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Takuto Ando - One of the best experts on this subject based on the ideXlab platform.
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Establishment of Upper Cretaceous bio- and carbon isotope stratigraphy in the northwest Pacific Ocean and radiometric ages around the Albian/Cenomanian, Coniacian/Santonian and Santonian/Campanian boundaries
Newsletters on Stratigraphy, 2019Co-Authors: Reishi Takashima, Hiroshi Nishi, Toshiro Yamanaka, Yuji Orihashi, Yasuyuki Tsujino, Xavier Quidelleur, Keiichi Hayashi, Ken Sawada, Hideto Nakamura, Takuto AndoAbstract:The Yezo Group, exposed in Hokkaido, northern Japan, is one of the few strata that recorded Cretaceous paleo-oceanographic changes in the Pacific Ocean. Although the group yields abundant marine macro- and microfossils, sporadic occurrences of age-diagnostic species in several stratigraphic intervals has prevented high-resolution international biostratigraphic correlation. The proposed integrated bio- and carbon isotope stratigraphy of the Yezo Group, which is exposed in northwest Hokkaido, enables high-resolution international stratigraphic correlation spanning from Upper Albian to Lower Campanian. The correlation of the present study identifies the detailed stratigraphic horizons of the Albian/Cenomanian, Cenomanian/Turonian, Turonian/Coniacian, Coniacian/Santonian, and Santonian/Campanian boundaries, as well as the Late Cretaceous paleo-environmental events in the Yezo Group. The Yezo Group is also important in order to complement the chronometric age of the Cretaceous geologic time scale because the group includes numerous felsic tuffs. The U-Pb zircon ages of some of these tuffs, which are interbedded near the Albian/Cenomanian, Coniacian/Santonian and the Santonian/Campanian boundaries in the Yezo Group, are dated at 99.7±0.3 Ma (Quidelleur et al. 2011), 86.87±0.60/0.67 (internal/total error) Ma and 84.7±0.7/1.8 (internal/total error) Ma, respectively. These radiometric ages are consistent with the latest age model of the Cretaceous time scale.
Richard J M Taylor - One of the best experts on this subject based on the ideXlab platform.
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strategies towards statistically robust interpretations of in situ u pb zircon geochronology
Geoscience frontiers, 2016Co-Authors: Christopher J Spencer, Christopher L Kirkland, Richard J M TaylorAbstract:Zircon U–Pb geochronology has become a keystone tool across Earth science, arguably providing the gold standard in resolving deep geological time. The development of rapid in situ analysis of zircon (via laser ablation and secondary ionization mass spectrometry) has allowed for large amounts of data to be generated in a relatively short amount of time and such large volume datasets offer the ability to address a range of geological questions that would otherwise remain intractable (e.g. detrital zircons as a sediment fingerprinting method). The ease of acquisition, while bringing benefit to the Earth science community, has also led to diverse interpretations of geochronological data. In this work we seek to refocus U–Pb zircon geochronology toward best practice by providing a robust statistically coherent workflow. We discuss a range of data filtering approaches and their inherent limitations (e.g. discordance and the reduced chi-squared; MSWD). We evaluate appropriate mechanisms to calculate the most geologically appropriate age from both 238U/206Pb and 207Pb/206Pb ratios and demonstrate the cross over position when chronometric power swaps between these ratios. As our in situ analytical techniques become progressively more precise, appropriate statistical handing of U–Pb datasets will become increasingly pertinent.
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strategies towards statistically robust interpretations of in situ u pb zircon geochronology
Geoscience frontiers, 2016Co-Authors: Christopher J Spencer, Christopher L Kirkland, Richard J M TaylorAbstract:Abstract Zircon U–Pb geochronology has become a keystone tool across Earth science, arguably providing the gold standard in resolving deep geological time. The development of rapid in situ analysis of zircon (via laser ablation and secondary ionization mass spectrometry) has allowed for large amounts of data to be generated in a relatively short amount of time and such large volume datasets offer the ability to address a range of geological questions that would otherwise remain intractable (e.g. detrital zircons as a sediment fingerprinting method). The ease of acquisition, while bringing benefit to the Earth science community, has also led to diverse interpretations of geochronological data. In this work we seek to refocus U–Pb zircon geochronology toward best practice by providing a robust statistically coherent workflow. We discuss a range of data filtering approaches and their inherent limitations (e.g. discordance and the reduced chi-squared; MSWD). We evaluate appropriate mechanisms to calculate the most geologically appropriate age from both 238U/206Pb and 207Pb/206Pb ratios and demonstrate the cross over position when chronometric power swaps between these ratios. As our in situ analytical techniques become progressively more precise, appropriate statistical handing of U–Pb datasets will become increasingly pertinent.
