﻿106 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  number 
  of 
  small 
  ones 
  of 
  the 
  character 
  of 
  progressive 
  overthrusts. 
  

   In 
  the 
  western 
  Normanskill 
  area 
  this 
  is 
  suggested 
  by 
  the 
  pinching 
  

   out 
  of 
  the 
  grit 
  belt, 
  as 
  stated 
  before, 
  against 
  the 
  western 
  boundary 
  

   of 
  the 
  area. 
  The 
  line 
  bounding 
  the 
  Willard 
  mountain 
  area 
  of 
  

   Normanskill 
  rocks 
  on 
  the 
  west 
  is 
  to 
  all 
  appearances 
  of 
  the 
  same 
  

   character, 
  for 
  this 
  would 
  explain 
  in 
  part 
  that 
  the 
  older 
  Normanskill 
  

   rocks 
  project 
  here 
  more 
  than 
  iooo 
  feet 
  above 
  the 
  younger 
  Snake 
  

   Hill 
  beds 
  adjoining 
  them 
  to 
  the 
  west, 
  and 
  that 
  we 
  find 
  structures, 
  

   as 
  the 
  cross 
  fold 
  in 
  the 
  southeast 
  corner 
  of 
  the 
  sheet, 
  cut 
  off 
  by 
  

   that 
  line. 
  

  

  If 
  the 
  eastern 
  Normanskill 
  belt 
  is 
  also 
  overthrust 
  westward, 
  it 
  

   would 
  seem 
  to 
  have 
  been 
  not 
  only 
  overthrust, 
  but 
  also 
  thrown 
  into 
  

   the 
  high 
  mountain 
  folds 
  of 
  Willard 
  mountain 
  before 
  the 
  oncoming 
  

   of 
  the 
  Georgian 
  overthrust 
  waves, 
  for 
  the 
  latter 
  were 
  clearly 
  turned 
  

   aside 
  by 
  this 
  projecting 
  mass, 
  as 
  shown 
  by 
  the 
  curving 
  strike 
  of 
  

   the 
  Georgian 
  rocks 
  northeast 
  of 
  Willard 
  mountain. 
  That 
  it 
  still 
  

   in 
  this 
  late 
  time 
  projects 
  so 
  boldly 
  is 
  of 
  course 
  mainly 
  due 
  to 
  the 
  

   great 
  hardness 
  of 
  the 
  grit 
  and 
  especially 
  of 
  the 
  white-weathering 
  

   chert 
  beds 
  which 
  form 
  its 
  backbone. 
  

  

  As 
  far 
  as 
  this 
  relatively 
  small 
  area 
  indicates, 
  we 
  have 
  here 
  a 
  

   series 
  of 
  successive 
  overthrust 
  masses, 
  producing 
  the 
  intricate 
  struc- 
  

   ture 
  which 
  in 
  various 
  parts 
  of 
  Europe 
  is 
  known 
  as 
  " 
  Schuppen- 
  

   struktur," 
  the 
  separate 
  Schuppen 
  being 
  pushed 
  over 
  each 
  other 
  

   like 
  scales 
  (Schuppen). 
  

  

  While 
  the 
  prevailing 
  material 
  of 
  the 
  rocks 
  that 
  have 
  been 
  over- 
  

   thrusted 
  consists 
  of 
  shales, 
  there 
  are, 
  it 
  appears 
  to 
  us, 
  sufficient 
  

   masses 
  of 
  solid, 
  hard 
  grit 
  and 
  chert 
  beds 
  in 
  the 
  Normanskill 
  and 
  

   Snake 
  Hill 
  shales 
  and 
  of 
  limestone 
  and 
  quartzite 
  beds 
  in 
  the 
  Geor- 
  

   gian 
  rocks 
  to 
  have 
  transmitted 
  the 
  stress 
  to 
  the 
  shales. 
  Also 
  the 
  

   compact 
  Bald 
  Mountain 
  limestone 
  and 
  dolomite 
  must 
  have 
  been 
  

   important 
  agents 
  in 
  the 
  development 
  of 
  the 
  overthrusts. 
  In 
  the 
  Bald 
  

   mountain 
  section 
  (see 
  page 
  109 
  and 
  sections 
  and 
  diagrams 
  in 
  pocket) 
  

   the 
  limestone 
  is 
  seen 
  to 
  be 
  bounded 
  by 
  overthrust 
  planes 
  from 
  the 
  

   shales 
  above 
  and 
  below, 
  showing 
  that 
  the 
  shear 
  followed 
  in 
  some 
  

   places 
  the 
  bedding 
  planes 
  between 
  the 
  limestone 
  and 
  shale, 
  thus 
  

   separating 
  the 
  two. 
  It 
  is 
  possible 
  that 
  the 
  successive 
  overthrusting 
  

   took 
  place 
  similarly 
  as 
  suggested 
  by 
  Bailey 
  Willis 
  1 
  for 
  the 
  Alpine 
  

   structure, 
  although 
  we 
  have 
  been 
  led 
  to 
  infer 
  from 
  our 
  observa- 
  

  

  1 
  Bailey 
  Willis. 
  Thrusts 
  and 
  Recumbent 
  Folds, 
  a 
  Suggestion 
  Bearing 
  on 
  

   Alpine 
  Structure. 
  Science, 
  25:1010. 
  

  

  