COLLABORATIVE RESEARCH: A Detailed Test of Cosmogenic Radionuclide Dating of Moraines: Pinedale and Bull Lake Moraines, Fremont Lake, Wyoming

合作研究：对冰碛宇宙成因放射性核素测年的详细测试：怀俄明州弗里蒙特湖的派恩代尔和布尔湖冰碛

• 批准号: 9208944
• 负责人: Roy Middleton
• 金额: --
• 依托单位: University of Pennsylvania
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1992
• 资助国家: 美国
• 起止时间: 1992-07-01 至 1994-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9208944&HistoricalAwards=false
• 关键词: COLLABORATIVE; RESEARCH; Detailed; Test; Cosmogenic

This research is a detailed test of cosmogenic radionuclide exposure dating based principally on measurements of 1OBe, 26Al, and 14C in quartz from boulders which lie on moraine crest of known or accepted ages at the Pinedale Glaciation type locality, Fremont Lake, Wyoming. The purpose is to determine the limits, accuracy, precision, and resolution of the cosmogenic dating technique. We will adher to a stringent sampling strategy which minimizes errors due to high erosion rate (i.e. fire-induced surface spallation), pre-exposure, cosmic radiation shielding, unsuitable boulder surface geometries, and disturbed exposure, cosmic radiation shielding, unsuitable boulder surface geometries, and disturbed exposure histories due to redeposition or burial of the boulder. In the first year we will determine the reliability and precision of the technique to date a moraine by sampling multiple boulders on single moraine ridges, and multiple samples from selected boulders. Based on direct dating, regional correlations to dated stratigraphic equivalents, and correlation to the high resolution oxygen isotope chronostratigraphy they Pinedale (Stage 2) and Bull Lake (Stage 6) deposits can be aged bracketed at 14-30 ka and 130-160ka. We will date 30 samples from each of the Pinedale and Bull Lake terminal moraines at Fremont Lake. In the second year, armed with a measure of the method's precision, we will date samples from each of 6 nested Pinedale recessional moraines in order to determine its resolution. If the ages of the outermost to innermost moraines yield progressively younger ages this will imply that the technique will be able to directly measure rates to alpine or continental glacial retreat. We will also date 10 boulders from a suspect Stage 4 moraine which lies between the Pinedale and Bull Lake deposits in order to establish whether or not Stage 4 (Early Pinedale) deposits are preserved at the Pinedale type locality. Finally, we will make a useful cross check of dates produced from our method with dates using F. Phillips' 36C1 technique on duplicate samples from 10 boulders which yield the best dates from Year 1.

这项研究是对宇宙成因放射性核素暴露测年的详细测试，主要基于怀俄明州弗里蒙特湖派恩代尔冰川类型地点已知或可接受年龄的冰碛顶部的巨石中的 1OBe、26Al 和 14C 测量。 目的是确定宇宙成因测年技术的极限、准确性、精密度和分辨率。 我们将坚持严格的采样策略，最大限度地减少由于高侵蚀率（即火引起的表面散裂）、预暴露、宇宙辐射屏蔽、不合适的巨石表面几何形状以及干扰暴露、宇宙辐射屏蔽、不合适的巨石表面几何形状而导致的错误，并由于巨石的重新沉积或掩埋而扰乱暴露历史。 在第一年，我们将通过对单个冰碛山脊上的多个巨石进行采样以及从选定的巨石中提取多个样本来确定冰碛年代测定技术的可靠性和精确度。 根据直接测年、与已测年地层当量的区域相关性以及与高分辨率氧同位素年代地层学的相关性，Pinedale（第 2 阶段）和 Bull Lake（第 6 阶段）沉积物的年龄可划分为 14-30 ka 和 130-160ka。 我们将对来自弗里蒙特湖派恩代尔和布尔湖终端冰碛各 30 个样本进行测定。 第二年，在对该方法的精确度进行测量后，我们将对 6 个嵌套的派恩代尔衰退冰碛中的每一个样本进行年代测定，以确定其分辨率。 如果最外层到最内层冰碛的年龄逐渐变小，这将意味着该技术将能够直接测量高山或大陆冰川退缩的速度。 我们还将对位于派恩代尔和布尔湖沉积物之间的可疑第四阶段冰碛中的 10 块巨石进行年代测定，以确定派恩代尔类型地点是否保留了第四阶段（早期派恩代尔）沉积物。 最后，我们将对我们的方法产生的日期与使用 F. Phillips 的 36C1 技术对 10 个巨石的重复样本进行的日期进行有用的交叉检查，这些样本产生第一年的最佳日期。