82 



NEW YORK STATE MUSEUM 



These introductory points having been stated, the areal geology 

 may be passed briefly in review and notes may be recorded upon 

 the more interesting features of each. 



Distribution of the Grenviile. The most extensive single area 

 of the Grenviile begins in the northern outskirts of Port Henry^ and 

 extends northward to and beyond the Cheever mine. The lime- 

 stones are comparatively thick and are well exposed both by the 

 railway cuts along the lake shore and in the quarries which have 

 been opened for stock for the furnaces. North of Craig harbor 

 and again north of Cheever dock the continuity is broken by in- 

 trusive masses of the syenite series which tongue into the lime- 

 stone and which have probably contributed to its extreme meta- 

 morphism and its rich content of silicates. 



This main area presumably extends westward under the heavy 

 cover of drift near Moriah Center but is broken up by hills of 

 syenite gneiss. Patches of the limestone and their associates ap- 

 pear, hov/ever, for as much as 4 miles west of Moriah. The last 

 exposure is at the ophicalcite quarry on the old road to the Schroon 

 valley and south of Broughton ledge. To the southwest and north, 

 the Grenviile is cut out by the syenitic gneisses. To the south 

 around Bullpout pond at the headwaters of Grove brook another 

 small area appears, and extends southward into the Paradox quad- 

 rangle where it widens out very much into a broad area along 

 Penfield pond. 



OPHiCA LCiTE 



N 4)4 E 



^ys^mre. 



Fig. IS Cross section of the Grenviile strata at the Ophicalcite quarry, near Port Henry. 

 The arrows indicate the strike in plan. • 



N toq.E; 



Fig. 16 Cross section cf the Grenviile strata i mile north of cross section represented in 



figure 15 



SW. OPHlCT SCHISTS AND GNEISSES fs] £^ 



Fig. 17 Cross section cf the Grenviile strata 2 miles west of Moriah Corners 



