246 NEW YORK STATE MUSEUM 



character and this eastward facing cHft and slope forms Morning- 

 side Park. St Nicholas Park, farther north, from 128th to 155th 

 streets has the same structural relations. In both cases the present 

 escarpment stands back from 200 to 500 feet from the actual 

 contact. 



As the formations all pitch southward and are prettv' closely 

 folded, the higher formations gradually appear and at iioth street 

 another parallel ridge of ^Manhattan comes in above the limestone 

 in the trough of the next syncline to the east. This forms the 

 north end of Central Park and from this point southward Man- 

 hattan schist is continuous. But between the ^lorningside belt of 

 schist and the Central Park belt at iioth street lies an anticline 

 of Inwood limestone also pitching southward and gradually pass- 

 ing beneath the schist which encroaches upon it in a long wedge 

 until a few blocks farther south it passes wholly beneath the schist, 

 which from that point is continuous. 



This anticlinal wedge and its accompanying structures and rock 

 condition was the subject of some detailed exploration. 



The records of a few drill holes together with an interpretation 

 of all the data will serve for the present purpose. 



The most important borings are summarized below : 



a Hole no. 3 on 113th street, 232 feet east of Morningside Park 



East 

 Surface elevation-F-42.6 feet 



Rock floor at depth of 81.5 feet=el. -38.9 feet. 

 Material : 



0-19 feet=:to el.-23.6 feet=5oil and mixed drift 



19-79 f eet^to el. -36.9 f eet=modified drift. Assorted sands 



and silts 

 81.5-94.58 feet=to el. -54 feet=Inwood limestone. Typical 



and in good condition 

 b Hole no. 7. On 113th street, corner of Manhattan avenue 

 Surface elevation-f38 feet 



Rock floor at depth of approximately 165 feet=el. -127 feet 

 Material : 



0-85 feet=to el. -47 feet=modified drift 



85-165 feet=to el. -127 feet^^sand with much more clay, part 



of which may be decayed rock 

 165-240 f eet=to el. -202 feet=disintegrated rock ledge. Some 



micaceous type believed to be the transitional facies of the 



schist-limestone contact 



