STYLOLITIC STRUCTURE IN TENNESSEE MARBLE 567 
It is held by some that the sutures seen in Tennessee marble 
represent original stratification planes or partings which are 
occupied by very thin laminae of silt, and beneath this silt unequal 
solution has taken place as indicated above. That the opposing 
faces along clay partings in limestones are affected by unequal 
solution is a matter of common observation. Often the opposing 
surfaces of the beds will be seen to have rounded elevations and 
depressions which alternate with each other, but there is no inter- 
locking as in the case of true stylolites. If the clay parting is 
very thin, however, it is quite likely that a true stylolitic structure 
may develop along such planes, and that some of the sutures in 
Tennessee marble are of this character is probable. But from the 
study of hundreds of examples of the sutures in the Tennessee 
marble, the writer is convinced that in the main they represent 
fracture planes. Convincing proof of this appears in their irregu- 
larity and frequent tendency to cut across the sedimentation 
planes obliquely or even at right angles. Wagner, who described 
them as occurring along fractures, stressed this point when he says 
_that, whereas under the pressure theory the sutures must follow 
the plane of sedimentation, in the solution theory they may inter- 
sect the stone in any direction. 
‘Inasmuch as the columns manifest a general tendency to assume 
a position at right angles to the plane of sedimentation and since 
it is probable that static as opposed to dynamic pressure has been 
most effective in furthering solution this would seem to offer evi- 
dence that the stylolitic structure was more or less advanced if not 
completed before the rocks assumed their present tilted position as 
a result of folding and faulting at the close of the Paleozoic era. 
Grabau considers that the length of the column is a fair measure 
of the amount of material removed from both sides of the fracture. 
SUMMARY 
Polished slabs of Tennessee marble are usually marked by irregu- 
lar zigzag lines likened by Vanuxem to the sutures of the human 
skull and now known generally as ‘‘stylolites,” the origin of which 
is a subject of frequent inquiry. These structures consist of striated 
