Information from river sections in the Hudson Bay lowland indicates that two pre-Holocene nonglacial episodes separated by glacial advances postdate the oldest recognized glaciation. Amino-acid data from in situ and transported marine shell fragments provide relative ages for glacial and nonglacial intervals. Absolute ages for nonglacial sediments as recent as mid-stage 3 were obtained from thermoluminescence (TL) data, although no finite radiocarbon ages have been obtained from wood. Déglaciation and deposition of the Bell Sea marine sediments are correlated to substage 5e by extrapolation from TL data. Ensuing stage 5 glaciation was dominated in Ontario by west-northwestward ice flow emanating from Quebec, and in Manitoba by southwestward ice flow. Déglaciation dated by TL at about 75 ka was followed by isostatic recovery and subaerial exposure in a climate which could have been warmer, but was no more than slightly colder than present. Extensive glaciolacustrine sediments deposited at the close of this interstade were TL dated at about 40 ka in Manitoba. If the TL method has systematically underestimated age, glaciolacustrine sedimentation may date to very late stage 5 or stage 4, or the two nonglacial episodes could be reassigned to substage 5e and stage 7. A resurgence of Quebec-derived ice that culminated as late Wisconsinan glaciation first flowed westward across the entire lowland, but was displaced in the north by southward ice flow. Southwestward and, locally, southward ice flow occurred during final ice retreat along a saddle extending across Hudson Bay and linking domes in Keewatin and Quebec.

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Thermolurninescence (TL) analyses of Quaternary nearshore marine sediments from the Hudson Bay Lowland revealed relatively high light emissions and linear growth curves to at least 400 Gy above the natural dose. Initial results indicate that anomalous fading may be circumvented by a preheating at 150°C for 16 h without substantial thermal draining of stable TL components. Both the total bleach method with unfiltered sunlamp light and the partial bleach method with light blocked below 400 nm resulted in overbleaching and thus overestimates of age. A TL age estimate of 5.3 + 0.8 ka on the Holocene control sample, similar to the radiocarbon age, was obtained using the partial bleach method with light blocked below 540 nm. This same method yielded an average TL age estimate of 73 + 10 ka for a Pleistocene unit, which corresponds to the amino-acidbased age estimate of ca. 76 ka. The agreement of the two age estimates is encouraging, since both methods rely on separate assumptions that have not been independently verified.Les analyses de thermoluminescence (TL) de sediments quatemaires du littoral des basses-terres de la baie dlHudson ont fourni des luminescences relativement fortes et des courbes de croissance IinCaires qui excbdent d'au moins 400 Gy la dose naturelle. Les ksultats initiaux kvblent que l'effacement anomal peut Ztre Climint par un pkchauffage i 150°C durant 16 h sans provoquer de decroissance thermale substantielle des composantes stables de TL. Les deux mCthodes, effacement total avec lampe solaire nonfiltrke et effacement partiel avec lumibre bloquCe sous 400 nm, ont produit un sureffacement et par consCquent une sur6valuation de l'ige. Un Lge TL de 5,3 + 0,8 ka pour I'Cchantillon-tCmoin holocbne, similaire 2i 1'Lge radiocarbone, a kt6 obtenu par la methode d'effacement partiel avec lumikre bloquCe sous 540 nm. Cette m&me mCthode a foumi un Lge moyen TL CvaluC i 73 + 10 ka pour une unite plCistocbne, lequel correspond i un Age amino acide estimC 2i 76 ka.L'accord entre ces deux Cvaluations d'ige est prometteur, car les deux mCthodes sont fondees sur des principes diffkrents qui n'ont pas encore fait l'objet d'une verification independante.[Traduit par la revue]Can.

Amino acid studies have identified pre-Holocene non-glacial sediments in the Hudson Lowland which are significantly younger than Bell Sea sediments of the Missinaibi Formation. This younger unit is represented by marine sediments on the Severn and Abitibi rivers. Buried organic material on Beaver River is correlated with the younger Severn and Abitibi river marine sediments based on amino acid evidence. Assuming that Bell Sea sediments are of last interglacial (130-120 ka) age, the younger nonglacial sediments may have been deposited late in 18O stage 5 (80-75 ka). Paleoecologic studies of the Beaver River organics indicate climate at least as warm as present.

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