Abstract

Data on the attitude of the cross-bedding in the Sioux, Baraboo, Waterloo, Barron, Sturgeon, Mesnard, Mississagi, and Lorrain quartzites, all of Precambrian age, are summarized. The azimuth and inclination of the cross-bedding, corrected for tilt of the beds, show a regional uniformity and a remarkable persistence through time. The prevailing southeasterly dip of the cross-laminations shows that these deposits were derived from a highland north and northwest of their present outcrops.

The inclination of the cross-laminations, tilt-corrected, commonly exceeds the angle of repose. Inasmuch as the corrected mean inclination in a given area is closely correlated with the mean dip of the strata and varies also with the position of the cross-strata on a fold, the cross-laminations are vectors rotated by internal shear of the quartzite during folding.

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