| 1. |
- 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. |
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| 3. |
- Japsen, P., et al.
(författare)
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Burial and exhumation history of the Labrador-Newfoundland margin and implications for hydrocarbon exploration
- 2016
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Ingår i: Arctic Technology Conference 2016. - : Offshore Technology Conference. - 9781510835801
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Konferensbidrag (refereegranskat)abstract
- The stratigraphic record along the continental margin of Labrador and Newfoundland provides ample evidence for vertical movements both prior to and after break-up. In the offshore domain, several major hiatuses punctuate the stratigraphic record. Along Labrador and the Grand Banks, Lower Cretaceous rocks rest on Paleozoic rocks or Precambrian basement in parts of the area. Onshore Labrador, the presence of a Cretaceous outlier on Precambrian basement adds to the evidence of one or more events of exhumation that has removed pre-Cretaceous sediments on a regional scale. Over much of the Labrador shelf, Miocene deposits are absent, and we show evidence based on vitrinite reflectance and sonic data that indicate that Miocene deposits of significant thickness may have been present prior to uplift and exhumation. We also present results from a pilot study comprising apatite fission-track analysis (AFTA) data that reveals a Phanerozic history involving a series of burial and exhumation episodes. The pilot study is a forerunner for a study of the onshore and offshore domain with three components. (1) A thermochronological study based on samples from outcrops and from onshore and offshore boreholes. (2) A stratigraphic landform analysis of the onshore study area based on mapping of denudation surfaces that will provide evidence of vertical motion using cross-cutting relationships between the denudation surfaces and stratigraphic constraints. (3) An integrated interpretation of the geological, geomorphological and thermochronological data to provide a coherent model of the timing and magnitude of the vertical movements along the margin both prior to and after break-up. Failure to account for greater depths of burial prior to exhumation may lead to serious underestimation of the petroleum resource maturity and to erroneous estimates of the timing of hydrocarbon generation. Uplift and exhumation may also lead to changes in migration routes and affect hydrocarbons present in reservoirs. Insights into the uplift history of a margin are important for understanding the sourceto- sink system of sediment input into offshore basins.
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| 4. |
- Solgaard, A. M., et al.
(författare)
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Mountain building and the initiation of the greenland ice sheet
- 2013
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Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier BV. - 0031-0182 .- 1872-616X. ; 392, s. 161-176
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Tidskriftsartikel (refereegranskat)abstract
- The effects of a new hypothesis about mountain building in Greenland on ice sheet initiation are investigated using an ice sheet model in combination with a climate model. According to this hypothesis, low-relief landscapes near sea level characterised Greenland in Miocene times until two phases of km-scale uplift in the late Miocene and in the latest Miocene-Pliocene (beginning at 10 and ~. 5. Ma, respectively) initiated the formation of the present-day mountains. The topography of Greenland, prior to these uplift events is reconstructed from the present-day, isostatically compensated bedrock by mapping the two main steps in the landscape that resulted from the two uplift phases. Ice sheet initiation is studied using the topography before uplift and after each phase of uplift by applying different forcing conditions relevant for the late Cenozoic, which was characterised by long-term cooling superimposed by cold and warm excursions. The modelling results show that no ice initiates in the case of the low-lying and almost flat topography prior to the uplifts. However, the results demonstrate a significant ice sheet growth in response to the orographically induced increase in precipitation and the cooling of surface temperatures accompanying the uplift. Large amounts of ice are able to form after the first uplift event, but the ice sheet is sensitive to changes in climate. The results show that the second phase of uplift facilitates ice sheet build-up further and increases the stability of the ice sheet by providing anchoring points which are not available to the same extent in the lower topographies. However, the results also reveal a Föhn effect that inhibits ice sheet expansion into the interior Greenland and thus shifts the threshold of formation of inland ice towards colder temperatures. Under conditions that are colder than the present, the ice can overcome the Föhn effect, flow into the interior and form a coherent ice sheet. The results thus indicate that the Greenland Ice Sheet of today is a relict formed under colder conditions. The modelling results are consistent with the observed climatic variability superimposed on the general cooling trend in the late Cenozoic: e.g., ice rafted debris in late Miocene deposits off southeast Greenland and the mid-Pliocene Warmth. The late Cenozoic mountain building in Greenland augments the effects of the climatic deterioration leading to the Northern Hemisphere glaciations, and without the second phase of uplift, the Greenland Ice Sheet would have been more sensitive to the changes in climate over the past millions of years.
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| 5. |
- 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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| 6. |
- Bonow, Johan M., et al.
(författare)
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Editorial
- 2020
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Ingår i: Geografiska Annaler: Series A, Physical Geography. - : Informa UK Limited. - 0435-3676 .- 1468-0459. ; 102:4, s. 331-332
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Another year has passed, and indeed it has been turbulent for many of us. Despite the hardship in many aspects of life, our Associated Editors have made tremendous effort and thus, Geografiska Annaler: Series A, Physical Geography have successfully published volume 102 with 4 issues, including a special issue on different aspects of dendrochronology in Asia.
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| 7. |
- Bonow, Johan M., et al.
(författare)
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Editorial
- 2020
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Ingår i: Geografiska Annaler. Series A, Physical Geography. - : Informa UK Limited. - 0435-3676 .- 1468-0459. ; 102:4, s. 331-332
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 8. |
- 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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| 9. |
- Bonow, Johan M., et al.
