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



entire satisfaction. The areal distribution, dips, and strikes suggest 

 that we have here the emergence of a syncline above the surface of the 

 country, but the underlying quartzite which one would naturally expect 

 to find bordering the limestone is absent, and the cause for this absence 

 is not entirely evident. It is easily recognized in the field that the 

 quartzite formation is thinning rapidly as one passes across the strike 

 from the broad exposures in the hills south of Stringtown to the thinner 

 development bordering the Butler-Belfast valley. Moreover, to the 

 southward the limestone rests immediately on the Baltimore gneiss. 

 These facts would seem to indicate that the quartzite did not extend 

 over the entire area of the Baltimore gneiss beneath the marble at the 

 time when the limestone was laid down. If this inference is true, it is 

 easy to explain the non-occurrence of the quartzite on the eastern bor- 

 der of the limestone, and possibly to define the limits of deposition of 

 the quartzite in this local area. Unfortunately, as is so often the case 

 in the southern Piedmont, the exposures along contacts are very poor 

 and frequently wanting at the critical point. 



DISTRIBUTION OF WISSAH1CKON FORMATION 



The Wissahickon formation, which overlies the marble, occupies the 

 remainder of the region, occurring in broad areas between the different 

 limestone valleys already described. The schists and gneisses of the 

 formation extend entirely around the northern anticline and occupy 

 very much of the region between it and the southern anticline. The 

 removal of the Wissahickon across the axis of the synclinorium along 

 the course of the Northern Central railroad between Lutherville and 

 Cockeysville separates the Wissahickon, however, into an eastern and 

 western portion. The western representative of the Wissahickon, lying 

 between the northern and southern anticlines and the Western Mary- 

 land and Northern Central railroads, forms a series of well rounded hills, 

 which reach to the level of the plateau along their summits. The ex- 

 posures throughout this region are poor, the material of the Wissahickon 

 formation yielding a good soil and breaking down easily to a protecting 

 mantle over the readily disintegrating garnet mica-schists. It is possi- 

 ble, however, to recognize that in this general basin are one or two minor 

 folds, giving an anticline across the area a little south of the center and 

 two minor synclinal axes just within the limits of the Wissahickon- 

 Cockeysville marble contact. 



The more eastern area of Wissahickon lying on either side of Dulany 

 valley and extending thence northeast appears to be somewhat more 

 complex. The rocks in the area about Loch Raven appear more gneissic 

 and even approach the Baltimore gneiss in appearance, while the schists 



