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Benjamin Levrard - One of the best experts on this subject based on the ideXlab platform.
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A long-term numerical solution for the insolation quantities of the Earth
Astronomy & Astrophysics, 2004Co-Authors: Jacques Laskar, Philippe Robutel, Frédéric Joutel, Mickael Gastineau, A.c.m. Correia, Benjamin LevrardAbstract:We present here a new solution for the astronomical computation of the insolation quantities on Earth spanning from -250 Myr to 250 Myr. This solution has been improved with respect to La93 (Laskar et al. [CITE]) by using a direct integration of the gravitational equations for the orbital motion, and by improving the dissipative contributions, in particular in the evolution of the Earth–Moon System. The orbital solution has been used for the calibration of the Neogene Period (Lourens et al. [CITE]), and is expected to be used for age calibrations of paleoclimatic data over 40 to 50 Myr, eventually over the full Palaeogene Period (65 Myr) with caution. Beyond this time span, the chaotic evolution of the orbits prevents a precise determination of the Earth's motion. However, the most regular components of the orbital solution could still be used over a much longer time span, which is why we provide here the solution over 250 Myr. Over this time interval, the most striking feature of the obliquity solution, apart from a secular global increase due to tidal dissipation, is a strong decrease of about 0.38 degree in the next few millions of years, due to the crossing of the resonance (Laskar et al. [CITE]). For the calibration of the Mesozoic time scale (about 65 to 250 Myr), we propose to use the term of largest amplitude in the eccentricity, related to , with a fixed frequency of /yr, corresponding to a Period of 405 000 yr. The uncertainty of this time scale over 100 Myr should be about , and over the full Mesozoic era.
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A long term numerical solution for the insolation quantities of the Earth
2004Co-Authors: Jacques Laskar, Philippe Robutel, Frédéric Joutel, Mickael Gastineau, A.c.m. Correia, Benjamin LevrardAbstract:We present here a new solution for the astronomical computation of the insolation quantities on Earth spanning from -250 Myr to 250 Myr. This solution has been improved with respect to La93 (Laskar et al, 1993) by using a direct integration of the gravitational equations for the orbital motion, and by improving the dissipative contributions, in particular in the evolution of the Earth-Moon System. The orbital solution has been used for the calibration of the Neogene Period (Lourens \etal, 2004), and is expected to be used for age calibrations of paleoclimatic data over 40 to 50 Myr, eventually over the full Palaeogene Period (65 Myr) with caution. Beyond this time span, the chaotic evolution of the orbits prevents a precise determination of the Earth motion. However, the most regular components of the orbital solution could still be used over a much longer time span, which is why we provide here the solution over 250 Myr. Over this time interval, the most striking feature of the obliquity solution, apart from a secular global increase due to tidal dissipation, is a strong decrease of about $0.38$ degree in the next few millions of years, due to the crossing of the $s_6+g_5-g_6$ resonance (Laskar et al, 1993). For the calibration of the Mesozoic time scale (about 65 to 250 Myr), we propose to use the term of largest amplitude in the eccentricity, related to $g_2-g_5$, with a fixed frequency of $3.200$ ''/yr, corresponding to a Period of 405000 yr. The uncertainty of this time scale over 100 Myr should be about $0.1\%$, and $0.2\%$ over the full Mesozoic era.
Pascal Bailly Du Bois - One of the best experts on this subject based on the ideXlab platform.
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Global variability in seawater Mg:Ca and Sr:Ca ratios in the modern ocean
Proceedings of the National Academy of Sciences of the United States of America, 2020Co-Authors: Mario Lebrato, Dieter Garbe-schönberg, Pascal Bailly Du BoisAbstract:Seawater Mg:Ca and Sr:Ca ratios are biogeochemical parameters reflecting the Earth-ocean atmosphere dynamic exchange of elements. The ratios dependence on the physical and chemical environment, facilitates their use as tools in marine sciences. It has been ~130 years since the last global survey. Here, we present a new measured single-laboratory global dataset, combined with previous data, to test the assumption of limited seawater Mg:Ca and Sr:Ca variability across marine environments. There is high variability in open ocean upwelling and polar regions, shelves, neritic, and river-influenced areas, where Mg:Ca and Sr:Ca range ~4.40-6.40 mmol:mol and ~6.95-9.80 mmol:mol, respectively. Open-ocean seawater Mg:Ca is semi-conservative (~4.90 to 5.30 mol:mol), while Sr:Ca is more variable and non-conservative (~7.70 to 8.80 mmol:mol); both ratios are non-conservative in coastal seas. Further, the Ca, Mg and Sr elemental fluxes are connected to total alkalinity (TA) deviations from IAPSO standard values. Because there is significant seawater Mg:Ca and Sr:Ca variability across marine environments we cannot absolutely assume that fossil archives secular changes using taxa-specific proxies reflect true global seawater chemistry, but taxa- and process specific ecosystem variations, reflecting regional conditions. This variability could reconcile secular seawater Mg:Ca and Sr:Ca ratios reconstructions using different taxa, techniques, and processes, by assuming an error of 1-1.50 mol:mol, and 1-1.90 mmol:mol, respectively. The modern ratios variability is similar to the reconstructed rise over 20 million years (Neogene Period), nurturing the question of semi non-conservative behavior of Ca, Mg, and Sr over modern Earth geological history with an overlooked environmental effect.
