In geomorphology and geology, a peneplain is a low-reliefplain formed by protracted erosion. This is the definition in the broadest of terms, albeit with frequency the usage of peneplain is meant to imply the representation of a near-final (or penultimate) stage of fluvialerosion during times of extended tectonic stability.[1] Peneplains are sometimes associated with the cycle of erosion theory of William Morris Davis,[1][A] but Davis and other workers have also used the term in a purely descriptive manner without any theory or particular genesis attached.[3]
Aerial view of the almost flat and drowned peneplain at Belcher Islands, Hudson Bay, Canada, cutting across numerous geologic folds.Sketch of a hypothetical peneplain formation after an orogeny.
The existence of some peneplains, and peneplanation as a process in nature, is not without controversy, due to a lack of contemporary examples and uncertainty in identifying relic examples.[1][4] By some definitions, peneplains grade down to a base level represented by sea level, yet in other definitions such a condition is ignored.[4] Geomorphologist Karna Lidmar-Bergström and co-workers consider the base level criterion crucial and above the precise mechanism of formation of peneplains, including this way some pediplains among peneplains.[5][6]
While peneplains are usually assumed to form near sea level it has also been posited that peneplains can form at height if extensive sedimentation raises the local base level sufficiently[7] or if river networks are continuously obstructed by tectonic deformation.[8] The peneplains of the Pyrenees and Tibetan Plateau may exemplify these two cases respectively.[7][8]
A common misconception about peneplains is that they ought to be so plain they are featureless.[4] In fact, some peneplains may be hilly as they reflect irregular deep weathering, forming a plain grading to a base level only at a grand-scale.[5][B]
At the grand-scale peneplains are characterized by appearing to be sculpted in rock with disregard of rock structure and lithology, but in detail, their shape is structurally controlled, for example, drainage divides in peneplain can follow more resistant rock.[9] In the view of Davis large streams do became insensitive to lithology and structure, which they were not during the valley phase of erosion cycle. This may explain the existence of superimposed streams.[9]
Canisteo River Valley from Pinnacle State Park, New York. The distant peaks at the same elevation represent the remnants of a peneplain that was uplifted to form the Allegheny Plateau, which is a dissected plateau in southwestern New York. In this area, the sharp relief that is seen on some of the Allegheny Plateau has been rounded by glaciation.
There are various terms for landforms that are either alternatives to classical peneplains, a sub-set of peneplains or partially overlap with the term. The last is the case of planation surfaces that may be peneplains or not, while some peneplains are not planation surfaces.[5]
In their 2013 work Green, Lidmar-Bergström and co-workers provide the following classification scheme for peneplains:[5]
Rhodes Fairbridge and Charles Finkl argue that peneplains are often of mixed origin (polygenetic), as they may have been shaped by etchplanation during periods of humid climate and pediplanation during periods of arid and semi-arid climate. The long time spans under which some peneplains evolve ensures varied climatic influences.[3] The same authors do also list marine abrasion[C] and glacial erosion among processes that can contribute in shaping peneplains.[3]
In addition, epigene peneplains can be distinguished from exhumed peneplains.[5] Epigene peneplains are those that have never been buried or covered by sedimentary rock.[5][11] Exhumed peneplains are those that are re-exposed after having been buried in sediments.[5]
The oldest identifiable peneplain in a region is known as a primary peneplain.[3][D] An example of a primary peneplain is the Sub-Cambrian peneplain in southern Sweden.[12]
Pediplains
The peneplain concept is often juxtaposed to that of pediplain. However authors like Karna Lidmar-Bergström classify pediplains as a type of peneplain.[5] On the contrary Lester Charles King held them as incompatible landforms arguing that peneplains do not exist. King wrote:[13]
A peneplain in the Davisian sense, resulting from slope reduction and downwearing, does not exist in nature. It should be redefined as "an imaginary landform."
