Final answer:
In a recent soil under pasture, the sequence of soil horizons is most likely to be O-A-B-C. The O horizon is the topsoil layer, rich in organic matter and nutrients. The A horizon is a mixture of organic and inorganic material, while the B horizon is a dense layer of accumulated fine material. The C horizon includes the parent material and broken-down organic and inorganic material.
Step-by-step explanation:
The sequence of soil horizons in a recent soil under pasture is typically O-A-B-C.
The O horizon is the topmost layer and consists of freshly decomposing organic matter-humus. It enriches the soil with nutrients and enhances soil moisture retention.
The A horizon is a mixture of organic material with inorganic products of weathering. It is typically darkly colored due to the presence of organic matter and is the beginning of true mineral soil.
The B horizon is an accumulation of fine material that has moved downward, creating a dense layer in the soil. It may also contain nodules or a layer of calcium carbonate.
The C horizon, or soil base, includes the parent material and both organic and inorganic material broken down to form soil.