﻿GEOLOGY 
  OF 
  THE 
  NORTH 
  CREEK 
  QUADRANGLE 
  59 
  

  

  hornblende 
  granite. 
  At 
  times 
  the 
  rock 
  is 
  pinkish 
  gray, 
  medium 
  to 
  

   coarse 
  grained, 
  and 
  not 
  very 
  gneissoid 
  ; 
  while 
  again, 
  and 
  by 
  rapid 
  

   changes, 
  the 
  rock 
  is 
  gray, 
  fine 
  grained, 
  and 
  very 
  gneissoid 
  to 
  al- 
  

   most 
  schistose. 
  Both 
  rock 
  types 
  have 
  the 
  same 
  composition 
  and 
  

   both 
  show 
  signs 
  of 
  granulation, 
  but 
  the 
  latter 
  rock 
  especially 
  so. 
  

   One 
  of 
  these 
  clearly 
  does 
  not 
  cut 
  the 
  other, 
  but 
  rather 
  there 
  is 
  a 
  

   rapid 
  gradation 
  from 
  one 
  to 
  the 
  other 
  parallel 
  to 
  the 
  foliation, 
  

   and 
  it 
  seems 
  clear 
  that 
  the 
  fine 
  grained, 
  very 
  gneissoid 
  rocks 
  were 
  

   produced 
  along 
  belts 
  of 
  shearing 
  perhaps 
  at 
  the 
  time 
  of 
  the 
  de- 
  

   velopment 
  of 
  the 
  foliation. 
  Such 
  a 
  rapid 
  transition 
  from 
  fine 
  to 
  

   medium 
  grained 
  granite 
  is 
  also 
  well 
  shown 
  even 
  in 
  a 
  hand 
  speci- 
  

   men 
  from 
  the 
  summit 
  of 
  Oven 
  mountain. 
  

  

  Many 
  dip 
  and 
  strike 
  observations 
  on 
  the 
  foliation 
  were 
  made, 
  

   the 
  more 
  representative 
  ones 
  being 
  plotted 
  on 
  the 
  accompanying 
  

   map. 
  Strike 
  observations 
  can 
  generally 
  be 
  made 
  with 
  a 
  fair 
  degree 
  

   of 
  accuracy, 
  but 
  dips 
  can 
  seldom 
  be 
  determined 
  to 
  nearer 
  than 
  5 
  

   or 
  10 
  degrees. 
  The 
  amount 
  of 
  dip 
  is 
  usually 
  rather 
  moderate, 
  most 
  

   often 
  ranging 
  from 
  30 
  to 
  60 
  degrees. 
  Considered 
  as 
  a 
  whole, 
  the 
  

   prevailing 
  strike 
  of 
  the 
  foliation 
  ranges 
  from 
  north 
  and 
  south 
  

   to 
  northwest 
  and 
  southeast 
  with 
  dips 
  almost 
  uniformly 
  toward 
  

   the 
  east. 
  The 
  northern 
  central 
  portion 
  is 
  exceptional 
  with 
  its 
  east 
  

   and 
  west 
  strike 
  and 
  northward 
  dip. 
  Also 
  there 
  are 
  important 
  

   departures 
  from 
  the 
  prevailing 
  direction 
  of 
  dip 
  and 
  strike 
  in 
  cer- 
  

   tain 
  Grenville 
  areas 
  as 
  south 
  of 
  Johnsburg, 
  south 
  of 
  Thurman, 
  and 
  

   between 
  Pottersville 
  and 
  Starbuckville, 
  in 
  which 
  areas 
  the 
  direc- 
  

   tions 
  are 
  very 
  variable. 
  On 
  the 
  Long 
  lake 
  sheet, 
  according 
  to 
  

   Professor 
  Cushing, 
  the 
  foliation 
  is 
  more 
  erratic 
  in 
  the 
  eruptives 
  

   than 
  in 
  the 
  Grenville, 
  but 
  here 
  precisely 
  the 
  reverse 
  is 
  true. 
  

  

  folding 
  

   Before 
  any 
  important 
  general 
  statements 
  can 
  be 
  made 
  regard- 
  

   ing 
  the 
  character 
  of 
  the 
  folding, 
  a 
  wider 
  area 
  will 
  have 
  to 
  be 
  

   studied. 
  A 
  striking 
  feature 
  is 
  the 
  almost 
  uniform 
  eastward 
  to 
  

   northeastward 
  dip 
  of 
  the 
  foliation, 
  which 
  suggests 
  the 
  possibility 
  

   of 
  isoclinal 
  folding 
  but 
  aside 
  from 
  this 
  uniform 
  direction 
  of 
  dip, 
  

   there 
  is 
  much 
  evidence 
  against 
  such 
  isoclinal 
  folding. 
  The 
  gen- 
  

   erally 
  moderate 
  angles 
  of 
  dip 
  ; 
  the 
  perfect 
  agreement 
  of 
  foliation 
  

   and 
  bedding 
  planes 
  even 
  where 
  the 
  strikes 
  and 
  dips 
  are 
  erratic; 
  

   and 
  the 
  utter 
  lack 
  of 
  any 
  evidence 
  for 
  repetition 
  of 
  the 
  strata 
  even 
  

   in 
  long 
  sections 
  like 
  that 
  of 
  figure 
  1 
  are 
  strong 
  points 
  against 
  

   isoclinal 
  folding. 
  Professors 
  Cushing 
  and 
  Kemp 
  recently 
  stated 
  

  

  