It appears you may very well be correct. The horizon labeled as a placic horizon does appear much thicker than the 25mm limit as you noted. It is difficult to tell from the photo how much of the dark layer is cemented. We have been unable to associate the photo with a particular description to know whether it was described as continuously cemented or the thickness. The photo is from a collection of Dr. Hari Eswaran. Information on the photo is quite limited, though it indicated the soil was a Placocryod.
The Illustrated Guide to Soil Taxonomy is a work in progress so the addition of ortstein in the next update is certainly appropriate. If the photo is continuous ortstein, then we now have need a photo image of a placic horizon. Thanks for helping make the Illustrated Guide a better product.
Anyone having better images of any of the diagnostic horizon, features and characteristics who would like to contribute to the Illustrated Guide are asked to contact Ken Scheffe or Shawn McVey at the National Soil Survey Center. The soil photo gallery is being expanded and in need of high quality images of soil features, soil profiles, and landscapes with associated metadata including photographer, location, date, resolution, and description of the central feature(s). Having complete metadata will enable photo credits to be given when used in publications and other presentations.