(författare)
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High-level landscapes along the margin of southern East Greenland-A record of tectonic uplift and incision after breakup in the NE Atlantic
- 2014
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Ingår i: Global and Planetary Change. - : Elsevier BV. - 0921-8181 .- 1872-6364. ; 116, s. 10-29
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Tidskriftsartikel (refereegranskat)abstract
- Elevated plateaux and deeply incised valleys characterise the large-scale landscapes along the East Greenland margin as in many elevated, passive continental margins around the world. The absence of syn- or post-rift rocks in, for example, the mountains of Norway, hampers the assessment of the age of these landscapes and of the present-day elevation. The mountains of southern East Greenland (68-71°N), however, expose thick basalts that were extruded onto a largely horizontal lava plain near sea level during breakup of the NE Atlantic at the Paleocene-Eocene transition. We take advantage of these favourable geological conditions to investigate the uplift history after continental breakup. In particular, it is clear that present-day elevations of these basalts up to 3.7. km above sea level (a.s.l.) were reached after breakup. We have mapped regional erosion surfaces and integrated the information about the landscape with the stratigraphic record (i.e. stratigraphic landscape analysis). The analysis led to the following relative denudation chronology for southern East Greenland: At breakup, the margin subsided and underwent km-scale burial. Around the Eocene-Oligocene transition, the first phase of uplift, tilting and subsequent erosion led to the formation of an extensive, low-relief erosion surface (the Upper Planation Surface, UPS) that was graded towards the base level of the adjacent ocean before the eruption of Miocene lavas onto that surface. A second uplift that most likely occurred after the Miocene produced a new erosion surface (the Lower Planation Surface, LPS) by incision below the UPS. Finally, a third event in the late Cenozoic lifted the UPS and the LPS to their present elevations of up to 3 and 2. km. a.s.l., respectively and shaped the present-day valleys and fjords by incision of rivers and glaciers below the LPS. The general picture of landscape development is highly similar to West Greenland and the common characteristics between the stepped landscapes in East Greenland and those on the conjugate margin in Scandinavia lead us to conclude that the mountains of Norway also formed after the North Atlantic breakup.
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| 10. |
- Bonow, Johan M., 1969-
(författare)
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Palaeosurfaces and palaeovalleys on North Atlantic previously glaciated passive margins : reference forms for conclusions on uplift and erosion
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Palaeosurfaces and palaeovalleys are landforms under destruction in the present climate and/or tectonic regime, and thus mainly reflect processes not active today. Uplifted palaeosurfaces exist along the formerly glaciated passive continental margins around the North Atlantic. Large-scale landform development has recently become a matter of interest also for geologists and geophysicists as the result of an increasing awareness that a thorough knowledge of uplift, erosion, deposition and development of landforms along continental margins can only be accomplished by combined studies using independent data from different scientific disciplines. The present study focuses on one of these above data sets; the landform record. Two uplifted areas, southern Norway and central West Greenland, were selected for landform analysis of high resolution digital elevation models, aerial photographs, relation between landforms in basement and cover rocks, offshore seismic lines and X-ray diffraction of clay minerals in saprolites. In southern Norway, analysis of slope angles within the range of pediment slopes was combined with analysis of main valley incision. This resulted in the identification of three main planation surfaces in a stepped sequence formed along the main valleys as a consequence of tectonic uplift events, maybe in the Palaeogene, (in total >1000 m). Two phases of late uplift (~900 m), probably in the Neogene, triggered incision of deep fluvial valleys, later reshaped by glacial erosion (up to 300 m). In central West Greenland palaeosurfaces were analysed in relation to cover rock of different age. An exhumed etch surface, characterized by a typical hilly relief, occurs on Disko and south of Disko Bugt, and are by the presence of cover rocks shown to be sub-Palaeocene in origin. To the north, a post-Eocene erosion surface on Nuussuaq, cuts across basement and basalt and was probably formed close to sea level. Uplift in two phases elevated this surface up to 2000 m above present sea level and broke it in differently tilted tectonic blocks. South of Disko Bugt, a planation surface, of probably the same age as the one on Nuussuaq, cuts the tilted etch surface, and also cuts across different bedrock types. The planation surface rises towards the south and splits in two surfaces, separated in altitude up to 300 m, within two highly elevated areas. The separation into two surfaces indicate two uplift events: A first minor event of a few hundred metres in the uplift centres resulted in incision of the lower planation surface. This event was later followed by a major uplift event amounting to >1000 m. Correlation with the offshore sedimentary record suggests that both uplift events occurred in the Neogene. The erosion pattern calculated from one reconstructed palaeosurface to present topography shows large spatial variations. This is interpreted as an effect of differential bedrock resistance and local variations of glacial erosion (400–1300 m in low areas). The results presented in this thesis demonstrate the usefulness of palaeosurfaces and palaeovalleys as tools for deciphering magnitude of uplift events, establishing relative event chronologies and for calculation of erosion. Moreover integrated studies of palaeolandforms, offshore geology and thermal chronologies, are shown to be invaluable when used to solve the spatial and temporal patterns of uplift, erosion and deposition.
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| 11. |
- Bonow, Johan M., et al.
(författare)
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Palaeosurfaces in central West Greenland as reference for identification of tectonic movements and estimations of glacial erosion
- 2006
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Ingår i: Global and Planetary Change. - : Elsevier BV. - 0921-8181 .- 1872-6364. ; 50:3-4, s. 161-183
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Tidskriftsartikel (refereegranskat)abstract
- Landform analysis of basement rocks has been undertaken with the aid of digital elevation data, aerial photographs and field observations in central West Greenland (69°15′N–66°00′N). Palaeosurfaces have been identified, dated relatively to each other, used to quantify uplift and fault movements and also used to estimate differential erosion. Two types of palaeosurfaces were mapped across the Precambrian basement: a surface at low elevation with distinct hills (hilly relief), and two planation surfaces formed across different types of basement rocks. The hilly relief surface emerges as an inclined surface from Cretaceous cover rocks in Disko Bugt and is interpreted as a stripped late Mesozoic etch surface. This surface is cut off towards the south by a less inclined planation surface, which is younger and thus of Cenozoic age. It is similar to the post-Eocene (Miocene?) planation surfaces identified on Disko and Nuussuaq in other studies. The planation surface splits in two southwards towards high areas around Nordre Isortoq and Sukkertoppen Ice Cap. The upper planation surface forms near-summit areas of tectonic blocks dipping in different directions and with different tilts. The uplift centres define the crests of two mega blocks, separated by the ‘Sisimiut Line’ which coincides with the Precambrian Ikertôq thrust zone. A partially developed lower planation surface indicates a first uplift of maximum 500 m followed by a second uplift of maximum 1000 m. We infer that these uplift events occurred during the late Neogene based on correlation with similar surfaces on Nuussuaq and the timing of exhumational events estimated from apatite fission track analyses of samples from a deep borehole on Nuussuaq (reported elsewhere). The difference between a reconstruction of the upper planation surface across the entire area and the present topography was used as an estimate of erosion of basement rock since the formation of the upper planation surface. The erosion is unevenly distributed and varies from almost none on the well-preserved planation surfaces to 800–1300 m along valleys, and even more in the fjords. Erosion is less within areas of gneiss in granulite facies, than in areas of gneiss in amphibolite facies.
