- Email: [email protected]
Circular scars dating to the Earth's accretionary period
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Energy Procedia 00 (2018) 000–000 Available online www.sciencedirect.com Available online atatwww.sciencedirect.com Energy Procedia 00 (2018) 000–000
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www.elsevier.com/locate/procedia www.elsevier.com/locate/procedia
Energy Procedia Procedia 00 146(2017) (2018)000–000 12–16 Energy www.elsevier.com/locate/procedia
International Carbon Conference 2018, ICC 2018, 10–14 September 2018, Reykjavik, Iceland International Carbon Conference 2018, ICC 2018, 10–14 September 2018, Reykjavik, Iceland
Circular scars dating to the Earth's accretionary period Circular scars dating to the Earth's accretionary period The 15th International Symposium on a,* District Heating and Cooling
John M. Saula,* John M. Saul
ORYX, 16 rue du Pré-aux-Clercs, 75007 Paris Assessing the feasibility of using the heat demand-outdoor ORYX, 16 rue du Pré-aux-Clercs, 75007 Paris temperature function for a long-term district heat demand forecast Abstract a a
Abstract a,b,c a a b c c I. Andrić *, A.thePina , P. Ferrão , J. Fournier Lacarrière O. Le Corre Large impact craters that pierced early Earth’s thin hot crust formed scars ., thatB. never fully healed., These scars provided initial Large impact craters that pierced theand early Earth’s thin hotsystem. crust formed scars crust that never fully healed. scars provided initial geological conditions for our planet its deep plumbing On oceanic they provide arcuateThese downdipping sites, which, a IN+eventually Center for allowed Innovation, Technology and Policy Research - Instituto Superior Técnico, Av.provide Rovisco Pais 1, 1049-001 Lisbon, Portugal geological conditions for our planet andtoits deep plumbing system. Onthey oceanic crust they arcuate downdipping sites, which, eroded, subduction occur. On continental crust, determine many geological features, which are generally b Veolia Recherche & Innovation, 291 Avenue Dreyfous Daniel,many 78520geological Limay, France eroded, eventually allowed subduction to occur. On continental crust, they determine features, which are generally difficult to see c because they are covered by later formations through which repropagated fractures have not attained the surface. Département Systèmes Énergétiques et Environnement IMT Atlantique, 4 rue Alfred Kastler, 44300 Francethe surface. difficult to see for because they are covered by later formations fractures haveNantes, not Shock criteria the identification of astroblemes are absentthrough becausewhich they repropagated were immediately swamped by attained the disproportionate Shock criteria the identification of astroblemes are absent because they were immediately swamped by the disproportionate amount of meltfor produced by very large impacts. amount of melt produced by very large impacts. Copyright © 2018 Elsevier Ltd. All rights reserved. Abstract © Copyright Elsevier Ltd. rights Copyrightand © 2018 2018 Elsevierunder Ltd. All All rights reserved. reserved. Selection peer-review responsibility of the the publication publication committee committee of of the the International International Carbon Carbon Conference Conference 2018. 2018. Selection and peer-review under responsibility of Selection and peer-review under responsibility of the publication committee of the International Carbon Conference 2018. District heating networks are commonly addressed in the literature as one of the most effective solutions for decreasing the Keywords: Accretionary period;from Late the Heavy Bombardment; circularsystems scars; initial geological conditions; Rodinia; Great Unconformity; greenhouse gas emissions building sector. These require high investments which erosion; are returned through the heat Keywords: subduction Accretionary sites; deep gasperiod; Late Heavy Bombardment; circular scars; initial geological conditions; Rodinia; erosion; Great