MARYLAND GEOLOGICAL SURVEY 



105 



be considered perfectly trustworthy. Nor are the apparent strati- 

 graphic relations necessarily the true relations of the two formations. 



Another hypothesis as to the relations will be discussed later. 



The stratigraphic relations which the Wissahickon mica-gneiss was 

 found to sustain to a crystalline limestone in Delaware and Pennsyl- 

 vania, have a bearing upon the age and origin of this formation and 

 may ultimately prove the means of determining both questions. 



The facts are as follows: Some five miles northeast of the extreme 

 northeastern corner of Cecil county, in the state of Delaware, are four 

 abandoned limestone quarries, situated in the mica-gneiss formation 

 and approximately normal to the strike. The limestone is a white, 

 crystalline, saccharoidal formation, somewhat stained with iron oxide. 

 It shows considerable plication and in each quarry is brought to the 



Fig. 



gneiss. 



-Section showing conformable contact of limestone with overlying mica- 



surface by a low unsymmetrical anticlinal fold. The northwest limbs 

 of the anticlines are always steeper than the southeast limbs. The 

 strike varies from N 30° E to N 60° E; the southeast dips are 15°, 

 25° and 35°; the northwest dips are 55° and 65°. A massive mica- 

 gneiss overlies the limestone with a sharp conformable contact. 



Essentially the same conditions prevail northeast of Cecil county 

 and south of Landenburg, Pennsylvania. Here again gentle unsym- 

 metrical anticlines have brought a blue or white crystalline limestone 

 so near the surface that quarries in the formation were opened by 

 Isaac Sharpless, by David Nevins and by John Eevins. At John 

 Kevins' quarry the mica-gneiss and limestone of the northwest limb 

 of the anticline are solidly welded together and show no evidence 

 of adjustment. 



