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标题：Peneplains and tectonics in North-East Greenland after opening of the North-East Atlantic
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作者：Johan M.Bonow ; Peter Japsen
期刊名称：Geological Survey of Denmark and Greenland Bulletin
印刷版ISSN：1604-8156
出版年度：2021
卷号：45
期号：1
页码：1-35
语种：English
出版社：De Nationale Geologiske Undersoegelser for Danmark og Groenland
摘要：Elevated plateaus with deeply incised valleys characterise elevated, passivecontinental margins (EPCMs) in all climate zones. These features are, however, a topic of debate regarding when and how the large-scale landscapesformed. We have investigated and mapped the partly glaciated landscapeof North-East Greenland (70–78°N). The area consists of crystalline basement and Palaeozoic–Mesozoic rift basins, capped by Palaeogene basaltsthat erupted during the northeast Atlantic break-up. Our stratigraphiclandscape analysis reveals a typical EPCM dominated by two elevated erosion surfaces, extending 200 km east–west and 900 km north–south. Thelow-relief Upper Planation Surface (UPS; c. 2 km above sea level) cuts acrossbasement and Palaeogene basalts, indicating that it was graded to baselevel defined by the Atlantic Ocean in post-basalt times and subsequentlyuplifted. The UPS formed prior to the deposition of mid-Miocene lavas thatrest on it, south of the study area. In the interior basement terrains, theLower Planation Surface (LPS) forms fluvial valley benches at c. 1 km abovesea level, incised below the UPS. The LPS is thus younger than the UPS,which implies that it formed post mid-Miocene. Towards the coast, thevalley benches merge to form a coherent surface that defines flat-toppedmountains. This shows that the LPS was graded to near sea level and wassubsequently uplifted. Hence, both the UPS and the LPS formed as peneplains – erosion surfaces graded to base level. The fluvial valley benchesassociated with the LPS further indicates that full glacial conditions wereonly established after the uplift of the LPS in the early Pliocene (c. 5 Ma). Theuplift of the LPS led to re-exposure of a Mesozoic etch surface. We concludethat episodes of late Neogene tectonic uplift shaped the stepped landscapeand elevated topography in North-East Greenland.
关键词：Cenozoic;denudationchronology;passive margin;stratigraphiclandscape analysis;uplift