Christopher L Kirkland - One of the best experts on this subject based on the ideXlab platform.
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strategies towards statistically robust interpretations of in situ u pb zircon geochronology
Geoscience frontiers, 2016Co-Authors: Christopher J Spencer, Christopher L Kirkland, Richard J M TaylorAbstract:Zircon U–Pb geochronology has become a keystone tool across Earth science, arguably providing the gold standard in resolving deep geological time. The development of rapid in situ analysis of zircon (via laser ablation and secondary ionization mass spectrometry) has allowed for large amounts of data to be generated in a relatively short amount of time and such large volume datasets offer the ability to address a range of geological questions that would otherwise remain intractable (e.g. detrital zircons as a sediment fingerprinting method). The ease of acquisition, while bringing benefit to the Earth science community, has also led to diverse interpretations of geochronological data. In this work we seek to refocus U–Pb zircon geochronology toward best practice by providing a robust statistically coherent workflow. We discuss a range of data filtering approaches and their inherent limitations (e.g. discordance and the reduced chi-squared; MSWD). We evaluate appropriate mechanisms to calculate the most geologically appropriate age from both 238U/206Pb and 207Pb/206Pb ratios and demonstrate the cross over position when chronometric power swaps between these ratios. As our in situ analytical techniques become progressively more precise, appropriate statistical handing of U–Pb datasets will become increasingly pertinent.
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strategies towards statistically robust interpretations of in situ u pb zircon geochronology
Geoscience frontiers, 2016Co-Authors: Christopher J Spencer, Christopher L Kirkland, Richard J M TaylorAbstract:Abstract Zircon U–Pb geochronology has become a keystone tool across Earth science, arguably providing the gold standard in resolving deep geological time. The development of rapid in situ analysis of zircon (via laser ablation and secondary ionization mass spectrometry) has allowed for large amounts of data to be generated in a relatively short amount of time and such large volume datasets offer the ability to address a range of geological questions that would otherwise remain intractable (e.g. detrital zircons as a sediment fingerprinting method). The ease of acquisition, while bringing benefit to the Earth science community, has also led to diverse interpretations of geochronological data. In this work we seek to refocus U–Pb zircon geochronology toward best practice by providing a robust statistically coherent workflow. We discuss a range of data filtering approaches and their inherent limitations (e.g. discordance and the reduced chi-squared; MSWD). We evaluate appropriate mechanisms to calculate the most geologically appropriate age from both 238U/206Pb and 207Pb/206Pb ratios and demonstrate the cross over position when chronometric power swaps between these ratios. As our in situ analytical techniques become progressively more precise, appropriate statistical handing of U–Pb datasets will become increasingly pertinent.
Daniel Richter - One of the best experts on this subject based on the ideXlab platform.
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evidence for the age and timing of environmental change associated with a lower palaeolithic site within the middle pleistocene reinsdorf sequence of the schoningen coal mine germany
Palaeogeography Palaeoclimatology Palaeoecology, 2021Co-Authors: Mario Tucci, Daniel Richter, Kim J Krahn, Thijs Van Kolfschoten, Barbara Rodriguez Alvarez, Ivo Verheijen, Jordi Serangeli, Jens Lehmann, Detlev DegeringAbstract:Abstract The discovery of a tusk and a rib of a straight-tusked elephant within layer 13 II-2c3 of the famous Lower Palaeolithic archaeological site Schoningen (district Helmstedt, Lower-Saxony, Germany) provided the reason for studying the climatic and ecological conditions of this part of the Middle Pleistocene Reinsdorf sequence in high resolution in relation to new chronometric data. Sediment, pollen, aquatic microfossil (diatoms, ostracods, gyrogonites of charophytes) and micro mammalian analyses provide evidence for a strong environmental change and landscape opening following the post-temperate boreal forest phase of the Reinsdorf Interglacial. Palynological and palaeontological evidence from this horizon suggest increasing dryness and seasonality. The high proportions of non-arboreal pollen including Poaceae as well as a major decrease of thermophile tree taxa indicate the development of zonal steppe environments. The assemblage of small mammal remains includes indicators of temperate as well as cold climatic conditions. A bone tool together with flint artefacts clearly show the presence of hominins in this context. Based on palaeoecological evidence and new luminescence dating, previous correlations of the Reinsdorf sequence to Marine Isotope Stage (MIS) 9 and thus of the interglacial sediments to MIS 9e are confirmed and the onset of the first post-interglacial steppe phase represented by layer 13 II-2c3 to MIS 9d is proposed.