According to King the difference between pediplains and Davis’ peneplains is in the history and processes behind their formation, and less so in the final shape. A difference in form that may be present is that of residual hills, which in Davis’ peneplains are to have gentle slopes, while in pediplains they ought to have the same steepness as the slopes in the early stages of erosion leading to pediplanation.[13] Given that the coalesced pediments of the pediplains form a series of very gentle concave slopes, a difference with Davis' understanding of peneplains may lie in the fact that his idealized peneplains had very gentle convex slopes instead. However, Davis' views on the subject are not fully clear.[13] Contrary to this view Rhodes Fairbridge and Charles Finkl argue that the precise mechanism of formation (pediplanation, etc.) is irrelevant and that the term peneplain has been used and can be used in a purely descriptive manner. Further, alternation of processes with varying climate, relative sea level and biota make old surfaces unlikely to be of a single origin.[3]
Preservation and destruction of peneplains
The Hardangervidda plateau in southern Norway is a peneplain formed in the Miocene epoch and then uplifted to its present altitude of 1200 m a.s.l.[14]
Peneplains that are detached from their base level are identified by either hosting an accumulation of sediments that buries it or by being in an uplifted position. Burial preserves the peneplain. Any exposed peneplain detached from its baselevel can be considered a paleosurface or paleoplain.[5][15] Uplift of a peneplain commonly results in renewed erosion. As Davis put it in 1885:[16]
"the decrepit surface must wait either until extinguished by submergence below the sea, or regenerated by elevation into a new cycle of life"
Uplifted peneplains can be preserved as fossil landforms in conditions of extreme aridity or under non-eroding cold-based glacier ice.[5] Erosion of peneplains by glaciers in shield regions is limited.[17][18] In the Fennoscandian Shield average glacier erosion during the Quaternary amounts to tens of meters, albeit this was not evenly distributed.[18] For glacier erosion to be effective in shields a long "preparation period" of weathering under non-glacial conditions may be a requirement.[17]
^The term was coined around 1900 by William Morris Davis who described it as follows: Given sufficient time for the action of denuding forces on a mass of land standing fixed with reference to a constant base-level, and it must be worn down so low and so smooth, that it would fully deserve the name of a plain. But it is very unusual for a mass of land to maintain a fixed position as long as is here assumed.... I have therefore elsewhere suggested that an old region, nearly base-levelled, should be called an almost-plain; that is a peneplain.[1][2]
^Akin to what in German scientific literature is known as a Primärrumpf.[3]
References
^ abcd Phillips, Jonathan D (2002). "Erosion, isostatic response, and the missing peneplains". Geomorphology. 45 (3–4): 225–241. Bibcode:2002Geomo..45..225P. doi:10.1016/S0169-555X(01)00156-8.
^Chorley, R.J. (1973). The History and Study of Landforms or The Development of Geomorphology. Vol. Two: The Life and Work of William Morris Davis, Methuen.
^ abLidmar-Bergström, Karna; Bonow, Johan M.; Japsen, Peter (2013). "Stratigraphic Landscape Analysis and geomorphological paradigms: Scandinavia as an example of Phanerozoic uplift and subsidence". Global and Planetary Change. 100: 153–171. Bibcode:2013GPC...100..153L. doi:10.1016/j.gloplacha.2012.10.015.
^ abBabault, Julien; Van Den Driessche, Jean; Bonnet, Stephanie; Castelltort, Sébastien; Crave, Alain (2005). "Origin of the highly elevated Pyrenean peneplain". Tectonics. 24 (2): n/a. Bibcode:2005Tecto..24.2010B. doi:10.1029/2004TC001697.
^ abYang, Rong; Willett, Sean D.; Goren, Liran (2015). "In situ low-relief landscape formation as a result of river network disruption". Nature. 520 (7548): 526–530. Bibcode:2015Natur.520..526Y. doi:10.1038/nature14354. PMID 25903633. S2CID 1017663.
^ abPalmquist, Robert C. (1980) [1975]. "The Compatibility of Structure, Lithology and Geomorphic Models". In Melhorn, W.N.; Flemal, R.C. (eds.). Theories of Landform Development (2nd ed.). Allen & Unwin. pp. 145–168.
^Miller, A.A. (1955). "The origin of the South Ireland Peneplane". Irish Geography. 3 (2): 79–86. doi:10.1080/00750775509555491.
^Twidale, C.R. (1985). "Old landsurfaces and their implications for models of landscape evolution". Revue de Géomorphologie Dynamique. 34: 131–147.
^Lidmar-Bergström (1988). "Denudation surfaces of a shield area in southern Sweden". Geografiska Annaler. 70 A (4): 337–350. doi:10.1080/04353676.1988.11880265.
