450 



THE PENOKEE IRON-BEARING SERIES. 



^rcuvLte 



conglomerate adjacent bears fragments of Ixitli tlie Basement Complex and 

 also chert fragments, indicates the probability that this limestone belongs to 

 the Clierty limestone and that it, in common with the Basement Comjjlex, 

 has yielded fragments to the Qnartz-slate. 



Passing eastward, in Sec. 24, T. 47 N., R. 43 W., Michigan, test-pitting 

 has exposed a rock which is again a recomposed granite, and the coarse 

 granitoid gneiss itself is fonnd ])ut a short distance to the southward. Tlie 

 relations here are plainly the same as those in the northeast part of Sec. 23. 

 Near the center of Sec. 28, T. 47 N., R. 42 W., Michigan, the eastern- 

 most known exposures of the Penokee succession occur, and here is a 

 beautiful instance of a basal conglomerate in direct contact with the under- 

 lying granite. The profile t>f the rock expo- 

 sures here is shown by Fig. 12. The granite and 

 gneissoid granite have evidently formed a cliff 

 against which the basal conglomerate has been 

 deposited. The c< intact lietween the granite and 

 conglomerate strikes north 30° west, and the 

 granite dips back into the liill at an angle of 

 75°, so that the contact between the two gives 

 the granite an ap})earance of overhanging the 

 conglomerate. If the strata were turned back 

 to their original condition this would not be the 



Fig. 12. — Basal conplonipratB in contaft with l l l l l 



granite in s.c.i;8.T.j7N.,R. 42 w., Mich, t-ase; wc siiouldliavc a Conglomerate restmg 

 'e""- upon an ordinary slopi'. Flie liill faces north 



of east. The conglomerate upon the face of tlie clifl' at its ujiper part is 

 about () feet in thickness and its face is nearly vt-rtical. The granite- 

 schist ledge continues for some distance beyond the point at which the con- 

 glomerate is found ill a direction south 30° east. At inter%als along this 

 face conglomerate is touiid. At times it is so tine grained as to become 

 an ordinar}' ipiartzite. The underlying rocks in this vicinity are of both 

 the granitic and schistose classes, the former, however, being preckiminant; 

 which explains tlie fact that the conglomerate is mostly composed of gi-anite 

 deljris, lint also contains fragments of green schist. It might be concluded 

 from this exposure tliat the conglomerate was underneath the granite if the 



Co/ii/i'oincrate. 



