The Rocks loess section, in unglaciated western Kentucky, provides a high‐resolution environmental record during the last glacial maximum onset. The Peoria Silt (9 m thick) contains 26 terrestrial gastropod species, with up to 15 species within a single 5 cm interval. Thirteen radiocarbon ages, using shells or charcoal, range between 30 and 24.5 cal ka; younger loess has been leached or eroded. Stratigraphic shifts in gastropod assemblages imply significant cooling, particularly ~27 cal ka, as solar insolation was decreasing and the southern Laurentide Ice Sheet rapidly advancing. Midwestern to southern species (e.g. Anguispira kochi, Gastrocopta pentodon, Hawaii miniscula, Helicodiscus parallelus, Vallonia perspectiva) occur only in the lowermost Peoria Silt (~30–27 cal ka). In contrast, cold‐tolerant species (Columella alticola, Vertigo modesta, Vallonia gracilicosta) occur only in full glacial Peoria Silt (27–24.5 cal ka). Inferred mean July temperatures, from mutual climatic range methods, range from ~23 °C at 30 cal ka, cooling to ~18 °C by 26 cal ka; about 3–8 °C cooler than today (~26 °C). Superimposed on this cooling trend are multi‐centennial variations in detrital carbonate, fossil shell concentrations, palaeotemperature estimates, and oxygen isotope values (Vertigo, Discus, Helicodiscus). The finer‐scale variations imply relatively synchronous fluctuations in glacial sediment supply, loess sedimentation, and climate.

中文翻译：

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肯塔基州西部皮奥里亚黄土中陆生腹足动物组合的最新冰川最大生态和气候

在肯塔基州西部未冰化的岩石黄土区，在最后一次冰川最大爆发期间提供了高分辨率的环境记录。皮奥里亚淤泥（9 m厚）包含26种陆栖腹足动物，每5 cm间隔内最多有15种。使用贝壳或木炭的13个放射性碳年龄介于30到24.5千卡之间；较年轻的黄土已被淋滤或侵蚀。腹足动物组合的地层变化意味着明显的降温，尤其是约27 cal ka，这是因为日照量正在减少并且南部洛朗德冰盖迅速发展。中西部南部物种（如Anguispira高知，Gastrocopta pentodon，夏威夷miniscula，Helicodiscus parallelus，Vallonia酒店perspectiva）仅在最低的Peoria淤泥中发生（〜30–27 cal ka）。相比之下，耐寒物种（Columella alticola，Vertigo modesta，Vallonia gracilicosta）仅出现在完整的冰川皮奥里亚淤泥中（27-24.5 cal ka）。根据相互气候范围方法推算出的平均7月温度范围为：30 cal ka时约23°C，冷却至26 cal ka时约18°C。比今天（约26°C）低3–8°C。在这种冷却趋势上叠加的是碎屑碳酸盐，化石壳浓度，古温度估计值和氧同位素值（眩晕，铁饼，螺旋藻）的百年变化。较小尺度的变化意味着冰川沉积物供应，黄土沉积和气候的相对同步波动。