BASAL QUAETZITES. 89 



places throughout the Hills beds of hard, compact quartzite are found 

 interstratified with the ordinary soft sandstones Some of these localities 

 are far removed from any evident locus of igneous action, and indeed the 

 change of particular strata into quartzite while the overlying and under- 

 lying beds of sandstone are unaffected is an occurrence which can scarcely 

 be explained upon an igneous theory. 



Near the headwaters of Red Canon Creek in the southwestern corner 

 of the Hills, the Potsdam with its usual soft sandstone character is under- 

 laid by a bed of quartzite which rests upon the upturned mica schists. 

 This is a hard, fine-grained, compact quartzite with a glassy fracture, and 

 is seemingly composed of small grains of quartz sand, cemented by a 

 glassy quartzose cement into a dense rock. It has a lamellar structure and 

 breaks with some readiness parallel to the bedding. The color is a deep 

 brownish or purplish red slightly tinted with green. The entire mass is 

 filled with fossil remains of IAngula, Lingidepis, Obolella, etc., in a beautiful 

 state of preservation, altogether yielding the finest collection of fossils 

 obtained from the Potsdam in the Hills. A similar purplish quartzite was 

 found on the headwaters of Amphibious Creek, and on the same creek near 

 the beginning of the limertone canon a heavy bed of grayish quartzite rests 

 unconformably upon the schists and underlies strata of the usual coarse 

 sandstone. On Burntwood Creek, on French Creek, and north of Battle 

 Creek similar quartzites occupy a similar position. So hard and dense 

 is this rock that it sometimes caps the schists over considerable spaces 

 where the overlying more friable materials have been entirely removed. 

 This is particularly well seen on lower Burntwood Creek. On some of 

 the small streams north of Battle Creek it attains a thickness of about 50 

 feet. On Burntwood Creek it is not over 15 or 25 feet thick, and on 

 Amphibious Creek, where it covers several adjoining hills with its hard 

 and slippery fragments, it has a thickness of fully 50 feet. At these 

 localities it closely simulates the quartzite of the schists and slates, but it 

 is usually coarser in texture, betraying on close inspection the sand grains 

 of which it is composed. Sometimes it is found to contain considerable 

 portions of fine mica particles, but nowhere were any fossils seen in it. Its 