Unconformity; sales. Due to the changed climate conditions and building renovation policies, heat demand in the future could decrease, subduction sites; deep gas prolonging the investment return period. The main scope of this paper is to assess the feasibility of using the heat demand – outdoor temperature function for heat demand 1.forecast. Introduction The district of Alvalade, located in Lisbon (Portugal), was used as a case study. The district is consisted of 665 1. Introduction buildings that vary in both construction period and typology. Three weather scenarios (low, medium, high) and three district Earth andscenarios Moon are neighbors in (shallow, space andintermediate, the early Earth could not havethe escaped the bombardment ("LHB") renovation were developed deep). To estimate error, obtained heat demand values that were Earththe and Moon are neighbors in heat space and the early Earth could notthe have that scarred Moon. At the time of the bombardment, c.4100–3850 Ma, crust of the the Earth hot and("LHB") thin. compared with results from a dynamic demand model, previously developed andescaped validated bybombardment thewas authors. scarred the Moon. timeonly of the bombardment, c.4100–3850 Ma, the thebe Earth was hot thin. The results showed At thatthe when weather change is considered, the margin of crust error of could acceptable forand some applications (the error in annual demand was lower than 20% for all weather scenarios considered). However, after introducing renovation 2. Preservation of ancient impact scars 2.scenarios, Preservation of value ancient impactupscars the error increased to 59.5% (depending on the weather and renovation scenarios combination considered). The value of slope coefficient increased on impact average craters within the of 3.8% up to 8% per decade, then that corresponds the Erosion subsequently removed smaller thatrange had failed to penetrate the Earth's brittle crust.toBy decrease in the number of heating hours of 22-139h during the heating season (depending on the combination of weather and Erosion subsequently removed smaller impact craters that had failed to penetrate the Earth's then brittle crust. By contrast, erosion would not have eliminated the fractured and brecciated rim-zones of larger scars because fractures renovation scenarios considered). On the other hand,fractured function and intercept increased for 7.8-12.7% per scars decade (depending on the contrast, erosion would notdeep haveto eliminated brecciated rim-zones of larger fractures that had been sufficiently penetrate the the entire crust were perennially rejuvenated by risingbecause and descending coupled scenarios). The values suggested could be used to modify the function parameters for the scenarios considered, and that had been sufficientlyofdeep to penetrate entire crust perennially rejuvenated by rising and descending fluids andthe byaccuracy movements ductile materialsthe in contact with were the lowermost brittle crust [1-3]. improve of heat demand estimations. fluids and by movements of ductile materials in contact with the lowermost brittle crust [1-3]. © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the Scientific Committee of The 15th International Symposium on District Heating and Cooling. * Corresponding author. Tel.: +33 767681827 * Corresponding Tel.: +33 767681827 E-mail address:author. [email protected] Keywords: Heat demand; Forecast; Climate change E-mail address: [email protected]
1876-6102 Copyright © 2018 Elsevier Ltd. All rights reserved. 1876-6102 Copyright © 2018 Elsevier Ltd. All of rights reserved. committee of the International Carbon Conference 2018. Selection and peer-review under responsibility the publication Selection and peer-review under responsibility of the publication committee of the International Carbon Conference 2018. 1876-6102 © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the Scientific Committee of The 15th International Symposium on District Heating and Cooling.