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the age of the lower paleolithic occupation at schoningen
Journal of Human Evolution, 2015Co-Authors: Daniel Richter, Matthias KrbetschekAbstract:Abstract Thermoluminescence (TL) data are presented for eight samples of heated flint collected at the archaeological site of Schoningen 13/I-1 (Cycle I), for which a Holsteinian age is suggested by palynology of stratigraphically similar positions within a cyclic sedimentological model for the Quaternary sequence of Schoningen. Although the fire responsible for the zeroing of the TL-signal cannot be unequivocally attributed to human activities, any time difference between a natural fire and the human occupation is negligible for a site of this antiquity. The weighted mean age of 321 ± 16 ka places the last heating of the flints nominally in the age range of Marine Isotope Stages (MIS) 10 to 8. By inference this data would suggest an attribution of the Holsteinian to MIS 9 and may also serve as a maximum age estimate for the spear site of Schoningen 13/II-4 (Cycle II). Considering the chronometric data available and following an alternative sedimentological model the age of these two sites at Schoningen can be considered as belonging to the same climatic cycle. This suggests an attribution to MIS 9, and by inference provides an age estimate of 337–300 ka for the oldest spears in human history.
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heated flint tl dating for gruta da oliveira portugal dosimetric challenges and comparison of chronometric data
Journal of Archaeological Science, 2014Co-Authors: Daniel Richter, Diego E Angelucci, M I Dias, M I Prudencio, M A Gouveia, Guilherme Cardoso, C I Burbidge, Joao ZilhaoAbstract:The Mousterian stratigraphy of Gruta da Oliveira (Torres Novas, Portugal) contains one of the latest occupations by Neanderthals on the Iberian Peninsula. Thermoluminescence (TL) dates on heated flints were obtained for layers 13 and 14, and compared with the radiocarbon (charcoal and burnt bone) and U/Th (secondary carbonates) dating results available for those layers and the succession as a whole. As the internal dose rates are very low, the TL age estimates are very dependent on the external dose rates, which show significant variation, including indications of spatial patterning. Through close inspection of the radiation geometries of samples and dosemeters, the appropriate gamma dosimetry is identified and the weighted mean TL ages (1-σ) calculated accordingly are 55 ± 7 ka for layer 13 and 77 ± 8 ka for layer 14. These ages are stratigraphically consistent with the radiocarbon chronology for layers 9–11 and with the termini ante and post quem provided by U-series dating for the beginning and end of the accumulation of the deposits. The TL results corroborate that all radiocarbon dates below layer 11 are minimum ages only and, given the constraints derived from the proxy data available, place layer 13 and 14 post MIS 5. Sample as well as dosemeter numbers are low at Gruta da Oliveira, which limits the precision of TL-dating of a prehistoric human activity. Further refinement of the chronostratigraphy will be based on U-series dating of non-human-related, interstratified secondary carbonates.
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new data from the site of ifri n ammar morocco and some remarks on the chronometric status of the middle paleolithic in the maghreb
2012Co-Authors: Daniel Richter, Johannes Moser, Mustapha NamiAbstract:The definition and chronometric position of the Middle Paleolithic technocomplex of the “Aterian” are heavily debated. While for some, the presence of tanged lithics is sufficient to warrant the attribution of an assemblage to the “Aterian,” for others there is more to the “Aterian,” which is, however, defined in different ways. Here, we present thermoluminescence (TL) dating results on the multiple layer site of Ifri n’Ammar (Morocco), with an alternating double sequence of assemblages previously described as “Mousterian” and “Aterian” based on the presence/absence of tanged lithics. All the Middle Paleolithic industries at Ifri n’Ammar are technologically and typologically relatively similar to each other, as well as to the European Mousterian, with the most significant difference being the presence of tanged lithic artifacts in some layers. We prefer to use the term “Middle Paleolithic of Aterian facies/aspect,” instead of assigning it the status of a distinct technocomplex which is used in a chronostratigraphical sense. TL data of 83.3 ± 5.6 ka (weighted; n = 10) on heated lithics is obtained for the uppermost Middle Paleolithic level (Upper OS), which contains tanged lithic tools, as well as personal ornaments, while the underlying layer (Lower OS), which lacks tanged pieces, dates to 130.0 ± 7.8 ka (n = 9). The latter age is also a minimum for its underlying layer, which again contains tanged items, and thus the first appearance of tanging is significantly older in comparison with chronometric data from other sites. The discrepancy between TL and radiocarbon dates from the same levels at Ifri n’Ammar brings into question the reliability of radiocarbon analysis at the limits of the method.
