Abstract The crustal seismic velocity model (based on receiver functions) of Ellesmere Island and the structural geological cross-section of Ellesmere Island, both documented and discussed elsewhere in this volume, are here integrated into a crustal-scale transect crossing all the main tectonic domains. The velocity model satisfies much of the observed gravity field, but implies minor modifications with potentially important implications for characterizing the lower crust over the transect. The crust of the Pearya Terrane includes a high-velocity and high-density lower crustal body, suggested to represent a mafic underplate linked to the emplacement of the High Arctic Large Igneous Province. A similar body also lies directly beneath the Hazen Plateau, but this is more likely to be inherited from earlier tectonic stages than to be linked to the High Arctic Large Igneous Province. A large-scale basement-involving thrust, possibly linked to a deep detachment of Ellesmerian age, lies immediately south of the Pearya Terrane and forms the northern backdrop to a crustal-scale pop-up structure that accommodates Eurekan-aged shortening in northern Ellesmere Island. The thickest crust and deepest Moho along the transect are below the Central Ellesmerian fold belt, where the Moho is flexured downwards to the north to a depth of about 48 km beneath the load of the structurally thickened supracrustal strata of the fold belt.

Chicxulub is the only known impact structure on Earth with a fully preserved peak ring, and it forms an important natural laboratory for the study of large impact structures and understanding of large-scale cratering on Earth and other planets. Seismic data collected in 1996 and 2005 reveal detailed images of the uppermost crater in the central basin at Chicxulub. Seismic reflection profiles show a reflective layer ~1 km beneath the apparent crater floor, topped by upwardly concave reflectors interpreted as saucer-shaped sills. The upper part of this reflective layer is coincident with a thin high-velocity layer identified by analyzing refractions on the 6 km seismic streamer data. The high-velocity layer is almost horizontal and appears to be contained within the peak ring structure. We argue that this reflective layer is the predicted coherent melt sheet formed during impact, and it may be comparable with the unit known as the Sudbury Igneous Complex at the Sudbury impact structure. The Sudbury Igneous Complex, interpreted as a differentiated impact melt sheet, appears to have a similar scale and geometry, and an uppermost lithological sequence consisting of a high velocity layer at the top and a velocity inversion beneath. This comparison suggests that the Chicxulub impact structure also contains a coherent differentiated melt sheet.