﻿GEOLOGY 
  OF 
  SARATOGA 
  SPRINGS 
  AND 
  VICINITY 
  105 
  

  

  ern, 
  and 
  may 
  therefore 
  be 
  a 
  continuation 
  to 
  the 
  present 
  'day 
  of 
  the 
  

   " 
  progressive 
  overthrusting 
  " 
  here 
  described. 
  1 
  

  

  There 
  is, 
  however, 
  also 
  evidence 
  of 
  possible 
  larger 
  faults, 
  both 
  

   normal 
  and 
  overthrust, 
  in 
  the 
  folded 
  shales 
  of 
  the 
  Saratoga 
  plain. 
  

   One 
  larger 
  fault 
  is 
  directly 
  observable 
  at 
  Ballston 
  Spa, 
  separat- 
  

   ing 
  the 
  Canajoharie 
  shale 
  and 
  Snake 
  Hill 
  beds. 
  This 
  fault 
  is 
  

   traceable 
  southward 
  through 
  the 
  Ballston 
  lake 
  depression 
  toward 
  

   the 
  Mohawk 
  river. 
  Its 
  presence 
  is 
  shown 
  by 
  the 
  steep 
  eastward 
  

   dip 
  of 
  the 
  Snake 
  Hill 
  beds, 
  which 
  rapidly 
  decreases 
  as 
  one 
  goes 
  

   east, 
  the 
  part 
  of 
  the 
  Snake 
  Hill 
  belt 
  between 
  Ballston 
  Spa 
  and 
  

   the 
  lake 
  being 
  but 
  little 
  disturbed 
  by 
  crumpling. 
  From 
  present 
  

   evidence 
  we 
  infer 
  that 
  an 
  important 
  thrust 
  plane 
  separates 
  the 
  

   Snake 
  Hill 
  and 
  associated 
  now 
  intensely 
  crumpled 
  formations 
  of 
  

   the 
  eastern 
  basin 
  from 
  the 
  relatively 
  undisturbed 
  Canajoharie 
  

   shales, 
  along 
  this 
  fault 
  line 
  northeastward 
  beyond 
  the 
  limits 
  of 
  

   the 
  map. 
  This 
  fault, 
  which 
  is 
  probably 
  a 
  nearly 
  horizontal 
  thrust 
  

   fault 
  (see 
  diagram), 
  is 
  of 
  the 
  character 
  of 
  a 
  " 
  scission" 
  fault 
  or 
  

   " 
  charriage." 
  The 
  eastern 
  formations 
  have 
  been 
  pushed 
  westward 
  

   over 
  this 
  plane 
  for 
  an 
  unknown, 
  but 
  probably 
  considerable, 
  distance. 
  

   If 
  our 
  conclusion 
  that 
  the 
  Rysedorph 
  Hill 
  conglomerate 
  properly 
  

   comes 
  in 
  the 
  upper 
  part 
  of 
  the 
  Normanskill 
  shale 
  is 
  correct, 
  then 
  

   its 
  absence 
  near 
  the 
  boundary 
  line 
  of 
  the 
  two 
  on 
  the 
  Schuylerville 
  

   quadrangle 
  would 
  also 
  indicate 
  that 
  this 
  line 
  is 
  not 
  one 
  of 
  normal 
  

   stratigraphic 
  succession, 
  but 
  of 
  diastrophism 
  or 
  movement 
  of 
  the 
  

   earth 
  crust. 
  As 
  we 
  have 
  shown 
  above, 
  the 
  entire 
  shale 
  belt 
  is 
  tran- 
  

   sected 
  by 
  a 
  great 
  number 
  of 
  slips 
  or 
  thrusts 
  of 
  small 
  throw, 
  which 
  

   combined 
  might 
  be 
  competent 
  to 
  bring 
  up 
  the 
  older 
  shales 
  in 
  over- 
  

   lying 
  position 
  to 
  the 
  younger 
  ones 
  ; 
  they 
  would, 
  however, 
  not 
  throw 
  

   the 
  Rysedorph 
  Hill 
  conglomerate 
  out 
  of 
  its 
  supposed 
  normal 
  posi- 
  

   tion 
  near 
  the 
  top 
  of 
  the 
  Normanskill 
  beds. 
  

  

  Whatever 
  the 
  character 
  of 
  the 
  contact 
  along 
  the 
  western 
  edges 
  

   of 
  the 
  Normanskill 
  areas 
  may 
  be, 
  it 
  seems 
  clear 
  that 
  it 
  is 
  in 
  the 
  

   nature 
  of 
  an 
  overthrust, 
  either 
  a 
  single 
  large 
  overthrust 
  or 
  a 
  

  

  1 
  Woodworth 
  (op. 
  cit. 
  p. 
  26) 
  is 
  inclined 
  to 
  explain 
  these 
  small 
  faults 
  as 
  step 
  

   faults 
  with 
  a 
  downthrow 
  to 
  the 
  northwest, 
  which 
  would 
  produce 
  the 
  same 
  

   effect 
  as 
  an 
  overthrust 
  from 
  the 
  east, 
  and 
  to 
  consider 
  them 
  as 
  part 
  of 
  a 
  tilting 
  

   of 
  the 
  land 
  in 
  and 
  about 
  the 
  New 
  England 
  district, 
  since 
  the 
  retreat 
  of 
  the 
  

   Wisconsin 
  sheet, 
  or 
  as 
  resulting 
  from 
  the 
  lifting 
  out 
  of 
  the 
  cores 
  of 
  synclines 
  

   through 
  lateral 
  pressure 
  from 
  the 
  east. 
  Since 
  the 
  synclines, 
  as 
  a 
  rule, 
  are 
  

   overturned 
  to 
  the 
  west 
  and 
  compressed 
  into 
  close 
  folds 
  in 
  the 
  shale 
  district, 
  

   it 
  is 
  improbable 
  that 
  the 
  forcing 
  out 
  of 
  the 
  core 
  of 
  the 
  synclines 
  could 
  be 
  

   responsible 
  for 
  the 
  numerous 
  small 
  overthrusts 
  observed 
  by 
  us. 
  

  

  