What is the primary characteristic of windblown deposits composed of eolian materials?

Windblown deposits, known as eolian deposits, primarily consist of materials that have been transported and settled by wind action. These deposits are characterized by their well-sorted nature, especially in the context of grain size. Among the options provided, very well sorted fine to medium sand is the primary characteristic of these windblown deposits.

The sorting occurs as wind is selective in transporting smaller particles like fine sand, while larger grains are more difficult for wind to carry over long distances. This results in finely sorted layers of sand that typically accumulate in areas like dunes or sandy plains.

Eolian materials are less likely to contain coarse, poorly sorted sands, as this would suggest the influence of water or gravity rather than wind. Additionally, being rich in clay and organic matter or being deposited in wetland areas describes different types of sedimentary processes unrelated to wind action. Thus, the distinctive feature of eolian materials is their very fine and uniform grain size due to effective wind sorting, highlighting option B as the correct choice.