Frits Hilgen - One of the best experts on this subject based on the ideXlab platform.
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The Neogene Period
The Geologic Time Scale, 2012Co-Authors: Frits Hilgen, Lucas Joost Lourens, Jan Van DamAbstract:An Astronomically Tuned Neogene Time Scale (ATNTS2012) is presented, as an update of ATNTS2004 in GTS2004. The new scale is not fundamentally different from its predecessor and the numerical ages are identical or almost so. Astronomical tuning has in principle the potential of generating a stable Neogene time scale as a function of the accuracy of the La2004 astronomical solution used for both scales. Minor problems remain in the tuning of the Lower Miocene. In GTS2012 we will summarize what has been modified or added since the publication of ATNTS2004 for incorporation in its successor, ATNTS2012. Mammal biostratigraphy and its chronology are elaborated, and the regional Neogene stages of the Paratethys and New Zealand are briefy discussed. To keep changes to ATNTS2004 transparent we maintain its subdivision into headings as much as possible.
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What, if Anything, is Quaternary?
Episodes, 2009Co-Authors: John A. Van Couvering, Felix M Gradstein, Frits Hilgen, Lucas Joost Lourens, William A. Berggren, Marie-pierre Aubry, Dennis V. Kent, Brian McgowranAbstract:The formal recognition of Quaternary as a Period/ System was approved by IUGS in June 2009, in accordance with a proposal originated by INQUA. There are reasons to believe that this will have destabilizing consequences for the geological time scale. Until now, the primary divisions of the stratigraphic record, at the Period level and above, have been based on the progressive change of Earth's biota. The Quaternary, on the other hand, is a paleoclimatic concept based on glacial-interglacial variability, expressed in lithological change. The IUGS vote holds that this paradigm now supersedes the biochronological identity of the Neogene Period/System. Furthermore, to accomodate the most recent INQUA opinion about "when the Ice Ages began", the ICS agreed to relocate the base of the Pleistocene to 2.59 Ma from 1.81 Ma, enlarging the epoch by 43% and again without regard for its original paleontological definition, or for the vast literature in other fields of Pleistocene research. If history is a guide, the resulting disruption in late Cenozoic marine and vertebrate paleontology, human evolution, paleoceanography and paleoclimatology will be widely resisted, with potential impact on the authority of IUGS. The consequence of abandoning basic principles in order to satisfy the interest of a special group deserves a wider consideration than it has so far received.
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Neogene and Quaternary coexisting in the geological time scale: The inclusive compromise
Earth-Science Reviews, 2009Co-Authors: Brian Mcgowran, Frits Hilgen, Lucas Joost Lourens, Bill Berggren, Fritz F. Steininger, Marie-pierre Aubry, John A. Van CouveringAbstract:Removing the Tertiary and Quaternary Periods whilst conserving the Paleogene and Neogene Periods in The Geological Timescale 2004 caused a storm of protest. One response was to advocate restoring an enlarged Quaternary and consigning the Neogene to a minor role within the Tertiary. Amongst an array of practical, traditional, sentimental and anthropocentric reasons for this response, the one hard-core justification was that the rigidly nested hierarchy of the geological timescale must be preserved. The central objective of this paper is conserving the historically legitimate, Miocene-present, Neogene Period and System. There are two options for conserving the Quaternary concurrently with the Neogene: (i) an inclusive compromise in a flexible hierarchy, and (ii) an upgrading of Pliocene and Pleistocene divisions to the level of epoch. In the inclusive compromise there coexist alternative pathways through the hierarchical ranks. Thus geohistorians and biohistorians have two options for traversing the hierarchy from era to age, as in this example using the hierarchical positioning of the Calabrian Age and Stage: either Cenozoic [era]↔Neogene [Period]↔Pleistocene [epoch]↔Calabrian [age], or Cenozoic [era]↔Quaternary [subera]↔Pleistocene [epoch]↔Calabrian [age]. We reaffirm that the inclusive compromise is entirely viable. In so doing we (i) challenge the necessity of the rigidly nested hierarchy, which should be capable of a little flexibility; (ii) reject all analogies of the arbitrary and conventional chronostratigraphic hierarchy with three natural biological hierarchies; (iii) reaffirm the integrity of the Neogene extending to the present; and (iv) see no reason to doubt the harmonious coexistence of the two options preserving the Quaternary and Neogene traditions in an orderly working and stable time scale. In the alternative schema conserving the Neogene, divisions of the Pliocene and Pleistocene are upgraded, so that the Late Pleistocene, Early Pleistocene and Late Pliocene Epochs comprise the Quaternary SubPeriod, itself equivalent to Late Neogene. The inflexibly nested hierarchy is preserved but the Tertiary is lost.
