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- Bonow, Johan M., et al.
(författare)
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A multi-disciplinary study of Phanerozoic landscape development in West Greenland
- 2007
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Ingår i: Geological Survey of Denmark and Greenland Bulletin: Review of Survey activities 2006. - 1604-8156. ; :13, s. 33-36
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Tidskriftsartikel (refereegranskat)abstract
- The western margin of the Greenland craton has been muchless stable in the Phanerozoic than previously thought. Thisnew insight has come from close integration of independentdata sets: geomorphological analysis of large-scale landscapes,apatite fission track analysis (AFTA), onshore and offshorestratigraphy and analysis of onshore fault and fracture sys -tems. Each data set records specific and unique parts of theevent chronology and is equally important to establish a con-sistent model. A key area for understanding the Mesozoic-Cenozoic landscape evolution and into the present is theuplifted part of the Nuussuaq Basin, where remnants of pla-nation surfaces cut across the Cretaceous to Eocene sedimen-tary and volcanic rocks. Our integrated analysis concludedthat the West Greenland mountains were formed by lateNeogene tectonic uplift (Fig. 1) and also provided newinsight into early Phanerozoic development. To understandour model, we present the different methods and the resultsthat can be deduced from them.
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| 2. |
- Bonow, Johan M., et al.
(författare)
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Cenozoic uplift of Nuussuaq and Disko, West Greenland : elevated erosion surfaces as uplift markers of a passive margin
- 2006
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Ingår i: Geomorphology. - : Elsevier BV. - 0169-555X .- 1872-695X. ; 80:3-4, s. 325-337
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Tidskriftsartikel (refereegranskat)abstract
- Remnants of a high plateau have been identified on Nuussuaq and Disko, central West Greenland. We interpret the plateau as an erosion surface (the summit erosion surface) formed mainly by a fluvial system and graded close to its former base level and subsequently uplifted to its present elevation. It extends over 150 km east–west, being of low relative relief, broken along faults, tilted westwards in the west and eastwards in the east, and having a maximum elevation of ca. 2 km in central Nuussuaq and Disko. The summit erosion surface cuts across Precambrian basement rocks and Paleocene–Eocene lavas, constraining its age to being substantially younger than the last rift event in the Nuussuaq Basin, which took place during the late Maastrichtian and Danian. The geological record shows that the Nuussuaq Basin was subjected to subsidence of several kilometres during Paleocene–Eocene volcanism and was transgressed by the sea later during the Eocene. By comparing with results from apatite fission track analysis and vitrinite reflectance maturity data, it is suggested that formation of the erosion surface was probably triggered by an uplift and erosion event starting between 40 and 30 Ma. Surface formation was completed prior to an uplift event that started between 11 and 10 Ma and caused valley incision. This generation of valleys graded to the new base level and formed a lower erosion surface, at most 1 km below the summit erosion surface, thus indicating the magnitude of its uplift. Formation of this generation of valleys was interrupted by a third uplift event also with a magnitude of 1 km that lifted the landscape to near its present position. Correlation with the fission-track record suggests that this uplift event started between 7 and 2 Ma. Uplift must have been caused initially by tectonism. Isostatic compensation due to erosion and loading and unloading of ice sheets has added to the magnitude of uplift but have not significantly altered the configuration of the surface. It is concluded that the elevations of palaeosurfaces (surfaces not in accordance with present climate or tectonic conditions) on West Greenland's passive margin can be used to define the magnitude and lateral variations of Neogene uplift events. The striking similarity between the landforms in West Greenland and those on many other passive margins is also noted.
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| 3. |
- Bonow, Johan M., et al.
(författare)
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Elevated erosion surfaces in central West Greenland and southern Norway: their significance in integrated studies of passive margin development
- 2007
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Ingår i: Norwegian Journal of Geology. - 0029-196X. ; 87, s. 197-206
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Tidskriftsartikel (refereegranskat)abstract
- Elevated erosion surfaces were used as an independant data set in an integrated study of the landscape development in central West Greenland. The study resulted in a time-constrained model describing multiple episodes of post-rift uplift, erosion and burial on a passive margin. The model is based on full integration of three data sets: analysis of large-scale landforms, apatite fission track analysis (AFTA) of samples from outcrops and deep boreholes, and the geological record. These data are equally important as they record specific an unique parts of the landscape history. The relative chronology obtained from the landform record is constrained by geology, which gives the maximum age of an erosin surface, and AFTA that records the cooling history of the subsurface rock. This combined approach validates the interpretation of erosion surface as having been goverened by different base levels in the past, and shows that erosion surfaces can be used to reconstruct tectonic events. Geomorphological key observations for the landscapes of southern Norway are presented and the similarities with landscapes in central West Greenland emphasised, especially the elevated plateaux and the Mesozoic etch surfaces. This similarity suggests that it may be possible to construct a time-constrained model for the landscape development of southern Norway based on our West Greenland approach.
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