Dipping and Folded Strata

The texm fold is used in the geological sense when one or more originally flat and planar surfaces, such as sedimentary strata, are bent or curved as a result of permanent deformation. Throughout 

Glacial drift Modern valley fill Gray shale Sandstone Limestone Black shale Coal 

FIGURE 1.3 Coal seam discontinuities (a) recent erosion, (b) preglacial erosion, and (c) and (d) stream beds at the time of debris accumulation. 

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