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Axel Heiberg Island (Arctic Archipelago, northern Nunavut, Canada) contains the thickest Mesozoic section in Sverdrup Basin (11 km). The ca. 370-km-long island is second only to Iran in its concentration of exposed evaporite diapirs. Forty-six diapirs of Carboniferous evaporites and associated minibasins are excellently exposed on the island. Regional anticlines, which formed during Paleogene Eurekan orogeny, trend roughly north on a regular ca. 20-km wavelength and probably detach on autochthonous Carboniferous Otto Fiord Formation evaporites comprising halite overlain by thick anhydrite. In contrast, a 60-km-wide area, known as the wall-and-basin structure ( WABS) province, has bimodal fold trends and irregular (<10 km) wavelengths. Here, crooked, narrow diapirs of superficially gypsified anhydrite crop out in tight anticline cores, which are separated by wider synclinal minibasins. We interpret the WABS province to detach on a shallow, partly exposed canopy of coalesced allochthonous evaporite sheets. Surrounding strata record a salt-tectonic history spanning the Late Triassic (Norian) to the Paleogene. Stratigraphic thinning against diapirs and spectacular angular unconformities indicate mild regional shortening in which diapiric roof strata were bulged up and flanking strata steepened. This bulging culminated in the Hauterivian, when diapiric evaporites broke out and coalesced to form a canopy. As the inferred canopy was buried, it yielded second-generation diapirs, which rose between minibasins subsiding into the canopy. Consistent high level emplacement suggests that all exposed diapirs inside the WABS area rose from the canopy. In contrast, diapirs along the WABS margins were sourced in autochthonous salt as first-generation diapirs. Apart from the large diapir-flanking unconformities, Jurassic-Cretaceous depositional evidence of salt tectonics also includes submarine debris flows and boulder conglomerates shed from at least three emergent diapirs. Extreme local relief, tectonic slide blocks, steep talus fans and subaerial debris flows suggest that many WABS diapirs continue to rise today. The Axel Heiberg canopy is one of only three known exposed evaporite canopies, each inferred or known at a different structural level: above the canopy (Axel Heiberg), through the canopy (Great Kavir) and beneath a possible canopy (Sivas). [ABSTRACT FROM AUTHOR]

ABSTRACT The geometry of estuarine and/or incised-valley basins and their protected character compared with open sea basins are favourable for the preservation of sedimentary successions. The Lower St. Lawrence Estuary Basin (LSLEB, eastern Canada) is characterized by a thick (>400 m in certain areas) Quaternary succession. High- and very high-resolution seismic reflection data, multibeam bathymetry coverage completed by core and chronostratigraphic data as well as a 3-D seismic stratigraphic model are used to document the geometrical relationships between the bedrock and the Quaternary units of the LSLEB. The bedrock geometry of LSLEB is characterized by two large troughs that are interpreted as resulting mainly from repeated (?) periods of glacial overdeepening of a pre-Quaternary drainage system. However, other mechanisms with complex feedback effects such as differential glacio-isostatic uplift, erosion, sedimentary supply, and subsidence may have contributed to the formation of bedrock troughs. The two large bedrock troughs are mostly filled by ∼200 m thick Wisconsinan (Marine Isotopic Stages 2-4) and possibly older sediments. Overlying units recorded the retreat of the Laurentian Ice Sheet during the Late Wisconsinan (Marine Isotopic Stage 2) and estuarine conditions during the Holocene. The strong correlation existing between the bedrock topography and the thickness of the Quaternary succession is indicative of the effectiveness of the LSLEB as a sediment trap. [ABSTRACT FROM AUTHOR]