1876-6102 Copyright © 2018 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the publication committee of the International Carbon Conference 2018. 10.1016/j.egypro.2018.07.003
2
John M. Saul / Energy Procedia 146 (2018) 12–16 Author name / Energy Procedia 00 (2018) 000–000
13
Movements at depth also cause fractures to be propagated upward into young overlying rocks. In such cases the fracture-patterns may be far older than the rocks in which they are observed: the 3-D "craterform" structures may thus remain after the rocks in which they were formed are gone, preserved by fracture inheritance. In most instances the circular scars will be faint and difficult to discern unless the crust is exceptionally thin (e.g. the Arizona transition zone) or has been denuded (the Canadian shield). 3. Arguments against preservation An objection arises from the absence of established criteria for shock metamorphism, i.e. shatter cones, planar deformation features, coesite, etc., which form in solid rocks and are used to confirm that a terrestrial scar-like feature is indeed an astrobleme [4]. The absence of these criteria at LHB scar sites has at least two explanations: the matter of fracture inheritance, just mentioned, which allows fracture patterns to be propagated into rocks that were not themselves impacted, and the disproportionately great amounts of melt-fluids generated by large impacts [3, 5-8]. As recently reconfirmed, established scaling laws "fail to estimate the melt volume" for "giant" impacts [8]. Such failure would be especially severe for impacts on the thin hot crust of the early Earth for which less shock-heating was needed to produce melt than in later times [8]. In such cases, resultant melt fluids may anneal, melt, dominate, or eliminate shock criteria formed in solid rock as soon as they are produced. Another type of objection comes with the claim that impact scars dating to the tail end of the accretionary period or to the Late Heavy Bombardment (presuming the two are not the same [9, 10]), should have by now been subducted. But this argument would not be valid if, as proposed below, the subduction arcs are themselves vestiges of the bombardment. Deep subduction would not have always been possible because the angle at which walls of fresh impact craters intersect the surface of the Earth is far steeper than the angle of 25° to 45° at which subduction usually occurs. As a consequence, deep subduction along arcuate crater walls was not possible until there had been sufficient net erosion to expose craters at lower levels. At those levels, the dips of the remnant crater walls, composed of fractured and mechanically weakened rocks, were less steep. See Fig. 1.
Fig. 1. A. Schematic cross-section of a complex terrestrial LHB impact crater with a central uplift showing infill before erosion, c.3850 Ma. A dotted square has been added to indicate the angle, approximately 53° in this particular example, at which the crater wall originally intersected the surface of the Earth. B. The same impact site, c.750 Ma, following enhanced erosion and denudation. A second dotted square has been added to indicate the angle, approximately 41° in this particular example, at which the greatly eroded crater wall then intersected the surface of the Earth. Adapted from the "generalized sketch" of Stöffler et al. [11] for complex impact craters tens to hundreds of kilometers in diameter.
14
John M. Saul / Energy Procedia 146 (2018) 12–16 Author name / Energy Procedia 00 (2018) 000–000
3
Such erosion occurred with the breakup of Rodinia commencing c.750 Ma, a unique geological event [12, 13] that is indicated by the Great Unconformity (c.740-525 Ma), which marks "the termination of an extended period of continental denudation that exhumed and exposed large areas of igneous and metamorphic rocks to subaerial weathering" [13]. This suggests that modern-style plate tectonics with deep subduction did not regularly occur in earlier times. 4. Types of early-Earth circular scars Textbooks show numerous types of geological faults and geological folds that have been observed, characterized, and named during the last two centuries. Circular LHB scars now require similar attention for they too exist in numerous styles and varieties, not just as manifested as arcuate subduction zones. No attempt to establish a nomenclature was made in earlier publications [1, 3, 14] and none will be made here, but a few of the descriptive phrases that were applied to types of LHB scars discussed and illustrated elsewhere include "major mineralization along circumference" (Fig. 2), "oil and gas near center" (Fig. 3), "oil and gas along tangent" (Fig. 3), "faults radiate inward or outward from circumference" (Fig. 3), "drainage basin" (Fig. 4), "neatly encompasses kimberlite zone", "uplifted within rim zone of larger scar", "has outer rim", "large and aligned along equator" and so on, with perhaps as many variations as there are geological settings.
Fig. 2. Circular scars, Arizona. The scars were photographed on a 3-D relief map illuminated at a low angle. The area covered includes a major mining district and the inset shows the locations of all the metal mines in the region shown in the figure; modified from Saul [1].
4
John M. Saul / Energy Procedia 146 (2018) 12–16 Author name / Energy Procedia 00 (2018) 000–000
15
5. Concluding remarks Topography, including drainage and land-water boundaries, was particularly useful in identifying scars, as was the choice of colours on diverse non-geological maps. Some scars were more readily visible on degraded imagery or on images with enhanced contrast but modern technology was not involved in the actual discovery of unseen scars. These features, all of which are four billion years old, have provided initial geological conditions. They formed the canvass on which later geology has been painted [3, 13].