Jacques Laskar - One of the best experts on this subject based on the ideXlab platform.
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A long-term numerical solution for the insolation quantities of the Earth
Astronomy & Astrophysics, 2004Co-Authors: Jacques Laskar, Philippe Robutel, Frédéric Joutel, Mickael Gastineau, A.c.m. Correia, Benjamin LevrardAbstract:We present here a new solution for the astronomical computation of the insolation quantities on Earth spanning from -250 Myr to 250 Myr. This solution has been improved with respect to La93 (Laskar et al. [CITE]) by using a direct integration of the gravitational equations for the orbital motion, and by improving the dissipative contributions, in particular in the evolution of the Earth–Moon System. The orbital solution has been used for the calibration of the Neogene Period (Lourens et al. [CITE]), and is expected to be used for age calibrations of paleoclimatic data over 40 to 50 Myr, eventually over the full Palaeogene Period (65 Myr) with caution. Beyond this time span, the chaotic evolution of the orbits prevents a precise determination of the Earth's motion. However, the most regular components of the orbital solution could still be used over a much longer time span, which is why we provide here the solution over 250 Myr. Over this time interval, the most striking feature of the obliquity solution, apart from a secular global increase due to tidal dissipation, is a strong decrease of about 0.38 degree in the next few millions of years, due to the crossing of the resonance (Laskar et al. [CITE]). For the calibration of the Mesozoic time scale (about 65 to 250 Myr), we propose to use the term of largest amplitude in the eccentricity, related to , with a fixed frequency of /yr, corresponding to a Period of 405 000 yr. The uncertainty of this time scale over 100 Myr should be about , and over the full Mesozoic era.
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A long term numerical solution for the insolation quantities of the Earth
2004Co-Authors: Jacques Laskar, Philippe Robutel, Frédéric Joutel, Mickael Gastineau, A.c.m. Correia, Benjamin LevrardAbstract:We present here a new solution for the astronomical computation of the insolation quantities on Earth spanning from -250 Myr to 250 Myr. This solution has been improved with respect to La93 (Laskar et al, 1993) by using a direct integration of the gravitational equations for the orbital motion, and by improving the dissipative contributions, in particular in the evolution of the Earth-Moon System. The orbital solution has been used for the calibration of the Neogene Period (Lourens \etal, 2004), and is expected to be used for age calibrations of paleoclimatic data over 40 to 50 Myr, eventually over the full Palaeogene Period (65 Myr) with caution. Beyond this time span, the chaotic evolution of the orbits prevents a precise determination of the Earth motion. However, the most regular components of the orbital solution could still be used over a much longer time span, which is why we provide here the solution over 250 Myr. Over this time interval, the most striking feature of the obliquity solution, apart from a secular global increase due to tidal dissipation, is a strong decrease of about $0.38$ degree in the next few millions of years, due to the crossing of the $s_6+g_5-g_6$ resonance (Laskar et al, 1993). For the calibration of the Mesozoic time scale (about 65 to 250 Myr), we propose to use the term of largest amplitude in the eccentricity, related to $g_2-g_5$, with a fixed frequency of $3.200$ ''/yr, corresponding to a Period of 405000 yr. The uncertainty of this time scale over 100 Myr should be about $0.1\%$, and $0.2\%$ over the full Mesozoic era.
Lucas Joost Lourens - One of the best experts on this subject based on the ideXlab platform.
