﻿Walcott 
  — 
  Appalachian 
  Type 
  of 
  Folding 
  in 
  California. 
  171 
  

  

  Silver 
  Canyon 
  penetrates 
  deep 
  into 
  the 
  range, 
  and 
  about 
  

   four 
  miles 
  from 
  its 
  mouth 
  cuts 
  across 
  a 
  great 
  synclinal 
  fold. 
  

   This 
  is 
  outlined 
  in 
  fig. 
  C, 
  page 
  173. 
  A 
  short 
  distance 
  above 
  the 
  

   mouth 
  of 
  the 
  canyon 
  the 
  siliceous 
  argillites, 
  with 
  the 
  inter- 
  

   bedded 
  layers 
  of 
  quartzite, 
  dip 
  to 
  the 
  eastward 
  about 
  20°. 
  

   This 
  dip 
  increases 
  until 
  the 
  beds 
  are 
  in 
  places 
  vertical. 
  

   Usually 
  at 
  the 
  bed 
  of 
  the 
  canyon 
  there 
  is 
  still 
  a 
  slight 
  eastward 
  

   dip. 
  As 
  the 
  strata 
  rise 
  on 
  the 
  side 
  of 
  the 
  canyon 
  they 
  become 
  

   vertical, 
  and 
  finally, 
  about 
  three 
  and 
  one 
  half 
  miles 
  from 
  the 
  

   mouth, 
  they 
  are 
  overturned 
  to 
  the 
  eastward 
  so 
  as 
  to 
  assume 
  a 
  

   westward 
  dip 
  and 
  to 
  produce 
  a 
  rough 
  fan 
  structure 
  in 
  the 
  sec- 
  

   tion 
  between 
  the 
  mouth 
  of 
  the 
  canyon 
  and 
  the 
  limestones. 
  

   The 
  series 
  of 
  argillites 
  and 
  quartzites 
  is 
  broken 
  by 
  minor 
  faults 
  

   and 
  closely 
  compressed 
  folds. 
  The 
  synclinal 
  structure 
  is 
  clearly 
  

   shown 
  by 
  the 
  limestone 
  series. 
  The 
  dip 
  of 
  the 
  western 
  limb 
  

   of 
  the 
  syncline 
  next 
  to 
  the 
  quartzite 
  is 
  from 
  70° 
  to 
  80° 
  west. 
  

   This 
  increases 
  to 
  about 
  60° 
  near 
  the 
  center 
  of 
  the 
  syncline. 
  

   The 
  strata 
  of 
  the 
  eastern 
  limb 
  dip 
  westward 
  at 
  about 
  60° 
  at 
  a 
  

   point 
  nearest 
  the 
  center, 
  and 
  from 
  that 
  down 
  to 
  40° 
  near 
  the 
  

   quartzite. 
  

  

  The 
  section 
  of 
  the 
  syncline 
  exposed 
  on 
  the 
  north 
  side 
  of 
  

   Silver 
  Canyon 
  is 
  over 
  2,000 
  feet 
  in 
  depth, 
  and 
  when 
  viewed 
  

   from 
  the 
  high 
  ridge 
  on 
  the 
  south 
  side 
  of 
  the 
  canyon, 
  is 
  beauti- 
  

   fully 
  exhibited, 
  both 
  in 
  the 
  canyon 
  and 
  in 
  its 
  extension 
  to 
  the 
  

   northward, 
  along 
  the 
  western 
  face 
  of 
  the 
  range. 
  Frequently 
  

   the 
  eastern 
  limb 
  of 
  the 
  limestone 
  of 
  the 
  syncline 
  rises 
  to 
  the 
  

   summit 
  of 
  the 
  range, 
  but 
  as 
  a 
  whole 
  the 
  upper 
  limestone 
  syn- 
  

   cline 
  rests 
  against 
  the 
  western 
  side 
  of 
  the 
  range 
  for 
  twenty 
  

   miles 
  or 
  more 
  north 
  of 
  Silver 
  Canyon. 
  

  

  At 
  the 
  mouth 
  of 
  Black 
  Canyon 
  the 
  lower 
  limestone 
  (No. 
  4) 
  

   is 
  exposed. 
  It 
  dips 
  eastward 
  and 
  passes 
  beneath 
  the 
  quartzite 
  

   (No. 
  3) 
  at 
  an 
  angle 
  of 
  from 
  25° 
  to 
  30°. 
  A 
  fault 
  breaks 
  the 
  

   section 
  along 
  the 
  line 
  of 
  the 
  north 
  fork 
  of 
  Black 
  Canyon, 
  but 
  

   by 
  following 
  the 
  section 
  northward 
  about 
  two 
  miles 
  and 
  view- 
  

   ing 
  it 
  from 
  the 
  high 
  ridges 
  to 
  the 
  south 
  of 
  Black 
  Canyon, 
  it 
  is 
  

   seen 
  that 
  the 
  dip 
  of 
  the 
  quartzites 
  above 
  the 
  limestone 
  

   increases 
  to 
  the 
  vertical, 
  and 
  at 
  the 
  western 
  edge 
  of 
  the 
  

   syncline 
  formed 
  by 
  the 
  upper 
  limestone 
  the 
  dip 
  is 
  to 
  the 
  

   westward. 
  

  

  The 
  lower 
  limestone, 
  owing 
  to 
  the 
  northward 
  pitch 
  of 
  the 
  

   syncline, 
  passes 
  beneath 
  the 
  Pleistocene 
  beds 
  on 
  the 
  margin 
  of 
  

   the 
  valley, 
  before 
  reaching 
  Silver 
  1 
  Canyon. 
  In 
  fig. 
  B, 
  I 
  have 
  

   theoretically 
  restored 
  the 
  synclinal 
  section 
  of 
  the 
  range 
  so 
  as 
  to 
  

   include 
  the 
  lower 
  limestone. 
  What 
  comes 
  out 
  from 
  beneath 
  

   the 
  limestone 
  on 
  the 
  eastern 
  side 
  of 
  the 
  range 
  is 
  unknown 
  to 
  

   me, 
  as 
  I 
  was 
  unable 
  to 
  reach 
  that 
  portion 
  of 
  the 
  section. 
  

   Viewed 
  from 
  the 
  distance, 
  it 
  is 
  apparently 
  a 
  dark-colored 
  rock, 
  

  

  