ABSTRACT In Michigan’s Upper Peninsula, sand dunes are widespread on the sandy floor of former Glacial Lake Algonquin, and many of the nearby uplands also have thin mantles of loess. Previous work concluded that these dunes formed during the early Holocene, long after the lake had drained. Where these dunes have migrated against bedrock uplands, many have accreted into larger dune complexes. South and east of these complexes, uplands are mantled with well-sorted sediment, comparatively rich in finer sands and much like the thin, locally sourced loess deposits in Wisconsin and Michigan. Near the dunes, this loess is typically 50–75 cm thick, and rich in very fine sands; presumably much of this sand was deposited as short-range “blow-over” while the dunes were forming. The loess thins to ≈45 cm and becomes siltier on sites farther downwind, to the southeast. Because the dune complexes contain almost no silt, the silt in the loess was likely generated by deflation of saltating sands on the lake plain, transported in suspension, and deposited generally uniformly across the forested uplands, as indicated by spatial trends in silt contents. Periodic Holocene drought may have thinned the forest and helped to intermittently facilitate this type of eolian activity.

中文翻译：

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美国密歇根州北部沙丘下风处的全新世粉砂黄土

摘要 在密歇根州的上半岛，前冰河阿尔冈昆湖的沙地上广泛分布着沙丘，附近的许多高地也有薄薄的黄土覆盖层。先前的研究得出的结论是，这些沙丘形成于全新世早期，即湖泊干涸很久之后。在这些沙丘向基岩高地迁移的地方，许多沙丘已经增生成更大的沙丘复合体。在这些复合体的南部和东部，高地覆盖着分类良好的沉积物，相对富含较细的沙子，很像威斯康星州和密歇根州当地产的薄黄土沉积物。在沙丘附近，这种黄土通常厚 50-75 厘米，富含非常细的沙子；据推测，这些沙子的大部分是在沙丘形成时作为短程“吹袭”沉积的。黄土变薄至约 45 厘米，在更远的下风处变得更粉，到东南方。由于沙丘复合体几乎不含粉砂，黄土中的粉砂很可能是由湖平原上的盐渍沙子泄气产生的，悬浮运输，并大体均匀地沉积在森林高地，如粉砂含量的空间趋势所示。周期性的全新世干旱可能使森林变薄，并有助于间歇性地促进这种类型的风成活动。