GRGC: High Resolution (Century to Dacadal) Isotopic (18O and 13C) Record Preserved in Speleothem Calcite: Holocene Vegetation and Climate Change in the Midwest

GRGC：Speelothem 方解石中保存的高分辨率（世纪到 Dacadal）同位素（18O 和 13C）记录：中西部的全新世植被和气候变化

• 批准号: 9316875
• 负责人: Luis Gonzalez
• 金额: $ 14.5万
• 依托单位: University of Iowa
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1994
• 资助国家: 美国
• 起止时间: 1994-06-01 至 1997-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9316875&HistoricalAwards=false
• 关键词: GRGC; Resolution; Century; Dacadal; Isotopic

9316875 Gonzalez The eastern portion of Iowa and surrounding states, Minnesota, Wisconsin, Illinois, and Missouri are characterized by the presence of a well developed karst in which cave development is extensive. We propose to study the stalagmite age and isotopic record in three to four different "basins" in a region encompassing the karsted southern edge of the Prairie Peninsula where the Holocene history of the peninsula is virtually unknown. This research compliments current and proposed research by R. G. Baker and others that study the palynological, plant macrofossil and soil record and attempts to fill information gaps in the Holocene vegetation and climatic history. We propose to use the picomole to subpicomole resolution of combined isotope dilution and mass spectrometry U-Th methods to accurately date speleothems (stalagmites) and the carbon and oxygen isotopic composition of calcite to extract a record reflecting climatic change. The goals of these research are; 1) Better define the extent of the climate-induced vegetation change in the upper Midwest utilizing delta 13C shifts and U-series dates; 2) Provide a more precise and accurate timing of climate-induced vegetation change in the region; 3) Attempt to generate a quantitative record of temperature change at the decadal scale for the Midwest; 4) Attempt to define rates of vegetation change and biomass turnover over the cave areas using changes in the delta 13C; 5) Attempt to resolve annual and possibly semi-annual changes in speleothem calcite; 6) Provide a well dated history of changes in the southern edge of the Prairie Peninsula; 7) Attempt to estimate precipitation from growth rate changes. Multiple speleothems will be analyzed within individual basins and caves to replicate and validate timing and magnitude of isotopic shifts, growth rate changes, or the presence of basin wide desiccation events. Careful attention will be given to cave selection with special emphasis in the identificati on of evidence of desiccation and flooding events which will diminish and validity and utility of isotopic analysis for climatic inferences. Attempt will be made to find study sites in close proximity to those being studies by Baker and others so that precise timing for vegetation changes can be provided.

9316875 冈萨雷斯 爱荷华州东部及周边各州、明尼苏达州、威斯康星州、伊利诺伊州和密苏里州的特点是存在发育良好的喀斯特地貌，其中洞穴发育广泛。 我们建议研究三到四个不同“盆地”的石笋年龄和同位素记录，这些盆地位于草原半岛喀斯特南部边缘的地区，而该半岛的全新世历史实际上是未知的。 这项研究补充了 R. G. Baker 和其他人当前和拟议的研究，这些研究研究孢粉学​​、植物大化石和土壤记录，并试图填补全新世植被和气候历史的信息空白。 我们建议使用皮摩尔至亚皮摩尔分辨率的同位素稀释和质谱U-Th组合方法来准确测定洞穴石（石笋）和方解石的碳和氧同位素组成的年代，以提取反映气候变化的记录。 这些研究的目标是； 1) 利用三角洲 13C 变化和 U 系列日期更好地定义中西部北部气候引起的植被变化的程度； 2）提供该地区气候引起的植被变化更精确的计时； 3）尝试生成中西部十年尺度温度变化的定量记录； 4) 尝试利用 13C 三角洲的变化来定义洞穴区域植被变化和生物量周转率； 5) 尝试解决洞穴方解石的年度和可能半年的变化； 6）提供草原半岛南缘变迁的详细历史记录； 7) 尝试根据增长率变化来估计降水量。 将分析各个盆地和洞穴内的多个洞穴，以复制和验证同位素变化的时间和幅度、生长速率变化或盆地范围内的干燥事件的存在。 将仔细注意洞穴的选择，特别强调干燥和洪水事件证据的识别，这将削弱同位素分析对气候推论的有效性和实用性。 我们将尝试寻找与贝克和其他人正在研究的地点非常接近的研究地点，以便提供植被变化的精确时间。