ICE WORK IN SOUTHEASTERN MICHIGAN 211 
appearance of being more heavily bedded as they occupy a 
deeper position in the series. The same stratum dipping from 
the surface may have the disrupted condition just beneath the 
till which is shown in Fig. 8 and still be as solid and compact 
at a depth as the lower strata shown in this figure. This con- 
dition of the rock is believed to have been caused by a tremen- 
Fic. 8.— View showing shattered condition of the upper strata at the Sibley 
quarry, west wall. This is believed to be due to the slow creeping movement of a 
vast ice-sheet, combined with the subsequent action of frost. 
dous weight of ice slowly and spasmodically creeping over the 
rock surface, the effect of which was to open up the incon- 
spicuous sedimentation seams to a considerable depth. This 
permitted the entrance of water, the freezing of which would 
tend to completely disrupt the strata and give them the thin- 
bedded, shattered appearance. 
SCORINGS IN MONROE COUNTY. 
Eastern portion—This county furnishes more numerous 
exposures of the rock surface than does Wayne, but none are 
