Vertical profile AFT dating in East Greenland

Following the break-up of the Caledonian orogeny, East Greenland experienced protracted rifting from the Devonian until the separation of the Jan Mayen microcontinent in the Late Eocene-Early Oligocene. The present-day continent-ocean boundary is proximal to the coast of East Greenland (Scott, 2000). Therefore, a large volume of East Greenland-derived sediment is likely to now reside in basins of hydrocarbon importance on the Norwegian conjugate margin. The Caledonian basement in East Greenland is locally cut by planation surfaces that are of uncertain age. Post-Caledonian stratigraphy includes several biostratigraphically dated unconformities. Apatite fission track dating constrains the timing of the denudation events that resulted in these surfaces and contributed abundant sediment to Mid Norway. A suite of 69 samples from 14 vertical profiles (up to 1 km thick) was taken from Devonian and Carboniferous strata and Caledonian basement across East Greenland (70-75°N). Following the method of Johnson and Gallagher (2000), data from multiple samples along individual profiles were modelled together to better constrain the cooling history of the rock columns represented by the profiles. Palaeotemperature gradients were combined with thermal conductivity data on individual samples to estimate palaeoheatflow and thereby the thickness of the missing sections. Central AFT ages range from 274 ± 13 Ma to 32 ± 3 Ma. AFT age peaks define four distinct periods of denudation at 205-176 Ma, 156-148 Ma, 107-86 Ma, and 50-20 Ma. The age peaks are spatially correlated with major Caledonian structures, implying reactivation until at least the Neogene. The results highlight the importance of a Mid-Late Permian angular unconformity that is overlain by minimal synrift sediment, and a Mid Jurassic unconformity that is overlain by abundant synrift sediment. AFT ages from two planation surfaces that cut the Caledonian basement indicate rapid denudation during the Mid Permian-Early Triassic and a second phase during the Late Cretaceous-Mid Palaeogene, which may account for the limited Cretaceous strata on Jameson Land. It is likely that other planation surfaces located variously beneath Palaeogene, Triassic, and Mid Jurassic strata also originated during the Mid-Late Permian. The most recent period of denudation followed the emplacement of flood basalts at ~58-56 Ma. The results indicate that the basalts were once widely distributed between the Blosseville Kyst and Hold with Hope. Denuded sediment volume estimates exceed the present-day accommodation space of the East Greenland margin. This provides additional evidence that much East Greenland-derived sediment now resides on the Mid Norway continental margin.