224 



N. L. BOWEN 



complex as essentially a sheetlike mass with syenite overlying 

 anorthosite, the facts of Adirondack igneous geology seem to 

 arrange themselves more rationally. On this supposition one would 

 expect to find areas of the Grenville roof covering the syenite in 

 places and to find it relatively little disturbed. In the interior and 



Fig. 2. — A. Adirondack complex interpreted as batholitic. +Anorthosite, a Syenite 



B. Adirondack complex interpreted as laccolithic (undisturbed) 



C. Same as B after disturbance. Heavy line indicates erosion surface 



eastern region of maximum uplift one would expect to find the 

 deeper-seated anorthosite laid bare and to find it free from areas of 

 the roof since it was for the most part separated from the roof by a 

 layer of syenite. (In Fig. 2 the alternative interpretations of the 

 Adirondack complex are presented.) 



On this supposition of the origin of syenite and anorthosite by 

 gravitative differentiation of a sheetlike mass it is by no means 



