Figure 3-2. A: A calcite-filled fracture (large red arrow) cross-cut by a stylolite (small red arrow) at which quartz grains (Q) have accumulated. B: A dolomite-filled fracture (large red arrow) that cross-cuts a stylolite (small red arrow) in the same rock. These kinds of cross-cutting relationships allow determination of the relative age of diagenetic and tectonic events. For example, here the fracture in A formed before stylolite development and the stylolite in B formed after stylolite development, if we can assume the stylolites shown formed at the same time.

      Photomicrographs were taken in plane -polarized light. Field of view on left is 1.2 mm wide; field of view on right is 1.9 mm wide. Roadcut on US 322 bypass outside State College, Pennsylvania; Sample PA4-2; thin section S-1-146. Sample collected by L. Bruce Railsback.

   
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