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Lac Guillaume-Delisle Estuary and Nastapoka Sound are two sedimentary basins that recorded the late Quaternary deglaciation on the eastern coast of Hudson Bay. Acoustic profiles reveal an average sediments thickness of 15 m in the estuary and 6 m in the sound. These sediments reach 70 m thick in deep glacial troughs. Within the studied basins, four seismo-stratigraphic units overlying the acoustic basement were recognized. Unit 1 (subaqueous ice-contact and draped glaciomarine deposits associated with the Quebec–Labrador Ice Sector (QLIS) of the Laurentide Ice Sheet (LIS) and the Tyrrell Sea) records the presence of a short ice-marginal stillstand during glacial retreat. Unit 2 (paraglacial and postglacial fluvial-deltaic deposits) and unit 3 (postglacial silty deposits) result from erosion of emerged sediments and redeposition in response to changes in relative sea level (RSL). Finally, unit 4 is composed of deformed deposits associated with a mass wasting event. The stratigraphic sequence and the spatial distribution patterns of deposits show that Lac Guillaume-Delisle is a good model to explain the dynamics of the QLIS margin during and after successive ice stillstands, continuous RSL fall, river discharge (ablation on land), and its final ablation inland. Additionally, seven cores were sampled in the southeast part of the estuary. Geochemical (organic carbon and total nitrogen) and carbon isotopic contents, used as alternative proxy, indicate that the sampled sediments correspond to the postglacial estuarine deposits of unit 3. Allochthonous sources of carbon dominate the supply to the sediments where the environment is regularly flushed by fresh and marine waters.

Eastern Hudson Bay is characterized by falling relative sea level as a result of post-glacial isostatic rebound, which makes the region a natural laboratory for rapid forced regression, where the evolution of deltaic systems and offshore sedimentation patterns can be studied. A multidisciplinary approach involving airphoto analysis, offshore geophysical surveys, sediment coring, and facies and diatom analyses was used in this study of the Nastapoka River delta. The delta has formed as a result of the fluvial erosion of emerged Quaternary sediments but is mainly subaqueous. Offshore, in the prodelta zone, the oldest deposits are glaciomarine, laid down when the ice front of the receding Laurentide ice sheet stood on the Nastapoka hills some 7700–6800 years BP. Lateral equivalents of this glaciomarine unit are presently exposed on land. The shallow-water platform of the delta shows a thin surficial unit of wave-worked sand that overlies fine-grained, deeper water deposits derived from erosion of clay soils in the river catchment a few centuries ago, probably during periods of intense thermokarst activity. As the isostatic uplift continues, the deltaic platform will gradually emerge and be incised by the river channel.