COLLABORATIVE RESEARCH: Dating Quaternary Deposits and Soils with TIMS U-Series on Pedogenic Carbonate and Silica

合作研究：利用 TIMS U 系列对成土碳酸盐和二氧化硅测定第四纪沉积物和土壤

• 批准号: 9725573
• 负责人: Ronald Amundson
• 金额: $ 1.71万
• 依托单位: University of California-Berkeley
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1997
• 资助国家: 美国
• 起止时间: 1997-12-15 至 2000-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9725573&HistoricalAwards=false
• 关键词: COLLABORATIVE; RESEARCH; Dating; Quaternary; Deposits

9725573 Amundson Funds are requested to further develop and apply TIMS (Thermal Ionization Mass Spectrometry) U-series dating to pedogenic carbonate and silica. The research will seek to understand the potential and limitations of U-series dates on chemically/mineralogically-characterized, micro-sampled clast rinds by detailed work in two climatically and lithologically distinct areas. Two localities will be studied, using techniques that build on the results of recent, independent studies by the P.I.'s. Kyle Canyon (Nevada) provides a sequence of carbonate-clast alluvial deposits and morphologic surfaces ranging from Holocene to 780 ka, whereas the Wind River Basin (Wyoming) provides a sequence of granitic-clast dominated alluvial deposits from Holocene to early Pleistocene age. In both localities, the Quaternary geology and pedology have been well studied by one or more of the investigators of this proposal. This is a collaborative proposal among 3 institutions: Ken Ludwig and Warren Sharp at the Berkeley Geochronology Center will be responsible for sampling and uranium-series analyses using the new TIMS facility and clean lab at BGC; Ron Amundson at U.C. Berkeley and Oliver Chadwick at U.C. Santa Barbara will provide field and laboratory expertise in Quaternary geology and pedology, as well as familiarity with the study localities. All of the named investigators will participate in the chemical and microscopic characterization of the pedogenic carbonate and silica, and Amundson will be responsible for the stable-isotopic work and interpretation. The single-sample/single-date approach developed by Ludwig and J.B. Paces for a recent study at Crater Flat, Nevada, in which sub-millimeter laminae of individual carbonate/silica rinds are micro-sampled to avoid detrital contamination, will be applied to carefully-characterized clast rinds of the deposits in both localities. The limitations of the approach will be explored including the reliability of the detrital 230Th corrections, the textural and geochemical indicators of open systems, and the practicality of extending the method into the Early Pleistocene using 234U/238U. Analyses of Holocene clast-rinds will be of special interest, as these samples will provide an understanding of the likely time-lag between clast deposition and the accumulation of datable carbonate or carbonate/silica rinds. Knowledge of this time lag (and its variability in different climatic and lithologic contexts) will be essential in using U-series dates of innermost clast-rinds to date the Quaternary deposits themselves. Some development of micro-sampling techniques will be required to explore the limits of sample size and spatial resolution, but this can be done with relatively modest equipment. The laboratory challenges involve mainly those of small-sample 230Th analyses, in which one of the P.I.'s has extensive experience. The results of the dating studies will be applied to understanding the history and timing of erosion and sedimentation in Kyle Canyon, and of glacial events in the Wind River Basin. A limited number of stable-isotope analyses will be used to evaluate the usefulness of the rinds as a paleoclimate record, as well as to check for open-system histories of the mid-and early Pleistocene rinds.

要求9725573 Amundson资金进一步开发和应用TIMS（热电离质谱法）U系列的u系列，可追溯到Pedogenic碳酸盐和二氧化硅。 该研究将寻求通过在两个气候和岩性不同的区域中的详细工作来了解化学/矿物学特征，微采样的碎屑果皮的U系列日期的潜在和局限性。 使用P.I.最近的独立研究结果的技术，将研究两个地方。 Kyle Canyon（内华达州）提供了一系列碳酸盐冲积沉积物和形态学表面，从全新世到780 ka，而风河盆地（Wyoming）则提供了一系列从整体上统治的冲积外科沉积物，从房屋中到Pleistercene早期，都提供了一系列的层次。 在这两个地方，该提案的一个或多个研究人员都对第四纪地质和培训进行了很好的研究。 这是3个机构之间的一项协作提案：伯克利年代学中心的肯·路德维希（Ken Ludwig）和沃伦·夏普（Warren Sharp）将负责使用BGC的新TIMS设施和清洁实验室进行采样和铀系列分析； U.C.的Ron Amundson U.C.伯克利和奥利弗·查德威克圣塔芭芭拉（Santa Barbara）将提供第四纪地质和人工学的现场和实验室专业知识，以及对研究地区的熟悉。 所有指定的研究人员将参与Pedogenic Carbenate和Silica的化学和微观表征，Amundson将负责稳定的同位素工作和解释。 由路德维格（Ludwig）和J.B.速度开发的单样本/单日期方法在内华达州火山口平面（Crater Flat）进行了一项研究，在该研究中，将单个碳酸盐/二氧化硅皮肤的亚毫米层板膜微采样是微采样，以避免在两个地方仔细地将其置入碎屑冲突，以仔细地应用于两个地方。 将探索该方法的局限性，包括使用234U/238U将方法扩展到早期更新世的实用性，包括第230校正校正的可靠性，开放系统的纹理和地球化学指标的可靠性。 全新世碎屑的分析将具有特殊的兴趣，因为这些样品将对碎屑沉积与碳酸盐或碳酸盐或碳酸盐/硅胶的积累之间的可能时间停滞。 了解这段时间的知识（及其在不同气候和岩性环境中的可变性）对于使用第四纪沉积物本身的最内部碎屑的u系日期至关重要。 需要一些微采样技术的一些开发来探索样本量和空间分辨率的限制，但这可以使用相对适度的设备来完成。 实验室的挑战主要涉及第230分析的小样本，其中一位P.I.具有丰富的经验。 约会研究的结果将应用于了解凯尔峡谷侵蚀和沉积的历史和时机以及风河盆地中冰川事件的历史和时机。 有限数量的稳定异位分析将用于评估果皮作为古气候记录的有用性，并检查中期和早期更新世的开放系统历史。