科研之友
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摘要
Soil development during the Quaternary was investigated, by comparing and integrating analytical datasets of three soil chronosequences developed on different terrace staircases along the Tyrrhenian (western) and Ionian (eastern) coasts of northern Calabria, southern Italy. Two of these soil chronosequences developed on early to late Pleistocene marine terraces in two sectors of the Praia area (western coast), whereas the third one developed on fluvial terraces in the Rossano area (eastern coast) spanning from middle to late Pleistocene ages, respectively. We present and discuss both novel results and already published data related to selected morphological, physical, chemical, mineralogical and SEM analyses from the two coastal sectors. We explored the effects of time on soil development, trying to unravel the role of soil-forming processes, parent material and geomorphic dynamics on direction and rates of pedogenesis. A complex nature of parent materials was indicated by the geochemical signature, coupling certain similarities with some heterogeneity between the two study sectors but also across single soil profiles, as a response to morphodynamic processes (soil reworking, aggradation, burial and/or erosion), in turn promoting soil ageing and/or rejuvenation. These processes and lithological discontinuities were also responsible for some data scattering from calculated soil chronofunctions for peculiar soil properties and pedogenic indices plotted against estimated soil ages. Among the main outcomes, good positive correlations were obtained for the (Fe-d-Fe-o)/Fe-t and Fe-d/Fe-t indices, weighted on the basis of total soil profile and single horizon thicknesses to minimize the effects of soil truncation by erosion processes. Our results confirm the reliability of these indices as soil development indicators. Moreover, they suggest that: (i) rates of soil development did not change significantly over ca. 100 -800 ka, despite the cyclical alternation of Pleistocene climate changes; (ii) dominant soil-forming processes tend to minimize original differences of pedogenic substrata and local (pedo)climatic conditions through time. In addition, soil chronofunctions permitted to estimate the unknown age (the time range of soil development before burial, about 200 ky) of a buried soil profile in the Rossano area, not correlated to any terrace surface of known age. The occurrence of etched quartz grains in soils of different ages for the two study sectors clearly indicates different rates of silica dissolution in the Tyrrhenian and Ionian coasts of Calabria, promoted by different climatic and pedoenvironmental conditions.
- 出版日期2015-7-30