Fig. 3. LHB scar circles associated with petroleum and deep gas in the region west of the Middle Urals. The supergiant Romashkino oilfield is situated within a 210 km diameter scar (infolded map in [15]) and the Arlan supergiant oilfield is located along the tangent shared by this scar and the adjacent c.420 km “Middle-Ural Ring Structure” [16-17].
Fig. 4: Continental drainage map of Australia. The circular pattern is also visible on satellite imagery obtained in especially wet conditions. Map from Division of National Mapping [18].
16
John M. Saul / Energy Procedia 146 (2018) 12–16 Author name / Energy Procedia 00 (2018) 000–000
References [1] [2] [3] [4] [5]
Saul John M. “Circular structures of large scale and great age on the Earth’s surface” Nature 271 (1978): 345-349. Jones Alan G. “Are impact-generated lower-crustal faults observable?” Earth and Planetary Science Letters 85 (1987): 248-252. Saul John M. “A Geologist Speculates” Les 3 Colonnes, Paris (2014): 1-159. Earth Impact Database. http://www.passc.net/EarthImpactDatabase/index.html (Feb. 2018). French Bevan M. “Traces of Catastrophe: A Handbook of Shock-Metamorphic Effects in Terrestrial Meteorite Impact Structures” LPI Contribution 954 (1998): 1-120. [6] Melosh H. Jay. “Can impacts induce volcanic eruptions?” in Catastrophic Events & Mass Extinctions: impacts and beyond, LPI Contribution 1053 (2000): 141-142. [7] Ryder Graham, Christian Koeberl, and Stephen J. Mojzsis. “Heavy bombardment of the Earth at ~3.85 Ga: the search for petrographic and geochemical evidence” in Robin M. Canup, and Kevin Righter (eds) Origin of the Earth and Moon, Tucson, University of Arizona (2000): 475-492. [8] Manske Lukas, Kai Wünnemann, and Nicole Güldemeister. “Impact-induced melting by Giant Impact Events” Geophysical Research Abstracts 20 (2018): EGU-2018-15883-3. [9] Hartmann William K. “Lunar 'cataclysm': A misconception?” Icarus 24 (1975): 181-185. [10] Hartmann William K. “Reviewing 'terminal cataclysm': What does it mean?” in Workshop on Early Solar System Impact Bombardment III, LPI Contribution 1826 (2015): 3003. [11] Stöffler Dieter, Christopher Hamann, and Knut Metzler. “Shock metamorphism of planetary silicate rocks and sediments: Proposal for an updated classification system” Meteoritics & Planetary Science 53 (2018): 5-49. [12] Liu Chao, Andrew H. Knoll, and Robert M. Hazen. “Geochemical and mineralogical evidence that Rodinian assembly was unique” Nature Communications 1950 (2017): 1-8. [13] Peters Shanan E., and Robert R. Gaines. “Formation of the 'Great Unconformity’ as a trigger for the Cambrian explosion” Nature 484 (2012): 363-366. [14] Saul John M. “Transparent gemstones and the most recent supercontinent cycle” International Geology Review 60 (2017): 889-910. [15] Trofimov Vladimir A. “Deep CMP Seismic Survey of Oil and Gas Bearing Areas” (in Russian) Moscow, GEOS (2014): 1-202, with 1:2,000,000 infolded map, ISBN 978-5-89118-644-6. [16] Burba George A. “Middle-Urals Ring Structure, USSR: Definition, description, possible planetary analogues” Abstracts, Lunar and Planetary Science Conference 22 (1991): 153. [17] Burba George A. “The geological evolution of the Ural Mountains: A supposed exposure to a giant Impact” Vernadsky/Brown Microsymposium 38 (2003): MS011. [18] Division of National Mapping, Department of National Development, Canberra (1969).
