3i8 J. H. BRADLEY, JR. 



S Feet 



5. Black limestones, some of them massive, weathering bluish-grey; 



interstratified toward the bottom with black and dark grey yellow 



weathering magnesian beds 350 



4. Black slaty thin-bedded nodular limestones with beds of purer 



limestone toward the base 300 



3, Dark bluish-grey thin-bedded nodular limestone with some magnesian 



slate 150 



2. Dark grey and black limestone, some of the beds magnesian 120 



1 . White and dove grey pure limestones, with some yellow- weathering 

 magnesian bands 120 



1,040 

 A 



3. Reddish-grey brown weathering dolomites, and black dolomites with 

 some thin-bedded black limestones 200 



2. White and dove grey pure compact limestones 100 



I. Dark grey and yellowish- white dolomites, weathering grey and 



veUowish-brown 400 



700 

 Total thickness 4,800 feet 



DIVISION A 



The lowest members of the series are well exposed at the town 

 of Philipsburg and follow the shore of Lake Champlain south to 

 the Vermont-Quebec boundary. At this place the rocks rise in 

 cliffs which form an almost perpendicular wall at the water's edge, 

 and are known locally as the "High Rocks." These cliffs continue 

 southward with diminishing height almost to Rock Bay, two miles 

 south of the boundary. Although these beds can be followed 

 northeastward from PhiUpsburg for about eight miles, it is the 

 ''High Rocks" exposure which sheds most light upon their structural 

 arrangement. At this point overthrust and reverse faulting, and 

 close folding are common phenomena. The evidence of this ex- 

 posure is that the thrusting force acted normal to the strike with the 

 overthrust from the southeast. The close folding so clearly dis- 

 played here is typical of folding throughout the entire Philipsburg 

 area. The pressure came probably after the beds had been Uthi- 

 fied, picking up the thinner beds into folds and overthrusting or 

 reverse faulting the thicker beds. Two minor overthrust faults 

 can be seen in this lake shore exposure and two minor reverse faults 