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| 12. |
- Bonow, Johan M., et al.
(författare)
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Peneplains and tectonics in North-East Greenland after opening of the North-East Atlantic
- 2021
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Ingår i: GEUS Bulletin. - : Geological Survey of Denmark and Greenland. - 2597-2154 .- 2597-2162. ; 45:1
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Tidskriftsartikel (refereegranskat)abstract
- 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 degrees N). The area consists of crystalline basement and Palaeozoic-Mesozoic rift basins, capped by Palaeogene basalts that erupted during the northeast 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. The low-relief Upper Planation Surface (UPS; c. 2 km above sea level) cuts across basement and Palaeogene 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, the 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 defines 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 pene-plains - erosion surfaces graded to base level. The fluvial valley benches associated with the LPS further indicates that full glacial conditions were only established after the 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.
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| 13. |
- Bonow, Johan M.
(författare)
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Re-exposed basement landforms in the Disko region, West Greenland : disregarded data for estimation of glacial erosion and uplift modelling
- 2005
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Ingår i: Geomorphology. - : Elsevier BV. - 0169-555X .- 1872-695X. ; 74:1-4, s. 106-127
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Tidskriftsartikel (refereegranskat)abstract
- Classifications of large-scale landscapes in Greenland have traditionally been based on type and intensity of glacial erosion, with the general idea that present landforms are mainly the result of erosion from ice sheets and glaciers. However, on southern Disko and in areas offshore in Disko Bugt, a basement surface has preserved remnants of weathered gneiss and pre-Paleocene landforms, recently exhumed from Paleocene basalt. Isolated hills and lineaments have been mapped in a digital terrain model and aerial photographs. Offshore have hills been mapped from seismic lines. The medium size bedrock forms on southern Disko as tors, clefts and roche moutonées have been studied in the field. Remnant saprolites were inventoried, sampled and analysed according to grain size and clay mineralogy. The basement surface retains saprolites up to 8 m thick in close relation to the cover rocks. The landforms in the basement rocks belong essentially to an etched surface only slightly remodelled by glacial erosion and, below the highest coastline, also by wave action. The outline of hills is governed by two lineament directions, ENE–WSW representing the schistocity of the gneiss and NW–SE fracture zones. These structures are thus interpreted to have been exploited by the deep weathering while the frequent N–S lineaments have not and thus might be younger. Main ice-flow has been from the NE and has resulted in plucking of SW facing lee sides, however the resulting bedrock forms are mainly controlled by structures and orientation of joints. The identification of re-exposed sub-Paleocene etch forms on Disko and the hills of similar size offshore, forming a hilly relief, have implications for identification of a hilly relief south of Disko Bugt, its relation to younger planation surfaces as well as for conclusions of uplift events.
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| 14. |
- Green, Paul F., et al.
(författare)
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Post-breakup burial and exhumation of passive continental margins : Seven propositions to inform geodynamic models
- 2018
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Ingår i: Gondwana Research. - : Elsevier BV. - 1342-937X .- 1878-0571. ; 53:January, s. 58-81
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Tidskriftsartikel (refereegranskat)abstract
- Despite many years of study, the processes involved in the post-breakup development of passive margins remain poorly understood. Integration of apatite fission track analysis (AFTA) and stratigraphic landscape analysis (SLA) at a number of margins has provided new insights into the development of elevated passive continental margins (EPCMs). In particular, by integrating evidence from the preserved rock record and landscape with information on the deposition and erosional removal of rock units which are no longer present (“missing section”) these studies have highlighted the importance of episodic positive and negative vertical km-scale crustal movements. Based on these studies we present seven propositions regarding the formation of EPCMs and the nature of the controlling processes, viz:1: EPCMs are not the inevitable consequence of rifting and breakup2: Elevated topography at present-day EPCMs developed long after breakup3: Similar EPCM landscapes at different margins suggest similar controlling processes4: EPCMs have undergone episodic km-scale burial and exhumation rather than slow monotonic denudation, both before rifting and after breakup5: Post-breakup km-scale exhumation at continental margins is not restricted to presently elevated onshore regions6: Post-breakup km-scale burial and exhumation have affected presently low lying margins as well as EPCMs7: Exhumation events show a broad level of synchroneity over continents and across oceans and correlate with plate boundary events and changes in plate motions.These propositions imply that positive and negative vertical motions at passive margins are controlled by plate-scale processes. Another key conclusion is that present-day elevation alone provides no clue to the earlier history of a margin.Many of the key aspects of these propositions are absent from current geodynamic models of passive margin development. Understanding the processes that control vertical movements at passive continental margins requires development of realistic geodynamic models that honour these propositions.
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| 15. |
- Green, Paul F., et al.
