Figure 5-3. A: At least three horizontal dissolution seams (large red arrows) that cross-cut and so presumably postdate a vertical stylolie (small red arrow). Area in red rectangle is shown in B.

      B: Higher-magnification view of area in red rectangle in A. Vertical stylolite is offset by horizontal dissolution seams (red arrows) and so predates them. More serrate nature of earlier pressure dissolution feature is typical of temporal relationships found by Andrews and Railsback (1997). Thickening of uppermost seam where it intersects upper segment of stylolite (large red arrow) presumably resulted from accumulation of minerals in stylolite into dissolution seam. It is thus evidence that minerals in seams and stylolites accumulate as an insoluble residue as the pressure dissolution feature (in this case, the seam) forms, rather than as a later precipitate. Upper segment of vertical stylolite is thicker than middle segment, probably because the upper and more brown layer contains more non-carbonate material. This constitutes another line of evidence that minerals in seams and stylolites accumulate as insoluble residues as the pressure dissolution feature forms, rather than as a later precipitate.

      Image was scanned directly from sample. Cambrian, Shawsville, Virginia, U.S.A.; Sample VA8-4D. Sample collected by L. Bruce Railsback and Lynn M. Andrews.

   
  Image
   
   
  Back to the Table of Contents of the Atlas of Pressure Dissolution Features.