Midwestern Holocene Paleoenvironments Revealed by Floodplain Deposits in Northeastern Iowa
Midwestern Holocene Paleoenvironments Revealed by Floodplain Deposits in Northeastern Iowa
复制标题
爱荷华州东北部洪泛区沉积物揭示的中西部全新世古环境
作者：
C. Chumbley;R. Baker;E. Bettis
对爱荷华州东北部一条河流上游的池塘沉积物进行的花粉分析，几乎完整地记录了过去12.5万年来的植被变化。爱荷华州东北部是最后一次冰川边缘之外的地区。61个放射性碳年代提供了很好的年代学控制。云杉林在910万年前被落叶林取代，其次是草原，从5.4万年到3.5万年，橡树稀树草原从3.5万年前到定居前。这里的草原入侵比爱荷华州和明尼苏达州的其他地方晚了近3000年，记录了中西部上部南部最温暖和最干燥的全新世晚期，而不是全新世早期-中期。
Pollen analysis of pond deposits in the upper reaches of a stream from northeastern Iowa, an area beyond the last glacial margin, provides a nearly complete record of vegetational changes during the last 12.5 thousand years. Sixty-one radiocarbon dates provide good chronological control. Spruce forest was replaced by deciduous forest before 9.1 thousand years ago, followed by prairie from 5.4 to 3.5 thousand years ago, and oak savanna from 3.5 thousand years ago until presettlement times. The prairie invasion was nearly 3 thousand years later here than at other sites in Iowa and Minnesota, documenting a late Holocene, rather than an early-middle Holocene, period of maximum warmth and dryness for the southern part of the upper Midwest.