(författare)
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Post-breakup burial and exhumation of the southern margin of Africa
- 2017
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Ingår i: Basin Research. - : Wiley-Blackwell. - 0950-091X .- 1365-2117. ; 29:1, s. 96-127
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Tidskriftsartikel (refereegranskat)abstract
- Despite many years of study, the processes involved in the development of the continental margin of southern Africa and the distinctive topography of the hinterland remain poorly understood. Previous thermochronological studies carried out within a monotonic cooling framework have failed to take into account constraints provided by Mesozoic sedimentary basins along the southern margin. We report apatite fission track analysis and vitrinite reflectance data in outcrop samples from the Late Jurassic to Early Cretaceous sedimentary fill of the Oudtshoorn, Gamtoos and Algoa Basins (Uitenhage Group), as well as isolated sedimentary remnants further west, plus underlying Paleozoic rocks (Cape Supergroup) and Permian-Triassic sandstones from the Karoo Supergroup around the Great Escarpment. Results define a series of major regional cooling episodes. Latest Triassic to Early Jurassic cooling which began between 205 and 180 Ma is seen dominantly in basement flanks to the Algoa and Gamtoos Basins. This episode may have affected a wider region but in most places any effects have been overprinted by later events. The effects of Early Cretaceous (beginning between 145 and 130 Ma) and Early to mid-Cretaceous (120-100 Ma) cooling are both delimited by major structures, while Late Cretaceous (85-75 Ma) cooling appears to have affected the whole region. These cooling events are all interpreted as dominantly reflecting exhumation. Higher Late Cretaceous paleotemperatures in samples from the core of the Swartberg Range, coupled with evidence for localised Cenozoic cooling, are interpreted as representing Cenozoic differential exhumation of the mountain range. Late Cretaceous paleotemperatures between 60 degrees C and 90 degrees C in outcropping Uitenhage Group sediments from the Oudtshoorn, Gamtoos and Algoa Basins require burial by between 1.2 and 2.2 km prior to Late Cretaceous exhumation. Because these sediments lie in depositional contact with underlying Paleozoic rocks in many places, relatively uniform Late Cretaceous paleotemperatures across most of the region, in samples of both basin fill and underlying basement, suggest the whole region may have been buried prior to Late Cretaceous exhumation. Cenozoic cooling (beginning between 30 and 20 Ma) is focussed mainly in mountainous regions and is interpreted as representing denudation which produced the modern-day relief. Features such as the Great Escarpment are not related to continental break up, as is often supposed, but are much younger (post-30 Ma). This history of post-breakup burial and subsequent episodic exhumation is very different from conventional ideas of passive margin evolution, and requires a radical re-think of models for development of continental margins.
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| 16. |
- Green, P. F., et al.
(författare)
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Stratigraphic landscape analysis, thermochronology and the episodic development of elevated, passive continental margins
- 2013
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Ingår i: Geological Survey of Denmark and Greenland Bulletin. - : Geological Survey of Denmark and Greenland. - 1811-4598 .- 1604-8156 .- 1904-4666. ; :30, s. 4-150
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Tidskriftsartikel (refereegranskat)abstract
- The continental margin of West Greenland is similar in many respects to other elevated, passive continental margins (EPCMs) around the world. These margins are characterised by extensive regions of low relief at elevations of 1-2 kilometres above sea level sloping gently inland, with a much steeper, oceanward decline, often termed a 'Great Escarpment', terminating at a coastal plain. Recent studies, based on integration of geological, geomorphological and thermochronological evidence, have shown that the high topography of West Greenland was formed by differential uplift and dissection of an Oligo-Miocene peneplain since the late Miocene, many millions of years after continental break-up between Greenland and North America. In contrast, many studies of other EPCMs have proposed a different style of development in which the high plateaux and the steep, oceanward decline are regarded as a direct result of rifting and continental separation. Some studies assume that the elevated regions have remained high since break-up, with the high topography continuously renewed by isostasy. Others identify the elevated plains as remnants of pre-rift landscapes. Key to understanding the development of the West Greenland margin is a new approach to the study of landforms, stratigraphic landscape analysis, in which the low-relief, high-elevation plateaux at EPCMs are interpreted as uplifted peneplains: low-relief surfaces of large extent, cutting across bedrock of different age and resistance, and originally graded to sea level. Identification of different generations of peneplain (re-exposed and epigene) from regional mapping, combined with geological constraints and thermochronology, allows definition of the evolution leading to the formation of the modern-day topography. This approach is founded particularly on results from the South Swedish Dome, which document former sea levels as base levels for the formation of peneplains. These results support the view that peneplains grade towards base level, and that in the absence of other options (e.g. widespread resistant lithologies), the most likely base level is sea level. This is particularly so at continental margins due to their proximity to the adjacent ocean. Studies in which EPCMs are interpreted as related to rifting or break-up commonly favour histories involving continuous denudation of margins following rifting, and interpretation of thermochronology data in terms of monotonic cooling histories. However, in several regions, including southern Africa, south-east Australia and eastern Brazil, geological constraints demonstrate that such scenarios are inappropriate, and an episodic development involving post-breakup subsidence and burial followed later by uplift and denudation is more realistic. Such development is also indicated by the presence in sedimentary basins adjacent to many EPCMs of major erosional unconformities within the post-breakup sedimentary section which correlate with onshore denudation episodes. The nature of the processes responsible is not yet understood, but it seems likely that plate-scale forces are required in order to explain the regional extent of the effects involved. New geodynamic models are required to explain the episodic development of EPCMs, accommodating post-breakup subsidence and burial as well as subsequent uplift and denudation, long after break-up which created the characteristic, modern-day EPCM landscapes. © 2013 Pushpa Publishing House, Allahabad, India.
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| 17. |
- Green, Paul F., et al.
