DISTRIBUTION 357 



this latter point will be more fully discussed in a later portion of the 

 paper. 



DISTRIBUTION OF COCKEYSVILLE MARBLE 



Areas in general. — The Cockeysville marble lies in a synclinal trough 

 between the southern and northern Baltimore gneiss areas and in the 

 synclinal folds on the northwest side of the northern anticline and out- 

 crops frequently within the limits thus outlined wherever the formation 

 is not covered by the Wissahickon schist. The occurrence of the car- 

 bonate rocks at the surface is always marked topographically by the 

 occurrence of limestone valleys, most prominent among which are the 

 Greenspring and Mine Bank valleys, lying to the north of the southern 

 Baltimore gneiss, between it and the overlying Wissahickon. Between 

 these two valleys and the corresponding valleys farther north the 

 Wissahickon gneiss has been removed, giving a very low divide in the 

 drainage system underlain by crystalline limestones extending from 

 Lutherville to Cockeysville. This, together with the narrow portion of 

 the Worthington valley and that of Green run, which border on the 

 southern flank of the northern anticline, represent crudely a recumbent 

 letter H. The limestone also extends northeastward from Lutherville, 

 forming the Dulany valley, which in turn has a small offshoot of the 

 limestone (the complementary flank of a small anticline) which runs up 

 the valley of the Gunpowder to the mouth of Royston branch, where the 

 limestone leaves the Gunpowder valley and occurs in a gentle anticline 

 in the valley of the smaller stream. 



From the western end of the Worthington valley the limestone wraps 

 around the narrow nose of the northern anticline and outcrops in a 

 series of narrow parallel valleys, separated by anticlinal ridges of quartz- 

 ite and gneiss or synclinal areas of Wissahickon schist. 



Beside these larger areas, which may be traced as one continuous mass, 

 there are three smaller areas, separated from the larger. The largest of 

 these is that forming the Long Green valley, which apparently is only a 

 portion of the Dulany valley and Glenarm bodies, from which it is sep- 

 arated on the higher land by the overlying Wissahickon schist. The 

 second area lies south of Taylor, and is apparently separated from the 

 Green Run arm of the main mass by a strike fault. The third area is' 

 represented by a single cutcrop of very small extent, occurring beside 

 the road just east of Glencoe station. 



Greenspring valley. — The marbles of the Greenspring valley extend 

 from west of the Reisterstown turnpike and the Western Maryland rail- 

 road eastward to the Northern Central railroad, where the valley broadens, 

 reaching out into the various valleys already described. The marbles 