5
ScienceDirect ScienceDirect
Energy Procedia 00 (2018) 000–000 Available online www.sciencedirect.com Available online atatwww.sciencedirect.com Energy Procedia 00 (2018) 000–000
ScienceDirect ScienceDirect
www.elsevier.com/locate/procedia www.elsevier.com/locate/procedia
Energy Procedia Procedia 00 146(2017) (2018)000–000 12–16 Energy www.elsevier.com/locate/procedia
International Carbon Conference 2018, ICC 2018, 10–14 September 2018, Reykjavik, Iceland International Carbon Conference 2018, ICC 2018, 10–14 September 2018, Reykjavik, Iceland
Circular scars dating to the Earth's accretionary period Circular scars dating to the Earth's accretionary period The 15th International Symposium on a,* District Heating and Cooling
John M. Saula,* John M. Saul
ORYX, 16 rue du Pré-aux-Clercs, 75007 Paris Assessing the feasibility of using the heat demand-outdoor ORYX, 16 rue du Pré-aux-Clercs, 75007 Paris temperature function for a long-term district heat demand forecast Abstract a a
Abstract a,b,c a a b c c I. Andrić *, A.thePina , P. Ferrão , J. Fournier Lacarrière O. Le Corre Large impact craters that pierced early Earth’s thin hot crust formed scars ., thatB. never fully healed., These scars provided initial Large impact craters that pierced theand early Earth’s thin hotsystem. crust formed scars crust that never fully healed. scars provided initial geological conditions for our planet its deep plumbing On oceanic they provide arcuateThese downdipping sites, which, a IN+eventually Center for allowed Innovation, Technology and Policy Research - Instituto Superior Técnico, Av.provide Rovisco Pais 1, 1049-001 Lisbon, Portugal geological conditions for our planet andtoits deep plumbing system. Onthey oceanic crust they arcuate downdipping sites, which, eroded, subduction occur. On continental crust, determine many geological features, which are generally b Veolia Recherche & Innovation, 291 Avenue Dreyfous Daniel,many 78520geological Limay, France eroded, eventually allowed subduction to occur. On continental crust, they determine features, which are generally difficult to see c because they are covered by later formations through which repropagated fractures have not attained the surface. Département Systèmes Énergétiques et Environnement IMT Atlantique, 4 rue Alfred Kastler, 44300 Francethe surface. difficult to see for because they are covered by later formations fractures haveNantes, not Shock criteria the identification of astroblemes are absentthrough becausewhich they repropagated were immediately swamped by attained the disproportionate Shock criteria the identification of astroblemes are absent because they were immediately swamped by the disproportionate amount of meltfor produced by very large impacts. amount of melt produced by very large impacts. Copyright © 2018 Elsevier Ltd. All rights reserved. Abstract © Copyright Elsevier Ltd. rights Copyrightand © 2018 2018 Elsevierunder Ltd. All All rights reserved. reserved. Selection peer-review responsibility of the the publication publication committee committee of of the the International International Carbon Carbon Conference Conference 2018. 2018. Selection and peer-review under responsibility of Selection and peer-review under responsibility of the publication committee of the International Carbon Conference 2018. District heating networks are commonly addressed in the literature as one of the most effective solutions for decreasing the Keywords: Accretionary period;from Late the Heavy Bombardment; circularsystems scars; initial geological conditions; Rodinia; Great Unconformity; greenhouse gas emissions building sector. These require high investments which erosion; are returned through the heat Keywords: subduction Accretionary sites; deep gasperiod; Late Heavy Bombardment; circular scars; initial geological conditions; Rodinia; erosion; Great Unconformity; sales. Due to the changed climate conditions and building