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Johan M Bonow - One of the best experts on this subject based on the ideXlab platform.
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The South Swedish Dome: a key structure for identification of Peneplains and conclusions on Phanerozoic tectonics of an ancient shield
GFF, 2017Co-Authors: Karna Lidmar-bergström, Mats Olvmo, Johan M BonowAbstract:AbstractThe 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 150 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...
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Episodic burial and exhumation of the southern Baltic Shield: Epeirogenic uplifts during and after break-up of Pangaea
Gondwana Research, 2016Co-Authors: Peter Japsen, Johan M Bonow, Paul F Green, Mikael ErlströmAbstract: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 Smaland 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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Stratigraphic Landscape Analysis and geomorphological paradigms: Scandinavia as an example of Phanerozoic uplift and subsidence
Global and Planetary Change, 2013Co-Authors: Karna Lidmar-bergström, Johan M Bonow, Peter JapsenAbstract: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 re ...
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episodic burial and exhumation in ne brazil after opening of the south atlantic
Geological Society of America Bulletin, 2012Co-Authors: Peter Japsen, Johan M Bonow, Paul F Green, Peter Robert Cobbold, Dario Chiossi, Ragnhild Lilletveit, Luciano P Magnavita, Augusto PedreiraAbstract:It is a common assumption that elevated passive continental margins have remained high since rifting and breakup. Here, we show that the Atlantic margin of NE Brazil has undergone a more complex history. Our synthesis of geological data, landscape analysis, and paleothermal and paleoburial data reveals a four-stage history: (1) After Early Cretaceous breakup, the margin under went burial beneath a thick sedimentary cover; (2) uplift episodes in the Campanian and Eocene led to almost complete removal of these deposits; (3) the resulting large-scale, low-relief erosion surface (Peneplain) was deeply weathered and finally reburied at the Oligocene-Miocene transition; and (4) Miocene uplift and erosion produced a new, lower-level Peneplain by incision of the uplifted and re-exposed Paleogene Peneplain. Previous studies have identified aspects of this interpretation, but we have defined the absolute timing and magnitude of discrete events of burial and exhumation that followed Early Cretaceous rifting and Eocene–Oligocene peneplanation. We suggest that a late sedimentary cover protected Paleogene weathering profiles until the present day. The uplift phases in Brazil are synchronous with uplift phases in Africa and the Andes. The Andean phases coincided with rapid convergence on the western margin of South America, and the Campanian uplift coincided with a decline in spreading rate at the Mid-Atlantic Ridge. Consequently, we suggest that both vertical movements and lateral changes in the motion of the plates have a common cause, which is lateral resistance to plate motion.
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Episodic burial and exhumation in NE Brazil after opening of the South Atlantic
Geological Society of America Bulletin, 2012Co-Authors: Peter Japsen, Johan M Bonow, Paul F Green, Peter Robert Cobbold, Dario ChiossiAbstract:It is a common assumption that elevated passive continental margins have remained high since rifting and breakup. Here, we show that the Atlantic margin of NE Brazil has under gone a more complex history. Our synthesis of geological data, landscape analysis, and paleothermal and paleoburial data reveals a four-stage history: (1) After Early Cretaceous breakup, the margin under went burial beneath a thick sedimentary cover; (2) uplift episodes in the Campanian and Eocene led to almost complete removal of these deposits; (3) the resulting large-scale, low-relief erosion surface (Peneplain) was deeply weathered and fi nally reburied at the Oligocene-Miocene transition; and (4) Miocene uplift and erosion produced a new, lowerlevel Peneplain by incision of the uplifted and re-exposed Paleogene Peneplain. Previous studies have identifi ed aspects of this interpretation, but we have defi ned the absolute timing and magnitude of discrete events of burial and exhumation that followed Early Cretaceous rifting and Eocene-Oligocene peneplanation. We suggest that a late sedimentary cover protected Paleogene weathering profi les until the present day. The uplift phases in Brazil are synchronous with uplift phases in Africa and the Andes. The Andean phases coincided with rapid convergence on the western margin of South America, and the Campanian uplift coincided with a decline in spreading rate at the Mid-Atlantic Ridge. Consequently, we suggest that both vertical movements and lateral changes in the motion of the plates have a common cause, which is lateral resistance to plate motion.
