. Root and K. G. Root Devonian Antler fold and thrust belt and foreland basin development in the southern Canadian Cordillera: implications for the Western Canada Sedimentary Basin Bulletin of Canadian Petroleum Geology, March 1, 2001; 49(1): 7 - 36. [Abstract] [Full Text] [PDF]