renovation policies, heat demand in the future could decrease, subduction sites; deep gas prolonging the investment return period. The main scope of this paper is to assess the feasibility of using the heat demand – outdoor temperature function for heat demand 1.forecast. Introduction The district of Alvalade, located in Lisbon (Portugal), was used as a case study. The district is consisted of 665 1. Introduction buildings that vary in both construction period and typology. Three weather scenarios (low, medium, high) and three district Earth andscenarios Moon are neighbors in (shallow, space andintermediate, the early Earth could not havethe escaped the bombardment ("LHB") renovation were developed deep). To estimate error, obtained heat demand values that were Earththe and Moon are neighbors in heat space and the early Earth could notthe have that scarred Moon. At the time of the bombardment, c.4100–3850 Ma, crust of the the Earth hot and("LHB") thin. compared with results from a dynamic demand model, previously developed andescaped validated bybombardment thewas authors. scarred the Moon. timeonly of the bombardment, c.4100–3850 Ma, the thebe Earth was hot thin. The results showed At thatthe when weather change is considered, the margin of crust error of could acceptable forand some applications (the error in annual demand was lower than 20% for all weather scenarios considered). However, after introducing renovation 2. Preservation of ancient impact scars 2.scenarios, Preservation of value ancient impactupscars the error increased to 59.5% (depending on the weather and renovation scenarios combination considered). The value of slope coefficient increased on impact average craters within the of 3.8% up to 8% per decade, then that corresponds the Erosion subsequently removed smaller thatrange had failed to penetrate the Earth's brittle crust.toBy decrease in the number of heating hours of 22-139h during the heating season (depending on the combination of weather and Erosion subsequently removed smaller impact craters that had failed to penetrate the Earth's then brittle crust. By contrast, erosion would not have eliminated the fractured and brecciated rim-zones of larger scars because fractures renovation scenarios considered). On the other hand,fractured function and intercept increased for 7.8-12.7% per scars decade (depending on the contrast, erosion would notdeep haveto eliminated brecciated rim-zones of larger fractures that had been sufficiently penetrate the the entire crust were perennially rejuvenated by risingbecause and descending coupled scenarios). The values suggested could be used to modify the function parameters for the scenarios considered, and that had been sufficientlyofdeep to penetrate entire crust perennially rejuvenated by rising and descending fluids andthe byaccuracy movements ductile materialsthe in contact with were the lowermost brittle crust [1-3]. improve of heat demand estimations. fluids and by movements of ductile materials in contact with the lowermost brittle crust [1-3]. © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the Scientific Committee of The 15th International Symposium on District Heating and Cooling. * Corresponding author. Tel.: +33 767681827 * Corresponding Tel.: +33 767681827 E-mail address:author. [email protected] Keywords: Heat demand; Forecast; Climate change E-mail address: [email protected]
1876-6102 Copyright © 2018 Elsevier Ltd. All rights reserved. 1876-6102 Copyright © 2018 Elsevier Ltd. All of rights reserved. committee of the International Carbon Conference 2018. Selection and peer-review under responsibility the publication Selection and peer-review under responsibility of the publication committee of the International Carbon Conference 2018. 1876-6102 © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the Scientific Committee of The 15th International Symposium on District Heating and Cooling.
