Geologists face a difficult task when mapping metasedimentary rocks over large areas where outcrops are scarce: reconstruction/interpretation of the macroscopic structure from information gathered at isolated outcrops. Situations can range from very simple to very complex, but most have a unique solution. The basic technique derives from Shackleton's rule: to compare the stratigraphic (polarity) and geometric (angular relation between bedding and cleavage) criteria at each outcrop, to evaluate accordance--it they are accordant, the structure is very simple because antiforms (geometry) are anticlines (polarity) and synforms are synclines (upward facing folds); otherwise antiforms and synforms are, respectively, synclines and anticlines, and the macro-structure is more complex (downward facing folds). When studying, for instance, polyphase deformed metasedimentary rocks of accretionary wedges, the geologist often finds a second deformation phase with a concomitant cleavage, and he must be much more careful because first deformation phase criteria are modified by second phase folds. Still, solutions are possible if there are no second phase recumbent folds with plunging brows. When the geologist observes first phase overthrusts folded by a second deformation phase, the solutions are reasonably easier if the sense of shear of fault is known. Otherwise, solutions are similar to the ones of second phase folds. Here we propose new rules for these more complex cases. The most important rule is: first phase criteria are non-accordant in the inverted limbs of second phase folds, when vergences of first and second phases are in the same sense, and in the second phases normal limbs, when first and second phases show opposite vergences.
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