REPORT OF THE DIRECTOR AND STATE GEOLOGIST 1901 vl 



The pre-Oambrian rocks were found to consist, in consider- 

 able part, of garnetiferous, quartz-feldspar gneisses, often hold- 

 ing graphite, which seem clearly of aqueous origin. They are 

 regarded as much altered sandstones and shales belonging to 

 the Grenville series, and are much like rocks described by Pro- 

 fessor Kemp from Warren and Washington counties. No 

 crystalline limestone was encountered, though boulders indicate 

 its presence not far outside the map limits. 



Aside from these rocks there is much of a variable gneiss 

 which has the composition of a syenite and is regarded as an 

 igneous rock. The Little Falls and Middleville outliers show 

 a porphyritic rock of this sort, whose igneous nature is clear. 

 In other exposures its igneous origin is not so evident. Unfor- 

 tunately no exposures were found which gave clear evidence 

 concerning its relations to the Grenville rocks. From field evi- 

 dence elsewhere this syenite is regarded as younger than and 

 intrusive in the Grenville rocks. 



The Paleozoic rocks were mapped areally, and their structure 

 and variations in thickness were worked out so far as possible. 

 Decisive evidence of their overlap on the old land surface of the 

 pre-Cambrian rocks was found. Attention was also given to 

 the glacial deposits and to the reasons for the present 

 topography. 



There are no rocks or mineral deposits of great economic 

 value in the region. There are good building stones for some 

 local uses, abundant road metal and a little iron ore, There 

 may also be good brick clays, though this is not certain. 



A short visit was also made to the Tupper lake region for 

 the purpose of taking photographs and of examining rock out- 

 crops exposed during road construction and soon covered by the 

 filling of road material. The exposures were of augite syenite 

 throughout. 



Mr E. C. Eckel, assistant in geology, spent most of the month 

 of October and part of November 1900 in Orange county, N. Y., 

 in a reconnaissance of the pre-Cambrian rocks. The boundary 

 between the pre-Cambrian and the Paleozoic formations was 



