CGRG Bibliography of Canadian Geomorphology
Search Results
Author : Doupe, J.P.; England, J.H.; Coulthard, R.; Heaman, L.; and Doornbos, C.
Date : 2007.
Title : Erratic provenance in the western Canadian Arctic Archipelago determined by in situ U-Pb dating of zircon: implications for the paleotopography of the NW Laurentide Ice Sheet.
Publication : CANQUA Ottawa 2007. Canadian Quaternary Association Conference, June 4-8, 2007. Carleton University, Ottawa, Ontario, Canada.
Issue :
Page(s) :
Abstract
Zircon U-Pb ages of erratics have been measured across several islands of the western Canadian Arctic Archipelago. The objective is to determine the provenance of far-travelled mainland erratics, assuming that their ages correspond to chronologically and geographically distinct terranes of the Canadian Shield. Application of U-Pb dating of zircon has benefited greatly from the development of Multicollector-Laser Ablation-Inductively Coupled Plasma Mass Spectrometery (MC-LA-ICPMS). Although less precise than the conventional method of Thermal Ionization Mass Spectrometry (TIMS), the laser ablation method can date erratics only large enough to produce thin-sections, and it has a much higher sample throughput than TIMS. Consequently, only hand-sized samples need to be collected in the field, allowing large numbers of samples to be screened quickly as possible candidates for unique source areas (ages). Here we report on zircon U-Pb ages for erratics from Banks, Prince Patrick, and Melville Islands. Erratic ages on Banks are generally around 2.6 Ga, suggesting an origin in the Slave and/or Churchill Provinces of the Canadian Shield. In contrast, erratics collected on Prince Patrick fall in the range of 1.8 to 2.0 Ga, corresponding to the Trans-Hudson and Taltson-Thelon Provinces. Erratics colected on Melville Island tend to show a mixture of ages, including those ages observed on Banks and Prince Patrick Islands, as well as one sample with an age of 2.45 Ga, attributed to the Queen Maud terrane of the Canadian Shield. Overall, these data indicate a net northward to northwestward transport of erratics from the mainland that requires a predominantly east-west oriented divide. The current age distribution of our dated samples therefore does not record the east-west displacement associated with the north-south oriented M’Clintock Ice Divide, previously attributed to the configuration of the Laurentide Ice Sheet during the Last Glacial Maximum. Combined with related studies in the western Canadian Arctic Archipelago, our data suggest that the Laurentide Ice Sheet was characterized by a widespread northward advance during the Late Wisconsinan that extended farther than previously recognized. Furthermore, the consistency of the ages specific to Prince Patrick, Banks and Melville Islands currently suggest that their transport from the mainland must have remained fundamentally the same for earlier ice advances as well (assuming transport of erratics to these sites is not confined to the Late Wisconsinan). This contrasts to well-documented changes in ice flow on islands farther south related
Bibliography of Canadian Geomorphology