(författare)
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The post-Caledonian thermo-tectonic evolution of Fennoscandia
- 2022
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Ingår i: Gondwana Research. - : Elsevier. - 1342-937X .- 1878-0571. ; 107, s. 201-234
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Tidskriftsartikel (refereegranskat)abstract
- The evolution of Fennoscandia following the early Devonian collapse of the Caledonian mountains is a matter of debate, due largely to the scarcity of post-Caledonian cover rocks. The preserved geological record therefore provides only partial documentation of the geological evolution. A more complete understanding is obtained by also considering evidence of rocks that were formerly present but have since been removed. We report apatite fission track data and associated thermal history constraints in 331 samples of Precambrian basement, younger sedimentary cover, Paleozoic and Mesozoic igneous rocks from outcrops and boreholes (up to 6 km depth) across Fennoscandia, which define thirteen phases of cooling (each representing kilometre-scale exhumation) over the last 1100 Myr. Key post-Caledonian episodes began in the intervals 311–307 Ma (late Carboniferous), 245–244 Ma (Middle Triassic), 170–167 Ma (Middle Jurassic), 102–92 Ma (mid-Cretaceous) and 23–21 Ma (early Miocene). These episodes, varying in magnitude, are recognised across Fennoscandia, and their effects are documented in the stratigraphic record and as prominent regional peneplains. The results define a history involving repeated episodes of regional burial and exhumation. Major offsets in Mesozoic paleotemperatures over short distances define kilometre-scale differential vertical displacements, emphasising the tectonic nature of the history. Results from Finland record the same events recognised in Norway and Sweden (though less pronounced), and are not consistent with long-term cratonic stability. The lack of preserved Phanerozoic sedimentary cover in Finland is interpreted to be due to complete removal during multiple episodes of denudation. In southern Norway and Sweden, early Miocene exhumation led to creation of a peneplain, which in Pliocene times was uplifted and dissected, producing the modern landscape. Post-Caledonian exhumation episodes defined here are broadly synchronous with similar events in Greenland, the British Isles and North America. Far-field transmission of plate-tectonic stress and/or mantle processes may explain the vertical movements described here.
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| 18. |
- Green, Paul F., et al.
(författare)
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Thermal history solutions from thermochronology must be governed by geological relationships : A comment on Jess et al. (2019)
- 2020
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Ingår i: Geomorphology. - : Elsevier BV. - 0169-555X .- 1872-695X. ; 360
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The recent study of the basement margin to the Nuussuaq Basin, West Greenland, by Jess et al. (2019) illustrates the problems introduced by extracting thermal histories from thermochronology data without taking into account the constraints provided by geological evidence. Their interpretations are incompatible with numerous aspects of the geology of the region, and as a result their conclusions are not valid.
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| 19. |
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| 20. |
- Japsen, Peter, et al.
(författare)
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Episodes of post-Caledonian burial and exhumation in Greenland and Fennoscandia
- 2024
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Ingår i: Earth-Science Reviews. - : Elsevier. - 0012-8252 .- 1872-6828. ; 248
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Forskningsöversikt (refereegranskat)abstract
- The forces that drive uplift of the continental lithosphere outside collision zones are a topic of considerable dispute. Here we review our studies of the post-Caledonian development of Greenland, Fennoscandia and adjacent regions based on apatite fission-track analysis (AFTA) and stratigraphic landscape analysis (SLA). AFTA defines episodes of cooling (exhumation) while SLA provides a relative denudation chronology. Integrating these results with the geological record can produce a coherent history of both positive and negative vertical crustal movements. Our studies reveal a history involving multiple regional episodes of burial and exhumation, leading to a) formation of peneplains graded to sea level, b) formation of distinct unconformities in sedimentary successions, and c) deposition of thick siliciclastic wedges in basins adjacent to the uplifting landmasses. Exhumation episodes which began in late Carboniferous, Middle Triassic and Middle Jurassic affected the entire study area (with some time variations). These episodes correlate with rifting episodes during the break-up of Pangea, attributed to accumulation of mantle heat beneath the supercontinent. Mid-Cretaceous exhumation affected wide parts of the study area and coincided with the inversion of the Sorgenfrei-Tornquist Zone in southern Scandinavia. This may be linked with changes in the relative motion between the European and African plates in the earliest Late Cretaceous. Maastrichtian exhumation affected wide areas around Greenland, probably reflecting doming above the rising Iceland Plume upon its arrival in the upper mantle, prior to the mid-Paleocene impact at the base of the lithosphere. The mid-Paleocene impact of the plume under Greenland contributed to the onset of sea-floor spreading west of Greenland. This represents the onset of the Eurekan Orogeny which affected wide areas around northern Greenland. End-Eocene exhumation interrupted the Eocene regime of subsidence following earliest Eocene break-up in the North-East Atlantic, coincided with a minimum rate of sea-floor spreading in the North-East Atlantic, possibly related to changes in the motion of Africa relative to Europe. Early Miocene exhumation affected only Fennoscandia and is attributed to intraplate stress transmitted across the Eurasian plate. Late Miocene uplift initiated the formation of Greenland's coastal mountains but did not affect Fennoscandia. This episode correlates with changes in the absolute motion of the North American Plate. Pliocene uplift – amplified by the isostatic response to erosion – raised all margins in the region with maximum elevations reached in coastal areas close to Iceland. This suggests support from the Iceland Plume due to outward-flowing asthenosphere extending beneath the conjugate margins of the North-East Atlantic. We use these observations to argue that these episodes reflect both lithospheric and sub-lithospheric forces, related either to changes in the motion of the plates caused by far-field stress induced by events outside the study area, or driven by movements within the mantle directly within the study area. Geodynamic modelling is required to obtain further insights into the properties of the Earth that allow recurrent episodes of uplift and subsidence of the continents.
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| 21. |
- Japsen, Peter, et al.