Peter Japsen - One of the best experts on this subject based on the ideXlab platform.
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Episodic burial and exhumation of the southern Baltic Shield: Epeirogenic uplifts during and after break-up of Pangaea
Gondwana Research, 2016Co-Authors: Peter Japsen, Johan M Bonow, Paul F Green, Mikael ErlströmAbstract: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 Smaland 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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Stratigraphic Landscape Analysis and geomorphological paradigms: Scandinavia as an example of Phanerozoic uplift and subsidence
Global and Planetary Change, 2013Co-Authors: Karna Lidmar-bergström, Johan M Bonow, Peter JapsenAbstract: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 re ...
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episodic burial and exhumation in ne brazil after opening of the south atlantic
Geological Society of America Bulletin, 2012Co-Authors: Peter Japsen, Johan M Bonow, Paul F Green, Peter Robert Cobbold, Dario Chiossi, Ragnhild Lilletveit, Luciano P Magnavita, Augusto PedreiraAbstract:It is a common assumption that elevated passive continental margins have remained high since rifting and breakup. Here, we show that the Atlantic margin of NE Brazil has undergone a more complex history. Our synthesis of geological data, landscape analysis, and paleothermal and paleoburial data reveals a four-stage history: (1) After Early Cretaceous breakup, the margin under went burial beneath a thick sedimentary cover; (2) uplift episodes in the Campanian and Eocene led to almost complete removal of these deposits; (3) the resulting large-scale, low-relief erosion surface (Peneplain) was deeply weathered and finally reburied at the Oligocene-Miocene transition; and (4) Miocene uplift and erosion produced a new, lower-level Peneplain by incision of the uplifted and re-exposed Paleogene Peneplain. Previous studies have identified aspects of this interpretation, but we have defined the absolute timing and magnitude of discrete events of burial and exhumation that followed Early Cretaceous rifting and Eocene–Oligocene peneplanation. We suggest that a late sedimentary cover protected Paleogene weathering profiles until the present day. The uplift phases in Brazil are synchronous with uplift phases in Africa and the Andes. The Andean phases coincided with rapid convergence on the western margin of South America, and the Campanian uplift coincided with a decline in spreading rate at the Mid-Atlantic Ridge. Consequently, we suggest that both vertical movements and lateral changes in the motion of the plates have a common cause, which is lateral resistance to plate motion.
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Episodic burial and exhumation in NE Brazil after opening of the South Atlantic
Geological Society of America Bulletin, 2012Co-Authors: Peter Japsen, Johan M Bonow, Paul F Green, Peter Robert Cobbold, Dario ChiossiAbstract:It is a common assumption that elevated passive continental margins have remained high since rifting and breakup. Here, we show that the Atlantic margin of NE Brazil has under gone a more complex history. Our synthesis of geological data, landscape analysis, and paleothermal and paleoburial data reveals a four-stage history: (1) After Early Cretaceous breakup, the margin under went burial beneath a thick sedimentary cover; (2) uplift episodes in the Campanian and Eocene led to almost complete removal of these deposits; (3) the resulting large-scale, low-relief erosion surface (Peneplain) was deeply weathered and fi nally reburied at the Oligocene-Miocene transition; and (4) Miocene uplift and erosion produced a new, lowerlevel Peneplain by incision of the uplifted and re-exposed Paleogene Peneplain. Previous studies have identifi ed aspects of this interpretation, but we have defi ned the absolute timing and magnitude of discrete events of burial and exhumation that followed Early Cretaceous rifting and Eocene-Oligocene peneplanation. We suggest that a late sedimentary cover protected Paleogene weathering profi les until the present day. The uplift phases in Brazil are synchronous with uplift phases in Africa and the Andes. The Andean phases coincided with rapid convergence on the western margin of South America, and the Campanian uplift coincided with a decline in spreading rate at the Mid-Atlantic Ridge. Consequently, we suggest that both vertical movements and lateral changes in the motion of the plates have a common cause, which is lateral resistance to plate motion.
