Vugs, fractures, interstices, and other voids in the Townsend carbonate mound (reef) are floored with internal sediment composed of well sorted calcite silt. Internal sedimentation predates precipitation of blocky cement, and post-dates both precipitation of early drusy cement and early internal erosion. The crystal silt differs from associated marine sediment in its scarcity of clay-size particles, sand-size particles, and recognizable skeletal debris.

The age relationships and texture of crystal silt seem best explained by sedimentation inside pre-existing crumbly rock in the vadose zone during early emergence. If the explanation is valid, similar internal sediment might be a valuable clue to previously unrecognized subaerial stages in other carbonate mounds.

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