Purpose

Loess in Northern Italy has been usually considered deposited during the MIS 4-2 period, which corresponds to the last Pleistocene glacial cycle. In particular, no absolute dating evidenced loess depositions older than ca. 89 ka. We investigated two strongly rubified soil profiles in the southern margin of the Alpine range in Lombardy to prove their aeolian origin and age of formation.

Methods

We analysed the granulometry of all genetic horizons of these strongly rubified soils, and a total of 8 samples were collected for luminescence dating purpose.

Results

Most of the analysed soil horizons were dominated by silt and were characterized by the s-shaped granulometric curve, typical of loess materials. A particularly high clay content evidenced a strong weathering degree. A deep horizon was particularly clay rich, and it was interpreted as a typical Terra-Rossa horizon. Luminescence dates increased with depth, reaching 122 ka for the deepest loess layer and 453 ka (minimum age) for the Terra-Rossa horizon.

Conclusions

The deepest observed loess layer represents the oldest quantitatively dated aeolian deposition in Northern Italy up to now.

中文翻译：

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意大利北部黄土矿床的新日期（Monte Orfano，南部阿尔卑斯山前，布雷西亚）

目的

意大利北部的黄土通常被认为是在MIS 4-2时期沉积的，这对应于最后的更新世冰川周期。特别是，没有绝对年代的证据表明黄土的沉积年龄早于Ca。89 ka。我们调查了伦巴第山脉南部边缘的两个强烈磨砂土壤剖面，以证明它们的风成因和形成年龄。

方法

我们分析了这些强烈磨光的土壤的所有遗传视野的粒度分析，总共收集了8个样品用于发光测年。

结果

分析的大部分土壤层位以粉土为主，并以黄土材料特有的S形粒度曲线为特征。粘土含量特别高表明其耐候性强。深层地平线特别富含粘土，被解释为典型的Terra-Rossa地平线。发光日期随深度增加，最深的黄土层达到122 ka，Terra-Rossa地平线达到453 ka（最小年龄）。

结论

观察到的最深的黄土层代表了迄今为止意大利北部最古老的定量风成沉积。