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The Neogene Period
The Geologic Time Scale, 2012Co-Authors: Frits Hilgen, Lucas Joost Lourens, Jan Van DamAbstract:An Astronomically Tuned Neogene Time Scale (ATNTS2012) is presented, as an update of ATNTS2004 in GTS2004. The new scale is not fundamentally different from its predecessor and the numerical ages are identical or almost so. Astronomical tuning has in principle the potential of generating a stable Neogene time scale as a function of the accuracy of the La2004 astronomical solution used for both scales. Minor problems remain in the tuning of the Lower Miocene. In GTS2012 we will summarize what has been modified or added since the publication of ATNTS2004 for incorporation in its successor, ATNTS2012. Mammal biostratigraphy and its chronology are elaborated, and the regional Neogene stages of the Paratethys and New Zealand are briefy discussed. To keep changes to ATNTS2004 transparent we maintain its subdivision into headings as much as possible.
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What, if Anything, is Quaternary?
Episodes, 2009Co-Authors: John A. Van Couvering, Felix M Gradstein, Frits Hilgen, Lucas Joost Lourens, William A. Berggren, Marie-pierre Aubry, Dennis V. Kent, Brian McgowranAbstract:The formal recognition of Quaternary as a Period/ System was approved by IUGS in June 2009, in accordance with a proposal originated by INQUA. There are reasons to believe that this will have destabilizing consequences for the geological time scale. Until now, the primary divisions of the stratigraphic record, at the Period level and above, have been based on the progressive change of Earth's biota. The Quaternary, on the other hand, is a paleoclimatic concept based on glacial-interglacial variability, expressed in lithological change. The IUGS vote holds that this paradigm now supersedes the biochronological identity of the Neogene Period/System. Furthermore, to accomodate the most recent INQUA opinion about "when the Ice Ages began", the ICS agreed to relocate the base of the Pleistocene to 2.59 Ma from 1.81 Ma, enlarging the epoch by 43% and again without regard for its original paleontological definition, or for the vast literature in other fields of Pleistocene research. If history is a guide, the resulting disruption in late Cenozoic marine and vertebrate paleontology, human evolution, paleoceanography and paleoclimatology will be widely resisted, with potential impact on the authority of IUGS. The consequence of abandoning basic principles in order to satisfy the interest of a special group deserves a wider consideration than it has so far received.
-
Neogene and Quaternary coexisting in the geological time scale: The inclusive compromise
Earth-Science Reviews, 2009Co-Authors: Brian Mcgowran, Frits Hilgen, Lucas Joost Lourens, Bill Berggren, Fritz F. Steininger, Marie-pierre Aubry, John A. Van CouveringAbstract:Removing the Tertiary and Quaternary Periods whilst conserving the Paleogene and Neogene Periods in The Geological Timescale 2004 caused a storm of protest. One response was to advocate restoring an enlarged Quaternary and consigning the Neogene to a minor role within the Tertiary. Amongst an array of practical, traditional, sentimental and anthropocentric reasons for this response, the one hard-core justification was that the rigidly nested hierarchy of the geological timescale must be preserved. The central objective of this paper is conserving the historically legitimate, Miocene-present, Neogene Period and System. There are two options for conserving the Quaternary concurrently with the Neogene: (i) an inclusive compromise in a flexible hierarchy, and (ii) an upgrading of Pliocene and Pleistocene divisions to the level of epoch. In the inclusive compromise there coexist alternative pathways through the hierarchical ranks. Thus geohistorians and biohistorians have two options for traversing the hierarchy from era to age, as in this example using the hierarchical positioning of the Calabrian Age and Stage: either Cenozoic [era]↔Neogene [Period]↔Pleistocene [epoch]↔Calabrian [age], or Cenozoic [era]↔Quaternary [subera]↔Pleistocene [epoch]↔Calabrian [age]. We reaffirm that the inclusive compromise is entirely viable. In so doing we (i) challenge the necessity of the rigidly nested hierarchy, which should be capable of a little flexibility; (ii) reject all analogies of the arbitrary and conventional chronostratigraphic hierarchy with three natural biological hierarchies; (iii) reaffirm the integrity of the Neogene extending to the present; and (iv) see no reason to doubt the harmonious coexistence of the two options preserving the Quaternary and Neogene traditions in an orderly working and stable time scale. In the alternative schema conserving the Neogene, divisions of the Pliocene and Pleistocene are upgraded, so that the Late Pleistocene, Early Pleistocene and Late Pliocene Epochs comprise the Quaternary SubPeriod, itself equivalent to Late Neogene. The inflexibly nested hierarchy is preserved but the Tertiary is lost.
