Which soil classification is characterized by the presence of irregular carbon?

The classification of soil characterized by the presence of irregular carbon is Psamment. Psamments are sandy soils that often contain a significant amount of quartz and are typically poorly developed with minimal horizon differentiation. The term "irregular carbon" can refer to the carbon content found in these sandy soils, which may result from the decomposition of organic matter over time. The lack of clay in Psamments causes a limited capacity for holding nutrients and water, which influences their development and classification.

In contrast, the other classifications mentioned do not specifically focus on the presence of irregular carbon. Aquitards are typically associated with layers that restrict water movement, but they do not denote an association with carbon content. Fluvents are characterized by their alluvial properties and are often associated with floodplains, not particularly defined by carbon presence. Paludalf soils are wetland soils with high organic matter but aren't characterized specifically by irregular carbon structures. Thus, understanding Psamment is key when considering irregular carbon in soil classification.