542 GEORGE DAVIS LOUDERBACK 



vicinity of Riddles, and continues along Cow Creek. The writer 

 traced it a few miles above Riddles on Cow Creek, but cannot state 

 how far it extends in that direction. 



The boundary contacts of the Myrtle Creek area are generally 

 formed by a heavy conglomerate which usually rests directly on the 

 pre-Myrtle intrusives, sometimes on the Dillard sediments. This 

 conglomerate, along the northwest border of the area, is very thick — 

 over 1,000 feet near the village of Myrtle Creek. It was traced by 

 the writer continuously for over fourteen miles, and, according to 

 Mr. Will Q. Brown, 1 is traceable without a break for over twenty 

 miles. The basal conglomerate is also found on the southeast border 

 of the area, where it is considerably thinner, and was studied only 

 along four or five miles of contact, about three of the miles near Myrtle 

 Creek, and the rest near Riddles. The lithologic characters of this 

 conglomerate have been described in a previous section. 2 



At the northeast extremity of the Myrtle Creek area the conglom- 

 erate does not appear to be basal, but is underlain by Aucella-bearing 

 shales (and very thin-bedded sandstone) which rest directly on the 

 igneous rocks without noticeable alteration. This may mean that 

 the syncline represents a trough of deposition, and that along the 

 median line the conglomerate may not be strictly basal, but may be 

 underlain by a deposit of shale, which has been overlapped along 

 the sides by the later deposited conglomerate. 



As noted earlier, conglomerates occur at various horizons in the 

 Myrtle group, and may some day serve to delimit its various members, 

 as, for example, the beds corresponding to the Horsetown from those 

 corresponding to the Knoxville. No attempt so to use them has been 

 possible in this investigation. 



Smaller areas between the Dillard and Myrtle Creek areas. — 

 Between the Dillard and the Myrtle Creek areas are mapped several 

 smaller ones. The largest of these is about six and one-half miles 

 long, and from about a quarter to a third of a mile wide. It lies 

 partly in the "metagabbro," and partly between the serpentine and 

 the other intrusive. It is also penetrated by small dikes of serpentine 

 and by small masses of greenstone (chiefly intrusive basalts) not 

 shown on the map. Associated with this area at one point is a patch 



1 Quoted by Becker, Geological Society of America Bulletin, Vol. II (1891), p. 203. 



2 See p. 534. 



