Twenty-four new optically stimulated luminescence (OSL) and radiocarbon ages from sediment cores in nine lakes associated with the Shipshewana and Sturgis moraines in northern Indiana and southern Michigan estimate when recession of the Saginaw Lobe of the Laurentide Ice Sheet was underway in the southern Great Lakes region, USA. Average OSL ages of 23.4 ± 2.2 ka for the Shipshewana Moraine and 19.7 ± 2.2 ka for the Sturgis Moraine are considered minimum limiting deglacial ages for these recessional moraines. The much younger radiocarbon ages are consistent with other regional radiocarbon ages from lakes, and record climate amelioration around ~16.5 cal ka BP. Early recession of the interlobate Saginaw Lobe was well underway by 23.4 ± 2.2 ka, when the adjacent Lake Michigan and Huron-Erie lobes were a few hundred kilometers farther south and near their maximum southerly limits. The results provide the first time constraints when sediment from the Lake Michigan and Huron-Erie lobes began filling the accommodation space left by the Saginaw Lobe. The difference between the oldest radiocarbon and OSL age is 7400 yr for the Shipshewana Moraine and 3400 yr for the Sturgis Moraine.

中文翻译：

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使用光学受激发光 (OSL) 和放射性碳方法对 Laurentide 冰盖的异相萨吉诺叶冰期的最小极限冰期年龄

来自印第安纳州北部和密歇根州南部与 Shipshewana 和 Sturgis 冰碛相关的 9 个湖泊的沉积物岩心的 24 个新的光学受激发光 (OSL) 和放射性碳年龄估计，当劳伦泰德冰盖的萨吉诺叶在大南部地区发生衰退时美国湖泊地区。Shipshewana 冰碛的平均 OSL 年龄为 23.4 ± 2.2 ka，Sturgis 冰碛的平均 OSL 年龄为 19.7 ± 2.2 ka，被认为是这些退行冰碛的最小极限冰期。更年轻的放射性碳年龄与来自湖泊的其他区域放射性碳年龄一致，并记录了约 16.5 cal ka BP 左右的气候改善。叶间萨吉诺叶的早期衰退正在顺利进行 23.4 ± 2.2 ka, 当相邻的密歇根湖和休伦-伊利叶瓣向南数百公里并接近其最大的南风极限时。当密歇根湖和休伦-伊利叶的沉积物开始填充萨吉诺叶留下的住宿空间时，结果首次提供了限制。最古老的放射性碳和 OSL 年龄之间的差异是 Shipshewana Moraine 的 7400 年和 Sturgis Moraine 的 3400 年。