How to enter texture class of M layers

I am completing a description of "soil material" exposed in a trench excavated beside a rural highway in Texas. The subgrade material is composed of gypsum, which extensively dissolved during an extended stretch of wet weather. The trench cut through the edge of the pavement, which evidently qualifies as an M layer. How should the texture of the 15 cm thick layer of asphalt pavement be entered into the NASIS database?

Thank you very much.

Regards,

Lynn Loomis