Radiometric Dating of Lake Sediments

金沢大学自然計測応用研究センタ

Radiometric Dating of Lake Sediments: A Review

金沢大学自然計測応用研究センタ

Radiometric Dating of Lake Sediments : A Reaview

金沢大学大学院自然科学研究科Scedule:17-18 March 2003, Vemue: Kanazawa, Japan, Kanazawa Citymonde Hotel, Project Leader : Hayakawa, Kazuichi, Symposium Secretariat: XO kamata, Naoto, Edited by:Kamata, Naoto

鉱物中の放射線損傷量をどう見積もるか?ラマン分光法とFT法を用いた研究

金沢大学環日本海域環境研究センター鉱物中に蓄積された放射線損傷は,鉱物の物性をコントロールしたり,年代測定を可能にする重要な情報である。本研究では,ラマン分光分析,ウランの自発核分裂飛跡観察(FT法),ウラン・トリウム濃度測定(LA-ICPMS分析およびFT法)を組み合わせる事により,推定放射線損傷量とラマン分光シグナルとの関係を数式化し,放射線損傷量の定量法を確立する事をめざすとともに,年代測定への応用や,物性変化への影響の吟味を行うことを目的としている。Nasdala et al.(2001)はラマンスペクトラの1000カイザー付近に現れるν3(SiO4)bandの半値幅(FWHM)がウラン・トリウム濃度とU-Pb年代から計算したα線量と直線関係にあることを示した。昨年度,化学組成の変化がラマンスペクトルのFWHMにどのように影響を与えるかを合成ジルコンを用いて調査したところ,3周期の元素はジルコンに入りやすく,またその濃度とFWHMは直線の関係を示すことが分かった。ただしその時の濃度は~5000ppm以上必要であるが,これは天然のジルコンでは滅多にないほどの高濃度である。従って天然ジルコンのラマン分析においてあまり化学組成を気にする必要はないといえる。今年度はFT法で利用される年代標準試料の化学分析,ラマン分析を行った。もっとも多くの微量元素を含むものでも3000ppmを超えることはなかったため,ラマン分析結果に化学組成の影響を考慮する必要がなかった。ラマン分析結果は試料によって差はでなかった。また人工的に誘導核分裂によってトラックを増やした試料のラマン分析も行ったが,これも差はでなかった。したがってFT密度とラマン分析には明快な関係が見られなかった。ただしこのラマン分析は顕微ラマン分光器を利用したため,測定点の設定に影響を受けている可能性がある。研究課題/領域番号:17654095, 研究期間(年度):2005 – 2006出典：「鉱物中の放射線損傷量をどう見積もるか?ラマン分光法とFT法を用いた研究」研究成果報告書　課題番号17654095（KAKEN：科学研究費助成事業データベース（国立情報学研究所））（https://kaken.nii.ac.jp/ja/grant/KAKENHI-PROJECT-17654095/)を加工して作

Advanced Java-based application to process thermoluminescence digital color images

Dielectric minerals that interact with ionizing radiation emit thermoluminescence when heated. The color of the emitted thermoluminescence varies among different samples, even for the same minerals. TL color analysis can be used to study mineral provenance. Thermoluminescence color images (TLCI) can be obtained using a digital camera. Inagaki et al. (2010) created a Java application to handle RGB (red-green-blue) information of each pixel. This Java application is able to visually represent thermoluminescence color on a CIE (Commission Internationale de l’Eclairage) chromaticity diagram. Here, we report an improved Java application that enables the numerical treatment of TLCI of various image sizes and resolutions. This application allows for the handling of many digital TLCI in a short time and it is useful for statistical color analyses

Records of the atmospheric inputs of loess and pollutants in Japanese lake sediments

金沢大学自然計測応用研究センター金沢大学大学院自然科学研究科Nankai University (CHINA)Chinese Academy of Sciences (CHINA)Abstract – The atmosphere is a significant pathway for the transport of loess and pollutants from Asian continental interior to Japan. Loess would play a critical role in many processes during transport either indirectly (e.g., climate) or directly (e.g., health). For kick-off of our research, loess as an Asian monsoon proxy and historical record of sedimentary PAH were reviewed, and research plans to investigate the impact of climate and human activity on loess delivery to Japanese lake systems were proposed

Records of the Atmospheric Inputs of Loess and Pollutants in Japanese Lake Sediments

金沢大学大学院自然科学研究科Nankai UniversityChinese Academy of SciencesScedule:17-18 March 2003, Vemue: Kanazawa, Japan, Kanazawa Citymonde Hotel, Project Leader : Hayakawa, Kazuichi, Symposium Secretariat: XO kamata, Naoto, Edited by:Kamata, Naoto

Decadal–centennial-scale solar-linked climate variations and millennial-scale internal oscillations during the Early Cretaceous

Understanding climate variability and stability under extremely warm ‘greenhouse’ conditions in the past is essential for future climate predictions. However, information on millennial-scale (and shorter) climate variability during such periods is scarce, owing to a lack of suitable high-resolution, deep-time archives. Here we present a continuous record of decadal- to orbital-scale continental climate variability from annually laminated lacustrine deposits formed during the late Early Cretaceous (123–120 Ma: late Barremian–early Aptian) in southeastern Mongolia. Inter-annual changes in lake algal productivity for a 1091-year interval reveal a pronounced solar influence on decadal- to centennial-scale climatic variations (including the ~ 11-year Schwabe cycle). Decadally-resolved Ca/Ti ratios (proxy for evaporation/precipitation changes) for a ~ 355-kyr long interval further indicate millennial-scale (~ 1000–2000-yr) extreme drought events in inner-continental areas of mid-latitude palaeo-Asia during the Cretaceous. Millennial-scale oscillations in Ca/Ti ratio show distinct amplitude modulation (AM) induced by the precession, obliquity and short eccentricity cycles. Similar millennial-scale AM by Milankovitch cycle band was also previously observed in the abrupt climatic oscillations (known as Dansgaard–Oeschger events) in the ‘intermediate glacial’ state of the late Pleistocene, and in their potential analogues in the Jurassic ‘greenhouse’. Our findings indicate that external solar activity forcing was effective on decadal–centennial timescales, whilst the millennial-scale variations were likely amplified by internal process such as changes in deep-water formation strength, even during the Cretaceous ‘greenhouse’ period