Joanie,
I commonly apply a liberal interpretation of the term "passive
folding."
Passive folding is a folding mechanism in which folded layers have no
mechanical significance in the folding process. In other words, the
layering is simply a set of marker lines that deform. These lines do
not in any way affect the amplitude, wavelength, profile shape, etc. of
the fold.
As far as what you wrote about "shear modification of an existing fold
without generating a cleavage," I have no idea whether this is passive
folding. I don't see where cleavage formation or any other mesofabric
is necessarily formed during "passive folding." Nor are these
mesofabrics necessarily indicators that passive folding took place. In
my mind the question is not whether a cleavage formed, but whether the
layering affected the folding process. If not, then you can put the
fold into the generic category of one that may have formed by "passive
folding."
Just my 2 cents worth.
--Mark
___________________________
Assistant Professor
Department of Geology & Environmental Geosciences
Northern Illinois University
DeKalb, IL 60115-2854
Ph. (815) 753-7939
FAX (815) 753-1945
http://jove.geol.niu.edu
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