﻿Appalachian 
  Geosyncline. 
  447 
  

  

  Portage 
  and 
  Cheniung, 
  attains 
  thicknesses 
  measured 
  from 
  3,500 
  

   to 
  4,400 
  feet. 
  

  

  The 
  Skunnemunk 
  conglomerate. 
  

  

  In 
  Passaic 
  County, 
  New 
  Jersey, 
  and 
  in 
  Orange 
  County, 
  JSTew 
  

   York, 
  occurs 
  an 
  isolated, 
  down-faulted 
  and 
  down-folded 
  syncline 
  

   of 
  Paleozoic 
  rocks 
  known 
  as 
  the 
  Green 
  Pond 
  Mountain 
  axis. 
  It 
  

   lies 
  20 
  to 
  25 
  miles 
  southeast 
  of 
  and 
  parallel 
  to 
  the 
  margins 
  of 
  

   the 
  main 
  area 
  of 
  Devonian 
  rocks. 
  It 
  is 
  about 
  50 
  miles 
  long, 
  

   from 
  1 
  to 
  4 
  miles 
  in 
  width, 
  and 
  through 
  most 
  of 
  its 
  length 
  is 
  

   hemmed 
  in 
  by 
  uplands 
  of 
  pre-Cambrian 
  gneiss. 
  The 
  synclinal 
  

   axis 
  includes 
  formations 
  ranging 
  from 
  Lower 
  Cambrian 
  to 
  upper 
  

   Devonian 
  and 
  gives 
  information 
  respecting 
  the 
  conditions 
  exist- 
  

   ing 
  during 
  the 
  deposition 
  of 
  the 
  neo-Paleozoic 
  formations 
  25 
  

   miles 
  nearer 
  to 
  the 
  old 
  land 
  of 
  Appalachia 
  than 
  is 
  seen 
  elsewhere 
  

   in 
  this 
  part 
  of 
  the 
  Appalachian 
  geosyncline. 
  Above 
  the 
  Bell- 
  

   vale 
  flags 
  holding 
  a 
  marine 
  Hamilton 
  fauna, 
  lies 
  the 
  massive 
  

   Skunnemunk 
  conglomerate 
  of 
  Upper 
  Devonian 
  age 
  which 
  Dar- 
  

   ton 
  was 
  the 
  first 
  to 
  discriminate 
  from 
  the 
  somewhat 
  similar 
  

   Green 
  Pond 
  conglomerate 
  of 
  the 
  Silurian. 
  

  

  " 
  The 
  typical 
  beds 
  of 
  the 
  Skunnemunk 
  formation 
  are 
  a 
  coarse, 
  

   purple-red, 
  massive 
  conglomerate, 
  the 
  pebbles 
  of 
  which 
  are 
  some 
  

   times 
  six 
  or 
  seven 
  inches 
  in 
  diameter. 
  Beds 
  of 
  red 
  sandstone 
  

   alternate 
  more 
  or 
  less 
  frequently 
  with 
  the 
  conglomerate, 
  and 
  

   there 
  are 
  many 
  gradations 
  between 
  the 
  two. 
  In 
  the 
  conglomer- 
  

   ate 
  the 
  most 
  conspicuous 
  pebbles 
  are 
  white 
  quartz, 
  owing 
  to 
  the 
  

   contrast 
  they 
  present 
  to 
  the 
  dull 
  red 
  matrix. 
  Dark 
  red 
  quartzite 
  

   and 
  sandstone 
  pebbles 
  are, 
  however, 
  almost 
  as 
  abundant 
  as 
  the 
  

   quartz 
  pebbles, 
  and 
  red 
  shale 
  pebbles 
  frequently 
  occur. 
  In 
  some 
  

   of 
  the 
  lower 
  layers 
  green 
  sandstone 
  or 
  graywacke 
  pebbles 
  are 
  also 
  

   abundant. 
  The 
  varicolored 
  cherts 
  which 
  were 
  noted 
  sparingly 
  in 
  

   the 
  Green 
  Pond 
  conglomerate 
  were 
  not 
  observed 
  here. 
  The 
  ma- 
  

   trix 
  is 
  in 
  general 
  the 
  same 
  material 
  as 
  the 
  pebbles, 
  only 
  finer, 
  and 
  

   is 
  firmly 
  cemented 
  together, 
  sometimes 
  so 
  much 
  so 
  as 
  to 
  present 
  

   a 
  vitreous 
  appearance. 
  On 
  the 
  whole, 
  however, 
  this 
  formation 
  is 
  

   not 
  so 
  vitreous 
  and 
  quartzitic 
  as 
  the 
  Green 
  Pond 
  conglomerate. 
  

   The 
  rock 
  is 
  locally 
  traversed 
  by 
  many 
  white 
  quartz 
  veins, 
  which 
  

   add 
  greatly 
  to 
  the 
  contrast 
  of 
  colors 
  and 
  the 
  variegated 
  appear- 
  

   ance. 
  

  

  " 
  Although 
  this 
  formation 
  is 
  typically 
  a 
  very 
  massive 
  dark 
  red 
  

   conglomerate, 
  forming 
  innumerable 
  ledges 
  and 
  cliffs 
  in 
  the 
  region 
  

   underlain 
  by 
  it, 
  yet 
  in 
  its 
  lower 
  portion 
  it 
  contains 
  many 
  beds 
  of 
  

   red 
  shale 
  and 
  sandstone 
  as 
  well 
  as 
  green 
  flags 
  and 
  greenish 
  con- 
  

   glomerates. 
  

  

  " 
  Since 
  these 
  conglomerates 
  rest 
  upon 
  the 
  Bellvale 
  flags, 
  which 
  

   are 
  of 
  Middle 
  Devonian 
  age, 
  they 
  must 
  be 
  somewhat 
  younger. 
  

   Darton 
  has 
  suggested 
  that 
  they 
  correspond 
  to 
  the 
  Oneonta 
  forma- 
  

  

  