Volcanic rocks from the Davis Strait were studied to elucidate the tectonomagmatic processes during rifting and the start of seafloor spreading, and the formation of the Ungava transform zone between Canada and Greenland. The rocks are from the wells Hekja O-71, Gjoa G-37, Nukik-2 and Hellefisk-1, and from dredges on the northern Davis Strait High. Ages range from Danian to Thanetian (dinocyst palynozones P2 to P5, 62.5–57.2 Ma). The rocks are predominantly basaltic, but include picrites on the Davis Strait High. Calculated mantle potential temperatures for the Davis Strait High are c. 1500°C, suggesting the volume of magma generated was large; this is consistent with geophysical evidence for magmatic underplating in the region. The rare earth element patterns indicate residual mantle lithologies of spinel peridotite and, together with Sr–Nd isotopes, indicate melting beneath regionally extensive, depleted asthenosphere beneath a lithosphere of thickness similar to, or thinner than, beneath Baffin Island and distinctly thinner than beneath West Greenland. Some sites include basalts with more enriched compositions. Depleted and enriched basalts in the Hellefisk well show contemporaneous melting of depleted and enriched mantle components in the asthenosphere. The Hekja and Davis Strait High basalts and picrites have unique, ultradepleted compositions with (La/Sm)N < 0.5, (Tb/Lu)N < 1 and Nb/Zr = 0.013–0.027. We interpret these compositions as a product of the melting regime within the Ungava transform zone, where the melting column would be steep-sided in cross-section and not triangular as expected at normal spreading ridges. Magmatism along the transform stopped when the tectonic regime changed from transtension to transpression during earliest Eocene time.

Strata exposed near Tabbowa Tank, Tabbowa Basin, western Sri Lanka have yielded the first representatives of the distinctive Permian Glossopteris flora from that country. The assemblage includes gymnosperm foliage attributable to Glossopteris raniganjensis, roots referable to Vertebraria australis, seeds assigned to Samaropsis sp., sphenophyte axes (Paracalamites australis) and foliage (Sphenophyllum emarginatum), and fern foliage (Dichotomopteris lindleyi). This small macroflora is interpreted to be of probable Lopingian (late Permian) age based on comparisons with the fossil floras of Peninsula India. Several Glossopteris leaves in the assemblage bear evidence of terrestrial arthropod interactions including hole feeding, margin feeding, possible lamina skeletonization, piercing-and-sucking damage and oviposition scarring. The newly identified onshore Permian strata necessitate re-evaluation of current models explaining the evolution of the adjacent offshore Mannar Basin. Previously considered to have begun subsiding and accumulating sediment during Jurassic time, we propose that the Mannar Basin may have initiated as part of a pan-Gondwanan extensional phase during late Palaeozoic – Triassic time. We interpret the basal, as yet unsampled, seismically reflective strata of this basin to be probable organic-rich continental strata of Lopingian age, equivalent to those recorded in the Tabbowa Basin, and similar to the Permian coal-bearing successions in the rift basins of eastern India and Antarctica. Such continental fossiliferous strata are particularly significant as potential source rocks for recently identified natural gas resources in the Mannar Basin.

We develop a two-dimensional thermo-mechanical numerical model in which the formation of oceanic crust and serpentinite due to the hydration of the uprising mantle peridotite has been implemented, with the aim of discussing the behaviour of the lithosphere of the Alps and Northern Apennines during the transition from continental rifting to ocean spreading of the Alpine Tethys. The predictions of the model are compared with natural data related to the Permian–Triassic high-temperature – low-pressure (HT-LP) metamorphism affecting the continental lithosphere and data from the Jurassic P–T evolution of the oceanic lithosphere from the Alps and the Northern Apennines. Our analysis indicates that a thinned continental crust, an ocean–continent transition zone and an oceanic lithosphere characterize the final structure of the system in a poor magma rift pre-Alpine configuration. We also find that mantle serpentinization starts before crustal break-up and that denudation occurs before ocean spreading. The mantle denudation starts several million years before the gabbros/basalt formation, generating an ocean–continent transition zone from the passive continental margin to the oceanic lithosphere of size 160–280 km. The comparative analysis shows that the extension of a hot and weak lithosphere, which promotes the development of hyperextended Alpine margins, better agrees with the natural data. Finally, our comparative analysis supports the hypothesis that the lithospheric extension preceding the opening of the Alpine Tethys did not start in a stable continental lithosphere, but developed by recycling part of the old Variscan collisional suture.