230 r. W. SAEDESON THE REDSTONE QUARTZITE 



conglomerate somewhat closely, and found pebbles of quartzite and even 

 of quartzite conglomerate like the rock which is in situ at Eedstone. By 

 this criterion, the New Ulm conglomerate quartzite is later than the 

 Courtland quartzite and may be of Cambrian age. Further, the fact that 

 this conglomerate is indurated is not evidence that it is Huronian or that 

 it is not Cambrian. Quartzite masses are not uncommon in neighboring 

 sandstones; for example, in the Jordan sandstone on the Blue Earth 

 river, and in the Shakopee formation at Manlvato, and therefore an 

 indurated conglomerate of Cambrian age is not anomalous. The dip of 

 the beds in such a coarse, thickly packed, unassorted conglomerate may 

 well be that of original cross-bedding, and the close relation or evident 

 contact witli the granitic rock is in accord with the known unconform- 

 ability of the Middle Cambrian upon older rocks in Minnesota. 



In regard to the contained j^ebbles, those of quartz and of jasper or 

 taconite are very abundant, while those of fine-grained gneiss are few and 

 those of quartzite are rare. The quartz may be considered as mainly 

 derived from Minnesota Valley granites, and the quartzite from the 

 Courtland quartzite, while the gneiss and jasper are from formations not 

 seen, though probably existing in this region. ISTumerically considered, 

 the quartz pebbles are most numerous and the granitic rocks are imme- 

 diately near ; the quartz pebbles are rarest, and the rock in situ is seen a 

 mile away. Accordingly the schist and "taconite" and jasjDer may reason- 

 ably be derived from an intermediate distance. Many of the jasper and 

 quartz pebbles of small size may be secondary from the Courtland quartz- 

 ite. A single pebble of vphat appears to be an altered red granite and 

 one of medium-grained, light-colored gneiss were collected. The absence 

 of pebbles of the unweathered red gneissoid or granitic rock which is now 

 exposed 150 paces west of the conglomerate may indicate simply that 

 there was no outcrop of unaltered rock of that type there at that time in 

 position to afford pebbles for this conglomerate. The conglomerate is not 

 uniform in composition. For example, quartzite pebbles are to be sought 

 in the middle of the exposure. It may be noted also that the pebbles are 

 of diverse sizes and more or less waterworn and roimded. Some are 

 etched or pitted and nearly all are quartzose and such as an encroaching 

 sea might have gathered from a deeply disintegrated rock surface. 



The New Ulm conglomerate may rest on either a weathered or a fresh 

 surface, as far as we know. It is exposed 50 feet thick in all and 20 feat 

 in single vertical outcrop. It is jointed with the bedding and forms 

 strata 1 to 6 feet thick. The dip of these beds varies between 10 and 15 

 degrees, and the strike changes somewhat in direction, but it is "roughly 

 represented by the direction of the exposure being north 15 degrees east" 

 (Hall, 10, page 23 and plate III). The direction of the dip is at nearly 



