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

这项研究是对宇宙成因放射性核素暴露测年的详细测试，主要基于对怀俄明州弗里蒙特湖松谷冰川型地点冰川峰上的巨石中的10Be、26Al和14C的测量。其目的是确定宇宙起源测年技术的极限、准确度、精密度和分辨率。我们将坚持严格的抽样策略，最大限度地减少因高侵蚀率(即火灾引起的表面剥落)、预曝光、宇宙辐射屏蔽、不合适的巨石表面几何形状、以及受干扰的曝光、宇宙辐射屏蔽、不合适的巨石表面几何形状以及由于巨石的再沉积或埋藏而引起的受干扰的暴露历史而产生的误差。在第一年，我们将通过对单个冰雹山脊上的多个巨石进行采样，并从选定的巨石中采集多个样本，来确定该技术的可靠性和精确度。根据直接测年、区域对比和高分辨率氧同位素年代学对比，松林(2期)和牛湖(6期)沉积物的年龄分别为14~30ka和130~160ka。我们将从弗里蒙特湖的松树湖和公牛湖码头各采集30个样品。在第二年，有了该方法的精确度的测量，我们将对6个嵌套的松林退化冰盖的样品进行日期测定，以确定其分辨率。如果最外到最内的冰川年龄逐渐变小，这将意味着这项技术将能够直接测量高山或大陆冰川消退的速度。我们还将测定位于Pinedale和Bull Lake矿床之间的可疑第四阶段冰雹的10块巨石的年代，以确定Pinedale类型的第四阶段(早期Pinedale)矿床是否保存下来。最后，我们将对我们的方法产生的日期与F.Phillips的36C1技术在10块巨石上的重复样本进行有用的交叉核对，这些重复样本产生了从第一年开始的最佳日期。

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 the 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.