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Elevated Peneplains truncating Palaeogene basalts as evidence of post-rift erosion and uplift in East Greenland
2011Co-Authors: Johan M Bonow, Peter Japsen, Paul F GreenAbstract:The landscape along the continental margin in East Greenland is generally characterised by a mainly ice-covered upland at 2 km or more a.s.l. with low relative relief. This upland is in part heavy dissected by deeply incised valleys that cut down to the present sea level. Whereas there is no debate about how to describe the landscape forms of this passive margin, there is a considerable debate whether these uplands represent rift topography or if the topography developed later, unrelated to rift processes. Our landscape analysis, based on mapped surfaces that cut across Palaeogene basalts (c. 55 Ma) and older rocks has shown that the presently uplifted upland (Peneplain) represent an erosional unconformity. Consequently, these surfaces (Peneplains) are post-basalt in age and we suggest that they formed by fluvial erosion towards the base level of the nearby sea during the opening of the North Atlantic. The dissection of the surface by deep valleys demonstrates that the surface was uplifted subsequent to its formation. We therefore find that the topography developed substantially later than during continental break-up. Detailed geomorphological mapping of the Kangerlussuaq area (68 ‐ 70 N) reveal that there are two different erosion surfaces, separated by an escarpment. This stepped landscape is evidence of a history of erosion (to form the Peneplains), followed by uplift (to dissect them). This cycle must have taken place twice to explain the presence of two uplifted surfaces. Tentatively, we suggest correlating the formation of the higher surface with an Oligocene ‐ Lower Miocene unconformity seen in the offshore record. New AFTA results from the Kangerlussuaq area reveal cooling phases that postdate formation of the high-lying erosion surface, with the implication that uplift to the present-day altitudes occurred since the Late Miocene. We conclude that the upland erosion surface represent a period of near sea-level topography, while the incised valleys formed as result of subsequent uplift. AFTA data constrain the timing of these uplift events to the late Cenozoic.
Karna Lidmar-bergström - One of the best experts on this subject based on the ideXlab platform.
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The South Swedish Dome: a key structure for identification of Peneplains and conclusions on Phanerozoic tectonics of an ancient shield
GFF, 2017Co-Authors: Karna Lidmar-bergström, Mats Olvmo, Johan M BonowAbstract:AbstractThe 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 150 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...
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Stratigraphic Landscape Analysis and geomorphological paradigms: Scandinavia as an example of Phanerozoic uplift and subsidence
Global and Planetary Change, 2013Co-Authors: Karna Lidmar-bergström, Johan M Bonow, Peter JapsenAbstract: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 re ...
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Saprolite Remnants as Indicators of Pre‐Glacial Landform Genesis in Southeast Sweden
Geografiska Annaler: Series A Physical Geography, 2005Co-Authors: Mats Olvmo, Karna Lidmar-bergström, Kerstin Ericson, Johan M BonowAbstract: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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Denudation surfaces and tectonics in the southernmost part of the Baltic Shield
Precambrian Research, 1993Co-Authors: Karna Lidmar-bergströmAbstract:Abstract The sub-Cambrian Peneplain is a fundamental landform in the scenery of the southernmost Baltic Shield. It had been shaped during an undefined time interval in the Late Precambrian and became conserved below a cover of Cambrian sedimentary rocks. After exhumation, the Peneplain was subjected to further remodelling. In the study of the Phanerozoic denudational and tectonic history, the sub-Cambrian Peneplain forms an important reference surface. Mesozoic and Tertiary denudation surfaces and sediments dominate in the south and reveal the sequence of events later in the Phanerozoic.
Ronald T Van Balen - One of the best experts on this subject based on the ideXlab platform.
