The dislocation structure of experimentally deformed marble

Five specimens deformed at differential stresses between 220 and 980 bar were selected for a transmission electron microscopy study from the suite of Yule Marble specimens of Heard and Raleigh (1972). The electron micrographs show twinning, curved free dislocations, sessile dislocation loops, and small angle boundaries. Both free dislocations and dislocation boundaries contain dislocation reactions which most likely involve the Burgers vectors 1/6〈1-102〉 and 1/12〈1-210〉 reacting to form 1/12〈10-14〉. The dislocation densities of specimens deformed at the higher stresses were greater than the starting density and fit the relation {Mathematical expression}. However, the dislocation densities of specimens deformed at the lower stresses decreased only partially with respect to the starting density during the deformation experiments and thus are larger than predicted by this relation.