Micromorphology of seasonally saturated soils in carboniferous glacial till

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Soils formed in dark-colored glacial till (chroma 3, value < 4) are common in southern New England. The low chroma, low-value colors reflect the carboniferous nature of the sedimentary and metasedimentary rocks that compose the till. Much of this till is very dense, resulting in soils with seasonal high water tables. The inherent dark colors of the soils make it difficult to use hydromorphic features to estimate depths of seasonal saturation. We examined thin sections to determine if micromorphology could be used to elucidate the apparent lack of hydromorphic features in seasonally saturated Bw horizons formed in dark till. Observation wells were monitored for 18 months to establish water table seasonal fluctuations in soils on shoulder positions. Hydromorphic features were examined in the field and in thin sections to correlate with the seasonal water table levels. Soils showed seasonal saturation and were classified as Humic Epiaquepts and Typic Humaquepts. Water levels frequently rose into the upper Bw horizons. One of the soils examined met hydric soil criteria based on hydrology. Hydric soil indicators such as a depleted matrix (F3) were absent. The dark parent materials were most likely preventing the observation of morphologic indicators of reducing conditions. Redoximorphic features were not identified by field observations in the seasonally saturated upper Bw horizons. Thin sections of the upper Bw horizons revealed redoximorphic features that were too faint, fine, or had boundaries too diffuse to be observed in the field. Identifying hydromorphic features in lower horizons and, with the aid of magnificafion, tracing these features carefully into overlying horizons may help identify the depth to aquic conditions in low chroma-low value seasonally saturated soils.

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Soil Science