Supplementary files for: Peneplains and tectonics in North-East Greenland after opening of the North-East Atlantic

• Main Authors: Bonow, Johan M., Japsen, Peter
• Format: Dataset
• Language: unknown
• Published: GEUS Dataverse 2021
• Subjects: Greenland; East Greenland; North East Atlantic
• Online Access: https://dx.doi.org/10.22008/fk2/tmdfp9; https://dataverse01.geus.dk/citation?persistentId=doi:10.22008/FK2/TMDFP9

Elevated plateaus with deeply incised valleys characterise elevated passive continental margins (EPCMs) in all climate zones. These features are, however, a topic of debate regarding when and how the large-scale landscapes formed. We have investigated and mapped the partly glaciated landscape of North-East Greenland (70–78°N). The area consists of crystalline basement and Palaeozoic–Mesozoic rift basins, capped by Palaeogene basalts that erupted during the North-East Atlantic break-up. Our stratigraphic landscape analysis reveals a typical EPCM dominated by two elevated erosion surfaces, extending 200 km east–west and 900 km north–south. A low-relief Upper Planation Surface (UPS; c. 2 km above sea level) cuts across basement and Paleogene basalts, indicating that it was graded to base level defined by the Atlantic Ocean in post-basalt times and subsequently uplifted. The UPS formed prior to the deposition of mid-Miocene lavas that rest on it, south of the study area. In the interior basement terrains, a Lower Planation Surface (LPS) forms fluvial valley benches at c. 1 km above sea level, incised below the UPS. The LPS is thus younger than the UPS, which implies that it formed post mid-Miocene. Towards the coast, the valley benches merge to form a coherent surface that define flat-topped mountains. This shows that the LPS was graded to near sea level and was subsequently uplifted. Hence, both the UPS and the LPS formed as peneplains – erosion surfaces graded to base level. The fluvial valley benches associated with the LPS further indicates that full glacial conditions were only established after uplift of the LPS in the early Pliocene (c. 5 Ma). The uplift of the LPS led to re-exposure of a Mesozoic etch surface. We conclude that episodes of late Neogene tectonic uplift shaped the stepped landscape and elevated topography in North-East Greenland.