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late miocene uplift of the ne tibetan plateau inferred from basin filling planation and fluvial terraces in the huang shui catchment
Global and Planetary Change, 2012Co-Authors: Xianyan Wang, Jef Vandenberghe, Shaohua Zheng, Ronald T Van BalenAbstract:The geomorphological evolution of the marginal areas of the Tibetan Plateau may provide valuable information for reconstructing the tectonic movements of the region. This study reports on a morpho-tectonic analysis of the Huang Shui catchment (tributary of the Yellow River), in the Northeastern Tibetan Plateau using a digital elevation model and field observations. One prominent bevelled surface, preliminarily interpreted as a Peneplain surface, is recognized at around 2750 m altitude. It corresponds with the top of the relict sedimentary fill of large tectonic basins, and the adjacent summits. After the formation of this Peneplain, a terrace sequence was formed along the Huang Shui river. The transition of Peneplain surface formation to incision was dated as older than 10–6 Ma using the biochronology of micromammalian assemblages from fluvial terraces and the depositional record of the basin fill. The river incision into the former Peneplain is attributed to an important uplift event around 10–17 Ma.
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Late Miocene uplift of the NE Tibetan Plateau inferred from basin filling, planation and fluvial terraces in the Huang Shui catchment
Global and Planetary Change, 2012Co-Authors: Xianyan Wang, Jef Vandenberghe, Shaohua Zheng, Ronald T Van BalenAbstract:The geomorphological evolution of the marginal areas of the Tibetan Plateau may provide valuable information for reconstructing the tectonic movements of the region. This study reports on a morpho-tectonic analysis of the Huang Shui catchment (tributary of the Yellow River), in the Northeastern Tibetan Plateau using a digital elevation model and field observations. One prominent bevelled surface, preliminarily interpreted as a Peneplain surface, is recognized at around 2750. m altitude. It corresponds with the top of the relict sedimentary fill of large tectonic basins, and the adjacent summits. After the formation of this Peneplain, a terrace sequence was formed along the Huang Shui river. The transition of Peneplain surface formation to incision was dated as older than 10-6. Ma using the biochronology of micromammalian assemblages from fluvial terraces and the depositional record of the basin fill. The river incision into the former Peneplain is attributed to an important uplift event around 10-17. Ma. © 2012 Elsevier B.V
Xianyan Wang - One of the best experts on this subject based on the ideXlab platform.
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late miocene uplift of the ne tibetan plateau inferred from basin filling planation and fluvial terraces in the huang shui catchment
Global and Planetary Change, 2012Co-Authors: Xianyan Wang, Jef Vandenberghe, Shaohua Zheng, Ronald T Van BalenAbstract:The geomorphological evolution of the marginal areas of the Tibetan Plateau may provide valuable information for reconstructing the tectonic movements of the region. This study reports on a morpho-tectonic analysis of the Huang Shui catchment (tributary of the Yellow River), in the Northeastern Tibetan Plateau using a digital elevation model and field observations. One prominent bevelled surface, preliminarily interpreted as a Peneplain surface, is recognized at around 2750 m altitude. It corresponds with the top of the relict sedimentary fill of large tectonic basins, and the adjacent summits. After the formation of this Peneplain, a terrace sequence was formed along the Huang Shui river. The transition of Peneplain surface formation to incision was dated as older than 10–6 Ma using the biochronology of micromammalian assemblages from fluvial terraces and the depositional record of the basin fill. The river incision into the former Peneplain is attributed to an important uplift event around 10–17 Ma.
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Late Miocene uplift of the NE Tibetan Plateau inferred from basin filling, planation and fluvial terraces in the Huang Shui catchment
Global and Planetary Change, 2012Co-Authors: Xianyan Wang, Jef Vandenberghe, Shaohua Zheng, Ronald T Van BalenAbstract:The geomorphological evolution of the marginal areas of the Tibetan Plateau may provide valuable information for reconstructing the tectonic movements of the region. This study reports on a morpho-tectonic analysis of the Huang Shui catchment (tributary of the Yellow River), in the Northeastern Tibetan Plateau using a digital elevation model and field observations. One prominent bevelled surface, preliminarily interpreted as a Peneplain surface, is recognized at around 2750. m altitude. It corresponds with the top of the relict sedimentary fill of large tectonic basins, and the adjacent summits. After the formation of this Peneplain, a terrace sequence was formed along the Huang Shui river. The transition of Peneplain surface formation to incision was dated as older than 10-6. Ma using the biochronology of micromammalian assemblages from fluvial terraces and the depositional record of the basin fill. The river incision into the former Peneplain is attributed to an important uplift event around 10-17. Ma. © 2012 Elsevier B.V