356 E. B. MATHEWS AND W. J. MILLER — COCKEYSVILLE MARBLE 



be found iii a few poorly developed exposures. The exposures along 

 the northern boundary east of the Northern Central railroad are very 

 poor, and the presence of the quartzite is only actually established at a 

 few points, owing to the cover of soil and the close similarity of the Balti- 

 more gneiss at this point. It is quite possible that the quartzite is cut 

 out locally, as it can not be recognized in the well exposed cuts along 

 the railroads just north of Monkton. If this is so, the lack of quartzite 

 only occurs for a short distance along the strike, as it is exposed in the 

 road from Monkton to Hereford, just west of the Gunpowder river, and 

 from this point may be traced without interruption through Pine Hill to 

 the sharply folded region between there and Glyndon. 



Along the southwestern limits of the Baltimore gneiss the quartzite i s 

 seldom found between it and the overlying marble, and wherever so 

 found it is usually very thin and poorly developed. It has been noted 

 along the northern edge of the Worthington valley near Councilmans 

 run and a little farther north above Slades run, but is apparently lack- 

 ing along the contact between the limestone and the Baltimore gneiss as 

 exposed along Western run. Such a rapid thinning of the quartzite from 

 a thousand feet or more in the ridges between Butler and Stringtown to 

 zero in Western run, a distance of less than 2 miles across the strike of 

 the folds, is quite unusual, but no facts were found indicating a fault, 

 and many observations point to a rapid thinning, due apparently to an 

 erosional unconformity. 



The unusual and rather peculiar development of garnet-schists and 

 garnet-mica-schists interbedded with the quartzite and apparently con- 

 stituting an upper member of that formation is best exhibited in this 

 northern region, especially between Pine hill and a point 1 mile 

 northwest of Butler, in the Stringtown valley. The quartzitic layers at 

 this point are not well developed, and the outcrops along the sides of the 

 hill strongly suggest the Wissahickon schist. The true position of this 

 bed is, however, shown by the folding of the quartzite-garnet rock and 

 limestone northwest of Belfast along Buffalo creek, where the areal dis- 

 tribution and structural observations seem to exclude the possibility of 

 a fault and demand the interpolation of an upper member in the quartz- 

 ite formation. This same conclusion is the most satisfactory deduction 

 from the observations made in the quartzite formation along the gorge 

 of the Gunpowder between Warren and Royston branch, where the gar- 

 netiferous rock interbedded with quartzitic layers is found resting on 

 more quartzose beds, and beneath the marble the whole conforming with 

 the structural relations shown by numerous exposures of marble in the 

 valley of Royston branch. The detailed character of the structure at 



