no it is found in the topsoil or a horizon
The C and R horizon
The topsoil horizon (A horizon) is nutrient-rich because it contains the most humus, which is a dark, organic material formed from the decayed remains of plants and animals. Humus helps to improve soil fertility, structure, and water retention, making it ideal for plant growth.
the O-Horizon is the topmost soil so it has the most humus
The first layer of soil is called the O Horizon, it is made of primarily humus. The second layer is the A horizon, this is the topsoil. Then there comes the E layer which is the eluvation layer. Next comes the B horizon which is the subsoil, then there is the C horizon which is the regolith, then the final layer is the R layer which is bedrock.
Humus is more concentrated in the topsoil layer, known as the A horizon, of soil profiles. This layer is rich in organic matter and nutrients, which support plant growth and microbial activity. The accumulation of humus in the A horizon occurs due to the decomposition of organic materials, such as leaves and dead organisms, contributing to soil fertility.
THe c horizon
The Fertile soil contains lots of microorganisms which decompose the complex dead bodies of animals and plants into simpler substance called Humus.
The C horizon contains mainly parent material, while the B horizon contains mainly clay particles and the A horizon; mainly silt sized particles and humus
Soil layers are called soil horizons. Typically, a soil includes an A horizon, a B horizon and a C horizon. In laymen's terms: A horizon = topsoil B horizon = subsoil C horizon = parent material (the stuff in which the soil formed)
The uppermost layer of the soil which is the O-horizon, and is called "Humus".
The top layer of soil, called the O horizon or organic layer, contains humus. Humus is a dark, organic material that forms as plant and animal matter decomposes. It is rich in nutrients and helps improve soil structure and fertility.
you are likely to find dark, humus-rich soil in an A-horizon profile because that's where dark soil is found & the composition is the particles of weathered rock materials mixed with humus.