Structural geology . ind the simple relationships of cleavage to folds, discussed onpages 119-121, the following are some of the field inferences thatmay be drawn from cleavage. The student will find it to hisadvantage to reason out each of these inferences for himself. FOLDS AND CLEAVAGE 129 (a) Cleavage converging upward suggests an anticline. It isseldom, however, that this ideal condition may be recognized inthe field on any large scale. The slight overturning of cleavage orfolding makes it difficult to determine this relation, (b) Moreuseful are the inferences to be drawn perhaps from loc
Structural geology . ind the simple relationships of cleavage to folds, discussed onpages 119-121, the following are some of the field inferences thatmay be drawn from cleavage. The student will find it to hisadvantage to reason out each of these inferences for himself. FOLDS AND CLEAVAGE 129 (a) Cleavage converging upward suggests an anticline. It isseldom, however, that this ideal condition may be recognized inthe field on any large scale. The slight overturning of cleavage orfolding makes it difficult to determine this relation, (b) Moreuseful are the inferences to be drawn perhaps from local observa-tions of the relation of cleavage to bedding. Cleavage normal tobedding probably indicates the axial plane of the fold, (c) Cleav-age inclined to the bedding probably indicates the limb of a fold,(d) The inclination of the cleavage with reference to the beddingtells on which limb of the fold the observation is taken, (e) Ifbedding is vertical and inclined cleavage is present in the softer Shale bed --i^L2-. W///X//////A Second teve/ Fig. 63. Vertical section of Illinois mine, Baraboo district, Wisconsin. After Weidman. layers between harder ones, thereby indicating direction of dis-placement, it is possible to infer on what part of the fold thisrelation was doubtless developed and from this in turn it may beinferred which is the top and which the bottom of the bed. In the Baraboo district of Wisconsin, slate overlain by ironformation has been folded between a competent quartzite layerbelow and a dolomite bed above. The slate thus forms the foot-wall for the iron formation. A shaft sunk largely in the slatefollowed the cleavage, the bedding being very obscure. As aresult, the shaft penetrated the ground more steeply than thebedding, as would be expected, and where at considerable depth 130 STRUCTURAL GEOLOGY drifting was begun to cross cut the ore, it was found that thebottom of the shaft was a long distance away from the ore body. The greater part of the Lake Superio
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