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口頭

Using a 3-D heat transport model (PeCUBE) to invert OSL- and ESR-derived rock cooling histories into erosion rate changes in the Hida Range of Japan

Anderson, L.*; Bartz, M.*; King, G.*; Fox, M.*; Herman, F.*; Stalder, N.*; Biswas, R.*; 末岡 茂; 塚本 すみ子*; Ahadi, F.*; et al.

no journal, , 

Optically stimulated luminescence (OSL) and electron spin resonance (ESR) thermochronometry have the potential to resolve continuous erosion histories from rapidly eroding settings. These thermochronometers are viable over the past few hundred thousand to a million years. These time periods are defined by persistent oscillations between warm and cold states. During the Quaternary, fundamental questions about the relationship between climate and erosion remain unanswered. With further development, the OSL and ESR thermochronometers could answer these questions. To realize this potential new strategies are required to invert low-temperature thermal histories for erosion rates. Here, we explore the use of PeCUBE (Braun, 2003), a three-dimensional finite-element model that simulates heat conduction and advection in the upper crust. As a training dataset we use cooling histories derived from eight samples from the Tateyama region in the Hida Mountains of Japan. The flexibility of PeCUBE allows us to quantify the role of time varying surface temperatures between glacial and interglacial periods. In high-relief settings the three-dimensionality of the topography, for example between valleys and ridges, can substantially perturb rock temperatures. PeCUBE allows us to quantify and remove these confounding topographic effects. We additionally explore the role of changing topographic relief on time varying thermal fields and erosion rates. Lastly, we explore a generous range of model parameters to quantify the sensitivity and robustness of our inversions.

口頭

Unravelling rock cooling histories of the Japanese Alps using ESR thermochronometry

Bartz, M.*; King, G.*; Anderson, L.*; Herman, F.*; 末岡 茂; 塚本 すみ子*; Ahadi, F.*; Gautheron, C.*; Delpech, G.*; Schwarz, S.*; et al.

no journal, , 

Electron spin resonance (ESR) thermochronometry has the potential to resolve continuous erosion histories from rapidly eroding settings over 10$$^{6}$$ time scales. These time periods are defined by persistent oscillations between warm and cold states. However, questions about the relationship between climate and erosion remain unanswered. We further develop ESR thermochronometry of quartz (Al and Ti centres) to answer these questions in the Tateyama region in the Hida Mountains of Japan. In the result, the Al and Ti centres in quartz can successfully be inverted to unravel rock cooling histories. As future work, all ESR signals will be converted together with OSL data, providing further constraints on their thermal histories.

口頭

Unravelling rock cooling histories of the Japanese Alps using trapped-charge thermochronometry

Bartz, M.*; King, G.*; Anderson, L.*; Herman, F.*; 末岡 茂; 塚本 すみ子*; 田上 高広*

no journal, , 

捕獲電子を用いた熱年代手法に基づいて、日本アルプス飛騨山脈の岩石試料を対象に冷却史の解明を試みた。

口頭

Rates of erosion in the Japanese Alps during the Quaternary; Insights from trapped charge thermochronometry

Bartz, M.*; King, G. E.*; Anderson, L.*; Herman, F.*; 末岡 茂; 塚本 すみ子*; 田上 高広*

no journal, , 

The Japanese Alps uplifted throughout the Quaternary and reached elevations of up to 3,000 m. However, understanding the interaction between rates of Earth surface processes, tectonics and climate is challenging, partly due to the difficulties of measuring changes in the rates of Earth surface processes at the timescale of glacial-interglacial cycles. In particular, the youth of the Japanese Alps has made measurement of their exhumation histories complicated. Here we investigate the potential of ultra-low temperature thermochronometers based on the luminescence and electron spin resonance (ESR) of feldspar and quartz minerals respectively for understanding changes in exhumation rates. We focus on Tateyama (Hida range), which was glaciated during the late Quaternary period. In total, eight samples were analysed by luminescence and ESR thermochronometry. While most luminescence signals have already reached their upper dating limit, ESR signals give insights into Pleistocene exhumation rates. We measured the ESR dose response and thermal decay properties of all samples, specifically targeting the Al and Ti centres. In general, thermal stability is higher for the Ti signals, resulting in ESR ages of between 0.5-0.9 Ma, although some signals are close to or above the upper dating limit of the Ti centre. In contrast, the Al signal still grows with time and is suitable for determining finite exhumation rates. Initial inversions reveal rock cooling rates on the order of 80 deg. C/Ma, which can be inverted to preliminarily rates of rock exhumation of <3 mm/a within the past 1 Ma. In the next step, we will relate these rates to the climatic (glacial) and tectonic history of the Tateyama region.

