THE ANORTHOSITE BODY IN THE ADIRONDACKS 503 



portion of the map we were just beginning to recognize the green 

 syenite of the region as a later intrusive and to separate it from the 

 main body of the gneiss in mapping; hence comparatively little 

 syenite is shown as such on this map, and much of what is there 

 mapped as gneiss has been since shown to be syenite also. The 

 two inliers referred to are mapped as gneiss; but Kemp's descrip- 

 tion of the rocks clearly shows that the Placid inlier consists largely 

 or wholly of syenite and that the same rock is represented in the 

 Keene inlier. 1 Both of these inliers are entirely surrounded by 

 anorthosite, and lie well within the mass. 



By comparison with the anorthosite the syenites occur in 

 separate masses of smaller size, usually much smaller, and there 

 is a large number of such masses. Some of these directly border 

 the anorthosite, but there is nothing like a continuous rim of syenite 

 about it. These syenite masses range throughout the entire region 

 and, in my experience, are no more abundant near the anorthosite 

 than they are away from it. The anorthosite lies in the eastern 

 portion of the Adirondack pre-Cambrian, and its relationships to 

 other rocks on its eastern margin are largely hidden by down- 

 faulting and by the cover of Champlain Paleozoics. But to the 

 west and south abundant syenite ranges away to distances of 60 or 

 70 miles beyond the anorthosite border; and such pre-Cambrian 

 outliers as those at Little Falls and Middleville bear witness that it 

 runs an unknown distance beyond the pre-Cambrian margin under 

 the Paleozoic cover. 



The point here made is that the syenite is spottily distributed 

 over the region, is no more abundant near the anorthosite than it is 

 away from it, and extends so far from the surface exposures of 

 anothorsite that the latter must be given an enormous lateral 

 extent underground, on the supposition that the two constitute a 

 sheetlike mass, with the anorthosite beneath. It is candidly ad- 

 mitted that this point has no particular value if Dr. W. J. Miller's 

 conception of the constitution of the Adirondack pre-Cambrian 

 complex is the correct one. His view is that this complex con- 

 sists entirely of a foundation of intrusives of the anorthosite- 

 syenite-granite group, upon which' fragments of the Grenville 



1 Bull. 21, N.Y. State Mus., pp. 55-56. 



