Particle-size class control section for Terric Histosols

Can someone clarify what depth(s) should be used for determining the particle-size class for this soil (see attachment)? The control section for organic soils is made of three tiers and extends from the soil surface to 130 cm. The particle-size class of Terric subgroups of Histosols is determined using the upper 30cm of the mineral layer or of that part of the mineral layer that is within the control section, whichever is thicker.

This soil was described in a subalpine meadow in the Sierra Nevada. Depths are in cm. Assume the last horizon (A'b) is greater then 30 cm thick. If you would like more information about this soil please feel free to ask and I can send you my contact information.

Thanks,

Andysol Paolucci
Soil Scientist
USDA-NRCS