Final answer:
Folsom projectile points are found in a stratum with clay soil.
Step-by-step explanation:
Folsom projectile points are found in a stratum in which the soil has clay.
Clay is a type of soil that is formed over millions of years due to weathering processes.
It consists of fine particles of silt, feldspar, silica, and alkalis like iron, which give clay its reddish-brown color.