^ abcKing, L.C. (1953). "Canons of landscape evolution". Geological Society of America Bulletin. 64 (7): 721–752. Bibcode:1953GSAB...64..721K. doi:10.1130/0016-7606(1953)64[721:cole]2.0.co;2.
^Japsen, Peter; Green, Paul F.; Chalmers, James A.; Bonow, Johan M. (17 May 2018). "Mountains of southernmost Norway: uplifted Miocene peneplains and re-exposed Mesozoic surfaces". Journal of the Geological Society. 175 (5): 721–741. Bibcode:2018JGSoc.175..721J. doi:10.1144/jgs2017-157. S2CID 134575021.
^Bonow, Johan M.; Lidmar-Bergström, Karna; Japsen, Peter (2006). "Palaeosurfaces in central West Greenland as reference for identification of tectonic movements and estimation of erosion". Global and Planetary Change. 50 (3–4): 161–183. Bibcode:2006GPC....50..161B. doi:10.1016/j.gloplacha.2005.12.011.
^Orme, Anthony R. (2007). "The Rise and Fall of the Davisian Cycle of Erosion: Prelude, Fugue, Coda, and Sequel". Physical Geography. 28 (6): 474–506. doi:10.2747/0272-3646.28.6.474. S2CID 128907423.
^ abcFairbridge, Rhodes W. (1988). "Cyclical patterns of exposure, weathering and burial of cratonic surfaces, with some examples from North America and Australia". Geografiska Annaler. 70 A (4): 277–283. doi:10.1080/04353676.1988.11880257.
peneplain, geomorphology, geology, peneplain, relief, plain, formed, protracted, erosion, this, definition, broadest, terms, albeit, with, frequency, usage, peneplain, meant, imply, representation, near, final, penultimate, stage, fluvial, erosion, during, tim. In geomorphology and geology a peneplain is a low relief plain formed by protracted erosion This is the definition in the broadest of terms albeit with frequency the usage of peneplain is meant to imply the representation of a near final or penultimate stage of fluvial erosion during times of extended tectonic stability 1 Peneplains are sometimes associated with the cycle of erosion theory of William Morris Davis 1 A but Davis and other workers have also used the term in a purely descriptive manner without any theory or particular genesis attached 3 Aerial view of the almost flat and drowned peneplain at Belcher Islands Hudson Bay Canada cutting across numerous geologic folds Sketch of a hypothetical peneplain formation after an orogeny The existence of some peneplains and peneplanation as a process in nature is not without controversy due to a lack of contemporary examples and uncertainty in identifying relic examples 1 4 By some definitions peneplains grade down to a base level represented by sea level yet in other definitions such a condition is ignored 4 Geomorphologist Karna Lidmar Bergstrom and co workers consider the base level criterion crucial and above the precise mechanism of formation of peneplains including this way some pediplains among peneplains 5 6 While peneplains are usually assumed to form near sea level it has also been posited that peneplains can form at height if extensive sedimentation raises the local base level sufficiently 7 or if river networks are continuously obstructed by tectonic deformation 8 The peneplains of the Pyrenees and Tibetan Plateau may exemplify these two cases respectively 7 8 A common misconception about peneplains is that they ought to be so plain they are featureless 4 In fact some peneplains may be hilly as they reflect irregular deep weathering forming a plain grading to a base level only at a grand scale 5 B At the grand scale peneplains are characterized by appearing to be sculpted in rock with disregard of rock structure and lithology but in detail their shape is structurally controlled for example drainage divides in peneplain can follow more resistant rock 9 In the view of Davis large streams do became insensitive to lithology and structure which they were not during the valley phase of erosion cycle This may explain the existence of superimposed streams 9 Canisteo River Valley from Pinnacle State Park New York The distant peaks at the same elevation represent the remnants of a peneplain that was uplifted to form the Allegheny Plateau which is a dissected plateau in southwestern New York In this area the sharp relief that is seen on some of the Allegheny Plateau has been rounded by glaciation Contents 1 Types of peneplains 1 1 Pediplains 2 Preservation and destruction of peneplains 3 See also 4 Notes 5 ReferencesTypes of peneplains EditThere are various terms for landforms that are either alternatives to classical peneplains a sub set of