口頭

Working towards a robust thermochronometer based on the ESR of quartz minerals

King, G.*; Bartz, M.*; Bossin, L.*; Wen, X.*; 塚本 すみ子*; Herman, F.*; 小形 学; 末岡 茂

no journal, , 

Electron spin resonance dating of quartz minerals offers a significant advantage over luminescence dating because of its later signal saturation. We are seeking to exploit this to build upon earlier studies in the development of a thermochronometry system capable of resolving rock cooling rates throughout the Quaternary. In order to determine a rock cooling history, it is necessary to constrain both signal accumulation and signal thermal loss robustly within the laboratory. We have collated a series of geological samples including rocks from boreholes that have known isothermal histories to investigate the potential of this technique. Our objective is to use the latter rocks to confirm the validity of our laboratory measurements and data-fitting/numerical models. Specifically, we have investigated known-thermal history samples from the MIZ1 borehole (Japan) and the KTB borehole (Germany). Preliminary data reveal that the ESR dose response and thermal decay of different quartz samples is highly variable.

口頭

Will ESR thermochronometry reveal the timing of Rh$^o$ne valley incision?

King, G. E.*; Wen, X.*; Bartz, M.*; Anderson, L.*; Bossin, L.*; 塚本 すみ子*; Li, Y.*; Herman, F.*; 小形 学; 末岡 茂

no journal, , 

To determine a rock cooling history using ESR thermochronometry, signal accumulation and signal thermal loss must be robustly determined within the laboratory. We have collected a series of geological samples including rocks from boreholes that have known isothermal histories to investigate the potential of this technique. Our objective is to use the latter rocks to confirm the validity of our laboratory measurements and data-fitting/numerical models. Specifically, we have investigated known-thermal history samples from the MIZ1 borehole (Japan) and the KTB borehole (Germany) as well as samples from Sion in the Western European Alps. Preliminary data reveal that the ESR dose response and thermal decay of different quartz samples is highly variable. Whereas the Al-centre of some samples exhibits linear dose response to laboratory irradiation up to 15 kGy, the Al-centre of other samples exhibits exponential, or double exponential growth and saturates at doses of 3-4 kGy. The Ti-centre of most samples is well described by a single saturating exponential function, however samples from the MIZ1 borehole exhibit pronounced sub-linearity in the low-dose response region. Furthermore, whereas for some samples the Al-centre is less thermally stable than the Ti-centre, for other samples the inverse is observed. These observations suggest that a uniform measurement protocol and data-fitting approach may not be appropriate for quartz ESR data. Inversion of two KTB samples yielded temperatures within uncertainty of borehole temperature, however results for the MIZ1 borehole are more variable and can only recover temperature at best within c.a. 10%. Investigations into the cause of the poor results for the MIZ1 borehole are ongoing (i.e. measurement protocol, data-fitting/numerical model) and will be discussed. Preliminary data from Sion are promising and reveal consistent cooling rates.

口頭

High-relief exhumation history in the Japanese Alps within the past 1 Ma inferred from trapped charge thermochronometry

Bartz, M.*; King, G. E.*; Herman, F.*; Anderson, L.*; 末岡 茂; 塚本 すみ子*; 田上 高広*

no journal, , 

The interaction between rates of Earth surface processes, climate and tectonics determines the landscape in mountain regions. The Japanese Alps uplifted throughout the Quaternary and now reach elevations of up to 3,000 m. However, quantifying relief changes in response to tectonic activity, magmatism and Late Quaternary glaciation is challenging due to the young age of the Japanese Alps and the difficulty of measuring surface processes at the timescale of glacial-interglacial cycles. Here, we use ultra-low temperature thermochronometers based on the luminescence of feldspar minerals and the electron spin resonance (ESR) of quartz minerals, in combination with inverse modelling to derive rock cooling rates and time series of exhumation rates at 10$$^{4}$$-10$$^{6}$$ years timescales. We focus on the Tateyama region in the Hida range of the Japanese Alps, which was glaciated during the late Quaternary period. In total, 19 new samples were analyzed by luminescence and ESR thermochronometry. While most luminescence signals have already reached their upper dating limit, ESR signals (Al and Ti centres) yielded ESR ages of between 0.5-0.9 Ma. In general, thermal stability is lower for the Al centre compared to that of the Ti centre, but both centres constrain similar exhumation rates. Inversions reveal rock cooling rates on the order of 30-80 deg. C/Ma, which can be inverted to exhumation rates of less than 1 mm/a within the past 1 Ma. In the next step, we will relate the exhumation rates to the glacial and tectonic history of the Tateyama region.