(författare)
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Episodic burial and exhumation in North-East Greenland before and after opening of the North-East Atlantic
- 2021
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Ingår i: Geus Bulletin. - : GEOLOGICAL SURVEY DENMARK & GREENLAND. - 2597-2154 .- 2597-2162. ; 45:2
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Tidskriftsartikel (refereegranskat)abstract
- The geology of North-East Greenland (70-78 degrees N) exposes unique evidence of the basin development between the Devonian collapse of the Caledonian Orogen and the extrusion of volcanics at the Paleocene-Eocene transition during break-up of the North-East Atlantic. Here we pay special attention to unconformities in the stratigraphic record - do they represent periods of stability and non-deposition or periods of subsidence and accumulation of rocks followed by episodes of uplift and erosion? To answer that and other questions, we used apatite fission-track analysis and vitrinite reflectance data together with stratigraphic landscape analysis and observations from the stratigraphic record to study the thermo-tectonic history of North-East Greenland. Our analysis reveals eight regional stages of post-Caledonian development: (1) Late Carboniferous uplift and erosion led to formation of a sub-Permian peneplain covered by coarse siliciclastic deposits. (2) Middle Triassic exhumation led to removal of a thick cover including a considerable thickness of upper Carboniferous - Middle Triassic rocks and produced thick siliciclastic deposits in the rift system. (3) Denudation at the transition between the Early and Middle Jurassic affected most of the study area outside the Jameson Land Basin and produced a weathered surface above which Middle-Upper Jurassic sediments accumulated. (4) Earliest Cretaceous uplift and erosion along the rifted margin and further inland accompanied the Mesozoic rift climax and produced coarse-grained sedimentary infill of the rift basins. (5) Mid-Cretaceous uplift and erosion initiated removal of Cretaceous post-rift sediments that had accumulated above the Mesozoic rifts and their hinterland, leading to cooling of Mesozoic sediments from maximum palaeotemperatures. (6) End-Eocene uplift was accompanied by faulting and intrusion of magmatic bodies and resulted in extensive mass wasting on the East Greenland shelf. This event initiated the removal of a thick post-rift succession that had accumulated after break-up and produced a peneplain near sea level, the Upper Planation Surface. (7) Late Miocene uplift and erosion, evidenced by massive progradation on the shelf, resulted in the formation of the Lower Planation Surface by incision below the uplifted Upper Planation Surface. (8) Early Pliocene uplift raised the Upper and the Lower Planation Surfaces to their present elevations of about 2 and 1 km above sea level, respectively, and initiated the formation of the present-day landscape through fluvial and glacial erosion. Additional cooling episodes of more local extent, related to igneous activity in the early Eocene and in the early Miocene, primarily affected parts of northern Jameson Land. The three earliest episodes had a profound impact beyond Greenland and accompanied the fragmentation of Pangaea. Younger episodes were controlled by plate-tectonic processes, possibly including dynamic support from the Iceland Plume. Our results emphasise that gaps in the stratigraphic record often reflect episodes of kilometre-scale vertical movements that may result from both lithospheric and sub-lithospheric processes.
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| 22. |
- Japsen, Peter, et al.
(författare)
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Episodic burial and exhumation of the southern Baltic Shield : Epeirogenic uplifts during and after break-up of Pangaea
- 2016
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Ingår i: Gondwana Research. - : Elsevier BV. - 1342-937X .- 1878-0571. ; 35, s. 357-377
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Tidskriftsartikel (refereegranskat)abstract
- Abstract Cratons are conventionally assumed to be areas of long-term stability. However, whereas Precambrian basement crops out across most of the Baltic Shield, Palaeozoic and Mesozoic sediments rest on basement in southern Sweden, and thus testify to a complex history of exhumation and burial. Our synthesis of published stratigraphic landscape analysis and new apatite fission-track analysis data reveals a history involving five steps after formation of the extremely flat, Sub-Cambrian Peneplain. (1) Cambrian to Lower Triassic rocks accumulated on the peneplain, interrupted by late Carboniferous uplift and exhumation. (2) Middle Triassic uplift removed the Palaeozoic cover along the south-western margin of the shield, leading to formation of a Triassic peneplain with a predominantly flat relief followed by deposition of Upper Triassic to Lower Jurassic rocks. (3) Uplift that began during the Middle Jurassic to earliest Cretaceous caused denudation leading to deep weathering that shaped an undulating, hilly relief that was buried below Upper Cretaceous to Oligocene sediments. (4) Early Miocene uplift and erosion produced the South Småland Peneplain with scattered hills. (5) Early Pliocene uplift raised the Miocene peneplain to its present elevation leading to reexposure of the sub-Cretaceous hilly relief near the coast. Our results thus provide constraints on the magnitude and timing of episodes of deposition and removal of significant volumes of Phanerozoic rocks across the southern portion of the Baltic Shield. Late Carboniferous, Middle Triassic and mid-Jurassic events of uplift and exhumation affected wide areas beyond the Baltic Shield, and we interpret them as epeirogenic uplifts accompanying fragmentation of Pangaea, caused by accumulation of mantle heat beneath the supercontinent. Early Miocene uplift affected north-west Europe but not East Greenland, and thus likely resulted from compressive stresses from an orogeny on the Eurasian plate. Early Pliocene uplift related to changes in mantle convection and plate motion affected wide areas beyond North-East Atlantic margins.
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| 23. |
- Japsen, Peter, et al.
(författare)
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Formation, uplift and dissection of planation surfaces at passive continental margins - a new approach
- 2009
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Ingår i: Earth Surface Processes and Landforms. - : John wiley & sons Ltd. - 0197-9337 .- 1096-9837. ; 34:5, s. 683-699
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Tidskriftsartikel (refereegranskat)abstract
- The usefulness of large-scale, low-relief, high-level landscapes as markers of uplift events has become a subject of disagreement among geomorphologists. We argue that the formation of low-relief surfaces over areas of large extent and cutting across bedrock of different age and resistance must have been guided by distinct base levels. In the absence of other options the most likely base level is sea level. We have analysed West Greenland landscapes in a recent study by combining the cooling history from apatite fission-track analysis (AFTA) data with the denudation history from landscape analysis and the stratigraphic record. An important difference between our approach and that of classical geomorphology is that we now have the ability to document when thick sections of rocks have been deposited and then removed. The present-day high-level plateau in West Greenland is the remnant of a planation surface that was formed by denudation that lasted 1 km of cover was removed after maximum burial at the Eocene–Oligocene transition. Here we present additional AFTA data to show that the planation surface is the end-product of Cenozoic denudation even in basement areas and argue that Phanerozoic sediments – most likely of Cretaceous–Palaeogene age – must have been present prior to denudation. The planation surface was offset by reactivated faults and uplifted to present-day altitudes of up to 2 km. The uplift occurred in two late Neogene phases that caused incision of valleys below the planation surface and their subsequent uplift. We therefore find that the elevated and deeply dissected plateau is evidence of episodic post-rift uplift that took place millions of years after cessation of sea-floor spreading west of Greenland. We suggest that other margins with similar morphology may also be characterized by episodic post-rift uplift unrelated to the processes of rifting and continental separation, rather than being permanently uplifted since the time of rifting, as is commonly assumed.