peneplains or partially overlap with the term The last is the case of planation surfaces that may be peneplains or not while some peneplains are not planation surfaces 5 In their 2013 work Green Lidmar Bergstrom and co workers provide the following classification scheme for peneplains 5 Planation surfaces Pediplain Inselberg plain Etchplain Hilly relief Etched hilly reliefRhodes Fairbridge and Charles Finkl argue that peneplains are often of mixed origin polygenetic as they may have been shaped by etchplanation during periods of humid climate and pediplanation during periods of arid and semi arid climate The long time spans under which some peneplains evolve ensures varied climatic influences 3 The same authors do also list marine abrasion C and glacial erosion among processes that can contribute in shaping peneplains 3 In addition epigene peneplains can be distinguished from exhumed peneplains 5 Epigene peneplains are those that have never been buried or covered by sedimentary rock 5 11 Exhumed peneplains are those that are re exposed after having been buried in sediments 5 The oldest identifiable peneplain in a region is known as a primary peneplain 3 D An example of a primary peneplain is the Sub Cambrian peneplain in southern Sweden 12 Pediplains Edit The peneplain concept is often juxtaposed to that of pediplain However authors like Karna Lidmar Bergstrom classify pediplains as a type of peneplain 5 On the contrary Lester Charles King held them as incompatible landforms arguing that peneplains do not exist King wrote 13 A peneplain in the Davisian sense resulting from slope reduction and downwearing does not exist in nature It should be redefined as an imaginary landform According to King the difference between pediplains and Davis peneplains is in the history and processes behind their formation and less so in the final shape A difference in form that may be present is that of residual hills which in Davis peneplains are to have gentle slopes while in pediplains they ought to have the same steepness as the slopes in the early stages of erosion leading to pediplanation 13 Given that the coalesced pediments of the pediplains form a series of very gentle concave slopes a difference with Davis understanding of peneplains may lie in the fact that his idealized peneplains had very gentle convex slopes instead However Davis views on the subject are not fully clear 13 Contrary to this view Rhodes Fairbridge and Charles Finkl argue that the precise mechanism of formation pediplanation etc is irrelevant and that the term peneplain has been used and can be used in a purely descriptive manner Further alternation of processes with varying climate relative sea level and biota make old surfaces unlikely to be of a single origin 3 Preservation and destruction of peneplains Edit The Hardangervidda plateau in southern Norway is a peneplain formed in the Miocene epoch and then uplifted to its present altitude of 1200 m a s l 14 Peneplains that are detached from their base level are identified by either hosting an accumulation of sediments that buries it or by being in an uplifted position Burial preserves the peneplain Any exposed peneplain detached from its baselevel can be considered a paleosurface or paleoplain 5 15 Uplift of a peneplain commonly results in renewed erosion As Davis put it in 1885 16 the decrepit surface must wait either until extinguished by submergence below the sea or regenerated by elevation into a new cycle of life Uplifted peneplains can be preserved as fossil landforms in conditions of extreme aridity or under non eroding cold based glacier ice 5 Erosion of peneplains by glaciers in shield regions is limited 17 18 In the Fennoscandian Shield average glacier erosion during the Quaternary amounts to tens of meters albeit this was not evenly distributed 18 For glacier erosion to be effective in shields a long preparation period of weathering under non glacial conditions may be a requirement 17 Silicification of peneplain surfaces exposed to sub tropical and tropical climate for long enough time can protect them from erosion 17 See also EditAfrican Surface Land surface formed by erosion covering large swathes of Africa Erosion surface Natural surface created by rock erosion Summit accordanceNotes Edit The term was coined around 1900 by William Morris Davis who described it as follows Given sufficient time for the action of denuding forces on a mass of land