1876-6102 Copyright © 2018 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the publication committee of the International Carbon Conference 2018. 10.1016/j.egypro.2018.07.003
2
John M. Saul / Energy Procedia 146 (2018) 12–16 Author name / Energy Procedia 00 (2018) 000–000
13
Movements at depth also cause fractures to be propagated upward into young overlying rocks. In such cases the fracture-patterns may be far older than the rocks in which they are observed: the 3-D "craterform" structures may thus remain after the rocks in which they were formed are gone, preserved by fracture inheritance. In most instances the circular scars will be faint and difficult to discern unless the crust is exceptionally thin (e.g. the Arizona transition zone) or has been denuded (the Canadian shield). 3. Arguments against preservation An objection arises from the absence of established criteria for shock metamorphism, i.e. shatter cones, planar deformation features, coesite, etc., which form in solid rocks and are used to confirm that a terrestrial scar-like feature is indeed an astrobleme [4]. The absence of these criteria at LHB scar sites has at least two explanations: the matter of fracture inheritance, just mentioned, which allows fracture patterns to be propagated into rocks that were not themselves impacted, and the disproportionately great amounts of melt-fluids generated by large impacts [3, 5-8]. As recently reconfirmed, established scaling laws "fail to estimate the melt volume" for "giant" impacts [8]. Such failure would be especially severe for impacts on the thin hot crust of the early Earth for which less shock-heating was needed to produce melt than in later times [8]. In such cases, resultant melt fluids may anneal, melt, dominate, or eliminate shock criteria formed in solid rock as soon as they are produced. Another type of objection comes with the claim that impact scars dating to the tail end of the accretionary period or to the Late Heavy Bombardment (presuming the two are not the same [9, 10]), should have by now been subducted. But this argument would not be valid if, as proposed below, the subduction arcs are themselves vestiges of the bombardment. Deep subduction would not have always been possible because the angle at which walls of fresh impact craters intersect the surface of the Earth is far steeper than the angle of 25° to 45° at which subduction usually occurs. As a consequence, deep subduction along arcuate crater walls was not possible until there had been sufficient net erosion to expose craters at lower levels. At those levels, the dips of the remnant crater walls, composed of fractured and mechanically weakened rocks, were less steep. See Fig. 1.
Fig. 1. A. Schematic cross-section of a complex terrestrial LHB impact crater with a central uplift showing infill before erosion, c.3850 Ma. A dotted square has been added to indicate the angle, approximately 53° in this particular example, at which the crater wall originally intersected the surface of the Earth. B. The same impact site, c.750 Ma, following enhanced erosion and denudation. A second dotted square has been added to indicate the angle, approximately 41° in this particular example, at which the greatly eroded crater wall then intersected the surface of the Earth. Adapted from the "generalized sketch" of Stöffler et al. [11] for complex impact craters tens to hundreds of kilometers in diameter.
14
John M. Saul / Energy Procedia 146 (2018) 12–16 Author name / Energy Procedia 00 (2018) 000–000
3
Such erosion occurred with the breakup of Rodinia commencing c.750 Ma, a unique geological event [12, 13] that is indicated by the Great Unconformity (c.740-525 Ma), which marks "the termination of an extended period of continental denudation that exhumed and exposed large areas of igneous and metamorphic rocks to subaerial weathering" [13]. This suggests that modern-style plate tectonics with deep subduction did not regularly occur in earlier times. 4. Types of early-Earth circular scars Textbooks show numerous types of geological faults and geological folds that have been observed, characterized, and named during the last two centuries. Circular LHB scars now require similar attention for they too exist in numerous styles and varieties, not just as manifested as arcuate subduction zones. No attempt to establish a nomenclature was made in earlier publications [1, 3, 14] and none will be made here, but a few of the descriptive phrases that were applied to types of LHB scars discussed and illustrated elsewhere include "major mineralization along circumference" (Fig. 2), "oil and gas near center" (Fig. 3), "oil and gas along tangent" (Fig. 3), "faults radiate inward or outward from circumference" (Fig. 3), "drainage basin" (Fig. 4), "neatly encompasses kimberlite zone", "uplifted within rim zone of larger scar", "has outer rim", "large and aligned along equator" and so on, with perhaps as many variations as there are geological settings.
Fig. 2. Circular scars, Arizona. The scars were photographed on a 3-D relief map illuminated at a low angle. The area covered includes a major mining district and the inset shows the locations of all the metal mines in the region shown in the figure; modified from Saul [1].
4
John M. Saul / Energy Procedia 146 (2018) 12–16 Author name / Energy Procedia 00 (2018) 000–000
15
5. Concluding remarks Topography, including drainage and land-water boundaries, was particularly useful in identifying scars, as was the choice of colours on diverse non-geological maps. Some scars were more readily visible on degraded imagery or on images with enhanced contrast but modern technology was not involved in the actual discovery of unseen scars. These features, all of which are four billion years old, have provided initial geological conditions. They formed the canvass on which later geology has been painted [3, 13].
