EARLY PALEOZOIC PALEOGEOGRAPHY AND TECTONICS OF THE FRANKLINIAN MARGIN AT NORTHERN ELLESMERE ISLAND, CANADIAN HIGH ARCTIC

Onshore geological studies that constrain the pre-Cretaceous paleogeography and tectonic development of continental margin basins in the Canadian High Arctic are essential to test models for circum-Arctic lithosphere evolution. Some of the testable hypotheses for the Franklinian margin at northern Ellesmere Island concern the origins of two rock assemblages: (1) an Ediacaran-Cambrian marine succession of quartz sandstone, conglomerate, shale, and limestone; and (2) a Silurian marine succession of volcanic sandstone, conglomerate, shale, and mafic to felsic lavas. We conducted detrital zircon U-Pb studies of these two assemblages to test their predicted linkages with circum-Arctic source rocks and to improve the chronology of tectonic events along the Franklinian margin. Ediacaran-Cambrian clastic strata are characterized by 1000-1300, 1600-2000, and 2500-2800 Ma detrital zircon ages and imply provenance from rock units of the Laurentian craton. In combination with regional stratigraphic data, the detrital zircon results support an Ediacaran-Cambrian paleodrainage model for a north- to northeast-directed depositional network along the north-facing, rifted continental margin of northern Laurentia. Most Silurian units represent turbidity current deposits that were derived from areas to the north and east of northern Ellesmere Island. Silurian strata are composed of Paleozoic to Archean detrital zircons with dominant zircon U-Pb age peaks of 420-480, 500-700, 970, 1100, 1450, and 1650 Ma. These data support the hypothesis that Silurian strata were deposited in a convergent margin setting and sourced from the Caledonian mountain belt to the east and volcanically active regions of Axel Heiberg Island and Pearya terrane to the north. The transition from passive- to convergent-margin tectonics at northern Ellesmere Island occurred by the Early Silurian (Llandovery), and therefore was probably related to Caledonian evolution.