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

小行星9316875 爱荷华州东部及周边州、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岩溶，其中洞穴发育广泛。 我们建议研究的石笋年龄和同位素记录在三到四个不同的“盆地”在一个地区，包括喀斯特南部边缘的草原半岛的半岛的全新世历史几乎是未知的。 这项研究补充了R. G.贝克和其他人研究了孢粉学、植物宏体化石和土壤记录，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，亚皮摩尔分辨率相结合的同位素稀释和质谱铀-钍的方法，以准确地定年的洞穴石笋和方解石的碳和氧同位素组成，以提取反映气候变化的记录。 这些研究的目标是：1）利用δ 13 C变化和U系列数据更好地确定上中西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的更精确和准确的时间; 3）试图产生中西部十年尺度温度变化的定量记录;（4）试图利用三角洲13 C的变化来确定洞穴地区植被变化和生物量周转的速率;（5）试图解决洞穴沉积物方解石的年度和可能的半年变化;（6）提供草原半岛南部边缘变化的日期明确的历史; 7）尝试从生长率变化估计降水量。 将在各个盆地和洞穴内分析多个洞穴沉积物，以复制和验证同位素变化、生长速率变化或盆地范围内干燥事件的存在的时间和幅度。 将仔细注意洞穴的选择，特别强调识别干燥和洪水事件的证据，这将减少同位素分析对气候推断的有效性和实用性。 将试图找到研究地点在接近那些正在研究的贝克和其他人，以便精确的时间植被变化可以提供。

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.