Fig. 3. LHB scar circles associated with petroleum and deep gas in the region west of the Middle Urals. The supergiant Romashkino oilfield is situated within a 210 km diameter scar (infolded map in [15]) and the Arlan supergiant oilfield is located along the tangent shared by this scar and the adjacent c.420 km “Middle-Ural Ring Structure” [16-17].
Fig. 4: Continental drainage map of Australia. The circular pattern is also visible on satellite imagery obtained in especially wet conditions. Map from Division of National Mapping [18].
16
John M. Saul / Energy Procedia 146 (2018) 12–16 Author name / Energy Procedia 00 (2018) 000–000
References [1] [2] [3] [4] [5]
Saul John M. “Circular structures of large scale and great age on the Earth’s surface” Nature 271 (1978): 345-349. Jones Alan G. “Are impact-generated lower-crustal faults observable?” Earth and Planetary Science Letters 85 (1987): 248-252. Saul John M. “A Geologist Speculates” Les 3 Colonnes, Paris (2014): 1-159. Earth Impact Database. http://www.passc.net/EarthImpactDatabase/index.html (Feb. 2018). French Bevan M. “Traces of Catastrophe: A Handbook of Shock-Metamorphic Effects in Terrestrial Meteorite Impact Structures” LPI Contribution 954 (1998): 1-120. [6] Melosh H. Jay. “Can impacts induce volcanic eruptions?” in Catastrophic Events & Mass Extinctions: impacts and beyond, LPI Contribution 1053 (2000): 141-142. [7] Ryder Graham, Christian Koeberl, and Stephen J. Mojzsis. “Heavy bombardment of the Earth at ~3.85 Ga: the search for petrographic and geochemical evidence” in Robin M. Canup, and Kevin Righter (eds) Origin of the Earth and Moon, Tucson, University of Arizona (2000): 475-492. [8] Manske Lukas, Kai Wünnemann, and Nicole Güldemeister. “Impact-induced melting by Giant Impact Events” Geophysical Research Abstracts 20 (2018): EGU-2018-15883-3. [9] Hartmann William K. “Lunar 'cataclysm': A misconception?” Icarus 24 (1975): 181-185. [10] Hartmann William K. “Reviewing 'terminal cataclysm': What does it mean?” in Workshop on Early Solar System Impact Bombardment III, LPI Contribution 1826 (2015): 3003. [11] Stöffler Dieter, Christopher Hamann, and Knut Metzler. “Shock metamorphism of planetary silicate rocks and sediments: Proposal for an updated classification system” Meteoritics & Planetary Science 53 (2018): 5-49. [12] Liu Chao, Andrew H. Knoll, and Robert M. Hazen. “Geochemical and mineralogical evidence that Rodinian assembly was unique” Nature Communications 1950 (2017): 1-8. [13] Peters Shanan E., and Robert R. Gaines. “Formation of the 'Great Unconformity’ as a trigger for the Cambrian explosion” Nature 484 (2012): 363-366. [14] Saul John M. “Transparent gemstones and the most recent supercontinent cycle” International Geology Review 60 (2017): 889-910. [15] Trofimov Vladimir A. “Deep CMP Seismic Survey of Oil and Gas Bearing Areas” (in Russian) Moscow, GEOS (2014): 1-202, with 1:2,000,000 infolded map, ISBN 978-5-89118-644-6. [16] Burba George A. “Middle-Urals Ring Structure, USSR: Definition, description, possible planetary analogues” Abstracts, Lunar and Planetary Science Conference 22 (1991): 153. [17] Burba George A. “The geological evolution of the Ural Mountains: A supposed exposure to a giant Impact” Vernadsky/Brown Microsymposium 38 (2003): MS011. [18] Division of National Mapping, Department of National Development, Canberra (1969).
5