A Test of Secular Variations in Cosmic Radiation Using 36C1 in Pack Rat Middens

Bard等人（1990年）最近对U/TH和14 C的测量， 巴巴多斯岛的珊瑚表明两万年前 大气中14 C的活性比大气中的高出约50%。 现代活动。 他们将这种活动的增加归因于 由于更强烈的宇宙辐射， 这是地球偶极磁场较弱的结果。 我们提出 为了测试14 C增强的起源， 另一种宇宙成因放射性核素36 C1的沉积。 类似的 36 C1的增强将证明这两种核素都是 应对生产波动。 我们建议抽样 大气中的36 C1保存在化石packrat（Neotoma）尿液中， 位于内华达州西部的干旱地区。 这个地方有一个 14 C年代，覆盖时间间隔29，000至3，000年 在现在之前。 如果36 C1和巴巴多斯的相关性很强， 14 C记录，36 C1数据可能有助于重建 大气14 C活动在30，000年至20，000年期间 血压，其他数据很少。 我们还将比较 来自内华达州西部和其他地区的垃圾样品中的36 C1/C1比值 广泛分布的地方与流星36 C1比率相同， 为了建立老鼠之间的关系， 尿液和土壤-水36 C1。 除了解决这个问题之外， 宇宙成因核素生产的长期变化，记录 流星36 C1的变化可能提供了一个有价值的定年剂 地下水和土壤水。

Recent U/TH and 14C measurements by Bard et al. (1990) on corals from Barbados have indicated that 20,000 years ago the activity of 14C in the atmosphere was approximately 50% higher than the modern activity. They ascribed this increase in activity to enhanced 14C productions due to more intense cosmic radiation as a result of a weaker terrestrial dipole magnetic field. We propose to test this origin for the 14C enhancement by reconstructing the deposition of another cosmogenic radionuclide, 36C1. A similar enhancement of the 36C1 would demonstrate that both nuclides were responding to production fluctuations. We propose to sample atmospheric 36C1 preserved in fossil packrat (Neotoma) urine in an arid site in western Nevada. This site contains a midden that has been 14C dated to cover the time interval 29,000 to 3,000 years before present. If strong correlation of the 36C1 and the Barbados 14C records is found, the 36C1 data might help to reconstruct atmospheric 14C activity during the period 30,000 to 20,000 years B.P., for which other data are scarce. We will also compare 36C1/C1 ratios in midden samples from western Nevada and other widely spread localities with meteoric 36C1 ratios in the same localities in order to establish the relationship between the rat urine and soil-water 36C1. In addition to addressing the problem of secular variations in cosmogenic nuclide production, the record of variation in meteoric 36C1 may provide a valuable dating agent for goundwater and soil water.