Stratigraphy and Hydrology of the Jackson-Frazier Wetland, Oregon
2000
D'Amore, David V. | Stewart, Scott R. | Huddleston, J Herbert | Glasmann, J Reed
The relationship between wetland soils and hydrology can be better understood by linking soil geomorphological features to the measurement of groundwater depths in the soil. Soil stratigraphic analysis and long-term measurements of soil water levels in piezometers were used at the Jackson-Frazier wetland in western Oregon to investigate the interaction between local geomorphological history and the hydrology of the wetland. Morphological descriptions confirm the presence of a recent smectitic alluvial deposit (80–180 cm) overlying Malpass clay (≈35 cm thick), which overlies Irish Bend Silt. X-ray diffraction and isotope analysis support the conclusion of the presence of the Holocene alluvium and Irish Bend Silt, but are inconclusive regarding the Malpass clay. Piezometer data from 1992 to 1996 show that the smectitic alluvium controls saturation and drying of the wetland surface, and that a separate water table is present below the Malpass clay in the Irish Bend silt. The recent alluvium and Malpass clay act as an aquitard that restricts the vertical infiltration of surface water and helps restrict the groundwater table in the Irish Bend silt deposit. These stratigraphic relationships and associated hydrologic responses provide a means to identify wetlands and predict hydrologic conditions on similar wetland landscapes.
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