BASAL GNEISSES OF THE HIGHLANDS 367 



and white gneiss most characteristic of the series passes gradu- 

 ally and normally into a mica quartz schist, and this in turn, 

 into a few feet of rather pure quartzite. The best localities 

 are at Sparta, a mile below Ossining; on the Putnam division 

 of the New York Central Railroad, a mile south of Eastview; 

 m the small creek just south of Crugers Station; and on the 

 Harlem division of the New York Central Railroad about a 

 mile north of Chappaqua. At every one of these points, where 

 the relation can be clearly made out, the quartzite is conformable 

 to the banded gneiss. The outcrop at Sparta is by far the most 

 extensive one, but here it is repeated by folding and crumpling 

 to such extent as to make an estimate of thickness very unreli- 

 able. It may be more than ioo feet thick there, but it does 

 not reach that amount at any other point. This is the " Lowerre 

 quartzite " named after the locality from which it was first 

 described. 



At each of these places, a coarsely crystalline limestone or 

 dolomite, equivalent to the " Inwood limestone " of Manhattan 

 island, lies next above, but not in sufficiently close proximity 

 or sufficiently simple relationship to determine whether or not 

 it is perfectly conformable. Some other considerations [see 

 a later paragraph] indicate that this limestone may not be 

 strictly conformable, although it partakes of practically all of 

 the dynamic modifications that have affected the region. It is 

 suggested that it may be conformable at one group of localities, 

 as is stated in United States Geological Survey Folio 83, and 

 not exhibit the same relation in other parts of the district, 

 indicating overlap conditions. Such apparent conformity is 

 most prominent in the old quarry at Hastings on the northern 

 border of the Harlem quadrangle. 



The Lowerre quartzite, therefore, because of its gradational 

 relation with the banded gneisses is, in all essential features, 

 only an upper quartzitic facies of the basal or Fordham gneiss 

 formation. In comparison with the great formations of the area 

 it can scarcely claim a separate classification, but it is a dis- 

 tinguishable bed, the uppermost member, although not separate 

 in any fundamental sense. 



It would seem consistent with the characters known for the 

 uppermost members and the succeeding formation (Inwood) to 

 consider the interbedded limestones and quartzites and graphitic 

 schists, as seen along the Hudson river from Fort Montgomery 



