Loessial Soils of Delaware: Taxonomy and Map-Unit Assessment
- R. A. Rebertus *
Map units named for the Matapeake series (fine-silty, mixed, mesic Typic Hapludults) comprise one-third of the Coastal Plain in the soil survey of northern Delaware. The concept was one of well-drained soils formed in thin loess over coarse-textured fluvial sediments. This study uses characterization data from pedons within the loess-blanketed terrain of northern Delaware to assess the taxonomy and composition of Matapeake map units. All pedons are Alfisols rather than Ultisols, and this status has not been influenced by liming. Fine-loamy rather than fine-silty soils typically occur where loess is <80 cm thick. Much soil variability exists on interfluves where thin loess discontinuously blankets the irregular surface of the sandy Pensauken Formation. This results in an inability to map specific consociations, even for large-scale, detailed surveys. The existing soil survey used specific map units — consociations named for phases of soil series — that do not adequately depict the diversity on mappable landscapes. The Matapeake and associated series used in this area are too narrowly defined in ranges of characteristics, are too general in geographic setting, have loess thickness limits that are not concordant with particle-size classes, and leave gaps in the lithologic-hydrologic continuum. They therefore provide little utility for organizing knowledge, understanding relationships, or as objects for research. Soil survey in this area requires more generalized map units, greater emphasis on stratigraphy and geomorphology and their interaction to influence hydrology and lithology, and less emphasis on artificial conceptual groupings at the lowest taxonomic category, the series.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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