578 PROCEEDINGS OF THE SAINT LOUIS MEETING 



33. Argillite (Grinnell), 1 ,500 feet. Base not seen. Purple, gray, red, and black ; 

 fine grained, slaty. 



At present it is possible to give only the foregoing general section of the strata, 

 with provisional designations of their geological ages, the fossils collected not yet 

 having been studied. 



Of the foregoing, numbers 7 to 21, inclusive, represent the Jura-Trias, as pro- 

 visionally classified, and in this interval is a coal bed of economic promise, though 

 the points at which this coal is best known are in the Flint Creek valley, a tribu- 

 tary of the Hellgate from the south. 



In this series no plane of non-conformity was discovered. There seems to have 

 been an unbroken sedimentation from the Algonkian to the base of the Creta- 

 ceous. The great limestone mass extends apparently from the Black River lime- 

 stone to the commencement of the Mesozoic 



Cutting the Paleozoic is an intrusive granite, seen at Clinton and at Garnet. A 

 system of porphyry dikes preceded it and another followed it, the latter pene- 

 trating the granite. It is along the margins of the earlier porphyry dikes, and 

 more or less permeating the dikes themselves, that occur the gold ores and the 

 free gold which has been taken from the placer mines of the region. 



During the Cretaceous and at its close great igneous activity prevailed. Creta- 

 ceous volcanoes spread volcanic ash over extended areas. Much lava is found of 

 later date than the Cretaceous, some of it being Tertiary. Crater pits are not un- 

 common, and dikes and sheets of white quartz porphyry are conspicuous at Bear- 

 mouth. 



In general, there is a series of hill ranges or mountains, rising sometimes from 

 5,000 to 7,500 feet above the sea, which have a prevailing direction northwest- 

 southeast throughout the area examined. These are produced evidently by a 

 series of faults running in that direction, accompanied by lateral pressure, causing 

 one side of the fault plane to drop while the other was lifted. Frequently the 

 bold scarps face toward the northeast, and this is particularly the case in the 

 Algonkian part of the area. Still this is not always the structure apparent. Some 

 of the ranges are formed by sharp anticlinal folding. This great disturbance dates 

 from later than some of the lavas, as these lavas are found to be faulted, and now 

 form the crests of some of the fault scarps. It is evident, however, from the posi- 

 tion of Tertiary strata in the Hellgate valley unconformable on the Algonkian, 

 that the country had a bold relief at the opening of the Tertiary. The Hellgate 

 river, through most of its course from Garrison to Bonner, runs in the valley pro- 

 duced by a succession of faulting, descending in the strata from east to west by 

 cutting across such crests as it found thrown athwart its course. 



DEVELOPMENT AND RELATIONSHIPS OF THE RUGOSA 



BY J. E. DUERDEN* 



STRUCTURAL RELATIONS OF THE GRANITES OF NORTH CAROLINA 



BY THOMAS L. WATSON 



This paper will be published in the reports of the North Carolina 

 Geological Survey. 



The President declared the scientific program closed. 



* Introduced by G. B. Shattuck. 