口頭

Unravelling rock cooling histories of the Japanese Alps within the past 1 Ma using ESR and OSL thermochronometry

Bartz, M.*; King, G. E.*; Herman, F.*; Anderson, L.*; 末岡 茂; 塚本 すみ子*; 田上 高広*

no journal, , 

To resolve exhumation histories of the Japanese Alps throughout the Quaternary, we investigate the potential of ultra-low temperature thermochronometers based on the luminescence of feldspar minerals and electron spin resonance (ESR) of quartz minerals, in combination with inverse modelling to derive rock cooling rates and exhumation rates histories at 10$$^{4}$$-10$$^{6}$$ years timescales. We focus on the Tateyama region in the Hida range of the Japanese Alps. In total, 19 new samples were analyzed by luminescence and ESR thermochronometry. While most luminescence signals have already reached saturation, ESR signals (Al and Ti centres) still grow with dose and are suitable for determining finite exhumation rates in the Tateyama region. We used the ESR single aliquot regenerative additive (SARA) dose protocol for dose evaluation including protocol optimization (i.e., preheat-plateau test). We checked for sensitivity changes due to the high-temperature annealing step within the SARA procedure using SARA vs. single aliquot additive dose response, repeated dose points (i.e., recycling ratio) and dose recovery of an artificially zeroed sample. Thermal stabilities of the ESR signals were analysed by using isothermal decay experiments and simulations of the isothermal decay using the experimentally constrained kinetic parameters. Our experiments showed insignificant sensitivity changes during measurements, resulting in Al and Ti ages of between 0.3-0.9 Ma and 0.5-1.1 Ma, respectively. In general, thermal stability is lower for the Al centre compared to that of the Ti centre but simulations yielded valuable thermal stability over Quaternary timescales for both ESR centres. Inversions reveal rock cooling rates on the order of 30-80 deg. C/Ma, much lower than those of the luminescence thermochronometry technique, which helps to resolve erosion rates histories on the order of few mm/a. Thus, preliminary erosion rates of $$<$$1 mm/a within the past 1 Ma could be inverted.

口頭

Borehole calibration of ESR thermochronometry

King, G. E.*; Wen, X.*; Bartz, M.*; Bossin, L.*; 塚本 すみ子*; Li, Y.*; Herman, F.*; 小形 学; 末岡 茂

no journal, , 

Whereas the luminescence thermochronometry system is limited to areas experiencing very rapid rock cooling (exhumation) of 10s of mm/yr, our data indicate that ESR thermochronometry can resolve rates of $$<$$1 mm/yr over Quaternary timescales. To determine a rock cooling history using ESR thermochronometry, signal accumulation and signal thermal loss must be robustly determined within the laboratory. We have collected a series of borehole samples with known isothermal histories to investigate the potential of this technique. Our objective is to use the latter rocks to confirm the validity of our laboratory measurements and data-fitting/numerical models by using the ESR-thermochronometry method to recover their known in-situ temperatures. Specifically, we have investigated known-thermal history samples from the MIZ1 borehole (Japan) and the KTB borehole (Germany). Preliminary data reveal that the ESR dose response and thermal decay of different quartz samples is highly variable. Whereas the Al-centre of some samples exhibits linear dose response to laboratory irradiation up to 15 kGy, the Al-centre of other samples exhibits exponential, or double-exponential growth and saturates at doses of 3-4 kGy. The Ti-centre of most samples is well described by a single saturating exponential function, however samples from the MIZ1 borehole exhibit pronounced sublinearity in the low-dose response region. Furthermore, whereas for some samples the Al-centre is less thermally stable than the Ti-centre, for other samples the inverse is observed. These observations suggest that a uniform measurement protocol and data-fitting approach may not be appropriate for quartz ESR data.

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