﻿270 
  E. 
  B. 
  Branson 
  — 
  Geologic 
  Section 
  in 
  Missouri. 
  

  

  The 
  Jefferson 
  City 
  Dolomite 
  (Lower 
  Ordovician). 
  — 
  

   The 
  Jefferson 
  City 
  is 
  continuous 
  from 
  one 
  end 
  of 
  the 
  

   section 
  to 
  the 
  other 
  though 
  it 
  is 
  not 
  exposed 
  west 
  of 
  cen- 
  

   tral 
  Pettis 
  County, 
  about 
  165 
  miles 
  west 
  of 
  St. 
  Louis. 
  

   It 
  is 
  very 
  sparsely 
  fossiliferous 
  and 
  the 
  writer 
  has 
  never 
  

   collected 
  an 
  identifiable 
  fossil 
  from 
  it 
  in 
  this 
  region. 
  It 
  

   was 
  uplifted, 
  folded 
  into 
  a 
  great 
  many 
  small 
  folds 
  and 
  

   deeply 
  eroded 
  before 
  the 
  seas 
  advanced 
  over 
  it 
  to 
  deposit 
  

   another 
  formation. 
  

  

  The 
  St. 
  Peter 
  Sandstone 
  (Lower 
  Ordovician). 
  — 
  The 
  

   lands 
  were 
  deeply 
  covered 
  with 
  wind-blown 
  sand, 
  derived 
  

   from 
  unknown 
  sources, 
  when 
  the 
  seas 
  readvanced 
  over 
  

   the 
  Jefferson 
  City, 
  and 
  this 
  sand 
  was 
  used 
  to 
  form 
  a 
  

   marine 
  formation 
  that 
  filled 
  the 
  valleys 
  and 
  spread 
  

   widely 
  over 
  the 
  uplands. 
  The 
  maximum 
  thickness 
  that 
  

   still 
  remains 
  is 
  about 
  200 
  feet 
  and 
  this 
  is 
  in 
  old 
  valleys. 
  

   Over 
  the 
  uplands 
  the 
  maximum 
  is 
  little 
  more 
  than 
  100 
  

   feet. 
  The 
  irregularities 
  in 
  thickness 
  in 
  the 
  eastern 
  part 
  

   of 
  the 
  section 
  are 
  due 
  almost 
  entirely 
  to 
  the 
  irregularity 
  

   of 
  the 
  surface 
  on 
  which 
  the 
  sand 
  was 
  deposited. 
  West- 
  

   ward 
  the 
  formation 
  thins, 
  either 
  on 
  account 
  of 
  original 
  

   deposition 
  or 
  subsequent 
  erosion 
  of 
  the 
  top, 
  and 
  west 
  of 
  

   eastern 
  Callaway 
  County, 
  about 
  75 
  miles 
  from 
  St. 
  Louis, 
  

   becomes 
  discontinuous. 
  The 
  sand 
  between 
  the 
  old 
  val- 
  

   leys 
  has 
  been 
  removed 
  by 
  erosion 
  and 
  the 
  St. 
  Peter 
  is 
  

   left 
  as 
  isolated, 
  linear 
  masses, 
  usually 
  only 
  a 
  few 
  hun- 
  

   dred 
  feet 
  wide, 
  and 
  ranging 
  up 
  to 
  more 
  than 
  100 
  feet 
  in 
  

   thickness. 
  This 
  condition 
  continues 
  to 
  eastern 
  Pettis 
  

   County, 
  about 
  150 
  miles 
  from 
  St. 
  Louis 
  where 
  the 
  forma- 
  

   tion 
  dips 
  under. 
  In 
  a 
  linear 
  section 
  one 
  of 
  these 
  sand- 
  

   stone 
  masses 
  would 
  be 
  crossed 
  every 
  three 
  or 
  four 
  miles 
  

   on 
  the 
  eastern 
  end 
  and 
  every 
  five 
  or 
  six 
  miles 
  on 
  the 
  

   western. 
  

  

  In 
  many 
  places 
  the 
  Jefferson 
  City 
  and 
  St. 
  Peter 
  were 
  

   folded 
  into 
  sharp, 
  narrow 
  synclines 
  and 
  after 
  erosion 
  the 
  

   St. 
  Peter 
  remained 
  in 
  the 
  bottoms 
  of 
  the 
  synclines. 
  The 
  

   contact 
  between 
  the 
  St. 
  Peter 
  and 
  Jefferson 
  City 
  is 
  one 
  

   of 
  nonconformity, 
  the 
  latter 
  presenting 
  a 
  surface 
  of 
  trun- 
  

   cated, 
  minor 
  folds 
  to 
  the 
  former. 
  

  

  The 
  Joachim 
  Dolomite 
  (Lower 
  Ordovician). 
  — 
  In 
  east- 
  

   ern 
  Callaway 
  County, 
  about 
  75 
  miles 
  from 
  St. 
  Louis, 
  

   appears 
  a 
  thin 
  edge 
  of 
  dolomite, 
  representing 
  Broad- 
  

   head's 
  First 
  Magnesian 
  limestone, 
  the 
  Joachim 
  of 
  later 
  

   writers. 
  The 
  formation 
  gradually 
  thickens 
  to 
  40 
  feet 
  

  

  