standing fixed with reference to a constant base level and it must be worn down so low and so smooth that it would fully deserve the name of a plain But it is very unusual for a mass of land to maintain a fixed position as long as is here assumed I have therefore elsewhere suggested that an old region nearly base levelled should be called an almost plain that is a peneplain 1 2 Example of this are the Sub Mesozoic hilly peneplains of southern Sweden 6 Coastal geomorphologist Douglas Wilson Johnson has proposed to use the term peneplane instead of peneplain when a planation surface is thought to be of marine origin 10 Akin to what in German scientific literature is known as a Primarrumpf 3 References Edit a b c d Phillips Jonathan D 2002 Erosion isostatic response and the missing peneplains Geomorphology 45 3 4 225 241 Bibcode 2002Geomo 45 225P doi 10 1016 S0169 555X 01 00156 8 Chorley R J 1973 The History and Study of Landforms or The Development of Geomorphology Vol Two The Life and Work of William Morris Davis Methuen a b c d e f Fairbridge Rhodes W Finkl Jr Charles W 1980 Cratonic erosion unconformities and peneplains The Journal of Geology 88 1 69 86 Bibcode 1980JG 88 69F doi 10 1086 628474 S2CID 129231129 a b c Migon Piotr 2004 Peneplain In Goudie A S ed Encyclopedia of Geomorphology Routledge pp 771 772 a b c d e f g h i j Green Paul F Lidmar Bergstrom Karna Japsen Peter Bonow Johan M Chalmers James A 2013 Stratigraphic landscape analysis thermochronology and the episodic development of elevated passive continental margins Geological Survey of Denmark and Greenland Bulletin 30 18 doi 10 34194 geusb v30 4673 a b Lidmar Bergstrom Karna Bonow Johan M Japsen Peter 2013 Stratigraphic Landscape Analysis and geomorphological paradigms Scandinavia as an example of Phanerozoic uplift and subsidence Global and Planetary Change 100 153 171 Bibcode 2013GPC 100 153L doi 10 1016 j gloplacha 2012 10 015 a b Babault Julien Van Den Driessche Jean Bonnet Stephanie Castelltort Sebastien Crave Alain 2005 Origin of the highly elevated Pyrenean peneplain Tectonics 24 2 n a Bibcode 2005Tecto 24 2010B doi 10 1029 2004TC001697 a b Yang Rong Willett Sean D Goren Liran 2015 In situ low relief landscape formation as a result of river network disruption Nature 520 7548 526 530 Bibcode 2015Natur 520 526Y doi 10 1038 nature14354 PMID 25903633 S2CID 1017663 a b Palmquist Robert C 1980 1975 The Compatibility of Structure Lithology and Geomorphic Models In Melhorn W N Flemal R C eds Theories of Landform Development 2nd ed Allen amp Unwin pp 145 168 Miller A A 1955 The origin of the South Ireland Peneplane Irish Geography 3 2 79 86 doi 10 1080 00750775509555491 Twidale C R 1985 Old landsurfaces and their implications for models of landscape evolution Revue de Geomorphologie Dynamique 34 131 147 Lidmar Bergstrom 1988 Denudation surfaces of a shield area in southern Sweden Geografiska Annaler 70 A 4 337 350 doi 10 1080 04353676 1988 11880265 a b c King L C 1953 Canons of landscape evolution Geological Society of America Bulletin 64 7 721 752 Bibcode 1953GSAB 64 721K doi 10 1130 0016 7606 1953 64 721 cole 2 0 co 2 Japsen Peter Green Paul F Chalmers James A Bonow Johan M 17 May 2018 Mountains of southernmost Norway uplifted Miocene peneplains and re exposed Mesozoic surfaces Journal of the Geological Society 175 5 721 741 Bibcode 2018JGSoc 175 721J doi 10 1144 jgs2017 157 S2CID 134575021 Bonow Johan M Lidmar Bergstrom Karna Japsen Peter 2006 Palaeosurfaces in central West Greenland as reference for identification of tectonic movements and estimation of erosion Global and Planetary Change 50 3 4 161 183 Bibcode 2006GPC 50 161B doi 10 1016 j gloplacha 2005 12 011 Orme Anthony R 2007 The Rise and Fall of the Davisian Cycle of Erosion Prelude Fugue Coda and Sequel Physical Geography 28 6 474 506 doi 10 2747 0272 3646 28 6 474 S2CID 128907423 a b c Fairbridge Rhodes W 1988 Cyclical patterns of exposure weathering and burial of cratonic surfaces with some examples from North America and Australia Geografiska Annaler 70 A 4 277 283 doi 10 1080 04353676 1988 11880257 a b Lidmar Bergstrom Karna 1997 A long term perspective on glacial erosion Earth Surface Processes and Landforms 22 3 297 306 Bibcode 1997ESPL 22 297L doi 10 1002 SICI 1096 9837 199703 22 3 lt 297 AID ESP758 gt 3 0 CO 2 R Retrieved from https en wikipedia org w index php title Peneplain amp oldid 1148481741, wikipedia, wiki, book, books, library,