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new chronometric data from ifri n ammar morocco and the chronostratigraphy of the middle palaeolithic in the western maghreb
Journal of Human Evolution, 2010Co-Authors: Daniel Richter, Johannes Moser, Mustapha Nami, Josef Eiwanger, Abdeslam MikdadAbstract:In addition to South Africa, the Northwestern corner of the African continent is providing a wealth of data for the understanding of the behaviour of early modern humans. In NW Africa, this modern behaviour is associated with a technocomplex called 'Aterian'. However, its definition as well as chronological position is heavily debated. As a common notion, the 'Aterian' is placed as the (more or less) last technocomplex of the Middle Stone Age/Middle Palaeolithic. However, the stratigraphy of the Moroccan site of Ifri n'Ammar provides evidence that the 'Aterian' cannot serve as a chronostratigraphic entity because of its presence in a stratigraphical sequence before as well as after Middle Palaeolithic industries lacking tanged tools. These should supposedly all occur beneath any layer containing tanged lithic objects, which are, at present, the main criteria for assigning an assemblage to the 'Aterian'. According to the sequence of Ifri n'Ammar, the relative chronostratigraphical position of tanged tools is therefore shown not to be a single unit. Thermoluminescence (TL) dating of heated artefacts from the main layers of Ifri n'Ammar provides a first chronostratigraphic backbone for the site and for the Maghreb. Layer 'Upper OS', which contains tanged items as well as personal ornaments is dated to 83.3 ± 5.6 ka (n = 10), while the underlying 'Lower OS', which is lacking tanged pieces, is dated to 130.0 ± 7.8 ka (n = 9). The following layer (Upper OI), which again contains tanged items, and thus provides the earliest appearance of the technique of tanging is dated to 145 ± 9 ka. The base of the sequence is formed by a Middle Palaeolithic layer (Lower OI) again lacking tanged objects and dated to 171 ± 12 ka by TL on heated lithic artefacts. These data significantly push back in time the earliest occurrence of tanged tools and the sequence calls for a complete revision of the Maghreb chronostratigraphy.
Reishi Takashima - One of the best experts on this subject based on the ideXlab platform.
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Establishment of Upper Cretaceous bio- and carbon isotope stratigraphy in the northwest Pacific Ocean and radiometric ages around the Albian/Cenomanian, Coniacian/Santonian and Santonian/Campanian boundaries
Newsletters on Stratigraphy, 2019Co-Authors: Reishi Takashima, Hiroshi Nishi, Toshiro Yamanaka, Yuji Orihashi, Yasuyuki Tsujino, Xavier Quidelleur, Keiichi Hayashi, Ken Sawada, Hideto Nakamura, Takuto AndoAbstract:The Yezo Group, exposed in Hokkaido, northern Japan, is one of the few strata that recorded Cretaceous paleo-oceanographic changes in the Pacific Ocean. Although the group yields abundant marine macro- and microfossils, sporadic occurrences of age-diagnostic species in several stratigraphic intervals has prevented high-resolution international biostratigraphic correlation. The proposed integrated bio- and carbon isotope stratigraphy of the Yezo Group, which is exposed in northwest Hokkaido, enables high-resolution international stratigraphic correlation spanning from Upper Albian to Lower Campanian. The correlation of the present study identifies the detailed stratigraphic horizons of the Albian/Cenomanian, Cenomanian/Turonian, Turonian/Coniacian, Coniacian/Santonian, and Santonian/Campanian boundaries, as well as the Late Cretaceous paleo-environmental events in the Yezo Group. The Yezo Group is also important in order to complement the chronometric age of the Cretaceous geologic time scale because the group includes numerous felsic tuffs. The U-Pb zircon ages of some of these tuffs, which are interbedded near the Albian/Cenomanian, Coniacian/Santonian and the Santonian/Campanian boundaries in the Yezo Group, are dated at 99.7±0.3 Ma (Quidelleur et al. 2011), 86.87±0.60/0.67 (internal/total error) Ma and 84.7±0.7/1.8 (internal/total error) Ma, respectively. These radiometric ages are consistent with the latest age model of the Cretaceous time scale.