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| 24. |
- Japsen, P., et al.
(författare)
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From volcanic plains to glaciated peaks : BURIAL, uplift and exhumation history of southern East Greenland after opening of the NE Atlantic
- 2014
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Ingår i: Global and Planetary Change. - : Elsevier BV. - 0921-8181 .- 1872-6364. ; 116, s. 91-114
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Tidskriftsartikel (refereegranskat)abstract
- In southern East Greenland (68-70°N), voluminous flood basalts erupted onto a largely horizontal lava plain near sea level at the Paleocene-Eocene transition when sea-floor spreading started in the NE Atlantic. Based on synthesis of geological observations, stratigraphic landform analysis and apatite fission-track analysis data in 90 rock samples, we show how three regional phases of uplift and exhumation subsequently shaped the present-day margin and controlled the discontinuous history of the Greenland ice sheet. A late Eocene phase of uplift led to formation of a regional erosion surface near sea level (the Upper Planation Surface, UPS). Uplift of the UPS in the late Miocene led to formation of the Lower Planation Surface (LPS) by incision below the uplifted UPS, and a Pliocene phase led to incision of valleys and fjords below the uplifted LPS, leaving mountain peaks reaching 3.7. km above sea level. Local uplift affected the Kangerlussuaq area (~. 68°N) during early Eocene emplacement of the Kangerlussuaq Intrusion and during late Oligocene block movements, that may be related to the detachment of the Jan Mayen microcontinent from Greenland, while middle Miocene thermal activity, coeval with lava eruptions, heated rocks along a prominent fault within the early Cretaceous to Paleocene Kangerlussuaq Basin. The three regional uplift phases are synchronous with phases in West Greenland, overlap in time with similar events in North America and Europe and also correlate with changes in plate motion. The much higher elevation of East Greenland compared to West Greenland suggests support in the east from the Iceland plume. These observations indicate a connection between mantle convection, changes in plate motion and vertical movements along passive continental margins.
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| 25. |
- Japsen, P., et al.
(författare)
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Investigation of the burial and exhumation history of East Greenland based on apatite-fission track analysis, stratigraphic landform analysis and the geological record
- 2015
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Ingår i: OTC Arctic Technology Conference 2015. - : Offshore Technology Conference. - 9781510803916 ; , s. 454-461
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Konferensbidrag (refereegranskat)abstract
- Cenozoic uplift and erosion have an important impact on petroleum systems along East Greenland. We have undertaken a regional study of the thermo-tectonic development of the East Greenland margin (68-75°N) based on apatite fission-track analysis (AFTA) data and analysis of the large-scale landscapes. Our results reveal a long history of post-Palaeozoic burial and exhumation across the region. Following breakup at the Paleocene-Eocene transition, the margin underwent kilometerscale burial beneath a cover of Eocene basalts and sediments. Subsequently, three regional phases of uplift and exhumation subsequently shaped the present-day margin. A late Eocene phase of uplift led to formation of a regional erosion surface near sea level (the Upper Planation Surface, UPS). Uplift of the UPS in the late Miocene led to formation of the Lower Planation Surface (LPS) by incision below the uplifted UPS, and a Pliocene phase led to incision of valleys and fjords below the uplifted LPS, leaving mountain peaks reaching 3.7 km above sea level. Preliminary AFTA results from northern East Greenland indicate that the Eurekan Orogeny played a significant role in the thermotectonic development there, but it is difficult to distinguish between heating related to burial followed by erosion and heating caused by high heat flow or hydrothermal activity. A future study of northern East Greenland margin should thus investigate the development during the right-lateral, strike-slip tectonics that moved the Barents Sea relative to Greenland. The results are of importance in assessing the hydrocarbon prospectivity in the offshore basins because uplift and denudation of continental margins can have profound effects on the hydrocarbon system, not only through negative impact of processes but also by providing reservoir clastics to the offshore basin and by changing migration routes. Our results indicate that remnants of oil accumulations on Traill 0 are associated, not only with the deeper burial at the time of hydrocarbon formation, but also with locally increased heat flow from late Eocene intrusions. Further afield, in areas where heat flow was not enhanced, any source rocks present would have remained at lower maturity levels at the end of the Eocene.
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| 26. |
- Japsen, Peter, et al.
(författare)
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Mountains of southernmost Norway : uplifted Miocene peneplains and re-exposed Mesozoic surfaces
- 2018
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Ingår i: Journal of the Geological Society. - : GEOLOGICAL SOC PUBL HOUSE. - 0016-7649 .- 2041-479X. ; 175:5, s. 721-741
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Tidskriftsartikel (refereegranskat)abstract
- The origin of the Norwegian mountains (the Scandes) is a key controversy in modern geoscience. Are they remnants from the Caledonian Orogeny, modified shoulders of late Mesozoic rifts, or are they evidence of Neogene uplifts? Our synthesis of geological data, landscape analysis and new thermochronological data from Norway south of c. 60 degrees N, combined with previously published data from southern Sweden, reveals a four-stage history: (1) Middle Triassic and Middle Jurassic exhumation produced a weathered basement surface with a hilly relief; (2) after late Mesozoic rifting, Upper Jurassic-Oligocene sediments accumulated across most of the area; (3) early Miocene uplift and erosion to the base level of the adjacent ocean led to formation of a peneplain that extended across sedimentary basins and Caledonian rocks; the subhorizontal Hardangervidda plateau represents this peneplain; (4) early Pliocene uplift raised Hardangervidda to its present elevation of c. 1200 m above sea-level and led to re-exposure of the tilted, Mesozoic surface at lower elevations. The Southern Scandes are thus, like other elevated passive continental margins around the world, the product of post-breakup uplift. Identification of the mechanisms driving these uplifts awaits geodynamic modelling constrained by observations such as those presented in this study.
