Recent studies have shown the oxygen isotopic composition (δ18O) of modern terrestrial gastropod shells is determined largely by the δ18O of precipitation. This implies that fossil shells could be used to reconstruct the δ18O of paleo-precipitation as long as the isotopic system, including the hydrologic pathways of the local watershed and the gastropod systematics, is well understood. In this study, we measured the δ18O values of 456 individual gastropod shells collected from paleowetland deposits in the San Pedro Valley, Arizona that range in age from ca. 29.1 to 9.8 ka. Isotopic differences of up to 2‰ were identified among the four taxa analyzed (Succineidae, Pupilla hebes, Gastrocopta tappaniana, and Vallonia gracilicosta), with Succineidae shells yielding the highest values and V. gracilicosta shells exhibiting the lowest values. We used these data to construct a composite isotopic record that incorporates these taxonomic offsets, and found shell δ18O values increased by ~4‰ between the last glacial maximum and early Holocene, which is similar to the magnitude, direction, and rate of isotopic change recorded by speleothems in the region. These results suggest the terrestrial gastropods analyzed here may be used as a proxy for past climate in a manner that is complementary to speleothems, but potentially with much greater spatial coverage.

中文翻译：

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陆地腹足动物壳中的氧同位素追踪美国西南部的第四纪气候变化

最近的研究表明氧同位素组成（δ18O) 现代陆生腹足动物壳的数量主要由 δ18O 的降水。这意味着化石壳可用于重建 δ18只要同位素系统，包括当地流域的水文路径和腹足动物系统学，都很好地了解了古降水的 O 。在本研究中，我们测量了 δ18从亚利桑那州圣佩德罗谷的古湿地沉积物中收集到的 456 个个体腹足动物贝壳的 O 值，其年龄范围从大约 29.1 至 9.8 卡。在所分析的四种分类群（琥珀科，瞳孔,荸荠， 和纤细的瓦罗尼亚), 琥珀科贝壳产生最高值和五.细细目显示最低值的贝壳。我们使用这些数据构建了包含这些分类偏移量的复合同位素记录，并发现了壳 δ18O 值在末次冰期最大值和全新世早期之间增加了约4‰，这与该地区洞穴记录的同位素变化幅度、方向和速率相似。这些结果表明，这里分析的陆地腹足类动物可以作为过去气候的代表，以一种与 speleothems 互补的方式，但可能具有更大的空间覆盖范围。