Several years ago for the first time the technique for experimental folding of layered real rocks under conditions expected within sedimentary basins was developed in our laboratory. In the initial experiments the samples had to be loaded parallel with the layering simulating horizontal compression. Though these experiments produced many insights into the overall folding process, they are not representative of most folds in the Rocky Mountain forelands where the folds result from differential vertical movements of the basement. However, within the last year the technique has been modified to produce loads at high angles to the layering and now we can produce a form of drape folding that does, indeed, have much in common with folds in the Rocky Mountain foreland. Making on -to-one correlations of simplified laboratory experiments to complicated natural features can be fraught with danger and completely misleading. However, these experiments verify so many long suspected natural phenomena that selected comparisons may be significant.

Scale alone precludes complete observation of natural folds with thousands of feet of displacement, but if correlations to experimentally created folds can be validated, the overall fold process becomes subject to direct observation. Such observations lead to increased confidence in delineation of structural geometries on the natural scale. This is especially true for the more complicated fold forms that usually have to be predicted in the subsurface from limited exploration data. It is gratifying to see that the overall movements in the experiment correlate well with natural folds, because it allows us to develop conceptual models upon which we can draw when dealing with widespread subsurface control or masked seismic data.

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