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首页> 外文期刊>Quaternary Science Reviews: The International Multidisciplinary Review Journal >Middle to Late Pleistocene loess record in eastern Nebraska, USA, and implications for the unique nature of Oxygen Isotope Stage 2
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Middle to Late Pleistocene loess record in eastern Nebraska, USA, and implications for the unique nature of Oxygen Isotope Stage 2

机译：美国内布拉斯加东部中更新世黄土记录，及其对氧同位素第二阶段独特性质的启示

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摘要

New subsurface data reveal a nearly continuous stratigraphic record of Middle to Late Pleistocene loess sedimentation preserved beneath upland summits in eastern Nebraska, USA. Thickness and grain size trends, as well as pedologic evidence, indicate significant changes in loess sources, accumulation rates, and depositional environments. The newly defined Kennard Formation accumulated in the Middle Pleistocene, and may represent multiple thin increments of distal loess from nonglacial sources on the Great Plains. The overlying Loveland Loess, up to 18 in thick and deposited during Oxygen Isotope Stage 6 (OIS 6) (Illinoian glaciation), probably records the emergence of the Missouri River valley as a major glaciogenic loess source. The prominent Sangamon Geosol formed through long-term pedogenic alteration of the upper Loveland Loess during OIS 5 and 4. Thin loess of the Gilman Canyon Formation records slow loess accumulation and pedogenic alteration in OIS 3. The Peoria Loess (OIS 2) is similar in thickness to Loveland Loess, but may have accumulated more rapidly in an environment less favorable to bioturbation. More importantly, comparison of Peoria and Loveland loess thickness trends indicates much greater influx of nonglaciogenic loess from the Great Plains during OIS 2 than in OIS 6, suggesting colder and/or drier conditions in the Midcontinent during OIS 2 than in earlier glacial stages. (c) 2007 Elsevier Ltd. All rights reserved.
机译：新的地下数据揭示了美国内布拉斯加州东部山顶下保存的中更新世黄土沉积至近晚期的近乎连续的地层记录。厚度和晶粒尺寸趋势以及土壤学证据表明，黄土源，积累速率和沉积环境发生了显着变化。新定义的肯纳德组堆积在中更新世中，可能代表了大平原上来自非冰川源的远端黄土的多个薄增量。上覆的Loveland黄土厚达18层，在氧同位素第6阶段（OIS 6）（伊利诺斯冰川期）沉积，可能记录了密苏里河流域作为主要成冰川性黄土源的出现。在OIS 5和4期间，通过上洛夫兰黄土的长期成岩作用改变形成的显着的Sangamon地溶胶。吉尔曼峡谷地层的薄层黄土记录了OIS 3的缓慢黄土积累和成岩作用。厚度不超过Loveland Loess，但在不利于生物扰动的环境中积累速度可能更快。更重要的是，皮奥里亚和洛夫兰德黄土厚度趋势的比较表明，与OIS 6相比，OIS 2期间来自大平原的非生胶性黄土的流入量要多于OIS 6，这表明OIS 2期间中部大陆的寒冷和/或较干燥条件要比早期冰川期更冷。 （c）2007 Elsevier Ltd.保留所有权利。

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