Isotopic evidence for Younger Dryas aridity in the North American midcontinent
Isotopic evidence for Younger Dryas aridity in the North American midcontinent
复制标题
北美中部大陆新仙女木期干旱的同位素证据
作者：
J. A. Dorale;L. Woźniak;E. Bettis;S. J. Carpenter;R. Mandel;E. Hajic;N. H. Lopinot;Jack H. Ray
确定新仙女木（YD）气候事件对未冰川化的北美大陆中部的影响已被证明是困难的，由于缺乏合适的古气候代理。在这里，我们提出了一个良好的定年碳同位素（δ 13 C）记录，从一个埋藏的土壤序列在密苏里州，这揭示了一个大的同位素漂移在YD年代臭氧。在这个现代草原森林边界的地区，土壤有机质的δ 13 C特征是过去气候变化的可靠指标，因为δ 13 C值主要受C3和C4植物的相对丰度控制，这与环境背景有关。在CA之间。在13，200年和11，900年前，C4草的丰度增加了总生物量的50%以上，这表明草原的扩张很可能是由这一时期干旱的增加所驱动的。中部大陆的环境梯度一定非常陡峭，因为在密苏里州西南部存在富含C4的草原的同时，爱荷华州、伊利诺伊州和俄亥俄州也生长着云杉林。
Determining the impact of the Younger Dryas (YD) climate event on the unglaciated North American midcontinent has proved difficult due to a scarcity of suitable paleoclimate proxies. Here we present a well-dated carbon isotope (δ13C) record from a buried soil sequence in southwestern Missouri, which reveals a large isotopic excursion during the YD chronozone. In this region of the modern prairie-forest border, the δ13C signature of soil organic matter is a reliable indicator of past climatic change because δ13C values are controlled primarily by the relative abundance of C3 and C4 plants, which is tied to the environmental setting. Between ca. 13,200 and 11,900 yr ago, the abundance of C4 grasses increased by upwards of 50% of the total biomass, indicating expansion of grassland most likely driven by increased aridity during this period. Environmental gradients in the midcontinent must have been very steep, because at the same time that a C4-rich prairie existed in southwestern Missouri, spruce forests grew in Iowa, Illinois, and Ohio.