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| 27. |
- Lidmar-Bergström, Karna, et al.
(författare)
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Stratigraphic Landscape Analysis and geomorphological paradigms : Scandinavia as an example of Phanerozoic uplift and subsidence
- 2013
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Ingår i: Global and Planetary Change. - : Elsevier BV. - 0921-8181 .- 1872-6364. ; 100, s. 153-171
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Forskningsöversikt (refereegranskat)abstract
- Stratigraphic Landscape Analysis (SLA) is based on a) the relationship between peneplains (low-relief denudation surfaces) in basement and their cover rocks of different age, b) the crosscutting relationships between such re-exposed peneplains and never covered (epigene) peneplains, and c) the occurrence of valleys incised below peneplains. Previous studies based on detailed SLA of the South Swedish Dome (SSD) have identified two major re-exposed peneplains, the flat sub-Cambrian peneplain and the sub-Jurassic/Cretaceous peneplain with undulating hilly relief. Both surfaces developed dose to former sea levels, were subsequently transgressed, and buried below sedimentary covers. The preservation of these peneplains documents that uplift of the land surface was followed by subsidence. Crosscutting relationships between these re-exposed and tilted peneplains and a third peneplain, an epigene and horizontal plain with residual hills, demonstrate that the latter is younger and thus of post-Cretaceous age. Three topographic highs characterize Scandinavia, the Northern Scandes (NS), the Southern Scandes (SS), and the low SSD. We show that the three relief types of the SSD can be identified across Scandinavia and that they demonstrate phases of uplift/denudation and subsidence/burial of Scandinavia during the Phanerozoic. In particular, we show that the epigene peneplains of the NS, the SS and the SSD are Cenozoic erosion surfaces and this also leads us to identify three major Cenozoic morphotectonic units. A result of our studies is that the paradigm of continuous uplift of steady state landscapes cannot be assumed as a universal model of landform evolution.
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| 28. |
- Lidmar-Bergström, Karna, et al.
(författare)
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The South Swedish Dome : a key structure for identification of peneplains and conclusions on Phanerozoic tectonics of an ancient shield
- 2017
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Ingår i: GFF. - : Informa UK Limited. - 1103-5897 .- 2000-0863. ; 139:4, s. 244-259
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Tidskriftsartikel (refereegranskat)abstract
- The relationships between different denudation surfaces/peneplains formed across crystalline basement rocks give valuable information to the tectonic development of ancient shields. The denudation surfaces can be identified by the aid of their landforms, tilt and remnant weathering mantles in relation to cover rocks. Three types of denudation surfaces are identified across south Sweden (1) a tilted flat plain, (2) a tilted hilly surface with relative relief below 150Â m and (3) stepped horizontal plains with residual hills. All three types of denudation surfaces are peneplains, denudation surfaces graded to specific base levels. The re-exposed parts of the inclined flat sub-Cambrian peneplain (SCP) extend as a landscape feature from below cover rocks in the north and east and reaches up on the highest summits of the South Swedish Uplands. The SCP (the exact unconformity) is encountered again below Cambrian covers outside the west coast. Thus south Sweden is a geological dome, the South Swedish Dome (SSD), in relation to the Cambrian cover. The southern and western low flanks of the exposed part of the dome are instead characterized by a hilly peneplain, the inclined sub-Cretaceous denudation surface, with remnants of thick, kaolinitic, clayey saprolites. This sub-Cretaceous peneplain is cut off at a distinct level in the south and west by the almost horizontal South Småland Peneplain, a never covered, epigene, peneplain. The uplift history of the SSD aids to the understanding on the development of late Tertiary drainage systems of the Baltic Basin by the Eridano River.
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| 29. |
- Linderholm, Hans W., et al.
(författare)
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Editorial
- 2021
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Ingår i: Geografiska Annaler. Series A, Physical Geography. - : Taylor & Francis. - 0435-3676 .- 1468-0459. ; 103:4, s. 303-304
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 30. |
- Olvmo, Mats, 1956, et al.
(författare)
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Saprolite remnants as indicators of pre-glacial landform genesis in southeast Sweden
- 2005
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Ingår i: Geografiska Annaler Series a-Physical Geography. - : Informa UK Limited. - 0435-3676 .- 1468-0459. ; 87A:3, s. 447-460
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Tidskriftsartikel (refereegranskat)abstract
- Twenty-six sites with remnants of gravelly saprolites (grus) have been located in southeast Sweden. Joint block hills (castle kopjes) and steep rock walls with weathered joints as well as rounded boulders are documented to have an origin in deep weathering and subsequent stripping of saprolites. The saprolite remnants and landforms result from the fragmentation of the re-exposed sub-Cambrian peneplain along fracture systems. Only shallow saprolites occur on the elevated intact parts of the sub-Cambrian peneplain, while saprolites up to 20 m thick are encountered in areas where the sub-Cambrian peneplain is fractured and dissected. Neogene uplift with reactivation of the weathering system is thought to be the main cause of saprolite formation. Deep weathering is thus judged to have been the major agent of landform formation in the study area, while glacial and glaciofluvial erosion has contributed mainly by stripping saprolites, detaching corestones, and plucking joint blocks along weathered joints.
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