Knowledge Resource Center for Ecological Environment in Arid Area
| 项目编号 | 0715030 |
| SGER: Novel Approach to Arid Soil Dating: Extraction and 40Ar/39Ar Geochronology of Pedogenic Sepiolite and Palygorskite | |
| Brenda Buck | |
| 主持机构 | University of Nevada Las Vegas |
| 开始日期 | 2007-08-01 |
| 结束日期 | 2008-07-31 |
| 资助经费 | 29936(USD) |
| 项目类别 | Standard Grant |
| 资助机构 | US-NSF（美国国家科学基金会） |
| 项目所属计划 | Geobiology & Low-Temp Geochem |
| 语种 | 英语 |
| 国家 | 美国 |
| 英文简介 | Petrocalcic soil horizons containing authigenic clays cap geomorphic surfaces in many arid and semi-arid regions worldwide, and they also occur in the rock record as unconformities. Authigenic sepiolite and palygorskite clays form in stage II carbonate pendants and stage III - VI petrocalcic horizons. Accurately dating petrocalcic soils remains one of the largest scientific hurdles in both geomorphology and sedimentology. We propose an untested, novel approach to date authigenic sepiolite and palygorskite from petrocalcic horizons using 40Ar/39Ar geochronology. Our theoretical considerations suggest that the techniques we present herein are feasible, are applicable to many soils worldwide, and may help quantify rates of pedogenesis, landscape evolution, and climate change. If successful, our methodology would apply not only to extant petrocalcic soil landscapes, but also to the paleosol record. Lack of initial success will still enhance further soil geochronology research. We propose to analyze samples from two well-dated petrocalcic soil localities: Mormon Mesa, NV, and La Mesa, NM. We will also study purchased, reference sepiolite and palygorskite samples. We will extract sepiolite and palygorskite from 1) cemented, bulk soil samples and 2) microdrilled subsamples. Successful microdrill methods may expedite sample preparation for 40Ar/39Ar dating, given new micromorphological evidence (Brock & Buck, 2006) that authigenic clays often form within concentrated, macroscopically visible laminae. After each extraction step, we will analyze sample aliquots using SEM, XRD, and ICP-OES to identify or discount adverse effects on clay crystal lattice integrity or K content. TEM analyses will constrain compositional variability of extracted clays. 40Ar/39Ar measurements on successfully extracted clays will be made at the Nevada Isotope Geochronology Laboratory (NIGL) using vacuum encapsulation. Our final 40Ar/39Ar data and soil age interpretations will be compared to established tephrachonologic and morphostratigraphic ages for the Mormon Mesa and La Mesa surfaces. At the conclusion of our project, we will have answered the following questions: (1) Does chemical removal of pedogenic carbonate, amorphous silica, and iron-oxide cements affect crystal integrity or intracrystalline K and Ar content of fibrous clay minerals? (2) Does microdrilling of fibrous clays from petrocalcic samples affect crystal integrity or intracrystalline K and Ar content? (3) What mass of sepiolite or palygorskite is needed to minimize 40Ar/39Ar uncertainty? (4) Is 40Ar/39Ar geochronology of pedogenic sepiolite/palygorskite a viable means of numerically dating petrocalcic soilgeomorphologic surfaces? Broader impacts of this research include the dissertation research and graduate training of a Ph.D. student, Colin Robins, and the training of a (probable female) undergraduate student. NIGL personnel, including graduate research assistants, will improve methodologies and knowledge of dating fine-grained materials. This will enhance other cutting-edge research applications such as dating fault gouge to determine timing of motion on shallow crustal faults. Collaboration with NMSU personnel will strengthen arid-lands research on a regional scale. |
| 来源学科分类 | Geosciences |
| URL | https://www.nsf.gov/awardsearch/showAward?AWD_ID=0715030 |
| 资源类型 | 项目 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/342434 |
| 推荐引用方式 GB/T 7714 | Brenda Buck.SGER: Novel Approach to Arid Soil Dating: Extraction and 40Ar/39Ar Geochronology of Pedogenic Sepiolite and Palygorskite.2007. |
| 条目包含的文件 | 条目无相关文件。 | |||||
| 个性服务 |
| 推荐该条目 |
| 保存到收藏夹 |
| 导出为Endnote文件 |
| 谷歌学术 |
| 谷歌学术中相似的文章 |
| [Brenda Buck]的文章 |
| 百度学术 |
| 百度学术中相似的文章 |
| [Brenda Buck]的文章 |
| 必应学术 |
| 必应学术中相似的文章 |
| [Brenda Buck]的文章 |
| 相关权益政策 |
| 暂无数据 |
| 收藏/分享 |
除非特别说明，本系统中所有内容都受版权保护，并保留所有权利。
