GEOLOGY OF THE PARADOX LAKE QUADRANGLE 



48l 



invariably accompanies the sedimentary gneiss and the limestone. 

 It occurs in bands interbedded with limestone or gneiss, the bands 

 varying from a few inches to some feet in thickness. They are 

 never of sufficient size to be mapped separately. 



The association of limestone with schist and with banded gneiss 

 has frequently been noted in the Adirondacks. In the Paradox Lake 

 quadrangle the rocks were so involved and exposures so limited 

 that no stratigraphy could be made out. The relations, however, 

 were shown in a locality about forty miles to the west, in a gorge 

 cut by the Hudson river. Between the points where the Indian 

 and the Boreas rivers join the Hudson there are about eight miles 

 of rapids, frequently bounded by cliffs. Here a section is displayed, 

 notably in the cliffs forming the " Blue Ledge " and in the cliffs 

 above " Carter's Riff." It is evident that gneiss, schist and lime- 

 stone constitute a single conformable series, the gneiss being 

 beneath, the schist forming bands interstratified with both gneiss 

 and limestone. It is further evident that the contact between gneiss 

 and limestone is not a sharp one. There is an alternation of thin 

 beds of gneiss and of limestone, passing upwards into pure limestone. 



The evidence from the gorge of the Hudson can certainly be 

 applied to the same rocks when too much crushed to show structural 

 relations. In the Paradox Lake quadrangle both faulting and crush- 

 ing have been excessive, but it is safe to conclude that here also the 

 gneiss is beneath, the limestone above, with more or less inter- 

 mingling along the contact. 



Sillimanite gneiss. The outcrop of this rock at the mine at 

 Graphite has already been described by Professor Kemp. 1 



Both the foot and the hanging walls of . the mine consist of it. 

 The garnet and graphite are the only minerals to be distinguished 

 in the hand specimen. The graphite of the mine is developed in a 

 quartzose layer along which there has been shearing in the direction 

 of the bedding. 



Another occurrence of sillimanite gneiss is on Bear Pond moun- 

 tain, but it differs slightly from that at Graphite. Garnets made 



'Geology of Washington. Warren and Essex Counties N. Y. State Geol. 

 17th An. Rept 1899. p.539. 



