ELIZABETHTOWN AND PORT HENRY QUADRANGLES 8j 



In the way of structures it is not easy to make anything out of 

 these e:N,posures beyond individual monoclines. The exposures of 

 the large area along the lake dip at flat angle's westward. The re- 

 mote portions after the interval of drift, show easterly dips. A 

 broad flat syncline is suggested but the evidence is too fragmentary 

 to be unduly emphasized. Apparently a flat series of sediments 

 was invaded by the eruptive rocks which sometimes as intrusive 

 sheets, sometimes as batholiths of irregular shape and size, broke 

 them up, partially absorbed them, contorted them and separated 

 them into the patches which we see. 



In the case of two separated portions of this principal area in- 

 teresting relationships exist. Thus as one goes from the shores 

 of Lake Champlain westward across the outcrop of the Cheever ore 

 bed an exposure of gabbro and syenite gneiss is traversed with the 

 ore in the syenite and about 150 feet below Grenville limestone. 

 Ore, syenite and limestone make a westerly dipping half of a 

 shallow syncline and are cut off as nearly as can be told by a fault, 

 beneath a meadow at the foot of the ridge which culminates in 

 Bald knob. The ridge is a coarse granitic gneiss believed to be- 

 long to the syenite series and its summit is 800 feet above the 

 Cheever mine. Yet on the west side we find the green syenite 

 gneiss containing the Pilfershire ore bed which dips westward 

 in syenite beneath Grenville limestone just as at Cheever. Ap- 

 parently the ridge is a fault block, on each side of which the Gren- 

 ville has been dropped. 



For one who favored the sedimentary origin of the gneiss, here 

 interpreted as syenite, an argument is offered by these relations 

 which is not without its force. Thus a band of syenitic gneiss lies 

 just below the limestone, with which it has a rather sharp but fairly 

 regular contact, where seen along the lake shore just north of Craig 

 harbor. At this point the Crag (or Craig) ore bed was reported by 

 Ebenezer Emmons. A mile and a half north but farther back from 

 the lake the same relations are repeated at the Cheever ore bed. The 

 same distance west of Cheever, the same relations prevail at Pilfer- 

 shire. Thus there would seem to be a fairly definite horizon, with 

 the ore at about this position in three separate cases^ and sedi- 

 mentary stratigraphy is strongly suggested. Yet from the min- 

 eralogy of the walls and their close similarity with the wall rock 

 at Mineville, which in turn reproduces the characters of syenites, 

 elsewhere undoubtedly eruptive, the Crag, the Cheever and Pilfer- 

 shire wall rocks are believed to be intrusive sheets rather than con- 

 formable beds. 



